ARTICLE | doi:10.20944/preprints202211.0105.v1
Subject: Chemistry, Chemical Engineering Keywords: alkali leaching; red mud; high-iron waste; disposal; Al-goethite; conversion; magnetite
Online: 7 November 2022 (04:30:13 CET)
Bauxite residue (BR), also known as red mud, is a by-product of the production of alumina via the Bayer process. Because of the high sodium oxide and other impurities content, this material is not used to obtain iron or other iron-containing products. In this paper, the hydro-chemical conversion of goethite (FeOOH) to magnetite (Fe3O4) in high-iron BR from the Friguia alumina refinery (Guinea) by Fe2+ ions in highly concentrated alkaline media was studied. The simultaneous extraction of Al and Na made it possible to obtain a product containing more than 96% Fe3O4. The results show that the magnetization of Al-goethite and Al-hemetite accelerates the dissolution of the Al from the iron mineral solid matrix and from the desilication product (DSP). After ferrous sulfate (FeSO4·7H2O) was added directly at the FeO:Fe2O3 molar ratio of 1:1 at 120 °C for 150 min in the solution with the 360 g L-1 Na2O concentration, the alumina extraction ratio reached 96.27% for the coarse bauxite residue size fraction (Sands) and 87.06% for fine BR obtained from red mud. The grade of iron (total iron in the form of iron element) in the residue can be increased to 69.55% for Sands and 58.31% for BR. The solid residues obtained after leaching were studied by XRD, XRF, TG-DTA, VSM, Mössbauer spectroscopy and SEM to evaluate the conversion and leaching mechanisms and the recovery ratio of Al from different minerals. The iron-rich residues can be used in the steel industry or as a pigment.
REVIEW | doi:10.20944/preprints202209.0048.v1
Subject: Chemistry, Chemical Engineering Keywords: removal; PAHs; heavy metals; marine sponges; bacterial consortium
Online: 5 September 2022 (07:43:34 CEST)
Toxic materials in waste generally contain several components of global trending pollutant categories, especially PAHs and heavy metals. Bioremediation technology for managing waste utilizing microorganisms (bacteria) has not been fully capable of breaking down these toxic materials simple and environmentally friendly chemical products. This study examines the potential application of a marine sponge symbiont consortium with high performance and efficiency in removing PAHs and heavy metal contaminants. The method is carried out through a review of some related research articles by the author and published by other re-searchers. The study results concluded that bioremediation technology development GTP, can be carried out to improve remediation efficiency. Several types of marine sponge symbiont bacteria, hydrocarbonoclastic (R-1), metalloclastic (R-2), and metallohydro-carbonoclastic (R-3), have the potential to be applied to improve the removal performance of waste. Bacterial screening be done to find and categorize R-1 bacteria, R-2; R-3 to remediate GTP. Develop of R-1 bacteria, R-2; R-3 forms of the mobile formulation are needed in the future. A crystalline consortium of bacteria preparations is needed so that they can be quickly mobilized to locations exposed to GTP. Marine sponge symbiont bacteria be traced mainly to marine sponges whose body surface is covered with mucus.
ARTICLE | doi:10.20944/preprints202207.0052.v1
Subject: Chemistry, Chemical Engineering Keywords: alumina; catalysis; gasoline fraction of oil; hydrotreating; rare earth element; zeolite
Online: 4 July 2022 (10:39:29 CEST)
The oil produced in the oil fields of the Republic of Kazakhstan contains a high percentage of sulfur. Synthesis and improvement of the properties of catalytic systems for the production of fuels with high octane number and low sulfur content is currently an urgent task for Kazakhstan. In this study, catalytic systems with a new composition based on zeolites with the addition of rare-earth metals (E) and phosphorus (P) have been prepared and tested in the process of the catalytic hydrotreating of straight-run gasoline and gasoline of catalytic cracking. In case of NiO-MoO3-E-P-HZSM-HY-Al2O3 catalyst, the octane rating of the gasoline after hydro-processing was increased to 88-90, which is much higher than for other catalysts. The octane number of straight-run gasoline up to 400°C is a maximum of 90 (Research Method) and 83.7 (Motor Method). At the same time, the sulfur content in the resulting gasoline decreases from 0.0088% to 0.0011%. In the case of catalytic cracking gasoline, the sulfur content is reduced from 0.0134% to 0.0012%. The smallest residual sulfur content in the final product, 0.0005% is revealed in case of catalyst CoO-WO3-E-P-HZSM-HY-Al2O3, and it is 2-4 times lower than for catalysts CoO-MoO3-E-P-HZSM-HY-Al2O3 and NiO-MoO3-E-P-HZSM-HY-Al2O3. These amounts of sulfur residue in raw materials is lower than that required by the Euro-5 Standard. The surface of the prepared catalysts was 211.0-274.0 m2/g, diameter of pores d ≈ 1.5-2.5 nm and d ≈ 7.0 nm. The total pore volume of the catalysts was not higher than 0.28-0.41 ml/g. The catalysts developed in this study can be used for hydrotreating raw materials and producing high-octane gasoline with a low sulfur content, corresponding in its characteristics to the Euro-5 Standard.
ARTICLE | doi:10.20944/preprints202207.0019.v1
Subject: Chemistry, Chemical Engineering Keywords: catalysts; iron oxides; cobalt; oxygen; oxidation; phenol; magnetic composites
Online: 1 July 2022 (16:42:17 CEST)
The development and improvement of methods for the synthesis of environmentally friendly catalysts based on base metals is currently an urgent and promising task of modern catalysis. Catalysts based on nanoscale magnetite and maghemite have fast adsorption-desorption kinetics and high chemical activity. The purpose of this work was to obtain magnetic composites, determine their physicochemical characteristics and verify their activity in the process of liquid-phase oxidation of phenol with oxygen. Magnetic nanocomposites were obtained by chemical co-deposition of salts of ferrous and trivalent iron. The synthesized magnetic composites were studied by X-ray diffractometry, energy dispersive X-ray fluorescence and Mössbauer spectroscopy, IR-Fourier spectroscopy, elemental analysis. To increase the catalytic activity in oxidative processes, the magnetite surfaces were modified using cobalt nitrate salt. Further, CoFe2O4 was stabilized by adding polyethylenimine (PEI) as a surfactant. Preliminary studies of the oxidation of phenol with oxygen, as the most typical environmental pollutant were carried out on the obtained Fe3O4, CuFe2O4, CoFe2O4/PEI catalysts. The spectrum of the reaction product shows the presence of CH in the aromatic ring and double C=C bonds, stretching vibrations of the C=O groups of carbonyl compounds; the band at 3059 cm–1 corresponds to the presence of double C=C bonds, the band at 3424 cm–1 hydroquinone compounds. The band at 1678 cm–1 and the intense band at 1646 cm–1 refer to vibrations of the С=О bonds of the carbonyl group of benzoquinone. Peaks at 1366 cm–1 and 1310 cm–1 can be related to the vibrations of C–H and C–C bonds of the quinone ring. Thus it was demonstrated that produced magnetic composites based on iron oxide are quite effective in the oxidation of phenol with oxygen.
ARTICLE | doi:10.20944/preprints202206.0362.v1
Subject: Chemistry, Chemical Engineering Keywords: catalytic converters; waste gases; phosphating; oxidation
Online: 27 June 2022 (10:49:57 CEST)
Iron and chromium based alloys have found wide application in various fields of science and technology. Primary carrier based on Fe-Cr-Al alloy is used in block catalysts for high-temperature hydrocarbon conversion, in production of block metal catalysts for neutralization of toxic gases released during operation of internal combustion engines, as well as those present in smoke emissions from enterprises. Influence of thermal action on Fe-Cr-Al alloy foil and stability of secondary carrier on its surface was studied. Elemental composition of the surface layer of X15U5 alloy foil does not remain constant during heating and depends on the thermal treatment mode. Some of the elements come to surface and elemental composition of surface layer can differ significantly from that observed in the bulk of foil sample. This implies the possibility of changing the adhesive and adsorption properties of the foil surface, as well as the need to take this fact into account when supporting a secondary carrier and active phase to the foil. Applied technique of phosphating and supporting a secondary carrier to the foil surface makes it possible to obtain a sufficiently stable coating. There is no shedding of the secondary carrier from foil surface during high-temperature treatment in air.
ARTICLE | doi:10.20944/preprints202206.0109.v1
Subject: Chemistry, Chemical Engineering Keywords: Layered Double Hydroxides (LDH); mechano-chemical / co-precipitation synthesis; organic alkalis (tetramethylammonium hydroxides); memory effect; Claisen-Schmidt condensation; self-cyclohexanone condensation
Online: 8 June 2022 (03:23:29 CEST)
Using of the organic base tetramethylammonium hydroxides (TMAH) is a viable, cheap and fast route, for the MgZnAl-LDH type materials synthesis by both co-precipitation and mechano-chemical methods. TMAH provided several advantages as smaller quantity of water required in the washing step compared to the use of inorganic alkalis, prevention of LDH contamination with alkali cations, acting as template molecule in texture tailoring along with disadvantages as its presence in small quantities in the resulting layered materials. Regardless the use of organic / inorganic bases and co-precipitation / mechano-chemical methods, zincite stable phase was found in all the synthesized solids. The basicity of catalysts followed the trend: mixed oxides > reconstructed > parent LDH. The memory effect of LDH is supported only by the presence of Mg and Al cations, while Zn remains as zincite stable phase. The catalytic activities for Claisen-Schmidt condensation of benzaldehyde with cyclohexanone provided values higher than 90% after 2h, with a total selectivity in 2,6-dibenzylidenecyclohexanone, while in self-condensation of cyclohexanone no more than 7.29% after 5h. These behaviors depended on catalysts basicity as well as the planar rigidity of the compound.
REVIEW | doi:10.20944/preprints202203.0011.v2
Subject: Chemistry, Chemical Engineering Keywords: colloids; interface; formulation; surfactant; cosmetics; petroleum; food; paint; pharmaceutics; emulsions; foams; dispersions; HLDN
Online: 2 March 2022 (07:30:26 CET)
Formulation is an ancient concept, although the word has been used only recently. The first formulations made our civilization advance by inventing bronze, steel, and gunpowder; then, it was used in medieval alchemy. When chemistry became a science and with the golden age of organic synthesis, the second formulation period began. This made it possible to create new chemical species and new combinations “à la carte.” However, the research and developments were still carried out by trial and error. Finally, the third period of formulation history began after World War II, when the properties of a system were associated with its ingredients and the way they were assembled or combined. Therefore, the formulation and the systems’ phenomenology were related to the generation of some synergy to obtain a commercial product. Winsor’s formulation studies in the 1950s were enlightening for academy and industries that were studying empirically surfactant-oil-water (SOW) systems. One of its key characteristics was how the interfacial interaction of the adsorbed surfactant with oil and water phases could be equal by varying the physicochemical formulation of the system. Then, Hansen’s solubility parameter in the 1960s helped to reach a further understanding of the affinity of some substances to make them suitable to oil and water phases. In the 1970s, researchers such as Shinoda and Kunieda, and different groups working in Enhanced Oil Recovery (EOR), among them Schechter and Wade’s group at the University of Texas, made formulation become a science by using semiquantitative correlations to attain specific characteristics in a system (e.g., low oil-water interfacial tension, formulation of a stable O/W or W/O emulsion, or high-performance solubilization in a bicontinuous microemulsion system at the so-called optimum formulation). Nowadays, over 40 years of studies with the hydrophilic-lipophilic deviation equation (HLD) have made it feasible for formulators to improve products in many different applications using surfactants to attain a target system using HLD in its original or its normalized form, i.e., HLDN. Thus, it can be said that there is still current progress being made towards an interdisciplinary applied science with numerical guidelines. In the present work, the state-of-the-art of formulation in multiphase systems containing two immiscible phases like oil and water, and therefore systems with heterogeneous or micro-heterogeneous interfaces, is discussed. Surfactants, from simple to complex or polymeric, are generally present in such systems to solve a wide variety of problems in many areas. Some significant cases are presented here as examples dealing with petroleum, foods, pharmaceutics, cosmetics, detergency, and other products occurring as dispersions, emulsions, or foams, that we find in our everyday lives.
ARTICLE | doi:10.20944/preprints202111.0481.v1
Subject: Chemistry, Chemical Engineering Keywords: plastic waste; chemical recycling; mathematical modelling; carbon feedstock; circular economy; open-loop recycling; acrylonitrile butadiene styrene; polystyrene; toluene
Online: 25 November 2021 (15:26:23 CET)
The inherent value and use of hydrocarbon from waste plastics and solvents can be extended through open-loop chemical recycling as this process converts plastic to range of non-plastic materials. This process is enhanced by first creating plastic-solvent-combinations from multiple sources which are then streamlined through single process stream. We report on the relevant mechanics for streamlining industrially relevant polymers such as polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE) and acrylonitrile butadiene styrene (ABS) into chemical slurries mixed with various organic solvents such as toluene, xylene and cyclohexane. The miscibility of the polymer feedstock within the solvent was evaluated using the Relative Energy Difference method, and the dissolution process was evaluated using the “Molecular theories in a continuum framework” model. These models were used to design a batch process yielding 1 tonne/h slurry by setting appropriate assumptions including constant viscosity of solvents, disentanglement-controlled dissolution mechanism and linear increase of the dissolved polymer’s mass fraction over time. Solvent selection was found to be the most critical parameter for the dissolution process. The characteristics of the ideal solvent are high affinity to the desired polymer and low viscosity. This work serves as a universal technical guideline for open-loop chemical recycling of plastics avoiding the growth of waste plastic in a circular economy framework.
