Showing papers on "Methanol published in 1996"
411 citations
TL;DR: In this paper, the authors used polybenzimidazole membrane doped with phosphoric acid (PBI) for use as a polymer electrolyte in a high temperature (ca. 150 to 200 C) proton exchange membrane direct methanol fuel cell.
Abstract: Recently, polybenzimidazole membrane doped with phosphoric acid (PBI) was found to have promising properties for use as a polymer electrolyte in a high temperature (ca. 150 to 200 C) proton exchange membrane direct methanol fuel cell. However, operation at 200 C in strongly reducing and oxidizing environments introduces concerns of the thermal stability of the polymer electrolyte. To simulate the conditions in a high temperature fuel cell, PBI samples were loaded with fuel cell grade platinum black, doped with ca. 480 mole percent phosphoric acid (i.e., 4.8 H{sub 3}PO{sub 4} molecules per PBI repeat unit) and heated under atmospheres of either nitrogen, 5% hydrogen, or air in a thermal gravimetric analyzer. The products of decomposition were taken directly into a mass spectrometer for identification. In all cases weight loss below 400 C was found to be due to loss of water. Judging from the results of these tests, the thermal stability of PBI is more than adequate for use as a polymer electrolyte in a high temperature fuel cell.
395 citations
TL;DR: In this paper, the effects of temperature, pressure, reactant concentration, weight hourly space velocity, and the type of catalyst on the gasification of glucose are reported, and complete conversion of glucose (22% by weight in water) to a hydrogen-rich synthesis gas was realized at a weight hourly velocity (WHSV) of 22.2 h-1 in supercritical water at 600 °C, 34.5 MPa.
Abstract: Spruce wood charcoal, macadamia shell charcoal, coal activated carbon, and coconut shell activated carbon catalyze the gasification of organic compounds in supercritical water. Feedstocks studied in this paper include glycerol, glucose, cellobiose, whole biomass feedstocks (depithed bagasse liquid extract and sewage sludge), and representative Department of Defense (DoD) wastes (methanol, methyl ethyl ketone, ethylene glycol, acetic acid, and phenol). The effects of temperature, pressure, reactant concentration, weight hourly space velocity, and the type of catalyst on the gasification of glucose are reported. Complete conversion of glucose (22% by weight in water) to a hydrogen-rich synthesis gas was realized at a weight hourly space velocity (WHSV) of 22.2 h-1 in supercritical water at 600 °C, 34.5 MPa. Complete conversions of the whole biomass feeds were also achieved at the same temperature and pressure. The destruction efficiencies for the representative DoD wastes were also high. Deactivation of the...
391 citations
TL;DR: In this paper, the kinetics of simultaneous methanol synthesis and reverse water-gas shift from CO2/H2 and CO 2/CO/H 2mixtures have been measured at low conversions over a clean Cu(110) single-crystal surface at pressures of 5.1 bar.
356 citations
TL;DR: In this paper, a series of nine large-scale, open fires was conducted in the Intermountain Fire Sciences Laboratory (IFSL) controlled-environment combustion facility, and mid-infrared spectra of the smoke were recorded throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy at 0.12 cm−1 resolution over a 3 m cross-stack pathlength and analyzed to provide pseudocontinuous, simultaneous concentrations of up to 16 compounds.
Abstract: A series of nine large-scale, open fires was conducted in the Intermountain Fire Sciences Laboratory (IFSL) controlled-environment combustion facility. The fuels were pure pine needles or sagebrush or mixed fuels simulating forest-floor, ground fires; crown fires; broadcast burns; and slash pile burns. Mid-infrared spectra of the smoke were recorded throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy at 0.12 cm−1 resolution over a 3 m cross-stack pathlength and analyzed to provide pseudocontinuous, simultaneous concentrations of up to 16 compounds. Simultaneous measurements were made of fuel mass loss, stack gas temperature, and total mass flow up the stack. The products detected are classified by the type of process that dominates in producing them. Carbon dioxide is the dominant emission of (and primarily produced by) flaming combustion, from which we also measure nitric oxide, nitrogen dioxide, sulfur dioxide, and most of the water vapor from combustion and fuel moisture. Carbon monoxide is the dominant emission formed primarily by smoldering combustion from which we also measure carbon dioxide, methane, ammonia, and ethane. A significant fraction of the total emissions is unoxidized pyrolysis products; examples are methanol, formaldehyde, acetic and formic acid, ethene (ethylene), ethyne (acetylene), and hydrogen cyanide. Relatively few previous data exist for many of these compounds and they are likely to have an important but as yet poorly understood role in plume chemistry. Large differences in emissions occur from different fire and fuel types, and the observed temporal behavior of the emissions is found to depend strongly on the fuel bed and product type.
