ARTICLE | doi:10.20944/preprints202210.0354.v1
Online: 24 October 2022 (07:14:38 CEST)
Spider silk has excellent strength and elasticity in natural, researchers have been working for decades try to achieve natural spider silk outstanding mechanical properties using recombinant spider silk protein (spidroin) through artificial spinning. In this work, we chose wet spinning method to explore the relationship between concentration of coagulation bath and fiber performance. It was found that the concentration of methanol has important effect on fiber continuity, diameter and mechanical properties. Lower concentration favors spinning continuous thinner, fibers with high strain. Secondary stretching benefits spinning silk fibers with stable mechanical properties, and thermal stability. Through applying different methanol concentration and additional stretching, we obtained silk fibers with Young’s modulus of 3.052± 2.626 GPa, stress of 25.3944 ± 17.48 MPa, and strain of 140 ± 95.4%.
ARTICLE | doi:10.20944/preprints202308.2057.v1
Subject: Engineering, Energy And Fuel Technology Keywords: fuels; port; ship; bunker; biofuels; LNG; ammonia; methanol
Online: 31 August 2023 (03:25:20 CEST)
The International Maritime Organization (IMO) has recently revised its strategy for shipping de-carbonization, deepening the ambition to reduce annual greenhouse gas emissions until 2050. The accomplishment of this strategy requires the large-scale deployment of alternative maritime fuels, whose diversity and technical characteristics impose transition challenges. While several studies address the production of these fuels, a notable gap lies in the analysis of the required adaptations in vessels and ports for their usage. This study aims to fill this gap through a comprehensive re-view of material compatibility, storage in ports/vessels, and bunkering technology. Firstly, we an-alyze key aspects of port/vessel adaptation: physical and chemical properties; energy conversion for propulsion; fuel feeding and storage; bunkering procedures. Then, we perform a maturity as-sessment, placing each studied fuel on the technological readiness scale, revealing the most prom-ising options regarding infrastructure adaptability. Finally, we develop a case study for Brazil, whose economy is grounded on maritime exports. Findings indicate that multi-product ports may have potential to serve as multi-fuel hubs, while the remaining ports are inclined to specific fuels. In terms of vessel categories, we find that oil tankers, chemical ships and gas carriers are the most ready for conversion in the short-term
ARTICLE | doi:10.20944/preprints202306.1452.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: Electrocatalysts; direct methanol fuel cell; reduced graphene oxide
Online: 20 June 2023 (14:50:18 CEST)
This work reports the influence of reduced graphene oxide (rGO) support on the catalytic performance of Cu@PtRu/rGO catalysts towards methanol oxidation in acidic medium. These core-shell catalysts are synthesized by the reduction method in two steps being the first using ethylene glycol to obtain Cu/rGO and the second, the reduction of copper atoms synthesized in the previous step to produce Cu@PtRu/rGO. In order to compare the catalytic performance of the prepared catalysts, Pt/C, PtRu/C, Cu@PtRu/C catalysts are also synthesized on Vulcan XC-72R carbon. The theoretical loading of Pt used in the Vulcan XC-72R carbon supported catalysts is equal to that utilized in Cu@PtRu/rGO, and higher in the other prepared catalysts. The surface composition of the nanoparticles, as well as their sizes, particle size distribution and morphology of the catalyst particles are characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry (CV) and chronoamperometry (CA) are employed to measure the electrochemical performance of the prepared catalysts. The anodic scans show that for the region of technological interest (0.1 to 0.4 V), the Cu@PtRu/rGO-16 electrocatalyst exhibits higher current density value than the others as a result of its lower starting oxidation potential (0.250V against 0.437V for Pt/C) and its higher ratio between forward (iF) and reverse (iR) current densities (iF/iR 1.45 against 0.93 for Pt/C). Chronoamperometric tests depict that the current density value of Cu@PtRu/rGO-16 catalyst is about 4 times higher than that of Cu@PtRu/C-16 and Cu@PtRu/C-18 catalysts, ca. 4.8 times higher than that of PtRu/C-30 catalyst and around 6 times higher than that of Pt/C-30. These results suggest that Cu@PtRu/rGO-16 exhibits high bulk activity for the electrooxidation of methanol, high stability and high tolerance to CO poisoning, making it possible to reduce the platinum loading in proton exchange membrane fuel cells (PEMFCs).
