REVIEW | doi:10.20944/preprints202210.0212.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: metal-organic frameworks; chemical warfare agents; catalytic hydrolysis
Online: 14 October 2022 (11:36:08 CEST)
Organophosphorus nerve agents are amongst the most toxic chemicals known to human beings. 9 They interfere with the central nervous system, resulting in continuous muscle contractions, 10 paralysis and even death. Prohibition by many countries around the world cannot disguise the 11 remaining presence of nerve agents in stockpile storage and governmental deployment, 12 highlighting the dire need for an efficient catalyst to degrade and detoxify nerve agents by 13 hydrolysis. Metal-organic frameworks (MOFs) have raised a few eyebrows for their permanent 14 porosity, precise tunability, and lasting stability. Modern Reticular Chemistry fosters the design and 15 synthesis of well-defined crystalline MOFs with open Lewis acidic metal sites that can catalytically 16 hydrolyze nerve agents both in aqueous solution and in solid state systems, unveiling unparalleled 17 potential for MOF-based personal protection gears. In this review, a summary of the representative 18 catalytically active MOFs in nerve agent hydrolysis is discussed. MOFs are categorized by their 19 reticular structure, emphasizing the capability and mechanistic insights of each single MOF in nerve 20 agent hydrolysis. The author’s perspective on the current challenges and future directions of MOF- 21 based catalysts in real-world protection applications is also provided, which hopefully could shed some 22 light on the future development of commercially available MOF protection suits.
ARTICLE | doi:10.20944/preprints202311.1206.v1
Subject: Biology And Life Sciences, Biology And Biotechnology Keywords: Esterase; Thermoanaerobacter tengcongensis; C-terminal domain; substrate preference; catalytic activity
Online: 20 November 2023 (05:15:28 CET)
To search for novel thermostable esterase for optimized industrial applications, esterase from a thermophilic eubacterium species, Thermoanaerobacter tengcongensis MB4 was purified and characterised in this work. Sequence analysis of T. tengcongensis esterase with other homologous esterases of the same family revealed an apparent tail at the C-terminal that is not conserved across the esterase family. Hence, it was hypothesized that the tail is unlikely to have an essential structural or catalytic role. However, there is no documented report of any role for this tail region. We probed the role of the C-terminal domain on the catalytic activity and substrate preference of Thermoanaerobacter tengcongensis esterase EstA3 with a view to see how it could be engineered for enhanced properties. To achieve this, we cloned, expressed, and purified the wild-type and the truncated version of the enzyme. In addition, a naturally occurring member of the family (from B. brevis) that lacks the C-terminal tail was also made. In vitro characterization of the purified enzymes showed that the C-terminal domain contributes significantly to the catalytic activity and distinct substrate preference of T. tengcongensis esterase EstA3. All the three recombinant enzymes showed highest preference to paranitrophenyl butyrate (pNPC4), which suggests they are true esterases, not lipases. kinetic data revealed that truncation had a slight effect on the substrate-binding affinity. Thus, the drop in preference towards long-chain substrates might not be a result of substrate binding affinity alone.
ARTICLE | doi:10.20944/preprints202206.0362.v1
Subject: Chemistry And Materials Science, 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.
HYPOTHESIS | doi:10.20944/preprints202008.0607.v2
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: catalysis; kinetics; time; biological macromolecular enzyme; large biological macro-substrate; catalytic step; catalytic efficiency; turnover number
Online: 16 November 2020 (08:28:55 CET)
Classical enzyme kinetics are summarized and linked with modern discoveries here. The time course of sequential catalytic events by biological macromolecular enzyme is analyzed at the molecular level; the relationships between catalytic efficiency (turnover number), catalytic rate/velocity, the amount of time taken and physical/biochemical conditions of the system are discussed. This writing tries to connect the microscopic molecular behavior of enzyme to kinetic data obtained in experiment, and the hypothesis proposed here provide an interpretation to previous experimental observations and can be testified by future experiments.
ARTICLE | doi:10.20944/preprints201911.0191.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: catalytic combustion; dimethyl disulfide; bimetallic; supported catalyst
Online: 16 November 2019 (14:06:12 CET)
In this paper, the catalytic combustion of DMDS (dimethyl disulfide, CH3SSCH3) over bimetallic supported catalysts were investigated. It was confirmed that Cu/γ-Al2O3-CeO2 showed best catalytic performance among the five single-metal catalysts. Furthermore, six different metals were separately added into Cu/γ-Al2O3-CeO2 to investigate the promoting effect. The experiments revealed Pt as the most effective promoter and the the best catalytic performance was achieved as the adding amount of 0.3 wt%. The characterization results indicated that high activity and resistance to sulfur poisoning of Cu-Pt/γ-Al2O3-CeO2 could be attributed to the synergistic effect between Cu and Pt.
ARTICLE | doi:10.20944/preprints202312.0125.v1
Subject: Biology And Life Sciences, Biophysics Keywords: enzyme efficiency; entropy production; noise; evolution; catalytic cycle
Online: 4 December 2023 (04:29:58 CET)
Wolfenden and his coworkers observed the astronomical numbers for the catalytic proficiency of some enzymes. We connected that pinnacle of biological evolution to the universal thermodynamic evolution. We added or multiplied a random noise with chosen rate constants to explore the correlation between dissipation and enzyme efficiency for ten enzymes: beta-galactosidase, glucose isomerase, β-lactamases from three bacterial strains, ketosteroid isomerase, triosephosphate isomerase, and carbonic anhydrase I, II, and T200H. The turnover number kcat and catalytic efficiency kcat/KM are proportional to the overall entropy production – the main parameter from irreversible thermodynamics. For most enzymes with the Michaelis-Menten type cycle kinetics, the best increase in the forward kcat/KM follows after increasing the equilibrium constant of substrate-enzyme association. The Discussion section emphasizes the role of biological evolution in harvesting order (high enzyme efficiency) from disorder (high noise and dissipation). It also connects the applications of the maximum partial entropy production theorem in optimizing enzyme kinetics (D. Juretić "Bioenergetics - A Bridge across Life and Universe") with the present total entropy production role analysis. De novo enzyme design and various attempts to speed up the rate-limiting catalytic steps may profit from our theoretical insights.
REVIEW | doi:10.20944/preprints202308.1283.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: catalytic mechanism; edge engineering; defect engineering; phase engineering
Online: 17 August 2023 (11:48:21 CEST)
MoS2 has long been considered as a promising catalyst for hydrogen production. At present, there are many strategies to further improve its catalytic performance, such as edge engineering, defect engineering, phase engineering and so on. However, at present, there is still a great deal of controversy about the mechanism of MoS2 catalytic hydrogen production. For example, it is generally believed that the base plane of MoS2 is inert, but it has been reported that the inert base plane can undergo a transient phase transition in the catalytic process to play the catalytic role, which is contrary to the common understanding that the catalytic activity is only at the edge. Therefore, it is necessary to further understand the mechanism of MoS2 catalytic hydrogen production. In this article, we summarized the latest research progress on the catalytic hydrogen production of MoS2, which is of great significance for revisited the mechanism of MoS2 catalytic hydrogen production.