ARTICLE | doi:10.20944/preprints202111.0413.v1
Subject: Chemistry, Chemical Engineering Keywords: bauxite residue; red mud; scandium; acid leaching; kinetics; shrinking core model; waste utilization.
Online: 23 November 2021 (09:07:23 CET)
One of the potential sources of rare-earth elements (REEs) is the solid waste from alumina industry - bauxite residue, known as “red mud” (RM). The main REEs from the raw bauxite are concentrated in RM after the Bayer leaching process. The earlier worldwide studies were focused on the scandium (Sc) extraction from RM by concentrated acids to enhance the extraction degree. This leads to the dissolution of major oxides (Fe2O3 and Al2O3) from RM. This article studies the possibility of selective Sc extraction from alkali fusion red mud (RMF) by diluted nitric acid (HNO3) leaching at pH ≥ 2 to prevent co-dissolution of Fe2O3. RMF samples have been analyzed by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and inductively coupled plasma mass spectrometry (ICP-MS). Sc extraction has been found to be 71.2 % at RMF leaching by HNO3 at pH=2 and at 80 °C during 90 min. The kinetic analysis of experimental data by the shrinking core model has shown that Sc leaching process is limited by the interfacial diffusion and the diffusion through the product layer. The apparent activation energy (Ea) was 19.5 kJ/mol. We have established that according to EPMA of RMF, Sc is associated with iron minerals; it could act as the product layer. The linear dependence of Sc extraction of magnesium (Mg) extraction has been revealed. This fact indicates that Mg can act as a leaching agent of Sc presented in RMF by ion-exchangeable phase.
ARTICLE | doi:10.20944/preprints202111.0238.v1
Subject: Chemistry, Chemical Engineering Keywords: volatile suspended solids; anaerobic digestion; hydrogen; sour cabbage; microaeration
Online: 12 November 2021 (17:04:00 CET)
In the article, were checked influences of microaeration, pH, and VSS (Volatile Suspended Solid) for sour cab-bage anaerobic digestion. Results fermentation of sour cabbage under the condition of small oxygen addition are presented in this research can be classified as dark fermentation or hydrogenotrophic anaerobic digestion. The investigations were carried out for two concentrations 5 g VSS /L and 10 g VSS /L of sour cabbage at pH 6.0. The oxygen flow rates (OFR) for 5 g VSS /L were in the range of 0.53 to 3.3 mL/h for obtaining 2% to 8% of oxygen. In cases of low pH and microaeration, ethylene production was observed at a level below 0.05% in biogas. The highest volume of hydrogen for 5 g VSS/L was obtained for flow rate 0.58 O2 mL/h, giving hydrogen concentration in biogas in the range of 0 to 20%. For VSS 5 g/L and oxygen flow rate 0.58 mL/h; 0.021 L of hydrogen is produced per gram of VSS. In this case, VSS 10 g/L and oxygen flow rate 1.4 mL/h at pH 6.0, 0.03 L of hydrogen is generated per gram. Microaeration from 0.58 mL/h to 0.87 mL/h was propitious for hydrogen production at 5 g VSS/L of sour cabbage and 1.4 mL/h for 10 g/L. Another relevant factor is the volatile suspended solid factor of sour cabbage that caused optimal hydrogen production at VSS 89.32%.
ARTICLE | doi:10.20944/preprints202110.0323.v1
Subject: Chemistry, Chemical Engineering Keywords: Hydrogel; Blended paper; Slow-release fertilizer; Hydroxy Propyl Methyl Cellulose; polyvinyl alcohol
Online: 22 October 2021 (09:48:48 CEST)
In this study, a slow-release urea fertilizer hydrogel was synthesized from hydroxyl propyl methyl cellulose, polyvinyl alcohol and glycerol blends with paper (blended paper) as second layer. The fertilizer hydrogel was characterized by SEM, XRD and FTIR. Its retention in sandy soil, swelling behavior in distilled and tap water as well as slow-release behavior to urea were investigated. The results indicated that the fertilizer had good slow-release properties and ability to retain water in soil. However, the addition of blended paper as a second layer matrix was found to help improve the release properties of the fertilizer. The swelling kinetic of the hydrogel followed the Schott’s Second order model. The release kinetics of urea in water was best described by the Zero order model signifying that the release behavior was independent of fertilizer concentration
ARTICLE | doi:10.20944/preprints202110.0157.v1
Subject: Chemistry, Chemical Engineering Keywords: Adsorption; Cane Papyrus; Oily water; Produced water; Isotherm; Kinetic
Online: 11 October 2021 (11:53:37 CEST)
High quantities of wastewater produced from producing natural gas and oil from the aquifer, which called produced water. The produced water was comprised of dissolved solids, suspended solids, emulsified oil, and organic and inorganic compounds. That should be treated it's before disposal because it causes harm to the environment. This study takes the produced water from the southern Iraqi oilfield drilling company to adsorption by the Cane papyrus as natural and low-cost adsorbent. The analysis completed by using Fourier transforms infrared spectroscopy, EDX spectra and Scanning Electron Microscopic (SEM) for Cane papyrus. Investigating the effect of many parameters such as adsorbent dosage, temperature, solution pH, mixer speed and contact time. The Langmuir, Freundlich, Temkin and Harkins-Henderson isotherm models were tested, the results were 0.998,0.966, 0.931 and 0.966 respectively. The Langmuir model was more suitable described the adsorption process than the other models. The kinetics results were, 0.984 for Pseudo-first-order, 0.938 for Pseudo-second order is, 0.979 for Intra particle diffusion study and 0.912 for the Elovich model, the Pseudo-first-order kinetic equation best described the kinetics of the reaction. The thermodynamics study effect temperature changes on the thermodynamic parameters such as standard free energy change (∆G°), standard enthalpy change (∆H°) and standard entropy change (∆S°). The experimental data obtained demonstrated that Cane papyrus is a suitable adsorbent for removing oil from produced water.
ARTICLE | doi:10.20944/preprints202109.0398.v1
Subject: Chemistry, Chemical Engineering Keywords: Preparation of Off-Site Consequence Analyses; Chemicals Control Act; Risk Assessment; Paint Manufacturing Plant; Plating Industry Plant
Online: 23 September 2021 (10:18:56 CEST)
: Chemical accidents can occur anywhere. The need for chemical management in Korea was realized following the 2012 Gumi hydrofluoric acid accident in 2012. The Chemicals Control Act was enacted in 2015. This system evaluates the risks (high, medium, low) and consequent safety management at all plants that handle hazardous chemical substances. However, the system was criticized as excessive when most plants were designated high-risk without considering their size. Thus, laboratories and hospitals handling very small quantities were subject to regulation. Accordingly, in 2021 Korea revised the system to include off-site consequence analyses and a Korean-style risk analysis. Plants handling very small quantities, such as laboratories and hospitals, were exempt from regulation. In this study, plating and paint manufacturing companies, which were classified as high-risk in the previous system, even though they were medium-size business plants, were re-evaluated as low-risk plants. In the Korean-style risk analysis, it is possible to see at a glance what is lacking in the plants, such as cooperation between local residents and local governments and the construction of safety facilities according to the type of accident scenario. The revised system is a reasonable regulation for medium business plants.
ARTICLE | doi:10.20944/preprints202106.0325.v1
Subject: Chemistry, Chemical Engineering Keywords: Poultry litter; Carbon nanotubes; Catalyst; Experimental conditions; Adsorption
Online: 11 June 2021 (14:59:33 CEST)
Pakistan being an agricultural country is raising 146.5 million commercial and domestic poultry birds which generate around 544,831 tons of waste. This waste finds its final disposal in agricultural land as soil fertilizer or disposal site amendment. The uncontrolled use of poultry litter for this purpose results in environmental impacts such as the emission of methane, a greenhouse gas. However, other options like thermochemical conversion of this waste can offer a better solution wherein poultry litter can be used as low-cost carbon sources for the synthesis of Carbon Nanotubes (CNTs). In this study, efforts have been made to utilize this cheap and plenty of available carbon source for synthesis of CNTs in the presence of Ni/Mo/MgO as a catalyst, through pyrolysis. The optimum mole ratio of catalyst (4:0.2:1) was found to yield more carbon product. Furthermore, process parameters such as temperature, time, polymer & catalyst weight were also optimized. The best possible process parameters that resulted (pyrolysis time (12 min), temperature (825◦C), and catalyst weight (100 mg) good yield of CNTs . The structure and morphology of produced nanotubes were confirmed through X-ray Diffractometer (X-RD) & Scanning Electron Microscopy (SEM). The environmental application of the nanotubes was tested in synthetic chromium solution in the lab using a batch experiment. Different experimental conditions (pH, adsorbent dosage and contact time) were optimized to enhance the adsorption of Cr (VI) by carbon nanotubes and UV-Visible spectrophotometer was used at 540nm to measure the absorbance of Cr (VI). Results show that up to 81.83% of Cr (VI) removal was achieved by using 8 mg of CNTs at pH 3 with 400 rpm at 180 min of contact time. Thus, it was concluded that poultry litter can be a useful source for the synthesis of CNTs and thereby removal of Cr (VI) from industrial tanneries wastewater.
ARTICLE | doi:10.20944/preprints202012.0231.v1
Subject: Chemistry, Chemical Engineering Keywords: Plasma, zinc oxide, photocatalysis, nanomaterials.
Online: 9 December 2020 (15:51:59 CET)
In this work, zinc oxide (ZnO) nanoparticles were modified in a circulating fluidized bed through argon and hydrogen (Ar-H) alternative-current (AC) arc plasma, which shows the characteristics of non-equilibrium and equilibrium plasma at the same time. In addition, a circulating fluidized bed with two plasma jets was used for cyclic processing. The catalytic degradation performance on Rhodamine B (Rh B) by Ar-H plasma modified ZnO and pure ZnO was tested in aqueous media to identify the significant role of hydrogen atoms in Rh B degradation mechanism. Meanwhile, the effects of plasma treatment time on the morphology, size and photocatalytic performance of ZnO were also investigated. The results demonstrated that ZnO after 20 minutes-treatment by Ar-H plasma showed Rh B photocatalytic degradation rate is ten times greater than that of pure ZnO, and the reaction follows a first-kinetics for the Rh B degradation process. Furthermore, the photocatalyst cycle experiment curve exhibited that the modified ZnO still displays optimum photocatalytic activity after five cycles of experiment. The improvement of photocatalytic activity and luminescence performance attributes to the significant increase of the surface area, and the introduction of hydrogen atoms on the surface also could enhance the time of carrier existence where the hydrogen atoms act as shallow donors.
REVIEW | doi:10.20944/preprints202010.0378.v1
Subject: Chemistry, Chemical Engineering Keywords: Carbon dioxide capture; Deep eutectic solvents; Ionic liquids.
Online: 19 October 2020 (11:59:37 CEST)
Carbon dioxide capture and storage (CCS) is highly expected to be mitigating the discharges of carbon dioxide in a surrounding environment. Solvents are an integral part of CCS. So far, several solvents have been explored the interest of meeting the requirements such as accessibility, non-harmfulness, biocompatibility, recyclability, and inexpensiveness. However, most solvents face failure in fulfilling the requirements due to many factors, so, this review paper gives a brief discussion about another category of solvent, an analogue of ionic liquids (ILs) named deep eutectic solvent (DES). Extensive research has been done on DES in recent years because of their various attractive advantages, i.e., non-poisonousness, biodegradability, cheap cost and easy preparation, that make them as a promising green solvent for many industrial procedure and application, for instance, polymer synthesis, biodiesel treatment, green chemistry, electrochemistry etc. Therefore, this manuscript mainly focusses on CO2 capturing through DES in oil and gas field. In addition, the preparation and chemical structures of this novel solvent (DES) is also discussed. Moreover, a detailed study based on experimental solubility of CO2 in DESs is also reported in this article.
COMMUNICATION | doi:10.20944/preprints202008.0701.v1
Subject: Chemistry, Chemical Engineering Keywords: carbon dioxide; molybdenum carbide; methanol; copper; alkali; dopant
Online: 31 August 2020 (05:03:06 CEST)
Mitigation of Anthropogenic CO2 emissions possess a major global challenge for modern societies. Herein catalytic solutions are meant to play a key role. Among the different catalysts for CO2 conversion Cu supported on molybdenum carbide is receiving increasing attention. Hence, in the present communication we show the activity, selectivity and stability of fresh-prepared -Mo2C catalysts and compare the results with those of Cu/Mo2C, Cs/Mo2C and Cu/Cs/Mo2C in CO2 hydrogenation reactions. The results showed that all the catalysts were active and the main reaction product was methanol. The results showed that copper-cesium and molybdenum effectively interact and that cesium promoted the formation of metallic Mo. While, the incorporation of copper is positive to improve the activity and selectivity to methanol, the presence of Mo0 phase was detrimental for the conversion and selectivity. Moreover, the catalysts promoted by cesium underwent redox surface transformations during the reaction that diminished their catalytic performance. The molybdenum phase in Cu/Mo2C changes during reaction leading to metallic molybdenum and tuning the catalytic activity.