COMMUNICATION | doi:10.20944/preprints202304.0673.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: Methane conversion; Fuel cell; methanol; PEM; PdAu/ATO
Online: 21 April 2023 (05:33:46 CEST)
This study investigates the use of Au-doped Pd anodic electrocatalysts on ATO support for the conversion of methane to methanol. The study involves cyclic voltammetry, in-situ Raman spectra, polarization curves, and FTIR analysis to determine the optimal composition of gold and palladium for enhancing the conversion process. The results demonstrate the potential for utilizing methane as a feedstock for producing sustainable energy sources. Pd75Au25/ATO electrode exhibited the highest OCP value, and Pd50Au50/ATO had the highest methanol production value at a potential of 0.05 V. Therefore, it can be concluded that an optimal composition of gold and palladium exists to enhance the conversion of methane to methanol. The findings contribute to the development of efficient and sustainable energy sources, highlighting the importance of exploring alternative ways to produce methanol.
COMMUNICATION | doi:10.20944/preprints202008.0701.v1
Subject: Chemistry And Materials Science, 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/preprints201909.0152.v1
Subject: Chemistry And Materials Science, Medicinal Chemistry Keywords: chlorophyll; carotenoids; methanol; photo-protection; phytoextraction; Portulaca oleracea
Online: 15 September 2019 (15:04:55 CEST)
The chlorophyll is one of the most important natural pigments used extensively in the food industry. Two important factors for the production of chlorophyll are the use of plants rich in chlorophyll and efficiency of extraction method. Present investigation was performed to compare the extraction of photosynthetic pigments by using solvents of different chemical nature. The purslane plants with different growth behavior viz. Scrollable and standing were grown under shade and sunshine stress condition. Different solvents including diethyl ether, 5% ethanol, pure acetone, 20% acetone, pure methanol and 10% methanol were used to extract chlorophyll and carotenoids from the purslane plant. The results indicated that stress, growth type and different solvents had a significant effect on the extraction of chlorophyll and carotenoids. Different trend was observed in extraction rate for chlorophylls and carotenoids. Among the solvents, pure methanol was the best for extraction of chl a. Methanol and acetone were appropriate solvents to achieve the highest amount of chlorophyll from plant tissues. Among different solvents, pure methanol for chl a, pure acetone and methanol for carotenoids were best solvent for purslane plant with a growing type scrollable of under shade.
ARTICLE | doi:10.20944/preprints201801.0094.v2
Subject: Engineering, Energy And Fuel Technology Keywords: Direct Methanol Fuel Cell; Operation strategy; Multi-objective optimization
Online: 8 May 2018 (16:14:24 CEST)
An adaptive operation strategy for on-demand control of DMFC system is proposed as an alternative method to enhance the voltage stability. Based on a single-cell DMFC stack, a newly simplified semi-empirical model is developed from the uniform-designed experimental results to describe the I-V relationship. Integrated with this model, the multi-objective optimization method is utilized to develop an adaptive operation strategy. Although the voltage instability is frequently encountered in unoptimized operations, the voltage deviation is successfully decreased to a required level by adaptive operations with operational adjustments. Moreover, the adaptive operations are also found to be able to extend the range of operating current density or to decrease the voltage deviation according to ones requirements. Numerical simulations are implemented to investigate the underlying mechanisms of the proposed adaptive operation strategy, and experimental adaptive operations are also performed on another DMFC system to validate the adaptive operation strategy. Preliminary experimental study shows a rapid response of DMFC system to the operational adjustment, which further validates the effectiveness and feasibility of the adaptive operation strategy in practical applications. The proposed strategy contributes to a guideline for the better control of output voltage from operating DMFC systems.
