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Showing papers on "Methanol published in 1999"


Journal ArticleDOI
TL;DR: In this paper, the molar ratio of alcohol, reaction temperature, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing biodiesel.
Abstract: Vegetable oils and animal fats can be transesterified to biodiesel for use as an alternative diesel fuel. Conversion of low cost feedstocks such as used frying oils is complicated if the oils contain large amounts of free fatty acids that will form soaps with alkaline catalysts. The soaps can prevent separation of the biodiesel from the glycerin fraction. Alternative processes are available that use an acid catalyst. The objective of this study was to investigate the effect of process variables on acid-catalyzed transesterification. The molar ratio of alcohol, reaction temperature, catalyst amount, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing biodiesel. Food grade soybean oil was used to prepare esters using excess methanol and sulfuric acid as a catalyst. To compare the effect of different alcohol types on ester formation, methanol, ethanol, 2-propanol, and n-butanol were compared. The American Oil Chemists’ Society Method Ca 14-56 was used to measure the biodiesel’s total glycerin amount as an indicator of the completeness of the reaction. It was found that acid catalysis can provide high conversion rates but much longer times are required than for alkaline catalysts. The acid catalyst also requires the concentration of water to be less than 0.5%, which is about the same as is required for alkaline catalysts. Water formed by the esterification of free fatty acids limited their presence in the oil to 5%.

774 citations


Journal ArticleDOI
TL;DR: Fomepizole is the preferred antidote for methanol poisoning and although there are no clinical outcome data confirming the superiority of either of these antidotes over the other, there are significant disadvantages associated with ethanol.
Abstract: Epidemiology: Almost all cases of acute methanol toxicity result from ingestion, though rarely cases of poisoning have followed inhalation or dermal absorption. The absorption of methanol following oral administration is rapid and peak methanol concentrations occur within 30–60 minutes. Mechanisms of Toxicity: Methanol has a relatively low toxicity and metabolism is responsible for the transformation of methanol to its toxic metabolites. Methanol is oxidized by alcohol dehydrogenase to formaldehyde. The oxidation of formaldehyde to formic acid is facilitated by formaldehyde dehydrogenase. Formic acid is converted by 10-formyl tetrahydrofolate synthetase to carbon dioxide and water. In cases of methanol poisoning, formic acid accumulates and there is a direct correlation between the formic acid concentration and increased morbidity and mortality. The acidosis observed in methanol poisoning appears to be caused directly or indirectly by formic acid production. Formic acid has also been shown to inhibit cyto...

666 citations


Journal ArticleDOI
TL;DR: In this paper, the authors attempted continuous methanolysis of vegetable oil by an enzymatic process, which was conducted by adding methanol stepwise to avoid lipase inactivation.
Abstract: Biodiesel derived from vegetable oils has drawn considerable attention with increasing environmental consciousness. We attempted continuous methanolysis of vegetable oil by an enzymatic process. Immobilized Candida antarctica lipase was found to be the most effective for the methanolysis among lipases tested. The enzyme was inactivated by shaking in a mixture containing more than 1.5 molar equivalents of methanol against the oil. To fully convert the oil to its corresponding methyl esters, at least 3 molar equivalents of methanol are needed. Thus, the reaction was conducted by adding methanol stepwise to avoid lipase inactivation. The first step of the reaction was conducted at 30°C for 10 h in a mixture of oil/methanol (1:1, mol/mol) and 4% immobilized lipase with shaking at 130 oscillations/min. After more than 95% methanol was consumed in ester formation, a second molar equivalent of methanol was added and the reaction continued for 14 h. The third molar equivalent of methanol was finally added and the reaction continued for 24 h (total reaction time, 48 h). This three-step process converted 98.4% of the oil to its corresponding methyl esters. To investigate the stability of the lipase, the three-step methanolysis process was repeated by transferring the immobilized lipase to a fresh substrate mixture. As a result, more than 95% of the ester conversion was maintained even after 50 cycles of the reaction (100 d).

599 citations


Journal ArticleDOI
TL;DR: In this paper, the transesterification of rapeseed oil by methyl alcohol can be catalysed effectively by basic alkaline-earth metal compounds: calcium oxide, calcium methoxide and barium hydroxide.