ARTICLE | doi:10.20944/preprints202008.0427.v1
Online: 20 August 2020 (05:40:51 CEST)
The direct Cr (VI) reduction process by oxalic acid was conducted and the results showed that the Cr (VI) was efficiently reduced by oxalic acid at high reaction temperature and high dosage of oxalic acid. The reduced product, Cr (III), was easily generated stable complex compounds (Cr(HC2O4)3) with oxalate, which displayed a negative effect on the reduction process. The high reaction temperature and high acidic medium could destroy the stable structure of a complex compound to release oxalate, and facilitate the reduction of Cr (VI). Generally, the present study provided a versatile strategy for Cr (VI) reduction, exhibiting a bright application future for real wastewater treatment.
BRIEF REPORT | doi:10.20944/preprints202005.0355.v1
Subject: Chemistry, Chemical Engineering Keywords: microplastics; analysis; waste treatment; food; diet
Online: 23 May 2020 (04:58:22 CEST)
This preprint is focused in the presence of plastics and microplastics in food. We will discuss how many we eat, and how they arrive to the food, and why. We will treat many other things, such as the waste treatment in Europe and in Spain, with updated data; how much plastic waste is generated; what are microplastics and how they are analyzed, I will tell about the experience we have at the University of Alicante (UA); how they can be removed and we will estimate how many we eat over the course of a year.
Subject: Chemistry, Chemical Engineering Keywords: adsorption; lead; biocomposite; alginate; Ficus carica L.
Online: 7 May 2020 (08:03:17 CEST)
In this study, fig leaves, zeolite and alginate were used to prepare a biocomposite for the adsorption of Pb(II) ions from aqueous solutions. Effects of various parameters on the biosorption process such as pH, temperature, initial lead concentration and contact time have been investigated. Maximum uptake of Pb(II) ions (85%) has been achieved at pH 6, with 25 mg/L of initial concentration and at a temperature of 288.15 K. Among the applied models, the data correlated well with Freundlich and D-R models and it was established that the biosorption was physical in nature. The amount of adsorbed lead per gram of sorbent was found to be 150.3 mg/g. Thermodynamic parameters showed the exothermic heat of biosorption and the feasibility of the process. Results have suggested that the prepared biosorbent possesses promising biosorption potential.
ARTICLE | doi:10.20944/preprints202002.0266.v1
Subject: Chemistry, Chemical Engineering Keywords: deep eutectic solvents; absorption; biogas; dimethyl disulfide; green solvents; desulfurization
Online: 18 February 2020 (11:10:40 CET)
The paper presents a synthesis of deep eutectic solvents (DESs) based on choline chloride (ChCl) as hydrogen bond acceptor and phenol (Ph), glycol ethylene (EG), and levulinic acid (Lev) as hydrogen bond donors in 1:2 molar ratio. DESs were successfully used as absorption solvents for removal of dimethyl disulfide from (DMDS) from model biogas steam. Several parameters affecting the absorption capacity and absorption rate has been optimized including kind of DES, temperature, the volume of absorbent, model biogas flow rate, and initial concentration of DMDS. Furthermore, reusability and regeneration of DESs by means of adsorption and nitrogen barbotage followed by the mechanism of absorptive desulfurization by means of density functional theory (DFT) as well as FT-IR analysis were investigated. Experimental results indicate that the most promising DES for biogas purification is ChCl:Ph, due to high absorption capacity, relatively long absorption rate, and easy regeneration. The research on the absorption mechanism revealed that van der Waal interaction is the main driving force for DMDS removal from model biogas.
ARTICLE | doi:10.20944/preprints202002.0129.v1
Subject: Chemistry, Chemical Engineering Keywords: Graphene; Nanocomposite; photocatalyst; water splitting; hydrogen
Online: 10 February 2020 (15:20:21 CET)
The present study focuses on the synthesis, characterization, and investigation of a p-n heterojunction photocatalysis. Titanium dioxide (TiO2) can’t alone induce the photocatalytic water splitting due to its wide bandgap, which decreases its catalytic activity in the visible light. To make redshift of absorptivity for the TiO2, Nickel (Ni)-doped Graphene (rGO) supported TiO2 was synthesized. Several characterization techniques have been employed to validate the composition and the light absorption ability of the prepared photocatalysts including TEM, SEM, EDS, XRD, XPS, and UV-Vis spectroscopy. The characterization revealed successful doping of the Ni and TiO2 on the rGO nanosheet. Moreover, the UV-Vis spectroscopy indicated a significant shift of light absorption toward the visible spectrum. The photon-induced evolution of H2 was remarkably enhanced using the prepared Ni-rGO/TiO2 nanocomposite. Furthermore, the optimum ratio of rGO: TiO2: Ni in the hybrids was 10:1:4, while the higher Ni ratio would decrease the photocatalytic activity. The stability of the photocatalyst was also verified during 8 cycles of photocatalytic reactions. The kinetic study revealed the nature of the integrated reaction and the controlling step governing the reaction sequence. .
ARTICLE | doi:10.20944/preprints202001.0348.v1
Online: 29 January 2020 (04:35:25 CET)
PEBAX-2533/metal salt/Al salt membranes were prepared for mixed olefin/paraffin separation. PEBAX-2533 with 80% ether group and 20% amide group was suggested as the polymer matrix for comparison of separation performance according to the functional group ratio in copolymer PEBAX. In addition, Al salts were used to stabilize metal ions for a long time as additives. High permeance was expected with the proportion of high ether groups since these functional groups provided relatively permeable regions. As a result, the PEBAX-2533 composite membrane showed a selectivity of 5 (propylene/propane) with 10 GPU. However, the permeance of membrane was not unexpectedly improved and the selectivity was reduced. The result was analyzed by SEM, FT-RAMAN and TGA, including FT-IR. The reduction in separation performance was determined by FT-IR. From these results, in order to stabilize the metal ions interacting with the polymer through Al(NO3)3, it was concluded that specific ratio of amide group was needed in PEBAX as polymer matrix.
ARTICLE | doi:10.20944/preprints202001.0046.v1
Subject: Chemistry, Chemical Engineering Keywords: CO2; diethyl carbonate; ethanol; dehydrating agent; catalyst
Online: 5 January 2020 (16:58:11 CET)
Excessive CO2 emissions and alternative energy fuels are two major difficult issues. The utilization of CO2 into fine chemicals is an optimal route. Diethyl carbonate (DEC) is an extremely versatile chemical intermediate. DEC is used in gasoline, pharmaceutical, chemical and other fields. DEC synthesis from CO2 and ethanol is a typical green synthetic route. Ni-Cu@Na3PW12O40 catalysts were synthesized by two novel methods of supported and mixed. The catalyst prepared by mixed method showed nice catalytic performance. It was confirmed that water removal was the key to improving conversion efficiency. In the presence of dehydrating agent of ethylene, ethanol conversion increased from ca. 3% to ca. 40%. Propylene oxide (PO) was participated in the reaction and ethanol conversion continued to reach to ca.90% while DEC selectivity dropped by half. Under optimal conditions, our Ni-Cu@Na3PW12O40 catalyst effectively solved the two major issues above.
Subject: Chemistry, Chemical Engineering Keywords: ASP flooding; low permeability oil layer; partial quality tool; maximum injection pressure; oil recovery
Online: 13 November 2019 (03:38:54 CET)
In order to solve the problem of the poor oil displacement effect of high molecular weight alkali/surfactant/polymer (ASP) solution in low permeability reservoirs, Daqing Oilfield uses a partial quality tool to improve the oil displacement effect in low permeability reservoirs. Without changing the oil displacement capability of high molecular weight ASP solution in high permeability oil layers, the ASP solution is actively sheared in low permeability oil layers by using a partial quality tool to increase the injection capability of the solution and improve the overall oil recovery. In order to study the ability of the partial quality tool to improve the oil displacement effect, firstly, the matching degree of high molecular weight ASP solution to low permeability cores is studied, and the ability of quality control tools to change the molecular weight is studied. Then, experimental research on the pressure and oil displacement effect of high molecular weight ASP solution before and after the actions of the partial quality tool is carried out. The results show that ASP solutions with molecular weights of 1900 × 104 and 2500 × 104 have a poor oil displacement effect in low permeability reservoirs. After the action of the partial quality tool, the injection pressure is reduced by 5.22 MPa, and the oil recovery is increased by 7.79%. The injection pressure of the ASP solution after shearing by the partial quality tool is lower than that of the ASP solution with the same molecular weight and concentration without shearing, but the oil recovery is lower. On the whole, the use of the partial quality tool can obviously improve the oil displacement effect in low permeability reservoirs.
ARTICLE | doi:10.20944/preprints201911.0049.v1
Subject: Chemistry, Chemical Engineering Keywords: silk fibroin nanoparticles; cocoon degumming; bombyx mori; ionic liquids ultrasound; autoclave
Online: 6 November 2019 (09:30:22 CET)
In recent years, numerous research studies have shown the excellent characteristics of silk fibroin nanoparticles as a vehicle for drugs delivery and it is foreseeable that their production could reach industrial scale in the coming years. For this reason, it is essential to know all the parameters that affect the formation of nanoparticles in order to standardize the process. Several studies have stated that the process used for sericin removal (degumming) from silk cocoons has a strong impact in the silk fibroin integrity and their mechanical properties after processing it into biomaterials. In this work, silk cocoons were degummed following four standard methods: autoclaving, short alkaline (Na2CO3) boiling, long alkaline (Na2CO3) boiling and ultrasounds. The resultant silk fibroin fibers were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate and used for nanoparticle synthesis by rapid desolvation in polar organic solvents. The relative efficiencies of the degumming processes and the integrity of the resulting fibroin fibers obtained were analyzed by weight loss, optical microscopy, thermogravimetric analysis, infrared spectroscopy and SDS-PAGE. Particle sizes and morphology were analyzed by Dynamic Light Scattering and Field Emission Scanning Electronic Microscopy. The results showed that the different treatments had a remarkable impact on the integrity of the silk fibroin chains, as confirmed by gel electrophoresis which can be correlated with particle mean size and size distribution changes. The study confirm that all the parameters of the process must be controlled in order to reach an optimum reproducibility of the nanoparticle production.
ARTICLE | doi:10.20944/preprints201911.0009.v1
Subject: Chemistry, Chemical Engineering Keywords: ammonia borane; ptni/g-c3n4; hydrogen storage; dehydrogenation
Online: 1 November 2019 (11:27:00 CET)
Graphite carbon nitride (g-C3N4) supported PtNi alloy nanoparticles (NPs) were fabricated via a facile and simple impregnation and chemical reduction method and explored their catalytic performance towards hydrogen evolution from ammonia borane (AB). Interestingly, the resultant Pt0.5Ni0.5/g-C3N4 catalyst affords superior performance, including 100% conversion, 100% H2 selectivity, yielding the extraordinary initial total turnover frequency (TOF) of 250.8 molH2 min-1 (molPt)-1 for hydrogen evolution from AB at 10 °C, a relatively low activation energy of 38.09 kJ mol−1, and a remarkable reusability (at least 10 times), which surpass most of the noble metal heterogeneous catalysts. This notably improved activity is attributed to the charge interaction between PtNi NPs and g-C3N4 support. Especially, the nitrogen-containing functional groups on g-C3N4, serving as the anchoring sites for PtNi NPs, may be beneficial for becoming a uniform distribution and decreasing the particle size for the NPs. Our work not only provides a cost-effective route for constructing high-performance catalysts towards the hydrogen evolution of AB but also prompts the utilization of g-C3N4 in energy fields.
ARTICLE | doi:10.20944/preprints201910.0287.v1
Subject: Chemistry, Chemical Engineering Keywords: membrane bio-reactor (mbr); ozone oxidation; paper and papermill; fluorescent whitening agents; water reuse
Online: 25 October 2019 (11:34:11 CEST)
In this study, effluent water was produced through Submerged Membrane Bio-Reactor (SMBR) process, which is a simple system and decomposes organic matter contained in wastewater with biological treatment process and performs solid-liquid separation, Especially, ozone oxidation treatment process is applied to effluent water containing fluorescent whitening agent, which is a trace pollutant which is not removed by biological treatment, and influences the quality of reused water. The concentration of COD in the SMBR was 449.3 mg/ℓ-COD, and the concentration of permeate water was 100.3 mg/ℓ-COD. The removal efficiency was about 70.1%. The amount of ozone re- quired for the removal of the fluorescent whitening agent in the permeated water in SMBR was 6.67 g-O3/min, and the amount of ozone required to remove COD relative to the permeate water was calculated to remove 0.997 mg-COD for 1 mg of O3.
Subject: Chemistry, Chemical Engineering Keywords: hypercrosslinked polymer; p-hydroxy-phthalic acid; pollutants; adsorption; biodegradation
Online: 17 September 2019 (11:36:51 CEST)
Adsorption is an effective strategy for the removal of pollutants from the wastewater. Herein, a 2-hydroxyterephthalic acid (HTC) modified hypercrosslinked polymer (HTC-HCP) is successfully synthesized via Friedel-Crafts reactions, and used as an adsorbent for the different types of pollutants including organic contaminants and heavy metal ions from wastewater. Excellent adsorption capacities are observed for amines (aniline, p-methylaniline (p-MA), p-chloroaniline (p-CA), and p-aminobenzoic acid (p-ABA)), phenols (phenol, p-chlorophenol (4-CP) Bisphenol A (BPA), 1-Naphthol (1-NP)), dyes (rhodamine B (RhB) and methyl orange (MO)), and metal ions (Pb2+, Hg2+, and Cd2+). The resulting polymers exhibited excellent adsorption performance towards these pollutants. Especially, the removal rate of aniline is above 95% in the concentration of 2.5 mg/L in 40 min at 25 °C. The interaction mechanism has been investigated, and confirmed by FTIR and the theoretical calculation results. It is due to surface complexation and chemisorption between adsorbent and adsorbate. The polymer exhibits good performance such as high adsorption capacity, high separation efficiency, biodegradable properties, and easy regeneration, suggesting that its potential technological applications for the removal of organic compounds and heavy metal ions from actual industrial effluent.