ARTICLE | doi:10.20944/preprints202305.0590.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Catalytic pyrolysis; plum seed; TGA; bio-oil; zeolite
Online: 9 May 2023 (07:51:05 CEST)
In terms of obtaining fuels as well as chemicals with or without catalysts at different conditions, the plum seed stands out as an alternative biomass source. Under varying heating rates (10, 50, and 100ºC min-1) and pyrolysis temperatures (400, 450, 500, 550 and 600 °C), the plum seed was pyrolysed at constant sweep gas flow at a constant rate (100 cm3min-1) in a tubular fixed bed reactor. According to the results, an oil yield reaching to a maximum of %45 was procured at the heating rate of 100 ºCmin-1 and the pyrolysis temperature of 550ºC in non-catalytic procedure. The catalytic pyrolysis was carried out in optimum conditions with two selected commercial catalysts, namely ZSM-5 and PURMOL-CTX and clinoptilolite (natural zeolite, NZ) with catalyst ratio of 10 % of raw material. Along with the catalyst addition, the quantity and the quality of bio-oil increased including the calorific value, removal of oxygenated groups, and hydrocarbon distribution. An increase related to the desirable products like phenols, alkene, and alkane and a decrease in undesirable products like acids were observed in the presence of catalysts. When all the results are considered and evaluated, using zeolite materials in the pyrolysis as catalysts is a recommendable option to achieve enhanced chemicals and fuels.
REVIEW | doi:10.20944/preprints202105.0329.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: Carbon nanotubes; catalytic activity; nanomaterials; covalent immobilization; hydrolases
Online: 14 May 2021 (11:53:06 CEST)
Immobilization enables enzymes to be held in place so that they can be easily separated from the product when needed and can be used again. Conventional methods of immobilization include adsorption, encapsulation, entrapment, cross linking and covalent binding. However, conventional methods have several drawbacks including reduced stability, loss of biomolecules, less enzyme loading or activity and limited diffusion. The aim of this study is the evaluation of importance of nanomaterials for the immobilization of industrially important enzymes. Nano materials are now in trend for the immobilization of different enzymes due to their physiochemical properties. Gold nanoparticles, silver nanoparticles, nano diamonds, graphene, carbon nanotubes and others are used for immobilization. Among covalent and non-covalent immobilization of enzymes involving both single and multiwalled carbon nanotubes, non-covalent immobilization with functionalized carbon nanotubes is superior. Therefore, enzymes immobilized with nanomaterials possess greater stability, retention of catalytic activity and reusability of enzymes
ARTICLE | doi:10.20944/preprints202311.1196.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: Ag@Cu2O core-shell; rGO; 4-NP; chemical catalytic
Online: 20 November 2023 (03:24:11 CET)
We successfully fabricated Ag@Cu2O core-shell decorated on reduced graphene oxide (rGO) nanocomposites (ACRN) by a simple and convenient in situ substitution method. The properties of these ACRN with heterostructure layers were characterized by scanning and transmission electron microscopies and absorption spectroscopy. We used p-nitrophenol (4-NP) as a probe molecule to determine the chemical catalytic activity of the ACRN. Upon introduction of rGO, a high electron transfer efficiency was achieved; thus, the catalytic activity was improved significantly. Therefore, the ACRN exhibited significantly improved catalytic activity for the reduction of 4-NP and showed the high application value in the removal of toxic and harmful substances from water. In addition, the fabricated ACRN was used for the reduction of organic dyes and explosive pollutants to generate nontoxic products. Furthermore, the high charge redistribution and transfer among Ag, Cu2O and rGO in the ACRN induced the high catalytic reduction of organic pollutants, indicating the excellent potential of these materials for applications in water pollution treatment.
ARTICLE | doi:10.20944/preprints202311.0192.v1
Subject: Biology And Life Sciences, Biophysics Keywords: natural product; Lsd18; thermostability; FoldX; Rossetta-ddG; catalytic activity
Online: 3 November 2023 (09:15:02 CET)
Enzymes used in the synthesis of natural products are potent catalysts, capable of efficient and stereoselective chemical transformations. Lsd18 catalyzes two sequential epoxidations during the biosynthesis of lasalocid A, a polyether polyketide natural product. We performed protein engineering on Lsd18 to improve its thermostability and catalytic activity. Utilizing structure-guided methods of FoldX and Rosetta-ddG, we designed 15 mutants of Lsd18. Screening of these mutants using thermal shift assay identified stabilized variants Lsd18-T189M, Lsd18-S195M, and the double mutant Lsd18-T189M-S195M. Trypsin digestion, molecular dynamic simulation, circular dichroism (CD) spectroscopy, and X-ray crystallography provided insights into the molecular basis for the improved enzyme properties. Notably, enhanced hydrophobic interaction within the enzyme core and interaction of the protein with the FAD cofactor appear to be responsible for better thermostability.
REVIEW | doi:10.20944/preprints202310.0446.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: bimetallic single-atom; characterization; catalytic mechanism; hydrogen evolution reaction
Online: 8 October 2023 (11:59:21 CEST)
Electrocatalytic and photocatalytic hydrogen evolution reaction (HER) provides a promising approach to clean energy generation. Bimetallic single-atom catalysts raised and have been explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, Photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H2 production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions.
ARTICLE | doi:10.20944/preprints201805.0402.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: heterogeneous catalysis; transfer hydrogenation; biomass conversion; biofuels; catalytic materials
Online: 28 May 2018 (12:27:29 CEST)
Catalytic upgrading of bio-based platform molecules is one of promising approaches for biomass valorization. However, most solid catalysts are thermally and/or chemically unstable and difficult to prepare. In this study, a stable organic phosphonate-hafnium solid catalyst (PPOA-Hf) was synthesized, and acid-base bifunctional sites were found to play a cooperative role in the cascade transfer hydrogenation and cyclization of ethyl levulinate (EL) to γ-valerolactone (GVL). Under relatively mild reaction conditions of 160 ºC for 6 h, EL was completely converted to GVL in a good yield of 85%. The apparent activation energy was calculated to be 53 kJ/mol, which was lower than other solid catalysts for the same reaction. In addition, the PPOA-Hf solid catalyst did not significantly decrease its activity after five recycles, and no evident leaching of Hf was observed, indicating its high stability and potential practical application.
ARTICLE | doi:10.20944/preprints201807.0418.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: graphitic carbon spheres; catalytic graphitization; hierarchical pores; supercapacitors; dye adsorption
Online: 23 July 2018 (11:47:13 CEST)
Hierarchical micro-/mesoporous graphitic carbon spheres (HGCS) with a uniform diameter of ~0.35 μm were synthesized by Fe-catalyzed graphitization of amorphous carbon spheres resultant from hydrothermal carbonization. The HGCS resultant from 3 h at 900 °C with 1.0 wt% Fe catalyst had high graphitization degree and surface area as high as 564 m2/g. They also exhibited high specific capacitance of 140 F/g at 0.2 A/g, good electrochemical stability with 94% capacitance retention after consecutive 2500 cycles. The graphitization degree of the HGCS contributed about 60% of their specific capacitance, and their specific capacitance per unit surface area was as high as 0.2 F/m2 which was much higher than in the most cases of porous amorphous carbon materials reported before. In addition, the HGCS showed a high adsorption capacity of 182.8 mg/g for methylene blue (MB), which was 12 times as high as that in the case of carbon spheres before graphitization.