REVIEW | doi:10.20944/preprints202308.2106.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: Methane; Methanol; MOF; Spectroscopy; XAS; IR; Raman; Mössbauer; EPR; XPS
Online: 31 August 2023 (10:03:59 CEST)
The direct methane to methanol (MTM) oxidation is a grand challenge in catalysis, with profound economical implications for the modern chemical industry. Bioinspired metal-organic frameworks (MOFs) with active iron and copper sites have been emerging very recently as innovative catalytic platforms to accomplish the MTM conversion under mild conditions. This review discusses the current state of the art regarding the application of MOFs with iron and copper catalytic centers to perform the MTM reaction, with a focus on the diverse spectroscopic techniques used to unveil the electronic and structural properties of the MOF catalysts at a microscopic level. We explore the synthetic strategies employed to incorporate iron and copper sites into different MOF topologies, the efficiency and selectivity of the iron- and copper-bearing MOF catalysts, and the ensuing MTM reaction mechanisms proposed on the basis of spectroscopic characterization supported by theory. In particular, we evidence how the combination of complementary spectroscopic tools probing different regions of the electromagnetic spectrum is particularly useful to reach a satisfactory understanding of the key reaction pathways and intermediates. Finally, we provide a critical perspective on future directions to advance the use of MOFs to accomplish the MTM reaction.
ARTICLE | doi:10.20944/preprints202304.0179.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: Acmella oleracea; Anti-oxidant; In vitro; Anti-bacterial; Methanol extract
Online: 11 April 2023 (03:09:50 CEST)
Acemella oleracea is known as toothache plant belongs to the family of Asteraceae. It is treated as a medicinal remedy like tuberculosis, illness, cough, rheumatism, and illness. This study was concentrated on the antioxidant, cytotoxic, antimicrobial & thrombolytic activities of methanol extract of Acmella oleracea leaves using in vitro model. The antioxidant activity was estimated as trolox equivalent antioxidant capacity utilizing the DPPH and reducing power tests. The plant extract was tested for its cytotoxic action using a brine shrimp lethality bioassay, thrombolytic activity using clot disruption, and antibacterial activity using a disc diffusion assay technique against four distinct gram-positive and gram-negative bacteria. IC50 value of standard ascorbic acid for DPPH was 7.8µg/ml and the IC50 of the methanol extract of Acmella oleracea leaves was 198.34µg/ml that was moderate effect at all compare with ascorbic acid. Thrombolytic assay of Streptokinase as a positive control showed 88.49% where the extract shows 18.69% lytic activity shows the assay. In this study, the sample of LC50 results of cytotoxicity assay was 1.431 µg/mL which can be treated as less activity. Moreover, the extracts showed low to moderate antibacterial activity against both gram-negative and gram-positive bacterial stains (zone of inhibition-10-26 mm). Vibrio Mimicus bacteria stains exhibited the highest level of activity, with a range of 23 for the diameter of the growth inhibition zone. The current review shows leaf extracts of Acmella oleracea may be used as a source of antioxidant and thrombolytic activity, as well as a significant source of antibacterial and anticancer substances. Further research is required to evaluate in-vivo the pharmacological activity of Acmella oleracea leaves in order to identify the essential metabolites and potential mechanisms.
REVIEW | doi:10.20944/preprints202103.0731.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: alcoholic beverages; spirits; methanol; risk mitigation; legal limits; quality control.
Online: 30 March 2021 (10:58:06 CEST)
Methanol is a natural ingredient with major occurrence in fruit spirits, such as apple, pear, plum or cherry spirits, but also in spirits made from coffee pulp. The compound is formed during fermentation and the following mash storage by enzymatic hydrolysis of naturally present pectins. Methanol is toxic above certain threshold levels and legal limits have been set in most jurisdictions. Therefore, the methanol content needs to be mitigated and its level must be controlled. This article will review the several factors that influence the methanol content including the pH value of the mash, the addition of various yeast and enzyme preparations, fermentation temperature, mash storage, and most importantly the raw material quality and hygiene. From all these mitigation possibilities, lowering the pH value and the use of cultured yeasts when mashing fruit substances is already common as best practice today. Also a controlled yeast fermentation at acidic pH facilitates not only reduced methanol formation, but ultimately also leads to quality benefits of the distillate. Special care has to be observed in the case of spirits made from coffee by-products which are prone to spoilage with very high methanol contents reported in past studies.