ARTICLE | doi:10.20944/preprints201908.0086.v1
Subject: Chemistry, Chemical Engineering Keywords: carbonylation of glycerol; glycerol carbonate; CO2; nanoparticle catalyst; CuO; CeO2
Online: 7 August 2019 (03:43:55 CEST)
Two important types of metal oxide nanoparticle catalysts Copper (II) oxide (CuO) and Cerium oxide (CeO2) are prepared by a suitable method which was traditional precipitation (PT) method at calcination temperature of 400oC for 5h and used for the synthesis of glycerol carbonate GC (C4H6O4) from the direct reaction by the carbonylation of Glycerol GL (C3H8O3) with Carbone Dioxide. The precipitation (PT) was an important route for the preparation of nanoparticles catalyst. The effects of performance of (CuO and CeO2) nanoparticle catalysts on the conversion of glycerol GL, yield of glycerol carbonate GC, selectivity of glycerol carbonate are researched. XRD, XPS, BET, FT-IR, CO2-TPD, H2-TPR are used for the characterization of the prepared catalysts. Comparing the optimal performance between them under reaction conditions were 150 oC, 4MPa (40 bar.), 5h, and both CuO and CeO2 catalyst amount 37.6 % (based on ratio of glycerol weight) by using 2-pyridinecarbonitrate (C6H4N2) as dehydrating agent and dimethylformamide (DMF), (C3H7NO) as solvent. The glycerol conversion (XGL), glycerol carbonate yield (YGC) and glycerol carbonate selectivity (SGC) over 0.7g CuO are 57.151%, 47.524%, and 83.156%, respectively, and glycerol carbonate yield over 0.7 CeO2 is 36.2185% or 35.076%, and the yield of GC could reach as high as 78.234% over 1.73g CeO2, the both catalysts could be easily regenerated by washing with methanol and water after a reaction and then dried at 60 oC overnight after that calcination at 400 oC for 5h without loss of activity after five recycling times, In addition to, the (ICP- MS) results confirmed that the leaching of CuO and CeO2 was below the detection limit.
ARTICLE | doi:10.20944/preprints201907.0249.v1
Subject: Chemistry, Chemical Engineering Keywords: vehicle; shell thickness, coating; focused ion beam; containing cross-linking agents
Online: 23 July 2019 (07:36:14 CEST)
This research was conducted to manufacture thermally expandable microspheres (TEMs) for vehicles’ underbody coating and to apply them on an industrial scale. TEMs heat resistance was studied depending on the ratios of a cross-linking agent and an initiator. This research focused on the content of a cross-linking agent and how it affected the results. The TEMs’ outer shell was thickened to solve the problem of the foam expansion ratio’s reduction that occurred due to the shrinkage after the maximum expansion (Tmax) was reached. After foaming, the cross-sectional thickness and surface of the sample with thickened outer shell were observed. The TEMs with the thickened shell showed the least shrinkage, which indicated excellent shrinkage stability, even after prolonged exposure to heat.
ARTICLE | doi:10.20944/preprints201907.0232.v1
Online: 22 July 2019 (07:46:54 CEST)
This paper focused on the oxidative leaching process of vanadium from vanadium-chromium reducing residue in alkaline medium with MnO2. The effect of experimental parameters including reaction time, reaction temperature, dosage of MnO2, dosage of NaOH, and liquid-to-solid ratio on the leaching efficiency of vanadium had been studied. The results indicated that MnO2 was an efficient oxidant for leaching out of vanadium. The leaching efficiency of vanadium was up to 97.25% under optimal reaction conditions: reaction temperature of 90 ℃, reaction time of 60 min, dosage of MnO2 at 50 wt.%, concentration of NaOH at 30 wt.% and liquid-to-solid at 5:1 mL/g.
ARTICLE | doi:10.20944/preprints201907.0160.v1
Subject: Chemistry, Chemical Engineering Keywords: solar thermal systems; phase change materials; thermoplastic elastomer; mechanical property; photo-thermal performance
Online: 11 July 2019 (11:54:58 CEST)
Traditional phase change composites usually suffer poor mechanical property and easy collapsing in the phase changing process. Herein, a highly flexible phase change composite is fabricated using thermoplastic elastomer as the basic gel and the expanded graphite/paraffin as the filler. This new phase change composite shows a tensile strength of 2.1 MPa and a breaking elongation of 220%. It has a melting enthalpy of 145.4 J•g-1 and a thermal conductivity of 2.2 W•m-1•K-1 with 70% of expanded graphite/paraffin. The thermoplastic elastomer based phase change composite exhibits great reversible property after 200 heating/cooling cycles. This flexible phase change composite demonstrates good photo-thermal energy charging/discharging property and shows great potential to be applied in the solar thermal energy systems.
ARTICLE | doi:10.20944/preprints201907.0087.v1
Subject: Chemistry, Chemical Engineering Keywords: pinning-depinning; evaporation; chemically stripe-patterned surfaces; lattice Boltzmann
Online: 5 July 2019 (04:40:38 CEST)
The liquid-vapor phase change lattice Boltzmann method is used to investigate the pinning-depinning mechanism of the contact line during droplet evaporation on the stripe-patterned surfaces in 3D space. Considering the curvature of the contact line and the direction of the unbalanced Young’s force, the local force balance theory near the stripe boundary is proposed to explain the steady state of the droplets on the stripe-patterned surfaces. An equation is proposed to evaluate the characteristic contact angle of the stabilized droplets. During the evaporation of the droplet, the stick-slip-jump behavior and the CCR-Mixed-CCA mode can be well captured by the lattice Boltzmann simulation. When the contact line is pinned to the stripe boundary, the contact line in the direction perpendicular to the stripes is slowly moving while the curvature of the contact line is gradually increasing. The gradually increasing curvature of the contact line accelerates the movement of the contact line, and the final contact line is detached from the stripe boundary. The research results provide theoretical support and guidance for the design, improvement and application of patterned surfaces in the field of micro-fluidic and evaporation heat transfer.
ARTICLE | doi:10.20944/preprints201906.0284.v1
Subject: Chemistry, Chemical Engineering Keywords: TEM; underbody coating; UBC; FIB; thermally expandable microspheres
Online: 27 June 2019 (07:52:13 CEST)
This research was conducted to manufacture thermally expandable microspheres (TEMs) for vehicles’ underbody coating and to apply them on an industrial scale. TEMs heat resistance was studied depending on the ratios of a cross-linking agent and an initiator. This research focused on the content of a cross-linking agent and how it affected the results. The TEMs’ outer shell was thickened to solve the problem of the foam expansion ratio’s reduction that occurred due to the shrinkage after the maximum expansion (Tmax) was reached. After foaming, the cross-sectional thickness and surface of the sample with thickened outer shell were observed. The TEMs with the thickened shell showed the least shrinkage, which indicated excellent shrinkage stability, even after prolonged exposure to heat.
ARTICLE | doi:10.20944/preprints201906.0283.v1
Subject: Chemistry, Chemical Engineering Keywords: TEM; thermal degradation; wall paper; blowing agent; foam
Online: 27 June 2019 (06:29:11 CEST)
This study was conducted to improve the white index (WI) by preparing thermally expandable microspheres (TEMs) for wallpaper. The thermal properties, foam expansion ratio and WI were studied depending on the particle size of colloidal silica in the preparation of TEMs. As a result, the TEMs with small particles of colloidal silica showed the best results for whiteness and yellowing. Additionally, TGA results indicated that it was highly possible that colloidal silica with small particle sizes was physically or chemically attached to the surface of the TEMs that led to an improvement in whiteness at high temperatures.
ARTICLE | doi:10.20944/preprints201906.0055.v1
Subject: Chemistry, Chemical Engineering Keywords: Supercritical carbon dioxide, Modeling, Acid, Artificial intelligence, Solubility
Online: 7 June 2019 (12:18:48 CEST)
In the present work, a novel and the robust computational investigation is carried out to estimate solubility of different acids in supercritical carbon dioxide. Four different algorithms such as radial basis function artificial neural network, Multi-layer Perceptron artificial neural network, Least squares support vector machine and adaptive neuro-fuzzy inference system are developed to predict the solubility of different acids in carbon dioxide based on the temperature, pressure, hydrogen number, carbon number, molecular weight, and acid dissociation constant of acid. In the purpose of best evaluation of proposed models, different graphical and statistical analyses and also a novel sensitivity analysis are carried out. The present study proposed the great manners for best acid solubility estimation in supercritical carbon dioxide, which can be helpful for engineers and chemists to predict operational conditions in industries.
ARTICLE | doi:10.20944/preprints201903.0068.v2
Subject: Chemistry, Chemical Engineering Keywords: germanium; supported liquid membrane; transport; Cyanex 923; modeling
Online: 29 May 2019 (04:54:50 CEST)
A transport process was studied from an aqueous solution containing oxalic acid and 100 mg/L Ge using a flat sheet supported liquid membrane (FSSLM) system. Cyanex 923 immobilized in a polytetrafluoroethylene membrane was employed as a carrier. The solution chemistry and related diagrams were applied to study the transport of germanium. The effectual parameters such as oxalic acid, carrier concentration, and strip reagent composition were evaluated in this study. Based on the results, the oxalic acid concentration of 0.075 mol/L and the carrier concentration of 20 %v/v were the condition in which the efficient germanium transport occurred. Among strip reagents, NaOH (0.04-0.1 mol/L) had the best efficiency to transport germanium through the SLM system. Furthermore, the permeation model was obtained to calculate the mass transfer resistances of the membrane (Δm) and feed (Δf) phases. According to the results, the values of 1 and 1345 s/cm were evaluated for Δm and Δf, respectively.
ARTICLE | doi:10.20944/preprints201905.0298.v1
Subject: Chemistry, Chemical Engineering Keywords: silver nanoparticles; nano-TiO2; nano- ZnO; nanohybrids; antibacterial
Online: 24 May 2019 (12:44:36 CEST)
This work emphasizes to use silver decorative method to enhance the antibacterial activity of TiO2 and ZnO nanoparticles. These silver decorated nanoparticles (hybrid nanoparticles) were synthesized by using sodium borohydride as a reducing agent, with the weight ratio of Ag precursors: oxide nanoparticles = 1: 30. The morphology and optical property of these hybrid nanoparticles were investigated using transmission electron microscopy (TEM) and UV–vis spectroscopy. The agar-well diffusion method was used to evaluate their antibacterial activity against both Staphylococcus aureus and Escherichia coli bacteria, with or without light irradiation. The TEM images indicated clearly that silver nanoparticles (AgNPs, 5-10 nm) were well deposited on the surface of nano-TiO2 particles (30-60 nm). Besides, smaller AgNPs (< 2 nm) were dispersed on the surface of nano-ZnO particles (20-50 nm). UV-vis spectra confirmed that the hybridization of Ag and oxide nanoparticles led to shift the absorption edge of oxide nanoparticles to the lower energy region (visible region). The antibacterial tests indicated that both oxide pure nanoparticles did not exhibit inhibitory against bacteria, with or without light irradiation. However, the presence of AgNPs in their hybrids, even at low content (< 40 mg/mL) leads to a good antibacterial activity and the higher inhibition zones under light irradiation as compared to that in dark was observed.
ARTICLE | doi:10.20944/preprints201905.0045.v1
Subject: Chemistry, Chemical Engineering Keywords: fuel cell; carbon nanotube; catalyst; platinum-ruthenium
Online: 6 May 2019 (10:05:30 CEST)
Due to low working temperature, high energy density and low pollution, proton exchange fuel cells have been investigated under different operating conditions in different applications. Using platinum catalyst in methanol fuel cell leads to increasing the cost of this kind of fuel cells which is considered as a barrier to commercialism of this technology. For this reason, a lot of efforts have been made to reduce the loading of the catalyst required on different supports. In this study, carbon black (CB) and carbon nanotubes (CNT) have been used as catalyst supports of the fuel cell as well as using the double-metal combination of platinum-ruthenium (PtRu) as anode electrode catalyst and platinum (Pt) as cathode electrode catalyst. The performance of these two types of the electro-catalyst in oxidation reaction of methanol has been compared based on electrochemical tests. Results showed that the carbon nanotubes increase the performance of the micro-fuel cell by 37% at maximum power density, compared to the carbon black. Based on thee-electrode tests of chronoamperometry and voltammetry, it was found that oxidation onset potential of methanol for CNT has been around 20% less than CB, leading to the kinetic improvement of the oxidation reaction. In addition, the active electrochemical surface area of catalyst has been increased up to 90% by using CNT compared to CB which shows the significant rise of the electrocatalytic activity in CNT supported catalyst with 62% increase in current density of methanol oxidation reaction respect to CB supported one. Moreover, the resistance of CNT supported sample to poisonous intermediate species has been found 3% more than CB supported one. According to the chronoamperometry test results, it was concluded that the performance and sustainability of NCT electro-catalyst shows remarkable improvement compared to CB electro-catalyst in long term.