ARTICLE | doi:10.20944/preprints202308.0345.v1
Subject: Chemistry And Materials Science, Ceramics And Composites Keywords: catalytic dye reduction; cellulose nanocrystals; magnetic nanocomposite; 4-nitrophenol; wastewater treatment
Online: 4 August 2023 (08:00:00 CEST)
Novel effluent treatment solutions for dangerous organic pollutants are crucial worldwide. In recent years, chemical reduction using noble metal-based nanocatalysts and NaBH4, a reducing agent, has become common practice for eliminating organic contaminants from aquatic environments. We suggest a straightforward approach to synthesizing magnetic cellulose nanocrystals (CNC) modified with magnetite (Fe3O4) and silver nanoparticles (Ag NPs) as a catalyst for organic contamination removal. Especially, Ag NPs were decorated on the CNC surface without reducing agents or stabilizers by reducing AgNO3. XRD, FE-SEM, TEM, EDX, VSM, BET, and zeta potential tests characterized the Ag/Fe3O4/CNC nanocomposite. The nanocomposite's catalytic activity was tested by eliminating 4-nitrophenol (4-NP) and organic dyes methylene blue (MB) and methyl orange (MO) in an aqueous solution at 25 oC. The Ag/Fe3O4/CNC nanocomposite reduced 4-NP and decolored these hazardous organic dyes in short time (2 to 5 min) using a tiny amount of catalyst (2.5 mg for 4-NP and 15 mg for MO and MB). The magnetic catalyst was removed and reused three times without losing catalytic activity. This work shows that the Ag/Fe3O4/CNC nanocomposite can chemically reduce harmful pollutants in effluent for environmental applications.
COMMUNICATION | doi:10.20944/preprints202211.0246.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: hydrogen evolution reaction; catalytic trends; acidic media; neutral media; alkaline media
Online: 14 November 2022 (09:20:25 CET)
As the global energy crisis continues, efficient hydrogen production is one of the hottest topics these days. In this sense, establishing catalytic trends for hydrogen production is essential for choosing proper H2 generation technology and catalytic material. Volcano plots for hydrogen evolution in acidic media are well-known, while volcano plot in alkaline media was constructed ten years ago using theoretically calculated hydrogen binding energies. Here we show for the first time that the volcano-type relationships are largely maintained in a wide range of pH values, from acidic to neutral and alkaline solutions, using theoretically calculated hydrogen binding energies on clean metallic surfaces and experimentally measured hydrogen evolution overpotentials. If metallic surfaces are exposed to high anodic potentials, hydrogen evolution can be boosted or significantly impeded, depending on the metal and the electrolyte in which the reaction occurs. Such effects are discussed here and can be used to properly tailor catalytic materials for hydrogen production via different water electrolysis technologies.
ARTICLE | doi:10.20944/preprints202104.0007.v1
Subject: Engineering, Automotive Engineering Keywords: Biomedical; Green Synthesis; Silver Nanoparticles; Colloidal stability; Antimicrobial and catalytic activity
Online: 1 April 2021 (10:20:24 CEST)
The versatile one-pot green synthesis of a highly concentrated and stable colloidal dispersion of AgNPs was carried out using the self-assembled tannic acid without using any other hazardous chemicals. Tannic acid (Plant-based polyphenol) was used as a reducing and stabilizing agent for silver nitrate in a mild alkaline condition. The synthesized AgNPs were characterized for their concentration, capping, size distribution, and shape. The experimental results confirmed the successful synthesis of nearly spherical and highly concentrated (2281 ppm) AgNPs, capped with poly-tannic acid (AgNPs-PTA). The average particle size of AgNPs-PTA was found 9.90 ± 1.60 nm. The colloidal dispersion of synthesized nanoparticles was observed stable for more than 15 months in the ambient environment (25 oC, 65 % relative humidity). The synthesized AgNPs-PTA showed an effective antimicrobial activity against Staphylococcus Aureus Escherichia coli. Ag-PTA also exhibited enhanced catalytic properties. It reduces 4-nitrophenol into 4-aminophenol in the presence of NaBH4 with a normalized rate constant (Knor = K/m) of 615.04 mL·s-1·mg-1. Furthermore, AgNPs-PTA were stable for more than 15 months under ambient conditions. The unique core-shell structure and ease of synthesis render the synthesized nanoparticles superior to others, with potential for large-scale applications, especially in the field of catalysis and biomedical.
ARTICLE | doi:10.20944/preprints201908.0265.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Mesoporous Ni/KIT-6 catalyst; Active Ni species; Catalytic hydrodeoxygenation; Biodiesel
Online: 26 August 2019 (12:34:43 CEST)
A series of Ni/KIT6 catalystprecusors with 25wt.%Ni loading amount were reduced in H2 at 400, 450, 500, and 550ºC, respectively. The studied catalysts were investigated by XRD, Quasiin-situ XPS, BET, TEM, and H2-TPDanalysis methods.It was found that reduction temperature is an important factor affecting the hydrodeoxygenation (HDO) performance of the studied catalysts. The reduction temperature influences mainly the content of active components, crystal size, and the abilityfor adsorbing and activatingH2. The developed pore structure and large specific surface area of the KIT-6 support favored the Ni dispersion.The RT450 catalyst, which was prepared in H2 atmosphere at 450 ºC, has the best HDO performance. Ethyl acetate can be completely transformed, and maintain 96.8% ethane selectivity and 3.2% methane selectivity at 300 ºC. The calculated apparent activation energies of the prepared catalysts increased in the following order: RT550 > RT400 > RT500 > RT450.
ARTICLE | doi:10.20944/preprints201810.0223.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: Thermal pyrolysis; catalytic pyrolysis; TGA; plastics; HDPE; LDPE; gasoline; diesel; catalyst
Online: 10 October 2018 (15:23:03 CEST)
Thermal and catalytic pyrolysis of virgin low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and mixtures of LDPE/PP were carried out in a 200 ml laboratory scale batch reactor at 460 °C in a nitrogen atmosphere. Thermogravimetric analysis (TGA) was carried out to study the thermal and catalytic degradation of the polymers at a heating rate of 10 °C/min. The amount of PP was varied in the LDPE/PP mixture to explore its effect on the reaction. In thermal degradation (TGA) of LDPE/PP blends, a lower decomposition temperature was observed for LDPE/PP mixtures compared to pure LDPE, indicating interaction between the two polymer types. In the presence of a catalyst (CAT-2), the degradation temperatures for the pure polymers were reduced. The TGA results were validated in a batch reactor using PP and LDPE respectively. Thermal cracking results showed that the oil product contains a significant amount of gasoline (C7 − C12) and diesel (C13 − C20) hydrocarbon fractions. The catalyst enhanced cracking at lower temperatures and narrowed the hydrocarbon distribution in the oil towards the gasoline range fraction (C7 – C12). The result suggests that the oil produced from catalytic pyrolysis of waste plastics has a potential as an alternative fuel.
REVIEW | doi:10.20944/preprints202312.0068.v1
Subject: Chemistry And Materials Science, Chemical Engineering Keywords: Acid-base catalysis; Green catalytic transformation; Layered double hydroxides; Heterogeneous catalysis; Applications
Online: 1 December 2023 (10:03:56 CET)
Layered double hydroxides (LDHs) have emerged as promising catalysts for various acid-base catalytic reactions. Due to their unique structure and regulatable dual acid-base properties, they offer more environmentally friendly and sustainable alternatives to traditional liquid acid and base catalysts. This study introduces the structural composition, preparation methods, and acid-base catalytic properties of LDHs-based catalysts. Recent application progress of LDHs and rehydrated LDHs, LDHs-based metal nanocatalysts, and LDHs-based mixed metal oxide catalysts used as solid acid-base catalysts in acid-base green catalytic conversion is reviewed. The challenges and prospects of LDHs-based catalysts as green and sustainable catalysts are summarized and proposed.