REVIEW | doi:10.20944/preprints202005.0523.v1
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: water ice; hydroxyl radicals; methanol; hydroxyl groups; spectral identity; confusion
Online: 31 May 2020 (21:58:06 CEST)
This literature review found that it is doubtful that there is water ice in the polar craters on the Moon. In the course of this review, the following findings were found: (1) The absorption strength of hydroxyl radicals and hydroxyl groups are all 2.9μm, so it is easy to confuse hydroxyl radicals and hydroxyl groups when interpreting M3 spectra data. I do not doubt the ability of LCROSS to detect OH from water, but only suspect that LCROSS is unable to distinguish between hydroxyl radicals from water ice and hydroxyl groups from Moon's methanol due to ignore their spectral identity; (2) The water brought by comets and asteroids and the one caused by solar wind has been exhausted by reacts with the widespread methanol on the Moon in the presence of Pt/α-MoC or Pt/C catalysts. These reacts form large amount of hydrogen, thus clarifying a question NASA raised that "Scientists have long speculated about the source of vast quantities of hydrogen that have been observed at the lunar poles"; (3) The vast quantities of hydrogen in lunar polar craters at extremely low temperatures might be in liquid or solid state now, easy to confuse with water ice. It seems that all our previous misconceptions about water ice in the lunar polar craters might be due to the neglect of the widespread chemical role of lunar methanol. It is necessary to conduct in-depth research in this field in the future.
REVIEW | doi:10.20944/preprints201704.0137.v1
Subject: Chemistry And Materials Science, 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/preprints202309.0550.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: Microwave irradiation; CuO/ZnO/Al2O3 catalyst; Isomorphous substitution; Methanol steam reforming
Online: 8 September 2023 (02:54:21 CEST)
CuO/ZnO/Al2O3 catalyst is a commonly used catalyst for rea methanol steam reforming reaction. Oxalic acid was as precipitant in preparing oxalate precursor of CuO/ZnO/Al2O3 catalyst by co-precipitation, deionized water and ethanol were as solvents, microwave irradiation and water bath were as aging heating manner respectively. It indicated that ethanol selected crystal phase composition of oxalate precursors and restricted their growth. Microwave irradiation prompted the isomorphous substitution between Cu2+ of CuC2O4 and Zn2+ of ZnC2O4 in mother liquid, forming the master phase (Cu,Zn)C2O4 in precursor, the solid solution Cu-O-Zn formed after calcination, which exhibited nano-fibriform morphology. It possessed small CuO grains, large surface area and strong synergy between CuO and ZnO, which is beneficial to improve the catalytic performance of methanol steam reforming, the STY of H2 reached 516.7 mL·g-1·h-1, and the selectivity of CO was only 0.29%.
ARTICLE | doi:10.20944/preprints202307.0776.v1
Subject: Medicine And Pharmacology, Pharmacy Keywords: Pentaclethera macrophylla stem bark; Methanol extract; Bergenin; Acute toxicity; Antioxidant; DPPH.
Online: 12 July 2023 (08:56:04 CEST)
Purpose: Oxidative stress is responsible for over seventy five diseases and other harmful cytological challenges including cancer, type 2 diabetes mellitus, lipid peroxidation, distortion of cell membrane integrity, shortening of telomerase among others. Antioxidant potency of any plant is a very positive remedy to the debilitating effects of prooxidants and oxidants. The study was aimed at investigating the antioxidant potency of methanol extract of Pentaclethra macrophylla stem bark- in vitro and in vivo. Methods: Different phytochemicals were determined using standard methods. Nitric oxide, 1, 1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity, total antioxidant capacity and ferric reducing/anti-radical power were used to investigate the in vitro antioxidant activity. Catalase assay, superoxide dismutase, malondialdehyde and glutathione peroxidase were used to determine the in vivo antioxidant efficacy using six groups of five rats. Results: The result showed various quantities of phytochemicals, including antioxidant phytochemicals-flavonoids, tannins and total phenolics. The in vitro assay showed that 250 μg/ml of extract had the highest percentage inhibition of DPPH radical (93.93%). The 125 μg/ml had the highest scavenging activity of nitric oxide radical (49.47%) while 250μg/ml showed the least with 41.73%. Other methods showed various degrees of activity. The in vivo antioxidant showed that the principal mechanism of antioxidant activity is by modulating the iron-dependent catalase activity. Conclusion: Pentaclethra macrophylla has both in vitro and in vivo antioxidant activities and therefore is useful in ameliorating the debilitating effects of oxidants.