353 citations
TL;DR: In this paper, the performance of a liquid-feed direct methanol fuel cell employing a proton exchange membrane electrolyte with Pt-Ru/C as anode and Pt-C as cathode is reported.
Abstract: The performance of a liquid-feed direct methanol fuel cell employing a proton-exchange membrane electrolyte with Pt-Ru/C as anode and Pt/C as cathode is reported. The fuel cell can deliver a power density of ca. 0.2 $W/cm^2$ at 95°C, sufficient to suggest that the stack construction is well worthwhile.Methanol crossover across the polymer electrolyte at concentrations beyond 2 M methanol affects the performance of the cell which appreciates with increasing operating temperature.
335 citations
TL;DR: In this article, the role of metal oxides such as Ga 2 O 3, Al 2 O 4, ZrO 2 and Cr 2 O 5, contained in Cu/ZnO-based ternary catalysts for methanol synthesis from CO 2 and H 2 was classified into two categories: to improve the Cu dispersion and to increase the specific activity.
Abstract: The role of metal oxides such as Ga 2 O 3 , Al 2 O 3 , ZrO 2 and Cr 2 O 3 contained in Cu/ZnO-based ternary catalysts for methanol synthesis from CO 2 and H 2 was classified into two categories: to improve the Cu dispersion and to increase the specific activity The Cu/ZnO-based multicomponent catalysts developed on the basis of the role of metal oxides were highly active and stable for a long period in a continuous methanol synthesis operation
287 citations
Patent•
09 Dec 1996TL;DR: In this paper, the platinum and ruthenium are more exactly mixed together and different materials are substituted for these materials to improve the performance of the fuel cell electrode, and a sputtered electrode is formed which is extremely porous.
Abstract: Improvements to non acid methanol fuel cells include new formulations for materials. The platinum and ruthenium are more exactly mixed together. Different materials are substituted for these materials. The backing material for the fuel cell electrode is specially treated to improve its characteristics. A special sputtered electrode is formed which is extremely porous.
284 citations
TL;DR: In this paper, a re-evaluation of kinetic data showed that methoxide base-catalyzed methanolysis of soybean oil at 40°C (6:1 methanol:oil molar ratio) to form methyl esters proceeds approximately 15 times more slowly than butanolysis at 30°C.
Abstract: A re-evaluation of kinetic data shows that the methoxide base-catalyzed methanolysis of soybean oil at 40°C (6:1 methanol:oil molar ratio) to form methyl esters proceeds approximately 15 times more slowly than butanolysis at 30°C. This is interpreted to be the result of a two-phase reaction in which methanolysis occurs only in the methanol phase. Low oil concentration in methanol causes the slow reaction rate; a slow dissolving rate of the oil in the methanol causes an initiation period. Intermediate mono- and diglycerides preferentially remain in the methanol, and react further, thus explaining the deviation from second-order kinetics. The same explanations apply for hydroxide ion catalyzed methanolysis. At the 6:1 methanol:oil molar ratio the addition of a cosolvent, such as 1.25 volumes of tetrahydrofuran (THF) per volume of methanol, produces an oil-dominant one-phase system in which methanolysis speeds up dramatically and occurs as fast as butanolysis. The critical separation of the glycerol-rich phase still occurs and does so faster than in the cosolvent-free system. For THF, recycle of solvent is simplified because of the similar boiling points of THF (67°C) and methanol (65°C). Possible explanations for the abnormal slowing of the methanolysis reactions are presented in terms of (1) lower rate constants for mono- and diglyceride reactions due to the formation of cyclic intermediates, (2) a fall in the polarity of the reaction mixture due to either methanol depletion or mixing of the oil, methanol and cosolvent, and (3) depletion of hydroxide ion when this is present.