CASE REPORT | doi:10.20944/preprints202309.0420.v1
Subject: Business, Economics And Management, Economics Keywords: economic multipliers; remote work; local economies; business impact; economic stimulus; catalytic impact
Online: 7 September 2023 (05:04:45 CEST)
The advent of remote work has ushered in a new era of economic transformation, redefining the dynamics of local economies, and unleashing the multiplier effect on a national scale. This abstract explores the profound implications of remote work on local economies, dissecting how the multiplier effect operates within a nation's economic landscape. The multiplier effect is a fundamental economic concept that highlights how changes in spending and investment can create a ripple effect, leading to a magnified impact on an economy. This concept gains new significance in the context of remote work, as it triggers a chain reaction of economic activities that radiate from remote workers to their local communities. The increased flexibility and reduced geographical constraints of remote work have reshaped the allocation of resources. The continued reliance on remote work may lead to a reduction in demand for commercial real estate in urban centers, necessitating adaptive urban planning strategies. In conclusion, the rise of remote work has initiated a transformative era for local economies, driven by the multiplier effect. By amplifying the impacts of spending and investment, remote work fosters job diversification, innovation, and infrastructure development within communities. As remote work continues to reshape the landscape of work and life, understanding and harnessing its multiplier effect remains paramount for policymakers, businesses, and local communities alike. The multiplier effect is a concept in economics that illustrates how changes in spending can lead to larger impacts on a nation's economy through a chain reaction of economic activities. It demonstrates that an initial injection of spending, whether from government expenditure, investment, or consumption, doesn't just have a one-time impact. Instead, it sets off a series of interconnected spending and income-generation processes that result in a larger overall increase in economic activity. t's important to note that the multiplier effect can work in reverse as well. If there's a decrease in spending, it can lead to a decrease in economic activity and income through the same chain reaction process. This concept highlights the interconnected nature of economic activities and emphasizes the significance of changes in spending patterns on a nation's overall economic health. The magnitude of the multiplier effect is influenced by factors such as the marginal propensity to consume (the proportion of additional income that households spend), leakages (savings and taxes that reduce the multiplier effect), and the extent to which additional spending creates additional production capacity within the economy. Understanding the multiplier effect is essential for policymakers, as it helps them gauge the potential impacts of changes in fiscal and monetary policies on the economy.
ARTICLE | doi:10.20944/preprints202307.0715.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: plastic conversion; catalytic pyrolysis; low density polyethylene (LDPE); zinc oxide (ZnO); exergy
Online: 11 July 2023 (12:09:09 CEST)
Plastics are highly beneficial for the day-to-day activities of human beings; however, their decomposition is limited due to their strong covalent bonding. The concept of degradation of these big molecules into smaller ones or monomers was attempted by several researchers in the preceding decades with limited success. Pyrolysis is one of the ideas used to convert plastics into fuel, rather than small molecules, compared to the crowded structure of polymers. Among these plastics, low-density polyethylene (LDPE) is largely used as carry bags throughout the world, and, herein, the results of catalytic pyrolysis of the conversion of LDPE into fuel are reported. Different dosages of zinc oxide (ZnO) were used as a catalyst to do the pyrolysis at a specific temperature in a batch reactor specially designed at our laboratory. 0.6 g of ZnO was found to be the optimal dosage for a 50 g waste LDPE batch to get the maximum oil yield. The yielded oil was analyzed chemically through Fourier transform infrared spectroscopy (FTIR) and Reformulyzer M4 Hydrocarbon Group Type Analyzer. Evaluation of physical and chemical exergy along with exergetic efficiency of the process was done.
ARTICLE | doi:10.20944/preprints202305.1300.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: Apoptosis; PD-L1; catalytic topo I inhibitor; cyclin D1 overexpression; ATR; p53
Online: 18 May 2023 (08:31:34 CEST)
Apoptosis under severe hypoxia is induced through p53 phosphorylation and HIF-1?-dependent p53 accumulation via ATR activation by DNA damage response (DDR) activation through replication stress. We previously demonstrated that the topoisomerase I catalytic inhibitor, 3EZ, 20Ac-ingenol, specifically induced apoptosis in Jeko-1 and Panc-1 cells, both of which are cell lines that show cyclin D1 overexpression. After progression to the S phase facilitated by nuclear cyclin D1, in the presence of 3EZ, 20Ac-ingenol, an intra S phase checkpoint was induced in ATR activation as part of replication stress-induced DDR. In this study, we examined whether 3EE, 20Ac-ingenol induces a higher degree of p53 phosphorylation and additional HIF-1? and p53 accumulation in response to replication stress-induced DDR activation under the hypoxic condition than under the normoxic condition by controlling ATR activation. 3EE, 20Ac-ingenol induced p53 activation and HIF-1?-dependent p53 accumulation through cooperative ATR activation via induced DDR with the hypoxia in Panc-1 cells. The Jeko-1 cells showed slight HIF-1? accumulation under hypoxia, but this was not decreased by 3EE, 20Ac-ingenol, so that the cells remained resistant to hypoxia. 3EE, 20Ac-ingenol induces an intricate interplay between p53 and HIF-1? accumulation via ATR activations that results in high p53 accumulation, which advanced transient expression and early disappearance of HIF-1?. The strong p53 accumulation and consequent PTEN activation also decreased HIF-1? accumulation and PD-L1 expression, which resulted in intense apoptosis.
ARTICLE | doi:10.20944/preprints202010.0405.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: cap - pair effect; electrochemistry; electroreduction of Bi(III); active complexes; catalytic activity
Online: 20 October 2020 (08:36:05 CEST)
The paper discusses the electroreduction of Bi(III) ions in the aspect of expanding the ”cap – pair” effect. The ”cap – pair” rule is associated with the acceleration of the electrode’s processes by organic substances. The interpretation of the ”cap – pair” effect mechanism was expanded to include the effect of supporting electrolyte concentration on the acceleration process and the type of electrochemical active as well as used protonated organic substances. It has also been shown that the phenomena occurring at the electrode/solution interface can influence a change in the dynamics of the electrode’s process according to the ”cap – pair” rule.
REVIEW | doi:10.20944/preprints202009.0674.v1
Subject: Engineering, Automotive Engineering Keywords: microalgal biomass; thermochemical conversion; catalytic upgrading; liquid fuels; hydrothermal liquefaction; pyrolysis; gasification
Online: 27 September 2020 (10:35:33 CEST)
Over the last decades, microalgal biomass has gained a significant role in the development of different high-end (nutraceuticals, colorants, food supplements, and pharmaceuticals) and low-end products (biodiesel, bioethanol, and biogas) due to rapid growth and high carbon fixing efficiency. Therefore, microalgae are considered a useful and sustainable resource to attain energy security while reducing our current reliance on fossil fuels. From the technologies available for obtaining biofuels using microalgae biomass, thermochemical processes (pyrolysis, HTL, gasification) have proven to be processed with higher viability, because they use all biomass. However, because of the complexity of the biomass (lipids, carbohydrates , and proteins), the obtained biofuels from direct thermochemical conversion have large amounts of heteroatoms (oxygen, nitrogen , and sulfur). As a solution, catalyst-based processes have emerged as a sustainable solution for the increase in biocrude production. This paper's objective is to present a comprehensive review of recent developments on catalyst mediated conversion of algal biomass. Special attention will be given to operating conditions, strains evaluated, and challenges for the optimal yield of algal-based biofuels through pyrolysis and HTL.