528 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed a surface mechanism for methanol-steam reforming on Cu/ZnO/Al 2 O 3 catalysts which account for all three of the possible overall reactions: (i) hydrogen adsorption does not compete for the active sites which the oxygen-containing species adsorb on, (ii) there are separate active sites for the decomposition reaction distinct from the other two reactions, and (iii) the rate-determining step (RDS) for both the reaction and the reaction is the dehydrogenation of adsorbed
Abstract: Surface mechanisms for methanol–steam reforming on Cu/ZnO/Al 2 O 3 catalysts are developed which account for all three of the possible overall reactions: methanol and steam reacting directly to form H 2 and CO 2 , methanol decomposition to H 2 and CO and the water-gas shift reaction. The elementary surface reactions used in developing the mechanisms were chosen based on a review of the extensive literature concerning methanol synthesis on Cu/ZnO/Al 2 O 3 catalysts and the more limited literature specifically dealing with methanol–steam reforming. The key features of the mechanism are: (i) that hydrogen adsorption does not compete for the active sites which the oxygen-containing species adsorb on, (ii) there are separate active sites for the decomposition reaction distinct from the active sites for the methanol–steam reaction and the water-gas shift reaction, (iii) the rate-determining step (RDS) for both the methanol–steam reaction and the methanol decomposition reaction is the dehydrogenation of adsorbed methoxy groups and (iv) the RDS for the water-gas shift reaction is the formation of an intermediate formate species. A kinetic model was developed based on an analysis of the surface mechanism. Rate data were collected for a large range of conditions using a fixed-bed differential reactor. Parameter estimates for the kinetic model were obtained using multi-response least squares non-linear regression. The resultant model was able to accurately predict both the rates of production of hydrogen, carbon dioxide and of carbon monoxide for a wide range of operating conditions including pressures as high as 33 bar.

521 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that in order to explain the complete range of observed product compositions, rate expressions for all three reactions (methanol-steam reforming, water-gas shift and methanol decomposition) must be included in the kinetic analysis and variations in the selectivity and activity of the catalyst indicate that the decomposition reaction occurs on a different type of active site than the other two reactions.
Abstract: On-board generation of hydrogen by methanol–steam reforming on Cu/ZnO/Al 2 O 3 catalyst is being used in the development of fuel-cell engines for various transportation applications. There has been disagreement concerning the reactions that must be included in the kinetic model of the process. Previous studies have proposed that the process can be modelled as either the decomposition of methanol followed by the water-gas shift reaction or the reaction of methanol and steam, to form CO 2 and hydrogen, perhaps followed by the reverse water-gas shift reaction. Experimental results are presented which clearly show that, in order to explain the complete range of observed product compositions, rate expressions for all three reactions (methanol–steam reforming, water-gas shift and methanol decomposition) must be included in the kinetic analysis. Furthermore, variations in the selectivity and activity of the catalyst indicate that the decomposition reaction occurs on a different type of active site than the other two reactions. Although the decomposition reaction is much slower than the reaction between methanol and steam, it must be included in the kinetic model since the small amount of CO that is produced can drastically reduce the performance of the anode electrocatalyst in low temperature fuel cells.

500 citations


Journal ArticleDOI
TL;DR: In this article, a liquid-fed Direct Methanol Fuel Cell (DMFC) working at 145°C was demonstrated by using a composite membrane made of Nafion ® ionomer and silica.

410 citations


Journal ArticleDOI
TL;DR: In this paper, 4,6-dimethoxy-1, 3,5-triazin-2(1H)-one was obtained by esterification of caiboxylic acids with DMTMM in methanol, ethanol, isopropy1 alcohol, or t-butyl alcohol.

403 citations


Journal ArticleDOI
TL;DR: In this article, the 13 most likely intermediate species for methanol oxidation on clusters of all 2nd and 3rd row Group VIII transition metals for all three likely binding sites (top, bridge, and cap) were calculated.
Abstract: Using first principles quantum mechanics [nonlocal density functional theory (B3LYP)], we calculated the 13 most likely intermediate species for methanol oxidation on clusters of all 2nd and 3rd row Group VIII transition metals for all three likely binding sites (top, bridge, and cap). This comprehensive set of binding energies and structures allows a detailed analysis of possible reaction mechanisms and how they change for different metals. This illustrates the role in which modern quantum chemical methods can be used to provide data for combinatorial strategies for discovering and designing new catalysts. We find that methanol dehydrogenation is most facile on Pt, with the hydrogens preferentially stripped off the carbon end. However, water dehydrogenation is most facile on Ru. These results support the bifunctional mechanism for methanol oxidation on Pt−Ru alloys in direct methanol fuel cells (DMFCs). We find that pure Os is capable of performing both functionalities without cocatalyst. We suggest that...