ARTICLE | doi:10.20944/preprints201904.0020.v1
Subject: Chemistry, Chemical Engineering Keywords: Hydrotreating, mesoporous sulfide materials, waste Jatropha biomass, drop-in biofuels, upgrading technology
Online: 1 April 2019 (13:51:53 CEST)
The bio-oil was largely produced by thermal pyrolysis of Jatropha-derived biomass wastes (denoted as Jatropha bio-oil) using a Pilot Plant with a capacity of 20 kg h-1 at Thailand Institute of Scientific and Technological Research (TISTR), Thailand. Jatropha bio-oil is an unconventional type of bio-oil, which is mostly composed of fatty acids, fatty acid methyl esters, fatty acid amides and derivatives, and consequently it contained large amounts of heteroatoms (oxygen ~ 20 wt.%, nitrogen ~ 5 wt.%, sulfur ~ 1000 ppm.). The heteroatoms, nitrogen especially, are highly poisonous to the metal or sulfide catalysts for upgrading of Jatropha bio-oil. To overcome this technical problem, we reported a stepwise strategy for hydrotreating of 100 wt% Jatropha bio-oil over mesoporous sulfide catalysts of CoMo/γ-Al2O3 and NiMo/γ-Al2O3 to produce drop-in transport fuels, such as gasoline- and diesel-like fuels. This study is very different from our recent work on co-processing of Jatropha bio-oil (ca. 10 wt%) with petroleum distillates to produce a hydrotreated oil as a diesel-like fuel (Chen et al., Catalysts 2018, 8, 59; http://dx.doi.org/10.3390/catal8020059). Jatropha bio-oil was pre-treated through a slurry-type high pressure reactor under severe condition, resulting in a pre-treated Jatropha bio-oil with relatively low amounts of heteroatoms (oxygen < 20 wt.%, nitrogen < 2 wt.%, sulfur < 500 ppm.). The light and middle distillates of pre-hydrotreated Jatropha bio oil was then separated by distillation at temperature below 240 oC, and the temperature of 240-360 oC. Deep hydrotreating of light distillates over sulfide CoMo/γ-Al2O3 catalyst was performed on a batch-type high pressure reactor at 350 oC and 7 MPa of H2 gas for 5 h. The hydrotreated oil was a gasoline-like fuel, which contained 29.5 vol.% of n-paraffins, 14.4 vol.% of iso-paraffins, 4.5 vol.% of olefins, 21.4 vol. % of naphthene compounds and 29.6 wt.% of aromatic compounds, and little amounts of heteroatoms (nearly no oxygen and sulfur, and less than 50 ppm of nitrogen), corresponding to an octane number of 44, and it would be suitable for blending with petro-gasoline. The hydrotreating of middle distillates over sulfide NiMo/γ-Al2O3 catalyst using the same reaction condition produced a hydrotreating oil with diesel-like composition, low amounts of heteroatoms (no oxygen and less than 50 ppm of sulfur and nitrogen), and a cetane number of 60, which would be suitable for use in drop-in diesel fuel.
Subject: Chemistry, Chemical Engineering Keywords: polyethylene; nanocomposites; silver nanoparticles; Fe3O4-Ag hybrid nanoparticles; antibacterial activity
Online: 19 March 2019 (07:54:54 CET)
We report here the synthesis of uniform nanospheres-like silver nanoparticles (AgNPs, 5-10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAgNPs, 8-16 nm) by the use of seeding growth method in the presence of oleic acid (OA)/oleylamine (OLA) as surfactants. The antibacterial activity of pure nanoparticles and nanocomposites by monitoring the bacterial lag–log growth has been investigated. The electron transfer from AgNPs to Fe3O4NPs which enhances the biological of silver nanoparticles has been proven by nanoscale Raman spectroscopy. The lamellae structure in the spherulite of FeAgNPs/PE nanocomposites seems play the key role to the antibacterial activity of nanocomposites, which has been proven by nanoscale AFM-IR. An atomic force microscopy coupled with nanoscale infrared microscopy (AFM-IR) is use to highlight the distribution of nanoparticles on the surface of nanocomposite at the nanoscale. The presence of FeAgNPs in PE nanocomposites has a better antibacterial activity than that reinforced by AgNPs due to the faster Ag+ release rate from the Fe3O4-Ag hybrid nanoparticles and the ionization of AgNPs in hybrid nanostructure.
ARTICLE | doi:10.20944/preprints201903.0159.v1
Subject: Chemistry, Chemical Engineering Keywords: Taguchi method; experimental design; optimization; scandium; extraction; sulfuric acid
Online: 15 March 2019 (09:34:01 CET)
Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements such as rare earth elements including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies acid molarity, leaching time, solid/liquid ratio and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account applications constraints. The predicted values resulted by Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions depending on different applications.
ARTICLE | doi:10.20944/preprints201903.0134.v1
Subject: Chemistry, Chemical Engineering Keywords: Carbon-coated separator; polysulfide; shuttle effect; lithium-sulfur batteries
Online: 12 March 2019 (10:02:03 CET)
Lithium sulfur (Li–S) batteries are expected to be very useful for next-generation transportation and grid storage because of their high energy density and low cost. However, their low active material utilization and poor cycle life limit their practical application. The use of a carbon-coated separator in these batteries serves to inhibit the migration of the lithium polysulfide intermediate and increases the recyclability. We report the extent to which the electrochemical performance of Li–S battery systems depends on the characteristics of the carbon coating of the separator. Carbon-coated separators containing different ratios of carbon black (Super-P) and vapor-grown-carbon-fibers (VGCF) were prepared and evaluated in Li–S batteries. The results showed that larger amounts of Super-P on the carbon-coated separator enhanced the electrochemical performance of Li–S batteries; for instance, the pure Super-P coating exhibited the highest discharge capacity (602.1 mAh g-1 at 150 cycles) with a Coulombic efficiency exceeding 95%. Furthermore, the separators with the pure Super-P coating had a smaller pore structure, and hence limited polysulfide migration, compared to separators containing Super-P/VGCF mixtures. These results indicate that it is necessary to control the porosity of the porous membrane to control the movement of the lithium polysulfide.
ARTICLE | doi:10.20944/preprints201902.0017.v1
Subject: Chemistry, Chemical Engineering Keywords: FAEEs; biodiesel; mixed biocatalysts; lipases; microalgae
Online: 2 February 2019 (03:23:32 CET)
The production of fatty acids ethyl esters (FAEEs) to be used as biodiesel from oleaginous microalgae shows great opportunities as an attractive source for the production of renewable fuels without competing with human food. To ensure the economic viability and environmental sustainability of the microbial biomass as a raw material, the integration of its production and transformation into the biorefinery concept is required. In the present work, lipids from wet Isochrysis galbana microalga were extracted with ethyl acetate with and without drying the microalgal biomass (dry and wet extraction method, respectively). Then, FAEEs were produced by lipase-catalyzed transesterification and esterification of the extracted lipids with ethanol using lipase B from Candida antarctica (CALB) and Pseudomonas cepacia (PC) lipase supported on SBA-15 mesoporous silica functionalized with amino groups. The conversion to FAEEs with CALB (97 and 85.5 mol% for dry and wet extraction, respectively) and PS (91 and 87 mol%) biocatalysts reached higher values than those obtained with commercial Novozym 435 (75 and 69.5 mol%). Due to the heterogeneous nature of the composition of microalgae lipids, mixtures with different CALB:PC biocatalyst ratio were used to improve conversion of wet-extracted lipids. The results showed that a 25:75 combi-lipase produced a significantly higher conversion to FAEEs (97.2 mol%) than those produced by each biocatalyst independently from wet-extracted lipids and similar ones than those obtained by each lipase from the dry extraction method. Therefore, that optimised combi-lipase biocatalyst, along with achieving the highest conversion to FAEEs, would allow improving viability of a biorefinery since biodiesel production could be performed without the energy-intensive step of biomass drying.
ARTICLE | doi:10.20944/preprints201901.0054.v1
Subject: Chemistry, Chemical Engineering Keywords: heterogeneous catalysis; carbohydrates; HMF; Boehmite
Online: 8 January 2019 (08:36:49 CET)
A simple solid acid catalyst γ-AlOOH was employed to synthesize 5-hydroxymethylfurfural (HMF) from glucose in the dimethyl sulfoxide. Various reaction parameters, such as catalyst loading, temperature, reaction duration and solvent, were investigated. A high HMF yield of 61.24 % was obtained at the mild reaction condition of 130 °C for 3 h. More importantly, the catalyst γ-AlOOH could be reused for several times without the loss of its significant catalytic activities. After five reaction runs, a HMF yield about 57.23 % was obtained. In addition, the results demonstrated that the γ-AlOOH also had high catalytic activities on the degradation of other polysaccharides, like Maltose, Sucrose and Cellulose, into HMF using ionic liquid 1-butyl-3-methylimidazolium chloride, DMSO and a small amount of water as the reaction solvents. For instance, a high HMF yield of 50.26 % was obtained at 170 °C for 2.5 h on the decomposition of Cellulose.
ARTICLE | doi:10.20944/preprints201811.0586.v1
Subject: Chemistry, Chemical Engineering Keywords: Indoor, classrooms, residential rooms, air detector, PM, TVOC, EPA
Online: 26 November 2018 (11:24:49 CET)
Air quality has been a major concern throughout the world, Nigeria inclusive. The monitoring of air quality involves indoor and outdoor air quality. In this study, our concern was on indoor air quality. The aim of this study was to assess the air quality of residential homes (17), classrooms (3), hospitals (2), offices (5), Shops (2), and laboratories (5) in Akure, Nigeria in terms of formaldehyde (HCHO), total volatile organic compound (TVOC), Particulate matter (PM1.0; PM2.5, and PM10). A Multifunction Air Detector was used for the assessment using the manufacturers’ procedures and the locations were identified using a Mini GPS. The results revealed as follows: HCHO (0.001-0.030 mg/m3), TVOC (0.003-362 mg/m3), PM1.0 (004-014 µg/m3), PM2.5 (006-020 µg/m3), and PM10 (006-022 µg/m3). The results obtained were below the 24 h pollution recommended standards (0.1 mg/m3- HCHO; TVOC; 10-20 μ/m3 PM) of EPA and WHO. Statistically, there were correlations within the pollutants and weather. The Indoor air quality (IAQ) depicted the areas as ‘good,’ and toxicity potential (TP) were below unity. Although the locations looked safe, it is recommended that constant monitoring of the indoors should be ensured and proper ventilation should be provided.
ARTICLE | doi:10.20944/preprints201811.0396.v1
Subject: Chemistry, Chemical Engineering Keywords: polymerization modeling; kinetic; photoinitiator; optimal efficacy; crosslinking.
Online: 16 November 2018 (10:26:26 CET)
Optimal conditions for maximum efficacy of photoinitiated polymerization are theoretically presented. Analytic formulas are shown for the crosslink time, crosslink depth and efficacy function. The roles of photoinitiator (PI) concentration, diffusion depth and light intensity on the polymerization spatial and temporal profiles, for both uniform and non-uniform cases, are presented. For optimal efficacy, a strategy via controlled PI concentration is proposed, where re-supply of PI in high light intensity may achieve a combined-efficacy similar to low light intensity, but has a much faster procedure. A new criterion of efficacy based on the polymerization (crosslink) [strength] and [depth] is introduced. Experimental data are analyzed for the role of PI concentration and light intensity on the gelation time and efficacy.
ARTICLE | doi:10.20944/preprints201811.0331.v1
Subject: Chemistry, Chemical Engineering Keywords: gas mixtures; supported ionic liquid membrane; hydrogen sulfide; carbon dioxide; natural gas treating
Online: 14 November 2018 (10:06:01 CET)
Nowadays, the imidazolium-based ionic liquids containing acetate counter-ions are attracting much attention as both highly selective absorbents of the acidic gases and CO2 carriers in the supported ionic liquid membranes. In this regard, the investigation of the gas transport properties of such membranes may be appropriate for better understanding of various factors affecting the separation performance and the selection of the optimal operating conditions. In this work, we have tested CH4, CO2 and H2S permeability across the SILM impregnated by 1-butyl-3-methylimidazolium acetate (bmim[ace]) with the following determination of the ideal selectivity in order to compare the facilitated transport membrane performance with the SILM that dissolves acidic gases physically, namely, containing 1-butyl-3-methylimidazolium tetrafluoroborate (bmim[BF4]). Both SILMs have showed modest individual gases permeability and ideal selectivity of CO2/CH4 and H2S/CH4 separation that achieves values up to 15 and 32, respectively. The effect of the feed gas mixture composition on the permeability of acidic gases and permeselectivity of the gas pair was investigated. It turned out that the permeation behavior for the bmim[ace]-based SILM toward the binary CO2/CH4, H2S/CH4 and ternary CO2/H2S/CH4 mixtures was featured with high acidic gases selectivity due to the relatively low methane penetration through the liquid phase saturated by acidic gases.