Subject: Engineering, Energy And Fuel Technology Keywords: soot oxidation; catalytic; heterogeneous catalysis; oxygen vacancies; iron doped ceria catalyst; ceria
Online: 1 September 2019 (09:02:29 CEST)
This study investigates the role of oxygen vacancy on Fe-doped CeO2 catalyst activity for soot oxidation. The oxygen vacancy was assessed through Ce3+ content. The Fe content was varied between 0 and 30% for two catalyst preparation methods, co-precipitation (CP) and solution combustion synthesis (SCS). X-ray photoelectron spectroscopy indicates that ceria exists as both Ce4+ and Ce3+, while iron is present only as Fe3+. The catalyst’s activity was evaluated by ignition (T10) and combustion (T50) temperatures using thermogravimetric analysis. Optimum Fe contents yielding the highest activity were found to be 10% and 5% for CP and SCS catalysts, respectively. The surface area and morphology have shown moderate effect on catalyst activity, because catalytic soot oxidation involves solid-solid contact. More importantly, regardless of the fabrication method, it was found that Ce3+ content, which is closely related to oxygen vacancies, plays the most important role in affecting the catalyst activity.
ARTICLE | doi:10.20944/preprints201807.0530.v1
Subject: Chemistry And Materials Science, 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.
CONCEPT PAPER | doi:10.20944/preprints201610.0076.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: bio aerosol; Photo Catalytic Oxidation (PCO); hydroxyl; hydrogen peroxide; SPICE; surface sanitizer
Online: 19 October 2016 (10:02:08 CEST)
In this research paper a novel Ultra Violet Photo Catalyst Oxidation (UVPCO) sensor for air and surface sanitization using Common Source (CS) amplifier is presented. The ultra violet photo catalysis is the process in which the highly reactive radicals like H+, OH-and peroxides ions are produced from air in the presence of the ultra violet radiation and photo catalyst. In this process, the free radicals outbreaks the bio aerosols like bacteria, fungus and volatile organic compounds (VOCs) and destroy them. The proposed system is relies on the fast operation of PCS which operates under sub-threshold conditions and reduced computation time. The properties of common source amplifier like very high voltage gain and input output resistance increased the sensitivity as well as stability of the circuit. The system is more user friendly and the outcomes of simulation are fairly in agreement with the theoretical estimation. Keywords: bio aerosol, Photo Catalytic Oxidation (PCO), hydroxyl, hydrogen peroxide, SPICE, surface sanitizer.
ARTICLE | doi:10.20944/preprints202112.0064.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: spent fluid catalytic cracking catalyst; waste slag; leaching; lanthanum oxide; rare earths recovery
Online: 6 December 2021 (12:04:43 CET)
An laboratory procedure has been developed to obtain lanthanum oxide from spent fluid catalytic cracking catalyst, commonly used in the cracking the heavy crude oil process. Two different spent fluid catalytic cracking catalysts, which are mainly formed by silica and alumina, and a certain amount of rare earths were leached under several conditions to recover the rare earth from the solids waste. Subsequently, liquid phases were subjected to a liquid-liquid extraction process, and lanthanum was quantitatively stripped using oxalic acid to obtain the corresponding lanthanum oxalates. After the corresponding thermal treatment, these solids were transformed into lanthanum oxide. Both, lanthanum oxalates and oxides solids have been characterized by wide techniques in order to investigate the purity of the phases.
ARTICLE | doi:10.20944/preprints201807.0213.v1
Subject: Chemistry And Materials Science, 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/preprints202204.0017.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Residual fat; Red Mud; Chemical activation; Thermal catalytic cracking; Fixed bed reactor; Liquid hydrocarbons
Online: 4 April 2022 (11:54:32 CEST)
This work aims to investigate the effect of catalyst content and reaction time by catalytic upgrading from pyrolysis vapors of residual fat at 450 °C and 1.0 atmosphere, on the yields of reaction products, physicochemical properties (density, kinematic viscosity, refractive index, and acid value) and chemical composition of organic liquid products (OLP), over a catalyst fixed bed reactor, in semi pilot scale. Pellets of Red Mud chemically activated with 1.0 M HCl were used as catalysts. The experiments were carried out at 450 °C and 1.0 atmosphere, using a process schema consisting of a thermal cracking reactor of 2.0 L coupled to a catalyst fixed bed reactor of 53 mL, without catalyst and using 5.0, 7.5, and 10.0% (wt.) Red Mud pellets activated with 1.0 M HCl, in batch mode. Samples of liquid phase products were withdrawn during the course of reaction at 40, 50, 60, 70 and 80 min in order to analyze the process kinetics. The physicochemical properties (density, kinematic viscosity, acid value, and refractive index) of OLP were determined by official methods. The chemical functions present in OLP determined by FT-IR and the chemical composition by GC-MS. The thermal catalytic cracking of residual fat show OLP yields from 54.4 to 84.88 (wt.%), aqueous phase yields between 2.21 and 2.80 (wt.%), solid phase yields (coke) between 1.30 and 8.60 (wt.%), and gas yields from 11.61 to 34.22 (wt.%). The yields of OLP increases with increasing catalyst content while those of aqueous, gaseous and solid phase decreases. For all the thermal and thermal catalytic cracking experiments, the density, kinematic viscosity, and acid value of OLP decreases with increasing reaction time. The GC-MS of liquid reaction products identified the presence of hydrocarbons (alkanes, alkenes, cycloalkanes, and aromatics) and oxygenates (carboxylic acids, ketones, esters, alcohols, and aldehydes). For all the thermal and thermal catalytic cracking experiments, the hydrocarbon content within OLP increases with reaction time, while those of oxygenates decrease, reaching concentrations of hydrocarbons up to 95.35% (area.). The best results for the physicochemical properties (density, kinematic viscosity, and acid value) and the maximum hydrocarbon content of OLP were obtained at 450 °C and 1.0 atmosphere, using a catalyst fixed bed reactor, with 5.0% (wt.) Red Mud pellets activated with 1.0 M HCl as catalyst.
ARTICLE | doi:10.20944/preprints201810.0370.v1
Subject: Engineering, Energy And Fuel Technology Keywords: principal component analysis (PCA); fluid catalytic cracking (FCC); waste valorization; scrap tires; polyolefin pyrolysis
Online: 16 October 2018 (17:43:50 CEST)
Associating the most influential parameters with the product distribution is of uttermost importance in complex catalytic processes such as fluid catalytic cracking (FCC). These correlations can lead to the information-driven catalyst screening, kinetic modeling and reactor design. In this work, a dataset of 104 uncorrelated experiments, with 64 variables, has been obtained in an FCC simulator using 6 types of feedstock (vacuum gasoil, polyethylene pyrolysis waxes, scrap tire pyrolysis oil, dissolved polyethylene and blends of the previous), 36 possible sets of conditions (varying contact time, temperature and catalyst/oil ratio) and 3 industrial catalysts. Principal component analysis (PCA) has been applied over the dataset, showing that the main components are associated with feed composition (27.41% variance); operational conditions (19.09%) and catalyst properties (12.72%). The variables of each component have been correlated with the indexes and yields of the products: conversion, octane number, aromatics, olefins (propylene) or coke, among others.