399 citations


Journal ArticleDOI
TL;DR: In this paper, a series of different copper-containing catalysts are described and it is shown that of these sequentially precipitated Cu/ZnO/ZrO 2 /Al 2 O 3 materials have the highest activities and stabilities for the steam reforming reaction.

392 citations


Journal ArticleDOI
TL;DR: In this paper, polybenzimidazoleolemic membranes have been used for direct methanol fuel cell applications and have been shown to have up to a 15-fold improvement over Nafion.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated small-pore molecular sieves as catalysts for the conversion of methanol to light olefins (MTO) and found that SAPO-34 exhibits the best performance based on catalyst life, selectivity to C2-C4 olefs, minimum paraffinic and aromatic byproducts and catalyst stability and regenerability.

Journal ArticleDOI
TL;DR: A new enzymatic method of synthesizing methyl ester from plant oil and methanol in a solvent-free reaction system was developed and it is anticipated that such plant oil methyl esters can be used as a biodiesel fuel in the future.

Journal ArticleDOI
TL;DR: The role of zinc oxide as a base for methanol synthesis is investigated in this article, where it is shown that, only under conditions of deficiency of hydrogen on the copper phase, hydrogen dissociation on zinc oxide, followed by hydrogen spillover to copper, is significant.
Abstract: All commercial catalysts for methanol synthesis and for the water–gas shift reaction in the low temperature region contain zinc oxide in addition to the main active component, copper. The varied benefits of zinc oxide are analysed here. The formation of zincian malachite and other copper/zinc hydroxy carbonates is essential in the production of small, stable copper crystallites in the final catalyst. Further, the regular distribution of copper crystallites on the zinc oxide phase ensures long catalyst life. Zinc oxide also increases catalyst life in the water–gas shift process by absorbing sulphur poisons but it is not effective against chloride poisons. In methanol synthesis, zinc oxide (as a base) removes acidic sites on the alumina phase which would otherwise convert methanol to dimethyl ether. Although bulk reduction of zinc oxide to metallic zinc does not take place, reduction to copper–zinc alloy (brass) can occur, sometimes as a surface phase only. A new interpretation of conflicting measurements of adsorbed oxygen on the copper surfaces of methanol synthesis catalysts is based on the formation of Cu–O–Zn sites, in addition to oxygen adsorbed on copper alone. The possible role of zinc oxide as well as copper in the mechanisms of methanol synthesis is still the subject of controversy. It is proposed that, only under conditions of deficiency of adsorbed hydrogen on the copper phase, hydrogen dissociation on zinc oxide, followed by hydrogen spillover to copper, is significant.

Journal ArticleDOI
TL;DR: In this paper, the performance of a liquid feed direct methanol fuel cell based on a Nafion® solid polymer electrolyte membrane is reported, which uses a porous Pt-Ru-carbon supported catalyst anode.

Journal ArticleDOI
TL;DR: In this article, the modified nickel hydroxide/glassy carbon electrode (MNGC) showed a stable voltammetric response even when it was stored under dry conditions.

Journal ArticleDOI
TL;DR: In this paper, an enzymatically coupled sequential reduction of carbon dioxide to methanol by using a series of reactions catalyzed by three different dehydrogenases was described. But the authors did not consider the use of enzymes as catalysts for conversion.
Abstract: Strategies for effective conversion of atmospheric CO{sub 2} to methanol offer promising new technologies not only for recycling of the greenhouse gas but also for an efficient production of fuel alternatives. Partial hydrogenation of carbon dioxide has been accomplished by means of heterogeneous catalysis, electrocatalysis, and photocatalysis. Oxide-based catalysts are predominantly used for industrial fixation of carbon dioxide. A unique approach in this direction involves the use of enzymes as catalysts for conversion of carbon dioxide to methanol. The use of enzymes is particularly appealing since it provides a facile low-temperature route for generation of methanol directly from gaseous carbon dioxide. The authors report an enzymatically coupled sequential reduction of carbon dioxide to methanol by using a series of reactions catalyzed by three different dehydrogenases. Overall, the process involves an initial reduction of CO{sub 2} to formate catalyzed by formate dehydrogenase (F{sub ate}DH), followed by reduction of formate to formaldehyde by formaldehyde dehydrogenase (F{sub ald}DH), and finally formaldehyde is reduced to methanol by alcohol dehydrogenase (ADH). In this process, reduced nicotinamide adenine dinucleotide (NADH) acts as a terminal electron donor for each dehydrogenase-catalyzed reduction.