ARTICLE | doi:10.20944/preprints201811.0140.v1
Subject: Chemistry, Chemical Engineering Keywords: Smithsonite; Flotation; 2-(Hexadecanoylamino)acetic acid; Collector; Adsorption
Online: 6 November 2018 (11:59:07 CET)
Zinc is mostly extracted from zinc oxide and sulfide minerals, and this process involves flotation as a key step. While it is easier to float the sulfide mineral, its consumption and depletion has led to an increased reliance on zinc oxide minerals, including smithsonite; hence the development of efficient ways of collecting smithsonite by flotation is an important objective. Herein, we describe the use of 2-(hexadecanoylamino)acetic acid (HAA), a novel surfactant, as a collector during smithsonite flotation. The mechanism and flotation performance of HAA during smithsonite flotation were investigated by total organic carbon (TOC) content studies, zeta potential measurements, FTIR spectroscopy, and XPS analyses, combined with micro-flotation experiments. The flotation results revealed that HAA is an excellent collector in pulp over a wide pH range (9–12) and at a relatively low concentration (2 × 10‒4 mol/L), at which a recovery of close to 90% of the smithsonite mineral was obtained. TOC-content studies reveal that the good flotation recovery is ascribable to large amounts of collector molecule adsorbed on the smithsonite surface, while zeta potential measurements show that the HAA is chemically adsorbed onto the smithsonite. FTIR and XPS analyses reveal that the HAA-collector molecules adsorb onto the smithsonite surface as zinc-HAA complexes involving carboxylate moieties and Zn sites on the smithsonite surface in alkaline solution.
ARTICLE | doi:10.20944/preprints201810.0644.v1
Subject: Chemistry, Chemical Engineering Keywords: Hydrothermal liquefaction (HTL), Spirulina, Hydroprocessing, Hydrotreating, Upgrading, Hydrodeoxygenation (HDO), Hydrodenitrogenation (HDN), Fractional distillation, Drop-in biofuels, Nitrogen distribution
Online: 27 October 2018 (21:20:47 CEST)
To obtain drop-in fuel properties from non-feed biomass, we herein report the catalytic hydrotreatment of microalgae biocrude, produced from hydrothermal liquefaction (HTL) of Spirulina. Our contribution focuses on the effect of temperature, initial H2 pressure, and residence time on the removal of heteroatoms (O and N). In contrast to common hydrotreating experimental protocols at batch scale, we devised a set of two-level factorial experiments and studied the most influential parameters affecting the removal of heteroatoms. It was found that up to 350 °C, the degree of deoxygenation (de-O) is mainly driven by temperature, whereas the degree of denitrogenation (de-N) also relies on initial H2 pressure and temperature-pressure interaction.Based on this, complete deoxygenation was obtained at mild operating conditions (350 °C), reaching a concurrent 47 % denitrogenation. Moreover, three optimized experiments are reported with 100 % removal of oxygen. In addition, the analysis by GC-MS and Sim-Dis gives insight to the fuel quality. The distribution of heteroatom N in lower (<340 °C) and higher (>340 °C) fractional cuts is studied by a fractional distillation unit following ASTM D-1160. Final results show that 63-68 % of nitrogen is concentrated in higher fractional cuts.
ARTICLE | doi:10.20944/preprints201810.0064.v1
Subject: Chemistry, Chemical Engineering Keywords: gallium nitride; gallium; LED waste; LED recycling; leaching
Online: 3 October 2018 (17:16:07 CEST)
In recent years, with the increasing research and development of the LED industry which contains GaN, it is expected that there will be a large amount of related wastes in the future. Especially the gallium has extremely high value of economic, therefore, it is necessary to establish the recycling system of the GaN waste. However, GaN is a direct-gap semiconductor and with high energy gap, high hardness, and high melting point make it difficult to recycle. Therefore, this study will analyze the physical characteristics of LED wastes containing GaN and carry out various leaching method to leach the valuable metals from the waste optimally. Different acids are used to find out the best reagent for leaching the gallium. Different experimental parameters are discussed such as the effect of the different acid agents , concentration, pressure, solid-liquid mass ratio, temperature, and time which influence the leaching efficiency of the gallium. In this study, various leaching methods which effect the leaching efficiency of the gallium are compared and the advantages and disadvantages are discussed. Finally, pressurized acid leaching method is preferred to leach the GaN waste, and hydrochloric acid is used as the leaching solution because of its better leaching efficiency of gallium. Eventually, the leaching efficiency of the gallium can reach to 98%.
ARTICLE | doi:10.20944/preprints201809.0575.v1
Subject: Chemistry, Chemical Engineering Keywords: melanin like nanoparticles; sodium periodate; enzymatic activity; layer-by-layer films
Online: 29 September 2018 (04:16:12 CEST)
Polydopamine (PDA) deposition, obtained from the oxidation of dopamine and other catecholamines is an universal way to coat all known materials with a conformal coating which can subsequently be functionalyzed at will. The structural analogies between polydopamine and eumelanin, the black-brown pigment of the skin, incited to produce stable polydopamine nanoparticles in solution instead of amorphous precipitates obtained from the oxidation of dopamine. Herein, we demonstrate that size controlled and colloidally stable PDA based nanoparticles can be obtained in acidic conditions, where spontaneous auto-oxidation of dopamine is suppressed, using sodium periodate as the oxidant and a protein like alkaline phosphatase as a templating agent. The size of the PDA@Alp nanoparticles depends on the dopamine/enzyme ratio and the obtained particles display the enzymatic activity of alkaline phosphatase with an activity extending up to two weeks after particle synthesis. The PDA@ alkaline phosphatase (Alp) nanoparticles can be engineered in polyelectrolyte multilayered films to potentially design model biosensors.
ARTICLE | doi:10.20944/preprints201809.0471.v1
Subject: Chemistry, Chemical Engineering Keywords: algaecides; dirt; humidity; resilience; temperature; time
Online: 25 September 2018 (03:45:11 CEST)
Algaecides are chemicals that cause serious health problems. Conventional paints contain algaecides to improve the algae resistance on the paint film. Present research has suggested an environmental friendly paint formulation that focuses on developing algae resistance without having algaecides. In this research, Algae growth on newly developed paint is modeled by incorporating dirt resistance of paint and natural phenomena including humidity, temperature and time respectively. The fitted Model revealed explained variation of 59.65% in the average algae growth, of which, Dirt Resistance, Humidity and temperature and some of their interactions play significant role in this variation. Model suggests that the proposed newly developed paint without algaecides is more resilient to algae growth and significantly decreased the average algae growth rate by 0.53% as compared to conventional paints. Keeping the effect of all other factors constant, if dirt resistance of paint (Dc value) increases by one percent, average algae growth decreases by 12.98%; when temperature increases by 1oC, average algae growth decreases by 22.4%; a positive unit change in the joint linear effect dirt resistance, temperature and humidity caused a decrease in average algae growth by 0.0031%. It was also observed that the individual effect of humidity variable was inversely related with average algae growth. However the combination of humidity and temperature, humidity and dirt resistance, humidity and time, and the quadratic effect of humidity were found to increase the average algae growth rate. The cubic effect of temperature variable by one degree centigrade resulted in decrease of average algae growth by 0.000907%.
ARTICLE | doi:10.20944/preprints201809.0242.v1
Subject: Chemistry, Chemical Engineering Keywords: Phospholipid assembly; Bicelle; Membrane fluidity; Membrane polarity; Phase behavior
Online: 13 September 2018 (14:45:35 CEST)
Self-assembly membranes, composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), were characterized at the total lipid concentration below 20 mM. The sizes of the assemblies varied depending on the molar ratio of DMPC and DHPC (q = [DMPC]/[DHPC]). The small assemblies with diameter of ca. 10 nm were formed at q ≤ 2.0 at 20 ºC (below phase transition temperature of DMPC). The physicochemical membrane properties were then studied using fluorescence probes, 1,6-diphenyl-1,3,5-hexatriene and 6-dodecanoyl-N,N-dimethyl-2-naphthylamine, upon the dilution. DHPC micelle showed a higher membrane fluidity, while the DMPC/DHPC membranes at q ≥ 0.5 showed lower membrane fluidities as well as DMPC vesicle in gel (ordered) phase. Upon dilution, the ordered membrane properties were maintained while the solution turbidities increased, implying the morphological change of the self-assembly, bicelle to the vesicle in gel phase. Based on the obtained results, a phase diagram of DMPC/DHPC binary system (at 20 ºC) is described: (i) the bicelle suspension is transparent and the membrane is in ordered state, (ii) the micelle suspension is transparent and the membrane is in disordered state, (iii) the vesicle suspension is turbid and the membrane is in ordered state.
REVIEW | doi:10.20944/preprints201809.0225.v1
Subject: Chemistry, Chemical Engineering Keywords: heterogeneous catalytic oxidation, gas-solid, liquid-solid, partial and total oxidation, biomass based raw materials, activation methods
Online: 13 September 2018 (02:17:55 CEST)
In this short review paper we have assembled the main characteristics of partial oxidation reactions (oxidative dehydrogenation and selective oxidation to olefins or oxygenates, as aldehydes and carboxylic acids and nitriles), as well as total oxidation, particularly for depollution, environmental issues and wastewater treatments. Both gas-solid and liquid-solid media have been considered with recent and representative examples within these fields. We have also discussed about their potential and prospective industrial applications. Particular attention has been brought to new raw materials stemming from biomass and to liquid-solid catalysts cases. This review paper also summarizes the progresses made in the use of unconventional activation methods for performing oxidation reactions, highlighting the synergy of these technologies with heterogeneous catalysis. Focus has been centered on usual catalysts activation methods but also on less usual ones, such as the use of ultrasounds, microwaves, grinding (mechanochemistry) and photo-activated processes, as well as their combined use.
COMMUNICATION | doi:10.20944/preprints201809.0071.v1
Online: 4 September 2018 (15:02:50 CEST)
We demonstrated a new approach to the production of three-dimensional-coated patterns using liquid route. Metallic perovskite oxides were coated onto three-dimensional (3D) microstructured substrates with different aspect ratios. The success of the method relies on the solution viscosity monitored by adding viscous liquid. The process of oxide thin films consists in three steps: preparing the precursor solution, coating the solution by spin-coating process onto three-dimensional-Si substrates and post-annealing. The chemical solution 3D-coating is conformal.
TECHNICAL NOTE | doi:10.20944/preprints201808.0100.v1
Online: 6 August 2018 (08:14:51 CEST)
In this paper, a new anode environmentally friendly for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from recycling of spent Li-ion batteries cathode with composition LiCoO2. The electrodeposited cobalt behaves as supercapacitor in KOH 1M. In the linear voltammetry in KOH 1M, when the overpotential reaches 370 mV, the anodic density current for 430 SS/Co is 19 mA cm−2. Thus, the anode developed in this paper achieves the double of density current with half of production cost if compared with 316SS. Moreover the anode construction described in this paper is an excellent option for Li- ion battery recycling.
ARTICLE | doi:10.20944/preprints201808.0098.v1
Online: 6 August 2018 (06:25:05 CEST)
In this paper the application of recycled Li-ion batteries spent cathode (LIB-SC) combined with NaHCO3/H2O2 system is presented for the first time in the literature as an alternative for degradation of potentially toxic organic molecules. The model pollutant choice was methylene blue molecule. The spent cathode composition corresponds to LiCoO2, which was proved by the XRD and EDX. Regarding the decolorization of methylene blue solution, the addition of NaHCO3 in comparison with only H2O2 reduces the complete decolorization time in 96%. This reduction occurs because the radical CO3 is more stable than OH. In this way, the application the system proposed in this article is aimed at solving two major global problems: the disposal of cell phone batteries and the pollution of liquid effluents.
REVIEW | doi:10.20944/preprints201808.0023.v1
Subject: Chemistry, Chemical Engineering Keywords: catalyst; direct synthesis; hydrogen peroxide; Pd based catalyst; reactor engineering; microreactor
Online: 1 August 2018 (14:10:48 CEST)
Hydrogen peroxide is an important chemical of increasing demand in today’s world. Currently, the anthraquinone autoxidation process dominates the industrial production of hydrogen peroxide. Herein, hydrogen and oxygen are reacted indirectly in the presence of quinones to yield hydrogen peroxide. Owing to the complexity and multi-step nature of the process, it is advantageous to replace the process with an easier and straightforward one. The direct synthesis of hydrogen peroxide from its constituent reagents is an effective and clean route to achieve this goal. Factors such as water formation due to thermodynamics, explosion risk, and the stability of the hydrogen peroxide produced hinder the applicability of this process at an industrial level. Currently, the catalysis for the direct synthesis reaction is palladium based and the research into finding an effective and active catalyst has been ongoing for more than a century now. Palladium in its pure form, or alloyed with certain metals are some of the new generation of catalysts that are extensively researched. Additionally, to prevent the decomposition of hydrogen peroxide to water, the process is stabilised by adding certain promoters such as mineral acids and halides. A major part of today’s research in this field focusses on the reactor and the mode of operation required for synthesising hydrogen peroxide. The emergence of microreactor technology has helped in setting up this synthesis in a continuous mode, which could possibly replace the anthraquinone process in the near future. This review will focus on the recent findings of the scientific community in terms of reaction engineering, catalyst and reactor design in the direct synthesis of hydrogen peroxide.
ARTICLE | doi:10.20944/preprints201808.0005.v1
Subject: Chemistry, Chemical Engineering Keywords: polymer; characterization; sludge conditioning; UV; flocculant
Online: 1 August 2018 (08:18:34 CEST)
Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UV)-initiated system characterized with adjustable light intensity and redox-azo complex initiator was used to synthesize a CPAM flocculant named NP. Comparatively, another CPAM flocculant named SP with stable UV light intensity and single initiator was prepared. The chemical structure, morphology, and thermal stability were analyzed through instrumental analysis. Proton nuclear magnetic resonance indicated that NP was successfully prepared, and a small fraction of cationic homopolymer was mixed in the product. Polymerization conditions were optimized, and polymerization mechanism was determined by investigating the effects of various parameters on intrinsic viscosity, conversion, and dissolvability. Results showed that the best performance was obtained at indexes of 0.45 wt‰ redox initiator concentration, 0.2 wt‰ azo initiator concentration, 40.0 wt% of cationic monomer, first- and second-stage light intensities of 8.5 and 13 mW/cm2, respectively, and 3 wt% urea. Sludge conditioning performances of NP and SP were comparatively evaluated, and the mechanism was determined by investigating the sedimentation behavior and floc size distribution. High intrinsic viscosity, porous morphology structure, and the mixed cationic homopolymer of NP resulted in better sludge conditioning performance.