ARTICLE | doi:10.20944/preprints201703.0017.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: green synthesis; silver nanoparticles; trimethylchitosan nitrate; catalytic activity; antibacterial activity; multidrug-resistant Acinetobacter baumannii
Online: 2 March 2017 (08:49:35 CET)
We report a facile route for the green synthesis of trimethylchitosan nitrate-capped silver nanoparticles (TMCN-AgNPs) with positive surface charge. In this synthesis, silver nitrate, glucose, and trimethyl chitosan nitrate (TMCN) were used as silver precursor, reducing agent, and stabilizer, respectively. The reaction was carried out in a stirred basic aqueous medium at room temperature without the use of energy-consuming or expensive equipment. We investigated the effects of the concentrations of NaOH, glucose, and TMCN on the particle size, zeta potential, and formation yield. The AgNPs were characterized by UV-visible spectroscopy, photon correlation spectroscopy, laser Doppler anemometry, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalytic activity of the TMCN-AgNPs was studied by the reduction of 4-nitrophenol using NaBH4 as a reducing agent. We evaluated the antibacterial effects of the TMCN-AgNPs on Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus using the broth microdilution method. The results showed that both gram-positive and gram-negative bacteria were killed by the TMCN-AgNPs at very low concentration (< 6.13 μg/mL). Moreover, the TMCN-AgNPs also showed high antibacterial activity against clinically isolated multidrug-resistant A. baumannii strains, and the minimum inhibitory concentration (MIC) was ≤ 12.25 μg/mL.
ARTICLE | doi:10.20944/preprints202310.1340.v1
Subject: Engineering, Chemical Engineering Keywords: fluidized catalytic cracking; catalyst characterization; catalyst deactivation; coking mechanism; mass loss; catalyst kinetic; thermodynamic parameters
Online: 23 October 2023 (05:41:30 CEST)
In the FCC conversion of heavy petroleum fractions as atmospheric residues, the main challenge for refiners to achieve the quantity and quality of various commercial products depends essentially on the catalyst used in the process. A deep characterization of the catalyst at different steps of the process (fresh, regenerated, and spent catalyst) was investigated to study the catalyst's behavior including the physicochemical evolution, the deactivation factor, and kinetic-thermodynamic parameters. All samples have been characterized by various spectroscopy methods such as N2 adsorption-desorption, UV-visible spectroscopy, Raman spectroscopy, LECO carbon analysis, Scanning electron microscopy (SEM), X-ray diffraction (XRD), X‐ray fluorescence (XRF), nuclear magnetic resonance spectroscopy (NMR13C) analysis, and Thermogravimetric analysis. The results of N2 adsorption-desorption, UV-vis, Raman, LECO carbon, and SEM images showed that the main causes of catalyst deactivation and coking were the deposition of carbon species that covered the active sites and clogged the pores, and the attrition factor due to thermal conditions and poisonous metals. The XRD and XRF results showed the catalyst’s physicochemical evolution during the process and the different interlinks between catalyst and feedstock (Nickel, Vanadium, Sulfur, and Iron) elements which should be responsible for the coking and catalyst attrition factor. It has been found that, in addition to the temperature, the residence time of the catalyst in the process also has an influence on catalyst structure transformation. NMR13C analysis revealed that polyaromatic hydrocarbon is the main component in the deposited coke of the spent catalyst. Thermogravimetric analysis showed that the order of catalyst mass loss was fresh > regenerated > spent catalyst due to the progressive losses of the hydroxyl bonds (OH) and the structure change along the catalyst thermal treatment. Moreover, the kinetic and thermodynamic parameters showed that all zones are non-spontaneous endothermic reactions.
ARTICLE | doi:10.20944/preprints202307.1169.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Palm oil; Sodium carbonate; Catalytic cracking; Reused catalyst; Reaction time; Physical-chemistry properties; Distillation fractions
Online: 18 July 2023 (07:39:10 CEST)
In this work, the influence of catalyst reuse and reaction time on the yield and quality of organic liquid products (OLP) obtained in a cracking pilot plant at 450 °C and 1.0 atm has been systematically investigated. The distillation of OLP produced 04 (four) distilled fractions. The quality of the biofuels was certified by physical-chemical analysis, as well as FT-IR and GC-MS analysis. The experimental results showed the feasibility of applying the spent sodium carbonate twice in catalytic cracking of vegetable oils. The physical-chemical properties (density, viscosity, acid value, saponification value, and flash point) of OLP decrease as the reaction time increases. The distillation of OLP yields 62.35% (wt.), producing green-like gasoline, kerosene, and diesel fractions rich in hydrocarbons. Therefore, biofuels-like fractions produced by distillation of OLP have a great potential for replacing partially petroleum derived fuels.
ARTICLE | doi:10.20944/preprints202204.0213.v1
Subject: Engineering, Energy And Fuel Technology Keywords: residual fat; activated carbon pellets; chemical activation; thermal catalytic cracking; catalyst bed reactor; liquid hydrocarbons
Online: 24 April 2022 (02:55:25 CEST)
This work aims to investigate the influence of reaction time and catalyst-to-residual fat ratio by catalytic upgrading from pyrolysis vapors of residual fat at 400 °C and 1.0 atmosphere, on the yields of reaction products, physicochemical properties (density, kinematic viscosity, and acid value) and chemical composition of bio-oils, over a catalyst fixed bed reactor of activated carbon pellets impregnated with 10.0 M NaOH, in semi pilot scale. The experiments were carried out at 400 °C and 1.0 atmosphere, using a process schema consisting of a thermal cracking reactor of 2.0 L coupled to a catalyst fixed bed reactor of 53 mL, without catalyst and using 5.0, 7.5, and 10.0% (wt.) activated carbon pellets impregnated with 10.0 M NaOH, in batch mode. Samples of liquid phase products were withdrawn during the course of reaction at 50, 60, 70, 80, 90, 100 and 120 minutes in order to investigate the process kinetics. The physicochemical properties (density, kinematic viscosity, and acid value) of bio-oils were determined by official methods. The chemical composition of bio-oils determined by GC-MS. The thermal catalytic cracking of residual fat show bio-oils yields from 55.55 to 30.22 (wt.%), aqueous phase yields between 2.83 and 3.19 (wt.%), solid phase yields between 13.56 and 9.75 (wt.%), and gas yields from 27.89 to 55.60 (wt.%). The yields of bio-oil decreases from 74.41 to 30.22% (wt.) with increasing catalyst-to-Tallow kernel oil ratio, while that of gaseous phase increases from 12.87 to 55.60% (wt.). For all the thermal and thermal catalytic cracking experiments, the density, kinematic viscosity, and acid value of bio-oils decreases as the reaction time increases varying from 0.9266 to 0.8220 g/cm³, 8.10 to 2.24 mm²/s, and 144.14 to 2.37 mg KOH/g. The GC-MS of liquid reaction products identified the presence of hydrocarbons (alkanes, alkenes, ring-containing alkanes, ring-containing alkenes, and aromatics) and oxygenates (carboxylic acids, ketones, esters, alcohols, and aldehydes). For all the pyrolysis and catalytic cracking experiments, the hydrocarbon selectivity in bio-oil increases with increasing reaction time, while those of oxygenates decrease, reaching concentrations of hydrocarbons up to 95.35% (area.). The best results for the physicochemical properties density, kinematic viscosity, and acid value were 0.8220 g/cm³, 3.03 mm2/s, and 2.37 mg KOH/g, respectively, with a maximum hydrocarbon concentration of 97.194% (area.) and 2.806% ketones (area.) were obtained at 400 °C and 1.0 atmosphere, 80 minutes, without catalyst. For the catalytic cracking experiments, the maximum hydrocarbon content of 75.763% (area.) and 17.041% (area.) carboxylic acids, 4.702% (area.) ketones (area.), and 2.494% (area.) non-identified oxygenates was obtained at 400 °C and 1.0 atmosphere, 90 minutes, using a catalyst fixed bed reactor, with 10.0% (wt.) activated carbon pellets impregnated with 10.0 M NaOH as catalyst.