ARTICLE | doi:10.20944/preprints202204.0116.v1
Subject: Chemistry And Materials Science, Food Chemistry Keywords: coffee pulp; coffee by-products; sensory evaluation; fruit spirit; methanol; distillation
Online: 13 April 2022 (05:09:35 CEST)
Coffee pulp, obtained from wet coffee processing, is the major by-product accumulating in the coffee producing countries. One of the many approaches valorising this underestimated agricultural residue is the production of distillates. This research project deals with the production of spirits from coffee pulp using three different Coffea arabica varieties as a substrate. Coffee pulp was fermented for 72 hours with a selected yeast strain (Saccharomyces cerevisiae L.), acid, pectin lyase, and water. Several parameters, such as temperature, pH, sugar concentration and alcoholic strength were measured to monitor the fermentation process. Subsequently, the alcoholic mashes were double distilled with stainless steel pot stills and a sensory evaluation of the products was conducted. Furthermore, the chemical composition of fermented mashes and produced distillates were evaluated. It showed that elevated methanol concentrations were present in mashes and products of all three varieties. The sensory evaluation found the major aroma descriptor for the coffee pulp spirits as being stone fruit. The fermentation and distillation experiments revealed that coffee pulp can be successfully used as a raw material for the production of fruit spirits. However, the spirit quality and its flavour characteristics can be improved with optimised process parameters and distillation equipment.
ARTICLE | doi:10.20944/preprints202106.0308.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: CO2 hydrogenation; Methanol synthesis; Cu/ZnO catalyst; Pd catalyst; Energy storage
Online: 11 June 2021 (09:06:15 CEST)
Renewable methanol, obtained from CO2 and hydrogen provided from renewable energy, has been proposed as a way to close the CO2 loop. In industry, methanol synthesis using the catalyst CuO/ZnO/Al2O3 occurs at a high pressure. We intend to make certain modification on the traditional catalyst in order to work at lower pressure, maintaining high selectivity. Therefore, three heterogeneous catalysts have been synthesized by co-precipitation in order to improve the activity and the selectivity to methanol under mild conditions of temperature and pressure. Certain modifications on the traditional catalyst Cu/Zn/Al2O3 were employed such as the modification of the synthesis time and the addition of Pd as a dopant agent. The most efficient catalyst among those tested was a palladium-doped catalyst, 5% Pd/Cu/Zn/Al2O3. This had a selectivity of 64% at 210C and 5 bar.
ARTICLE | doi:10.20944/preprints202008.0713.v1
Subject: Chemistry And Materials Science, Food Chemistry Keywords: NMR; alcoholic beverages; ethanol; methanol; acetaldehyde; screening; validation; food control; PULCON
Online: 31 August 2020 (06:21:35 CEST)
Due to legal regulations, the rise of globalised (online) commerce and the need for public health protection, the analysis of spirits (alcoholic beverages > 15 % vol) is a task with growing importance for governmental and commercial laboratories. In this article a newly developed method using nuclear magnetic resonance (NMR) spectroscopy for the simultaneous determination of 15 substances relevant for the quality and authenticity assessment of spirits is described. The new method starts with a simple and rapid sample preparation and does not need an internal standard. For each sample a group of 1H-NMR spectra is recorded, among them a 2D spectrum for analyte identification and 1D spectra with suppression of solvent signals for quantification. Using the Pulse Length Based Concentration Determination (PULCON) method, concentrations are calculated from curve fits of the characteristic signals for each analyte. The optimisation of the spectra, their evaluation and the transfer of the results are done fully automatically. Glucose, fructose, sucrose, acetic acid, citric acid, formic acid, ethyl acetate, ethyl lactate, acetaldehyde, ethanol, methanol, n-propanol, isobutanol, isopentanol, 2-phenylethanol and 5-(hydroxymethyl)furfural (HMF) can be quantified with an overall accuracy better than 8 %. This new NMR-based targeted quantification method enables the simultaneous and efficient quantification of relevant spirits ingredients in their typical concentration ranges in one process with good accuracy. It has proven to be a reliable method for all kinds of spirits in routine food control.