Journal ArticleDOI
01 Sep 1999-Fuel
TL;DR: In this article, the depolymerization of Kraft and organosolv-derived lignins by KOH in supercritical methanol or ethanol was studied in rapidly heated batch microreactors.

Journal ArticleDOI
TL;DR: In this paper, the significance of abiological production of partially oxidized volatile organic carbons (POVOCs) from the decay of dead plant material was called to the attention of the authors.
Abstract: In this paper, attention is called to the significance of abiological production of partially oxidized volatile organic carbons (POVOCs) from the decay of dead plant material. Measured relative emission of acetone and methanol can be at least 10−4 and 3 - 5 × 10−4 g g−1of decaying dry plant matter, respectively. If these results may be extrapolated, global annual emissions of 6–8 Tg of acetone and 18 – 40 Tg of methanol would result, adding strongly to the estimated total emissions of these compounds to the atmosphere. Because acetone and methanol, through OH and HO2 formation, play significant roles in the chemistry of the atmosphere, further research is strongly needed to quantify the emissions of acetone, methanol, and other POVOCs

Journal ArticleDOI
TL;DR: Dimethyl carbonate was synthesized from methanol and CO2 with high selectivity using ZrO2 catalysts as discussed by the authors, but the amount of dimethyl ether and CO was below the detection limit.
Abstract: Dimethyl carbonate was synthesized from methanol and CO2 with high selectivity using ZrO2 catalysts. In this reaction, the amount of dimethyl ether and CO was below the detection limit. The catalytic activity seems to be related to acid–base pair sites of the ZrO2 surface from the results of temperature‐programmed desorption of NH3 and CO2.

Journal ArticleDOI
TL;DR: In this article, the reverse water-gas-shift reaction (RWReaction) was used to remove water before methanol was synthesized, and the purge gas volume was minimized as the recycle gas volume decreased.
Abstract: The CAMERE process (carbon dioxide hydrogenation to form methanol via a reverse-water-gas-shift reaction) was developed and evaluated. The reverse-water-gas-shift reactor and the methanol synthesis reactor were serially aligned to form methanol from CO2 hydrogenation. Carbon dioxide was converted to CO and water by the reverse-water-gas-shift reaction (RWReaction) to remove water before methanol was synthesized. With the elimination of water by RWReaction, the purge gas volume was minimized as the recycle gas volume decreased. Because of the minimum purge gas loss by the pretreatment of RWReactor, the overall methanol yield increased up to 89% from 69%. An active and stable catalyst with the composition of Cu/ZnO/ZrO2/Ga2O3 (5:3:1:1) was developed. The system was optimized and compared with the commercial methanol synthesis processes from natural gas and coal.


Journal ArticleDOI
TL;DR: In this article, the authors investigated the kinetics of the dual catalytic methanol and dimethyl ether (DME) synthesis process over a commercial CuO/ZnO/Al2O3 (methanol forming) and a γ-alumina (dehydration) catalyst using a gradientless, internal-recycle-type reactor.

Journal ArticleDOI
TL;DR: In this paper, the interaction of methanol with Cu/SiO 2, ZrO 2 /SiO2, and Cu/ZrO2 /Si O 2 has been investigated by in situ infrared spectroscopy and temperature programmed desorption and reaction with the aim of understanding the nature of the species and the mechanism involved in methanology decomposition.