ARTICLE | doi:10.20944/preprints201807.0593.v1
Subject: Chemistry, Chemical Engineering Keywords: forward osmosis; thin-film composite; dopamine; interfacial polymerization; structural stability; chlorine resistance
Online: 30 July 2018 (15:30:24 CEST)
The degradation and detachment of the polyamide (PA) layer in thin-film composite (TFC) membranes due to chlorine based chemical cleaning and material difference of PA layer and substrate are two major bottlenecks of forward osmosis (FO) technology. In this study, a new type of FO membranes were prepared by controlling self-polymerization of dopamine (DA) in the aqueous phase and the reaction with trimesoyl chloride (TMC) during interfacial polymerization (IP) process. These membranes were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM) and water contact angle measurements. The influence of synthesis parameters such as pH of the aqueous phase, reaction time, temperature, and monomer concentrations were systematically investigated. The optimized membrane showed enhanced structure stability in ethanol (7.1 times higher) and chlorine resistance (72.3 times higher) than the conventional Piperazine(PIP)/TMC membrane due to（poly-dopamine）PDA bio-adhesion and polyester groups in the membrane structure. In general, DA/TMC membranes could be an effective strategy to fabricate high-performance FO membranes with excellent structural stability and chlorine resistance.
ARTICLE | doi:10.20944/preprints201807.0592.v1
Subject: Chemistry, Chemical Engineering Keywords: CO2 electroreduction; CO2 valorization; Cu catalyst; Particle size; PEM; Acetaldehyde production; Methanol production
Online: 30 July 2018 (15:04:33 CEST)
A novel gas-phase electrocatalytic system based on a low-temperature proton exchange membrane (Sterion) was developed for the gas phase electrocatalytic conversion of CO2 to liquid fuels. This system achieved gas-phase electrocatalytic reduction of CO2 at low temperatures (below 90 ºC) over a Cu cathode by using water electrolysis-derived protons generated in-situ on an IrO2 anode. Three Cu-based cathodes with varying metal particle sizes were prepared by supporting this metal on an activated carbon at three loadings (50, 20, and 10 wt%; 50%Cu-AC, 20%Cu-AC, and 10%Cu-AC, respectively). The cathodes were characterized by N2 adsorption–desorption, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) whereas their performance towards the electrocatalytic conversion of CO2 was subsequently studied. The membrane electrode assembly (MEA) containing the cathode with the largest Cu particle size (50%Cu-AC, 40 nm) showed the highest CO2 electrocatalytic activity per mole of Cu, with methyl formate being the main product. This higher electrocatalytic activity was attributed to the lower Cu–CO bonding strength over large Cu particles. Different product distributions were obtained over 20%Cu-AC and 10%Cu-AC, with acetaldehyde and methanol being the main reaction products, respectively. The CO2 consumption rate increased with the applied current and the reaction temperature.
ARTICLE | doi:10.20944/preprints201807.0530.v1
Subject: Chemistry, Chemical Engineering Keywords: catalytic oxidation; oxide catalysts; C3-C4 mixture; ethylene; propylene; butylenes; heteropoly compound
Online: 27 July 2018 (04:07:12 CEST)
The processing of alkanes (the main components of natural gas) for obtaining of industrially important chemical products is one of the most urgent environmental problems, because the major share of raw materials are burned in torches. Therefore, the main goal of the work is the development of catalysts and conditions for obtaining of important petrochemical products from light alkanes. For the preparation of catalysts, Mo, Cr and Ga oxide catalysts as well as catalysts based on heteropoly compounds, supported on natural materials were used. The catalysts were prepared by the capillary impregnation method and used in oxidative conversion in a flowing unit while varying the process conditions. It has been determined that 5 and 10% MoCrGa catalysts are optimal for obtaining of liquid and gaseous products, and 1% catalyst is more favorable for the synthesis of gaseous products. Supported catalysts from heteropoly acid Н3PW12O40 are highly active in oxidative dehydrogenation and cracking processes, which are concurrent. High activity is caused by dispersity of catalysts, formation of crystal hydrates and amorphous phase of heteropoly acid in a condition of interaction with carrier. Maximum yield of C2H4 - 35.2% at 973 K, C3H6 – 20.0% and C4H8 – 14.3% at 773 К were observed.
ARTICLE | doi:10.20944/preprints201807.0289.v1
Subject: Chemistry, Chemical Engineering Keywords: surfactant polymer; supercritical carbon dioxide; foaming agent; blockage; recovery factor
Online: 16 July 2018 (13:12:14 CEST)
Optimum selectivity of enhanced oil recovery techniques would play a substantial role in the economic prosperity of petroleum industries which might be virtually eliminated unnecessary expenditures. In this paper, the simultaneous utilization of foaming agent, surfactant polymer (SP), and supercritical carbon dioxide were taken into the investigation under the miscible condition to evaluate the efficiency of each scenario on the cumulative recovery factor, water cut and pressure drop. According to the results of this experimental evaluation, SP-foam flooding had witnessed the highest blockage which is caused to have the maximum recovery factor due to the mobilization of more oil volume in the low permeable pores and cracks. Furthermore, the utilization of surfactant with supercritical carbon dioxide had experienced the least recovery factor regarding the insufficient foam generation which is led to less mobilization of oil phase in the pore throats.
ARTICLE | doi:10.20944/preprints201807.0213.v1
Subject: Chemistry, Chemical Engineering Keywords: Ni catalysts; bimetallic catalysts; hydrogen; catalytic decomposition of methane; thermogravimetric analysis; carbon nanofibers
Online: 12 July 2018 (08:07:03 CEST)
The catalytic decomposition of methane (CDM) process produces hydrogen in a single stage and avoids the CO2 emission thanks to the formation of high added value carbon nanofilaments as by-product. In this work, Ni monometallic and Ni-Co, Ni-Cu and Ni-Fe bimetallic catalysts are tested in the CDM reaction for the obtention of fishbone carbon nanofibers (CNF). Catalysts, in which Al2O3 is used as textural promoter in their formulation, are based on Ni as main active phase for the carbon formation and on Co, Cu or Fe as dopants in order to obtain alloys with an improved catalytic behaviour. Characterization of bimetallic catalysts showed the formation of particles of Ni alloys with a bimodal size distribution. For the doping content studied (5 mol. %), only Cu formed an alloy with a lattice constant high enough to be able to favor the carbon diffusion through the catalytic particle against surface diffusion, resulting in higher carbon formations, longer activity times and activity at 750 °C, where Ni, Ni-Co and Ni-Fe catalysts were inactive. On the other hand, Fe also improved the undoped catalyst performance presenting a higher carbon formation at 700 °C and the obtention of narrow carbon nanofilaments from active Ni3Fe crystallites.
ARTICLE | doi:10.20944/preprints201806.0187.v1
Subject: Chemistry, Chemical Engineering Keywords: membrane bioreactor (MBR); wastewater; rotating membranes; static membranes; fouling; modelling
Online: 12 June 2018 (10:48:01 CEST)
Fouling by activated sludge in membrane bioreactor (MBR) processes for wastewater treatment can be reduced using several strategies such as backflushing, relaxation, and chemical cleaning. Some proprietary systems such as Avanti’s RPU-185 Flexidisks MBR use novel circular rotating, flat sheet membranes to assist in limiting this fouling. An attempt has already been made to model this novel rotating fouling process by developing a simulation model based on first principles and traditional fouling mechanisms. In order to directly compare the potential benefits of rotational MBR system, a follow-up study was carried out using Avanti’s newly developed static (non-rotating) Flexidisks MBR system. This new process uses the same proprietary and patented membrane modular arrangement as used in the circular rotational unit, but is configured instead as a static square-shaped unit which is in-line with the more traditional and popular format used for submerged flat sheet MBR systems. During this study, the results from operating the static pilot unit were simulated and modelled using a standard fouling model coupled with a viscosity to mixed liquor relationship model. These results were then compared with those obtained from running the rotating MBR model however with rotational switching functions turned off and rotational parameters set to a static mode. This comparison was done to ascertain whether the basic premise of the developed rotational model was sound in empirical terms when compared to a standard MBR flux model. The study concluded that relatively good agreement was reached between the two types of models, thus vindicating the usage of a complex rotational MBR model. Follow on studies will now compare results from the rotating MBR system using rotational models developed by other researchers to ascertain the effectiveness rotating MBR modelling approach.
ARTICLE | doi:10.20944/preprints201805.0268.v1
Subject: Chemistry, Chemical Engineering Keywords: electric field; oxidative dehydrogenation; LPG, Cr-/HZSM-5; electrical properties
Online: 21 May 2018 (11:32:11 CEST)
CrHZSM-5 was placed in an electric field with appropriate strength in a quartz packed bed reactor with CO2 as oxidant to analyze its catalytic activity. Olefin yield increases with decrease in band gap since lattice oxygen mobility increases by reducing band gap. Fermi level change at the catalyst surface affects the catalytic activity. One way to change Fermi level is use electric field. In high voltage electric field, energy band was curved, bending of the energy band promoted the activity and Fermi level position is increasing. The CCD experiments were carried out with Design-Expert 7.3 software to determine the interaction between four operating variables, namely: temperature, electrical current, gap distance and metal loading. The levels of the independent variables were: temperature (550-700 °C), electrical current (0-12 mA), gap distance (6-14 mm), metal loading (0.5-7.5 %wt.). The conversion of LPG (Liquefied petroleum gas) was greatly increased by weak and effective application of an electric field to the catalyst bed. The obtained results indicated that the maximum yield value (46.94%) can be achieved under 673.66 °C, input electrical current of 11.01 mA, gap distance of 6.55 mm and metal loading of 3.98 wt.%.
ARTICLE | doi:10.20944/preprints201805.0219.v1
Subject: Chemistry, Chemical Engineering Keywords: metal hydrides; hydrogen storage; La-Ni based alloys; alloy modification and analysis; renewable energy storage
Online: 15 May 2018 (14:16:10 CEST)
Metal hydrides are one of the types of functional materials that allow safe and compact storage of a large amount of hydrogen, which is increasingly used today as an alternate fuel or energy source. The possibility of obtaining the initial energy necessary for the production of hydrogen by electrolysis process from renewable energy sources, such as solar panels and wind generators, makes hydrogen energetic quite attractive and rapidly developing industry sector. Solid form of hydrogen storage with the possibility of reversible sorption, gives opportunity for creation autonomous energy storage systems. La-Ni based alloys allow hydrogen storing at ambient temperatures and pressure not higher than 15 bar, which makes the application of these alloys quite practical, interesting and prospects for analysis and modifications on the ways of stored hydrogen capacity increasing, alloys price reducing and application for renewable energy storage.
ARTICLE | doi:10.20944/preprints201803.0101.v2
Subject: Chemistry, Chemical Engineering Keywords: onion; drying; bioactive; nutritional and organoleptic
Online: 9 April 2018 (09:51:30 CEST)
Onion (Allium cepa L.) is a strong-flavoring vegetable consumed in different ways. It is mainly due its distinctive flavor or simply pungency. Onion has also important natural compounds effective for medical functions such as inhibition of bone resorption, lower risk of cardiovascular disease and cancer. This importance is directly related to high content of organo-sulphur compounds. Shelf life of fresh onion bulb is short enough about two weeks at ambient storage conditions in Fogera district, Amhara region, Ethiopia. This is mainly due to the presence of high moisture in fresh onion bulbs. Postharvest loss of onion bulb reaches up to 50% in the production season in Fogera district. Consequently onion bulb had extreme variable market price during production and off season in the district which directly influences both the growers and consumers. In this study the effect of different drying techniques on nutritional and volatile components of onion were evaluated. Effect of different drying techniques on protein, carbohydrate, total sugar, fat, pyurvic acid, ascorbic acid, total phenol, total flovonol, rehydration ratio, color and sensory properties of onion slice were evaluated and found insignificant at (P > 0.05) for microwave and modified direct solar dryers taking fresh onion bulb as a control. But oven drying method had significant effect on onion physicochemical quality attributes at (P < 0.05) as compared to fresh onion bulbs.
ARTICLE | doi:10.20944/preprints201803.0267.v1
Subject: Chemistry, Chemical Engineering Keywords: surface-initiated vapor deposition polymerization; N-carboxyanhydrides; ring-opening polymerization; poly (γ-benzyl L-glutamate); solvent-free polymerization; solid state polypeptide synthesis
Online: 30 March 2018 (10:08:14 CEST)
Despite huge effort has been devoted to the design of the initiators and reaction conditions, it remains challenging to synthesize high molecular weight polypeptides with conventional solution phase synthesis. In this work, surface-initiated vapor deposition polymerization (SI-VDP) was utilized to graft synthetic polypeptides poly (γ-benzyl L-glutamate) (PBLG) from polystyrene (PS) resin beads by ring-opening polymerization of N-carboxyanhydrides (NCAs). It was demonstrated for the first time that high molecular weight bulk PBLG (> 500,000) could be readily obtained within one hour via solvent-free synthetic method which paves the way for the synthesis of copolypeptides with high molecular weight.