ARTICLE | doi:10.20944/preprints201804.0040.v1
Subject: Medicine And Pharmacology, Ophthalmology Keywords: Methanol exposure; toxic effects; subcontractor manufacturing; dispatched workers; visual defect; neurobehavioral function
Online: 3 April 2018 (16:11:15 CEST)
An outbreak of occupational methanol poisoning occurred in small-scale 3rd tier factories of large-scale smartphone manufacturer, in the Republic of Korea, in 2016. To investigate the working environment and the health effect of the methanol exposure among co-workers of the methanol poisoning cases, we performed a cross sectional study on 155 workers at the five aluminum CNC cutting factories. Air and urinary methanol concentration were measured by gas chromatography, and health examination included symptoms, ophthalmological examinations and neurobehavioral tests. Multiple logistic regression analyses controlled for age and sex were conducted for revealing association of employment duration with symptoms. Air concentrations of methanol in factory A and E were ranged from 228.5 to 2220.0 ppm. Mean urinary methanol concentrations of the workers in each factory were from 3.5 mg/L up to 91.2 mg/L. The odds ratios for symptom of deteriorating vision and CNS increased, according to the employment duration, after adjusting for age and sex. Four cases with injured optic nerve and two cases with decreased neurobehavioral function were founded among co-workers of the victims. This study showed that the methanol exposure under poor environmental control not only produce eye and CNS symptoms but also affect neurobehavioral function and optic nerve.
ARTICLE | doi:10.20944/preprints201807.0592.v1
Subject: Chemistry And Materials Science, 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.
REVIEW | doi:10.20944/preprints202309.0713.v1
Subject: Engineering, Chemical Engineering Keywords: Methane oxidation; catalysis; global warming; nanoparticles; metal-organic frameworks; renewable energy; zeolite; methanol synthesis
Online: 12 September 2023 (05:46:56 CEST)
Methane and carbon dioxide are the main contributors to global warming, being the methane effect twenty-five times more powerful than carbon dioxide. Although the sources of methane are diverse, it is a very volatile and explosive gas. One way to store the energy content of methane is its conversion to methanol. Methanol is liquid under ambient conditions, easy to transport and, apart from its use as an energy source, it is a chemical platform that can serve as a starting material for the production of various higher value-added products. Accordingly, the transformation of methane to methanol has been extensively treated in the literature, using traditional catalysts as different types of zeolites. However, in the last years, a new generation of catalysts have emerged to carry out this transformation with higher conversion and selectivity, and more importantly, under mild temperature and pressure conditions. These new catalysts typically involve the use of a highly porous supporting material such as zeolite, or more recently, metal-organic frameworks (MOFs) and graphene, and metallic nanoparticles or a combination of different types of nanoparticles that are the core of the catalytic process. In this review, the characteristics, the catalytic mechanisms, reactors, and the main results of these catalysts are presented as a way to overcome the challenges found in traditional catalysts.