Journal ArticleDOI
TL;DR: In this article, an AgBr/SiO2 catalyst prepared from Schumann emulsion has been used for photolysis of CH3OH/H2O solution under UV illumination, H2 generation was observed and hydrogen was continuously evolved for 200 h without destruction of AgBr although Ag0 was detected by X-ray diffraction analysis after the reaction.
Abstract: A AgBr/SiO2 catalyst prepared from Schumann emulsion has been used for photolysis of CH3OH/H2O solution. Under UV illumination, H2 generation was observed and hydrogen was continuously evolved for 200 h without destruction of AgBr although Ag0 was detected by X-ray diffraction analysis after the reaction. It is presumed that the hydrogen production from methanol in distilled water occurs on the Ag0 and the support plays important roles for the photocatalysis as well as TiO2/SiO2 (J. Phys. Chem. B 1997, 101, 2611).

Journal ArticleDOI
TL;DR: In this paper, the structural and catalytic properties of metal/zirconia catalysts are compared and possible reaction pathways are discussed, and possible routes of reaction are discussed.
Abstract: Metal/zirconia catalysts have attracted considerable interest for the hydrogenation of carbon dioxide. Various preparation methods such as impregnation, co-precipitation, sol–gel synthesis, and controlled oxidation of amorphous metal alloys have been used, leading to catalysts with very different properties. The catalytic behaviour of these materials is greatly influenced by the active metal and by the interfacial contact area between the metal and zirconia. Cu and Ag catalyse mainly methanol formation, while methane is formed over, e.g., Ni, Ru and Rh. Examples for less reactive metal constituents are Pd, Rh, Pt and Au, catalysing simultaneously the formation of methanol, carbon monoxide (by reverse water–gas shift reaction) and methane. The structural and catalytic properties of the various catalysts are compared and possible reaction pathways are discussed.

Journal ArticleDOI
TL;DR: In this article, a study was made of the reaction of transesterification of Cynara cardunculus L. oil by means of methanol, using sodium hydroxide, potassium hydroxides, and sodium methoxide as catalysts.
Abstract: A study was made of the reaction of transesterification of Cynara cardunculus L. oil by means of methanol, using sodium hydroxide, potassium hydroxide, and sodium methoxide as catalysts. The objective of the work was to characterize the methyl esters for use as biodiesels in internal combustion motors. The operation variables used were methanol concentration (5−21 wt %), catalyst concentration (0.1−1 wt %), and temperature (25−60 °C). The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by determining its density, viscosity, high heating value, cetane index, cloud and pour points, Ramsbottom carbon residue, characteristics of distillation, and flash and combustion points according to ISO norms. The biodiesel with the best properties was obtained using 15% methanol, sodium methoxide as catalyst (1%), and 60 °C temperature. This biodiesel has very similar properties to those of diesel ...

Journal ArticleDOI
TL;DR: In this article, the electrochemical reduction of CO2 with a Cu electrode in CsOH/methanol-based electrolyte was investigated, and the main products from CO2 were methane, ethylene, ethane, carbon monoxide, and formic acid.

Journal ArticleDOI
TL;DR: In this article, the photocatalytic oxidations of methanol, ethanol and chloroform, trichloroethylene (TCE), and dichloropropionic acid (DCP) in M/TiO2 aqueous slurries are studied.

Journal ArticleDOI
TL;DR: In this article, an isothermal steady-state model of an anode in a direct methanol feed, polymer electrolyte fuel cell is presented, where the anode is considered to be a porous electrode consisting of an electronically conducting catalyst structure.
Abstract: An isothermal, steady-state model of an anode in a direct methanol feed, polymer electrolyte fuel cell is presented. The anode is considered to be a porous electrode consisting of an electronically conducting catalyst structure that is thinly coated with an ion-selective polymer electrolyte. The pores are filled with a feed solution of 2 M methanol in water. Four species are transported in the anode: water, methanol, hydrogen ions, and carbon dioxide. All four species are allowed to transport in the x-direction through the depth of the electrode. Species movement in the pseudo y-direction is taken into account for water, methanol, and carbon dioxide by use of an effective mass-transfer coefficient. Butler-Volmer kinetics are observed for the methanol oxidation reaction. Predictions of the model have been fitted with kinetic parameters from experimental data, and a sensitivity analysis was performed to identify critical parameters affecting the anode`s performance. Kinetic limitations are a dominant factor in the performance of the system. At higher currents, the polymer electrolyte`s conductivity and the anode`s thickness were also found to be important parameters to the prediction of a polymer electrolyte membrane fuel cell anode`s behavior in the methanol oxidation region 0.5--0.6 V vs. a reversible hydrogen electrode.