REVIEW | doi:10.20944/preprints202007.0222.v1
Subject: Chemistry And Materials Science, Medicinal Chemistry Keywords: ROS; oxidative stress; catalytic antioxidants; superoxide dismutase; catalase; peroxidase; manganese; salen-type ligands; animal studies
Online: 11 July 2020 (03:30:41 CEST)
Manganosalen complexes are coordination compounds that possess a chelating salen-type ligand, a class of bis-Schiff bases obtained by condensation of salicylaldehyde and a diamine. They may act as catalytic antioxidants mimicking both the structure and the reactivity of the native antioxidant enzymes active site. Thus, manganosalen complexes have shown to exhibit superoxide dismutase, catalase, and glutathione peroxidase activities, and they could potentially facilitate the scavenging of excess ROS, thereby restoring the redox balance in the damaged cells and organs. Initial catalytic studies compared the potency of these compounds as antioxidants in terms of rate constants of the chemical reactivity against ROS, giving catalytic values approaching and even exceeding that of the native antioxidative enzymes. Although most of these catalytic studies lack of biological relevance, subsequent in vitro studies have confirmed the efficiency of many manganosalen complexes in oxidative stress models. These synthetic catalytic scavengers, cheaper than natural antioxidants, have accordingly attracted intensive attention for the therapy of ROS-mediated injuries. The aim of this review is to focus on in vivo studies performed on manganosalen complexes and their activity on the treatment of several pathological disorders associated with oxidative damage. This disorders, ranging from the prevention of fetal malformations to the extension of lifespan, include neurodegenerative, inflammatory and cardiovascular diseases, tissue injury, and other damages related to liver, kidney or lungs.
REVIEW | doi:10.20944/preprints202106.0373.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: metal assisted etching; metal assisted catalytic etching, silicon nanowires, porous silicon, porous powders, metal nanoparticles, deposition
Online: 14 June 2021 (15:04:41 CEST)
Electroless etching of semiconductors was elevated to an advanced micromachining process by the addition of a structured metal catalyst. Patterning of the catalyst by lithographic techniques facilitates the patterning of crystalline and polycrystalline wafer substrates. Galvanic deposition of metals on semiconductors has a natural tendency to produce nanoparticles rather than flat uniform films. This characteristic makes possible the etching of not only wafers but also particles with arbitrary shape. While it has been widely recognized that spontaneous deposition of metal nanoparticles can be used in connection with etching to porosify wafers, it is also possible to produced nanostructured powders. MACE can be controlled to produce (1) etch track pores with shapes and sizes closely related to the shape and size of the metal nanoparticle, (2) hierarchically porosified substrates exhibiting combinations of large etch track pores and mesopores, and (3) nanowires with either solid or mesoporous cores. This review discussed the mechanisms of porosification, processing advances and the properties of the etch product with special emphasis on the etching of silicon powders.
ARTICLE | doi:10.20944/preprints202001.0264.v2
Subject: Engineering, Energy And Fuel Technology Keywords: Activation; Catalyst; Catalytic pyrolysis; Fuel oil; Hydrocarbon fuel; Municipal wastes; Plastics wastes; Polyethylene; Pyrolysis; Thermal pyrolysis
Online: 27 January 2020 (10:13:24 CET)
Plastics have become an indispensable part of modern life today. The global production of plastics has gone up to 299million tones in 2013, which is believed to be increasing in the near future. The utilization of plastics and its final disposal pose a tremendous negative significance impacts on the environment. The aim of this study was to investigate the thermal and catalytic pyrolysis for production of fuel oil from the polyethene plastic wastes. Catalysts used in the experiment were acid activated clay mineral and aluminum chlorides on activated carbon. The clay mineral was activated by refluxing it with 6M Sulphuric acid for 3hours. The experiment was conducted in three different phases: the first phase of the experiment was done without a catalyst where 88mL oil was obtained at a maximum temperature of 39 and heating rates of 12.5, reaction time of 4hours. The second phase involves the use of acid activated clay mineral where 100mL of oil was obtained and heating rates of 12.5 and reaction time of 3hours 30minutes. The third phase was done using aluminium chlorides on activated carbon and 105ml oil was obtained at a maximum temperature of 400 and heating rates of 15.5 reaction time of 3hours 10minutes. From the results, catalytic pyrolysis is more efficient than purely thermal pyrolysis and homogenous catalysis (aluminum chlorides) shows a better result than solid acid catalyst (activated clay minerals) hence saving the energy needed for pyrolysis and making the process more economically feasible.
REVIEW | doi:10.20944/preprints201809.0225.v1
Subject: Chemistry And Materials Science, 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.
ARTICLE | doi:10.20944/preprints202307.0791.v1
Subject: Engineering, Energy And Fuel Technology Keywords: catalytic hydrocracking; aquathermolysis; heavy oil; FeSO4; NiSO4; water-soluble catalysts; resins and asphaltenes; destructive hydrogenation; in-situ upgrading
Online: 12 July 2023 (08:28:47 CEST)
Aquathermolysis is a promising method to upgrade heavy oil in reservoir conditions. However, application of catalysts can significantly promote transformation of the heavy fragments (resins and asphaltenes) and heteroatom-containing compounds of crude oil mixture into low-molecular-weight hydrocarbons. In this paper, the comparison study of the catalytic performance of the water-soluble metal salts such as NiSO4 and FeSO4 on the aquathermolytic upgrading of heavy oil samples produced from Ashal’cha reservoir was carried out at a temperature of 300 °C for 24 hours. Iron nanoparticles contributed to the highest viscosity reduction degree - 60% in contrast to the viscosity of the native crude oil sample. The viscosity alteration is reasoned by the changes in the group composition of heavy oil after catalytic (FeSO4) aquathermolysis, where the content of resins and asphaltenes were reduced by 17% and 7%, respectively. Moreover, the aquathermolytic upgrading of heavy oil in the presence of FeSO4 led to an increase in the yield of gasoline fraction by 13% and diesel fraction by 53%. The H/C ratio, which represents the hydrogenation of crude oil, increased from 1.52 (before catalytic upgrading) to 1.99 (after catalytic upgrading). The results of Chromatomass (GC-MS) and Fourier-infrared (FT-IR) spectroscopies confirmed the intensification of destructive hydrogenation of resins and asphaltenes in the presence of the water-soluble catalysts. According to XRD and SEM-EDX results, the metal salts are thermally decomposed during the aquathermolysis process into the oxides of corresponding metals and particularly sulfided by the sulfur-containing aquathermolysis products.
ARTICLE | doi:10.20944/preprints202212.0181.v1
Subject: Chemistry And Materials Science, Chemical Engineering Keywords: nanocomposites; ultralong carbon nanotubes; catalytic chemical vapor deposition; purification; catalyst removal; water vapor treatment; thermal analysis; Raman spectroscopy
Online: 9 December 2022 (13:11:58 CET)
Ultralong carbon nanotubes (UCNTs) are highly demanded for nanocomposites applications because of their magnificent physical and chemical properties. UCNTs are synthesized by catalytic chemical vapor deposition (CCVD) method and, before using as fillers in nanocomposites, should be purified from residual catalyst and non-CNT particles without significant destruction or scissoring of UCNTs. The role of water vapor for purification of UCNTs is investigated, the importance of water assistance in this process is confirmed. It was shown that wet air treatment of products of UCNTs CCVD synthesis under mild conditions can be used to decrease sufficiently residual catalyst content without significant carbon losses in comparison with the results obtained with dry air, while the residual iron content was shown to influence heavily on the subsequent oxidation of different forms of carbons, including UCNTs. The increasing of D/G ratio of Raman spectra after wet air treatment of products of UCNTs CCVD synthesis makes it possible to conclude that iron catalyst particles transform into iron oxides and hydroxides that caused inner structural strains and destruction of carbon shells improving removal of the catalyst particles by subsequent acid treatment. UCNTs purification with water assistance can be used to develop economically and ecologically friendly methods for obtaining fillers for nanocomposites of different applications.