ARTICLE | doi:10.20944/preprints202104.0018.v1
Subject: Biology And Life Sciences, Anatomy And Physiology Keywords: abiotic stress; acetaldehyde; hexenal; LOX products; mass spectrometry; methanol; proton-transfer reaction; tropical crop species
Online: 1 April 2021 (12:50:17 CEST)
Leaf mechanical wounding triggers a rapid, within minutes, release of a blend of volatile organic compounds (VOCs). Wounding-induced VOC blend is mainly composed of oxygenated ubiquitous stress volatiles such as methanol and volatile products of lipoxygenase (LOX) pathway (mainly C5 and C6 alcohols and aldehydes and their derivatives), but also includes multiple minor VOCs that collectively act as infochemicals inducing defences in non-damaged plant leaves, neighbouring plants and attracting herbivore enemies. Till present, interspecific variability of the rate of induction and magnitude of wounding-induced emissions, and the extent to which plant structural traits and physiological activity alter these emissions are poorly known. Particularly scarce is the information of the induced emissions in tropical agricultural plant species despite their economic importance and large area of cultivation at regional to global scales. We chose five tropical crops with varying photosynthetic activity and leaf structural characteristics: Abelmoschus esculentus, Amaranthus cruentus, Amaranthus hybridus, Solanum aethiopicum and Telfairia occidentalis to characterize the kinetics and magnitude of wounding-induced emissions, hypothesizing that the induced emission response is greater and faster in physiologically more active species with greater photosynthetic activity than in less active species. Rapid highly repeatable leaf wounds (12-mm cuts) were generated by a within-leaf-chamber cutting knife. Wounding-induced VOC emissions were measured continuously with a proton-transfer reaction time-of-flight mass spectrometer and gas-chromatography mass spectrometry was used to separate isomers. Twenty-three ion VOCs and twelve terpenoid molecule structures were identified, whereas ubiquitous stress volatiles methanol (on average 40% of total emissions), hexenal (24%), and acetaldehyde (11%) were the main compounds across the species. Emissions of low-weight oxygenated compounds (LOC, 70% of total), and LOX products (29%) were positively correlated across species, but minor VOC components, monoterpenoids and benzenoids were negatively correlated with LOC and LOX, indicating a reverse relationship between signal specificity and strength. There was a large interspecific variability in the rate of induction and emission magnitude, but the hypothesis of a stronger emission response in physiologically more active species was only partly supported. In addition, the overall emission levels were somewhat lower with different emission blend compared to the data reported for wild species, as well as different shares for the VOCs in the blend. The study demonstrates that wounding-dependent emissions from tropical agricultural crops can significantly contribute to atmospheric volatiles, and these emissions cannot be predicted based on current evidence of wild plant model systems.
ARTICLE | doi:10.20944/preprints202109.0427.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Hand sanitizer; COVID-19; alcohol; methanol substitution; gas chromatography; substandard products; falsified products; post-market surveillance
Online: 24 September 2021 (12:25:25 CEST)
The emergence of the COVID-19 pandemic has propelled the use of alcohol-based hand sanitizers to the fore as a SARS-CoV-2 control measure. To be effective these products must comply with relevant quality parameters such as alcohol concentration, methanol limits and purity. The current study was designed to determine the quality of alcohol-based hand sanitizer products in the Nairobi metropolitan area. For this purpose, 74 commercially marketed samples were collected and subjected to analysis by gas chromatography. Only three samples (4.1%) complied with the regulatory specifications for alcohol content, methanol limits and pH. Five samples (6.8%) complied with the specification for alcohol content but did not meet methanol or pH limits. A total of 44 (59.5%) samples had methanol levels that exceeded threshold limits. Eleven samples (14.9%) were found with methanol substitution (i.e., methanol, instead of ethanol or isopropanol, was the main alcohol component). The results show that users of alcohol-based hand sanitizers are being exposed to substandard and falsified products which in addition to being non-efficacious pose harm due to unacceptable levels of toxic impurities. Regular, routine post-market surveillance is needed to prevent such products from reaching the market.