ARTICLE | doi:10.20944/preprints201803.0116.v1
Subject: Chemistry, Chemical Engineering Keywords: oxazole-triazole; inhibition corrosion; mild steel; EIS; DFT
Online: 15 March 2018 (05:10:29 CET)
1-[(4-ethyl-2-phenyl-4,5-dihydro-1,3-oxazol-4-yl)methyl]-4-phenyl-1H-1,2,3-triazole (Ph4) and1-[(4-ethyl-2-phenyl-4,5-dihydro-1,3-oxazol-4-yl)methyl]-5-phenyl-1H-1,2,3-triazole (Ph5) are new isomers of the triazole derivative family, were synthesized and tested on the corrosion of mild steel in molar hydrochloric acid molar media using weight loss, electrochemical polarization and impedance spectroscopy. Then the experimental results were confirmed by quantum chemical calculations using DFT at B3LYP /6-31G (d,p). The compound Ph4 is the best inhibitor and its inhibitory efficiency increased with increasing concentration and reaching 95% at 10−3 M. Polarization curves studies show that both compounds tested are mixed-type inhibitors. Nyquist curves presented a single capacitive loop, their diameter increases progressively with both inhibitors concentration. The change of the substitution phenyl from position 5 to position 4 in the triazole ring increases the inhibitory effect of the triazole compounds. The effect of temperature on the corrosion behavior of iron indicates that the inhibitory efficiency of the two inhibitors decreases with increasing temperature in the range of 308 to 338K. DFT study is in good correlationwith the experimental results.
ARTICLE | doi:10.20944/preprints201711.0149.v1
Subject: Chemistry, Chemical Engineering Keywords: waste cotton fibers; recycling; carbon microsphere; physicochemical characteristics
Online: 23 November 2017 (08:19:15 CET)
In order to study the hydrothermal behavior of cotton fiber, the carbonization process and structural evolution of discarded cotton fiber (WCF) under hydrothermal conditions were discussed use microcrystalline cellulose (MCC) and glucose as model compounds. The results showed that high temperature was beneficial to the hydrolysis of discarded cotton fiber, and the yield of the sugar was 4.5% which was lower than that of MCC 6.51%. WFC and MCC are carbonized in 240~260 ℃ and 220~240 ℃ respectively, while the carbonation temperature of glucose is lower than 220 ℃. The quality ratio of C/O in WCF and glucose hydrothermal products is 5.79 and 5.85 respectively; three kinds of hydrothermal carbonization products have similar crystal structure and oxygen-containing functional groups, and the WCF carbonization products contain a lot of irregular particles while the main products of glucose carbonization are 0.5 μm carbon microspheres (CMCC). The results show that glucose is an important intermediate product of WCF hydrolysis carbonation, and there are two main paths of cotton fiber hydrothermal carbonization: some cotton fibers are completely hydrolyzed into glucose and the nucleation is formed, and then the carbon microspheres are grown; for the other part, the glucose ring of the polysaccharide oligosaccharide formed by the incomplete hydrolysis of cotton fiber in the hydrothermal environment of high temperature and pressure breaks, then forms the particulate matters.
ARTICLE | doi:10.20944/preprints201711.0106.v1
Subject: Chemistry, Chemical Engineering Keywords: ceria; zirconia; gold; sulfur; catalysts characterisation; glycerol oxidation
Online: 16 November 2017 (05:37:10 CET)
Ceria, zirconia and mixed cerium-zirconium mesoporous oxides were synthesized and used as supports for sulfur and gold species. The materials were characterised using selected advanced techniques (ICP-OES, elemental analysis, XPS, XRD, N2 adsorption and desorption isotherms, UV-vis, ATR-FTIR, TPR-H2, TG-DTA) which allowed monitoring of the oxidation state of metals (cerium and gold) and the surface properties of the catalysts, in particular the concentration of the components on the surface and in the bulk of materials. The interactions between gold, sulfur and metals from oxides were considered. The goal of this work was studied the changes in the chemical composition of materials and the oxidation states of cerium species after the modification of oxides with sulfur and gold species and the estimation of the influence of these changes on the surface properties. The chemical composition of surface affects the mobility of surface oxygen and the oxidation state of cerium, which can play the role of redox sites (e.g. Ce3+/Ce4+ species), and therefore it strongly influences on the adsorption of hydrogen sulfide and then gold loading. Additionally, gold catalysts modified with sulfur species were tested in the reaction of glycerol oxidation in the liquid phase at basic conditions as the test reaction of the catalytic oxidation of organic pollutants from water.
REVIEW | doi:10.20944/preprints201711.0071.v1
Subject: Chemistry, Chemical Engineering Keywords: CO2 hydrogenation; dimethyl ether; low-carbon processes; thermodynamics; catalysis; zeolites
Online: 11 November 2017 (01:16:47 CET)
Starting from the environmental issues related to global warming, climate change and reduction of greenhouse gas emissions, this review paper describes how CO2 recycling can represent a challenging strategy suitable to explore new concepts and opportunities for catalytic and industrial development. In this view, the production of dimethyl ether (DME) from catalytic hydrogenation of CO2 appears as a viable technology, able to meet also the ever-increasing need for alternative environmentally-friendly fuels and energy carriers. Basic considerations on thermodynamic aspects controlling DME production from CO2 are presented, then summarizing the main catalytic systems developed in such a field. Special attention is paid on the role assumed during last years by zeolite-based systems, either in the methanol-to-DME dehydration step or in the one-pot CO2-to-DME hydrogenation. On the whole, the productivity of DME results significantly to be dependent on several catalyst features, linked not only to the metal-oxide phase responsible for CO2 activation/hydrogenation, but also to specific properties of the zeolites (i.e., topology, porosity, surface area, acidity, interaction with active metals, distributions of metal particles, …) influencing activity and stability of hybridized bifunctional heterogeneous catalysts.
ARTICLE | doi:10.20944/preprints201705.0148.v1
Online: 19 May 2017 (16:06:15 CEST)
Deep eutectic solvents (DESs) are known as tunable solvents. It is possible to prepare ternary deep eutectic solvent (TDES) are used for desired purpose by selecting the suitable molar ratio and components of mixture. Therefore, four DESs and two TDESs were prepared in this work. DESs and TDESs were prepared with potassium carbonate (PC) as a hydrogen bond acceptor (HBA) and three hydrogen bond donors (HBDs) such as glycerol (GL), ethylene glycol (EG) and 2-amino-2methyl-1-3-propanediol (AMPD) known as a hindered amine (HA). Binary DESs were PC-GL with molar ratios 1:10 and 1:16 and PC-EG with the same molar ratios. TDES were prepared by adding AMPD in binary DESs such as PC-GL-AMPD 1:16:1 and PC-EG-AMPD 1:10:1. The experimental density and refractive index of all DESs and TDESs were measured at the temperature of 293.15 to 343.15 K with an interval of 5 K. The effect of temperature, molar ratio and alkyl chain length on the properties was investigated. The molar volumes and isobaric thermal expansion were calculated using experimental density data. The experimental refractive index data was used to derive the specific refraction, molar refraction, free molar volume, electronic polarization, polarizability constant and internal pressure at several temperatures.
REVIEW | doi:10.20944/preprints201704.0137.v1
Subject: Chemistry, Chemical Engineering Keywords: process simulation; kinetic modelling; ammonia; methanol; bioethanol; steam reforming; ethylene
Online: 21 April 2017 (10:00:46 CEST)
Process simulation represents an important tool for plant design and optimisation, either applied to well established or to newly developed processes. Suitable thermodynamic packages should be selected in order to properly describe the behaviour of reactors and unit operations and to precisely define phase equilibria. Moreover, a detailed and representative kinetic scheme should be available to predict correctly the dependence of the process on its main variables. This review points out some models and methods for kinetic analysis specifically applied to the simulation of catalytic processes, as a basis for process design and optimisation. Attention is paid also to microkinetic modelling and to the methods based on first principles, to elucidate mechanisms and calculate thermodynamic and kinetic parameters. Different case histories support the discussion. At first, we have selected two basic examples from the industrial chemistry practice, e.g. ammonia and methanol synthesis, which may be described through a relatively simple reaction pathway. Then, a more complex reaction network is deeply discussed to define the conversion of bioethanol into syngas/hydrogen or into building blocks, such as ethylene.
ARTICLE | doi:10.20944/preprints201704.0009.v1
Subject: Chemistry, Chemical Engineering Keywords: toluene methylation; zeolite extrudates; para-xylene selectivity; attapulgite; binder; stability
Online: 3 April 2017 (17:27:20 CEST)
This work describes the catalytic performances of attapulgite/ZSM-5 extrudate in comparison to conventional alumina-bound ZSM-5 extrudate in toluene methylation. The novel attapulgite/ZSM-5 extrudate is prepared by using natural clay attapulgite as binder which introduces mobile alkaline species and macropores to the extrudate. In contrast to alumina-bound extrudate, this novel extrudate shows significantly higher para-selectivity and stability. By using characterization techniques, including in-situ XRD, SEM, NH3 temperature programmed desorption (TPD), thermogravimetric analysis and n-hexane/cyclohexane physical adsorption, the catalytic performance improvement of attapulgite/ZSM-5 extrudate is correlated with the neutralization of Brønsted acid sites by mobile alkaline species during calcination and reaction process. Moreover, a higher para-selectivity was obtained over attapulgite-bound modified ZSM-5 extrudate. The strategy of extruding ZSM-5 catalysts with attapulgite as binder is facile and universal. Such method paves a new way for preparation of shaped toluene methylation catalyst with enhanced para-selectivity and stability.
ARTICLE | doi:10.20944/preprints201701.0053.v2
Subject: Chemistry, Chemical Engineering Keywords: chiral amines; biocatalysis; silica monolith; enzyme immobilization; flow chemistry
Online: 13 February 2017 (09:02:56 CET)
ω-Transaminases have been immobilized on macrocellular silica monoliths and used as heterogeneous biocatalysts in a continuous flow mode enantioselective transamination reaction. The support was prepared by a sol-gel method based on emulsion templating. The enzyme was immobilized on the structured silica monoliths both by adsorption, and by covalent grafting using amino-functionalized silica monoliths and glutaraldehyde as a coupling agent. A simple reactor set-up based on the use of a heat-shrinkable Teflon tube is presented and successfully used for the continuous flow kinetic resolution of a chiral amine, 4-bromo-α-methylbenzylamine. The porous structure of the supports ensures effective mass transfer and the reactor works in the plug flow regime without preferential flow paths. When immobilized in the monolith and used in the flow reactor, transaminases retain their activity and their enantioselectivity. The solid biocatalyst is also shown to be stable both on stream and during storage. These essential features pave the way to the successful development of an environmentally friendly process for chiral amines production.
ARTICLE | doi:10.20944/preprints201612.0114.v1
Subject: Chemistry, Chemical Engineering Keywords: relief system; safety instrumented system; pressure relief valve; safety integrity level; minimize design capacity
Online: 23 December 2016 (10:12:59 CET)
Bisphenol A production plant possesses considerable potential risks in the top of the methanol separation column, as pressurized acetone, methanol and water are processed at an elevated temperature, especially in the event of an abnormal pressure increase due to sudden power outage. This study assesses the potential risks in the methanol separation column through hazard and operability assessment and evaluates the damages in the case of fire and explosion accident scenarios. The study chooses three leakage scenarios: a 5-mm puncture on the methanol separation column, a 50-mm diameter fracture of a discharge pipe and a catastrophic rupture, and simulates using Phast (Ver. 6.531) the concentration distribution of scattered methanol, thermal radiation distribution of fires and overpressure distribution of vapor cloud explosions. Implementation of safety instrumented system equipped with two-out-of-three voting as a safety measure can detect overpressure at the top of the column and shut down the main control valve and the emergency shutoff valve simultaneously, all at the same time. By applying safety integrity level of three, the maximal release volume of the safety relief valve can be reduced and therefore, the design capacity of the flare stack can also be reduced. Such integration will lead to improved safety at a reduced cost.
ARTICLE | doi:10.20944/preprints201609.0110.v1
Subject: Chemistry, Chemical Engineering Keywords: hydrogen production; steam reforming; Ni/attapulgite; catalysts deactivation; agglomeration and sintering
Online: 28 September 2016 (10:14:11 CEST)
In this research, catalytic steam reforming acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated by using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by XRD, N2 adsorption-desorption, TEM and H2-TPR. The comprehensive results demonstrated that the interaction between active metallic Ni and ATC carrier was significantly improved in Ni/ATC catalyst prepared by precipitation method, and in which the mean Ni particle size was the smallest (~13 nm) resulted in the highest metal dispersion (7.5%). The catalytic performance of the three catalysts was evaluated through the process of steam reforming of acetic acid in a fixed-bed reactor under atmospheric pressure at two different temperatures, such as 550 ℃ and 650 ℃. Results showed that the Ni/ATC (PM-N/ATC) prepared by precipitation method, achieved the highest H2 yield of ~82% and little lower acetic acid conversion efficiency of ~85% than that (~95%) of Ni/ATC (IM-NATC) prepared by impregnation method. In addition, the deactivation catalysts after reaction for 4 h were analyzed by XRD, TGA-DTG and TEM, which demonstrated that the catalyst deactivation was not caused by the amount of carbon deposition, but owed to the significant agglomeration and sintering of Ni particles in the carrier.