ARTICLE | doi:10.20944/preprints202306.0660.v1
Subject: Engineering, Chemical Engineering Keywords: Electrochemical Promotion of Catalysis (EPOC); non-Faradaic electrochemical modification of catalytic activity (NEMCA); CO2 Hydrogenation; Rh; Rhodium; YSZ; XPS
Online: 9 June 2023 (03:50:24 CEST)
Electrochemical Promotion was used to modify the activity and selectivity of a Rh catalyst-electrode in the CO2 hydrogenation reaction. The experiments were carried out in a temperature range of 350-430οC at ambient pressure and at different CO2 to H2 gas feeding ratios (1:2 to 4:1). The only reaction products observed were CO and CH4, both under open and closed-circuit conditions. The CH4 formation rate was found to increase with both positive and negative potential or current application. The CO formation rate followed the opposite trend. The selectivity to CH4 increased under high values of hydrogen partial pressure and decreased at high pressures of CO2. The results demonstrate how Electrochemical Promotion can be used to finely tune activity and selectivity for a reaction of high technical and environmental importance.
REVIEW | doi:10.20944/preprints202010.0179.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: Non Michaelis-Menten Kinetics; High-throughput screening; allostery; cooperativity; processive kinetics; distributive kinetics; single-molecule; auto-catalytic; drug discovery
Online: 8 October 2020 (13:34:16 CEST)
Biological systems are highly regulated. They are also highly resistant to sudden perturbations enabling them to maintain the dynamic equilibrium essential for sustenance of life. This robustness is conferred by regulatory mechanisms that influence the activity of enzymes/proteins within their cellular context, to adapt to changing environmental conditions. However, the initial rules governing the study of enzyme kinetics were tested and implemented for mostly cytosolic enzyme systems that were easy to isolate and/or recombinantly express. Moreover, these enzymes lacked complex regulatory modalities. Now, with academic labs and pharmaceutical companies turning their attention to more complex systems (for instance, multi-protein complexes, oligomeric assemblies, membrane proteins and post-translationally modified proteins), the initial axioms defined by Michaelis-Menten (MM) kinetics are rendered inadequate and the development of a new kind of kinetic analysis to study these systems is required. The current review strives to present an overview of enzyme kinetic mechanisms that are atypical and, oftentimes, do not conform to the classical MM kinetics. Further, it presents initial ideas on the design and analysis of experiments in early drug-discovery for such systems, to enable effective screening and characterisation of small-molecule inhibitors with desirable physiological outcomes.
CONCEPT PAPER | doi:10.20944/preprints202009.0723.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: Glycogen Storage Disease Type 1a, Glucose-6-phosphatase Catalytic Subunit (G6PC), Glucose-6-phosphatase (G6Pase), prime editing, mRNA delivery, CRISPR
Online: 30 September 2020 (08:05:17 CEST)
One of the rare diseases throughout the world is Glycogen Storage Disease, which appears due to problems in glycogen metabolism. Among various subtypes of GSD, GSD Type 1a is the most abundant one of GSD Type 1, seen in approximately 80% and caused by different kinds of mutations in the Glucose-6-Phosphatase Catalytic Subunit (G6PC) gene in human chromosome 17q21. G6PC gene encodes for glucose-6-phosphatase (G6Pase) protein, which cleaves glucose-6-phosphate into glucose and inorganic phosphate (Pi), and GSD Type 1a patients fail to breakdown glucose-6-phosphate due to several mutations in the G6PC gene. In our study, we aim to create new therapeutic approaches for GSD 1a. We collected mutation data of 57 GSD Type 1a patients from Turkey. According to the data, 16 types of mutations were observed in the G6PC gene. Allele frequencies of these mutations are calculated as 59% for R83C/H, 11% for W160*, 7% for G270V, and 28% for others which have less frequency. Up to now, the tertiary protein structure of G6Pase has not been structured yet. To understand the possible impacts of these mutations, we statistically obtained possible tertiary structure predictions of G6Pase by running 5 different tools. At the end of the study, we suggest two effective and promising gene therapy methods for GSD Type 1a, Prime Editing for R83C/H mutations, and mRNA delivery for other mutations, in addition to a promising, commercially available drug suggestion for patients with W160*, W86*, and S15* mutations, although the drug belongs to another disease.
ARTICLE | doi:10.20944/preprints201704.0154.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: water bridging; dipole waves; coherent states; polymerase chain reaction; DNA amplification; DNA transduction; enzyme catalytic activity; fractal-like self-similarity
Online: 25 April 2017 (04:24:21 CEST)
We discuss the role of water bridging the DNA-enzyme interaction by resorting to recent 1 results showing that London dispersion forces between delocalized electrons of base pairs of DNA 2 are responsible for the formation of dipole modes that can be recognized by Taq polymerase. 3 We describe the dynamical origin of the high efficiency and precise targeting of Taq activity in 4 PCR. The spatiotemporal distribution of interaction couplings, frequencies, amplitudes, and phase 5 modulations comprise a pattern of fields instantiating the electromagnetic image of DNA in its 6 water environment, which is what the polymerase enzyme actually recognizes at long range. The 7 experimental realization of PCR amplification, achieved through replacement of the DNA template 8 by the treatment of pure water with electromagnetic signals recorded from viral and bacterial DNA 9 solutions, is found consistent with the gauge theory paradigm of quantum fields.
ARTICLE | doi:10.20944/preprints202306.2141.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: membrane technologies; palladium-containing films; surface modification; nanostructured sur-face; pentagonal structured particles; catalytic activity; hydrogen permeability; hydrogen carriers; high-purity hydrogen
Online: 29 June 2023 (13:16:46 CEST)
Thin Pd-40%Cu films were obtained by the classical melting and rolling method, magnetron sputtering and modified with nanostructured functional coatings to intensify the process of hydrogen transport. The films were modified by electrodeposition according to the classical method of obtaining palladium black and "Pd-Au nanoflowers" with spherical and pentagonal particles, respectively. The experiment results demonstrated the highest catalytic activity (89.47 mA cm–2), good resistance to CO poisoning and long-term stability of Pd-40%Cu films with a pentagonal structured coating. The investigation of the developed membranes in the hydrogen transport processes in the temperature range of 25-300°C also demonstrated high and stable fluxes up to 475.28 mmol s–1 m–2 (deposited membranes) and 59.41 mmol s–1 m–2 (dense-metal membranes), which turned out to be up to 1.5 higher compared to membrane materials with classic niello. For all-metal modified membranes, the increase in flux was up to 7 times, compared with a smooth membrane made of pure palladium, and for deposited films, this difference was several tens of times. The membrane materials selectivity was also high up to 4419. The developed strategy for modifying membrane materials with functional coatings of a fundamentally new complex geometry can shed new light on the development and fabrication of durable and highly selective palladium-based membranes for gas steam reformers.