ARTICLE | doi:10.20944/preprints202002.0345.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: platinum electrocatalys; PtCu/C; oxygen electroreduction; methanol electrooxidation; catalyst activity; durability; fuel cell life tests; de-alloyed catalysts; PEM FC
Online: 24 February 2020 (03:56:11 CET)
Behavior of supported alloyed and de-alloyed platinum-copper catalysts, which contained 14% - 27% wt. of Pt, was studied in the reactions of methanol electrooxidation (MOR) and oxygen electroreduction (ORR) in 0.1 M HClO4 solutions. Alloyed PtCux/C catalysts were prepared by a multistage sequential deposition of copper and platinum onto a Vulcan XC72 dispersed carbon support. De-alloyed PtCux-y/C catalysts were prepared by PtCux/C materials pretreatment in acid solutions. The effects of the catalysts initial composition and the acid treatment condition on their composition, structure, and catalytic activity in MOR and ORR were studied. Functional characteristics of platinum-copper catalysts were compared with those of commercial Pt/C catalysts when tested, both in an electrochemical cell and in H2/Air membrane-electrode assembly (MEA). It was shown that the acid pretreatment of platinum-copper catalysts practically does not have negative effect on their catalytic activity, but it reduces the amount of copper passing into the solution during the subsequent electrochemical study. The activity of platinum-copper catalysts in the MOR and the current-voltage characteristics of the H2/Air PEMFC MEAs measured in the process of their life tests were much higher than those of the Pt/C catalysts.
ARTICLE | doi:10.20944/preprints201903.0097.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: Te nanotubes decorated with Pt nanoparticles; fuel cell neutral pH; oxygen reduction reaction; methanol oxidation reaction; X-ray photoelectron spectroscopy.
Online: 7 March 2019 (13:49:46 CET)
In fuel-cell technological development, one of the most important objectives is to minimize the amount of Pt, the most employed material as oxygen reduction and methanol oxidation electro-catalyst. In this paper we report the synthesis and characterization of Te nanotubes (TeNTs) decorated with Pt nanoparticles, readily prepared from stirred aqueous solutions of PtCl2 containing a suspension of TeNTs and ethanol acting as a reducing agent, avoiding the use of any hydrophobic surfactants as capping stabilizing substance. The as obtained TeNTs decorated with Pt nanoparticles (TeNTs/PtNPs) have been fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area diffraction patterns (SAD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). We demonstrate that the new material can be successfully employed in fuel cell either as anodic (for methanol oxidation reaction) and cathodic (for oxygen reduction reaction) electrode with high efficiency in terms of related mass activities and on-set improvement. Remarkably, the cell operates in aqueous electrolyte buffered at pH 7.0, thus avoiding acidic or alkaline conditions that may lead e. g. to Pt dissolution (at low pH) and paving the way for the development of biocompatible devices and on chip fuel cells.
ARTICLE | doi:10.20944/preprints201802.0054.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: Nisin; water soaked tiger nut milk (WSTM); toasted tiger nut milk (TTM); methanol soaked tiger nut milk (MSTM); and the pasteurised tiger nut milk (PTM)
Online: 6 February 2018 (10:15:54 CET)
Tiger nut (Cyperus esculentus) is an edible perennial grass-like plant that has long been recognized for its health benefits as it is rich in fiber, protein, vitamins, minerals and natural sugars. It can be eaten raw, roasted or made into a refreshing milk which is very nutritive and healthy for consumption. There were several efforts to mass-produce the locally prepared tiger nut milk in our locality, but the fact that it has a shorter shelf-life, brings about a hindrance. The main objective of the present study is to unveil the cause for the easily spoilage of tiger nut milk and device ways to promote its production using different treatments. Tiger nut milk products were prepared using different methods; water soaked tiger nut milk (WSTM), toasted tiger nut milk (TTM), methanol soaked tiger nut milk (MSTM), and the pasteurised tiger nut milk (PTM). Each of these milk proucts prepared was divided into two portions; the first portion is treated with an antibiotic preservative, Nisin and the second portion was left untreated. The two portions were further divided into two; one stored at refrigerating temperature and the other at room temperature, making four different treatments per mixture and a total of 16 samples. These samples were subjected to proximate analysis; protein, fat, moisture, ash and carbohydrate. The chemical composition of the samples was significantly (P < 0.05) affected by processing treatment. All the samples had high moisture content, and a considerable amount of fat. The preservative treated samples that received pasteurized treatment were found to stay more than a week with fair quality. Findings from the study shows that the chemical characteristics of the various milk products were significantly affected by the different processing treatments.