277 citations
TL;DR: In this article, a wide compositional range of unsupported platinum-ruthenium alloy catalysts were prepared by thermal decomposition of the chlorides and chloroacids, and the electrocatalysts were also evaluated as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures.
Abstract: A wide compositional range of unsupported platinum-ruthenium alloy catalysts were prepared by thermal decomposition of the chlorides and chloroacids. The electrocatalysts were characterized by cyclic voltammetry, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The BET surface area of the electrocatalysts increases with increasing Ru content up to {approximately}70 atomic percent (a/o) and then reaches a plateau value. Electrodes fabricated from the electrocatalysts were also evaluated as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Unlike the situation for pure Pt, Ru is inactive for methanol electro-oxidation at 25 C but becomes active at higher temperatures. The peak current observed during an anodic potential scan gradually shifts to more cathodic potentials with increasing temperature. When a comparison is made on the basis of electrode geometric surface area, a {approximately}50 a/o ruthenium electrocatalyst provides the highest activity for methanol electro-oxidation at both 25 and 60C. The methanol electro-oxidation rate is 0.5 orders with respect to methanol concentration (between 0.1 and 2 M) for the Pt-Ru ({approximately}50:50) electrode.
273 citations
TL;DR: In this article, the role of hydrogen as inhibitor of methanol adsorption was confirmed once more by means of in situ FTIR spectra, which indicated that the splitting off of hydrogen atoms is superimposed on hydrogen desorption and gives rise to a well defined peak at polycrystalline and at Pt(100).
TL;DR: In this paper, the products of methanol crossover through the acid-doped polybenzimidazole polymer electrolyte membrane (PBI PEM) to the cathode of a prototype direct methanoline fuel cell (DMFC) were analyzed using multipurpose electrochemical mass spectrometry (MPEMS).
Abstract: The products of methanol crossover through the acid‐doped polybenzimidazole polymer electrolyte membrane (PBI PEM) to the cathode of a prototype direct methanol fuel cell (DMFC) were analyzed using multipurpose electrochemical mass spectrometry (MPEMS) coupled to the cathode exhaust gas outlet. It was found that the methanol crossing over reacts almost quantitatively to at the cathode with the platinum of the cathode acting as a heterogeneous catalyst. The cathode open‐circuit potential is inversely proportional to the amount of formed. A poisoning effect on the oxygen reduction also was found. Methods for the estimation of the methanol crossover rate at operating fuel cells are suggested.
TL;DR: In this article, a silicalite zeolite membrane supported on the inner surface of a porous stainless-steel cylindrical tube was used to separate organic and water mixtures.
TL;DR: In this article, aqueous nitrate solution was photolysed at 254 nm in the absence of oxidizable additives, in the presence of methanol or propan-2-ol and oxygen and in the case of cyclopentane under anaerobic conditions.
Abstract: Aqueous nitrate solutions were photolysed at 254 nm in the absence of oxidizable additives, in the presence of methanol or propan-2-ol and oxygen and in the presence of cyclopentane under anaerobic conditions. The main nitrogen-containing products are nitrite and peroxynitrite. The quantum yields depend on the pH, nitrate concentration, nature of the additive and the light intensity. The intrinsic nitrite yield in alkaline solutions could not be determined directly because, under the conditions of the nitrite assay, the accompanying peroxynitrite decomposes to form nitrite and nitrate; it is smaller than the apparent nitrite yield. In the acidic (pH 4–7) range, the intrinsic nitrite quantum yield is equal to the apparent nitrite yield because there is no buildup of peroxynitrite under these conditions. The apparent nitrite quantum yield increases from 0.01 (no oxidizable additive) to approximately 0.03 (cyclopentane (millimolar range), oxygen free) to 0.06 (methanol (millimolar range), air saturated). At pH 13 and in the absence of oxidizable additives, the apparent nitrite quantum yield increases to about 0.1, whereas from material balance considerations the intrinsic nitrite quantum yield is estimated to be 0.06, twice the oxygen quantum yield of 0.03. Spectrophotometrically, peroxynitrite is detected in the alkaline range only, because its protonated form is unstable.
In the absence of oxidizable additives, the quantum yield of peroxynitrite is about 0.1, i.e. only about two-thirds of the quantum yield in the presence of oxidizable additives. Mechanistic considerations on the basis of the pH dependence of the quantum yields of the products nitrite, peroxynitrite and oxygen, as well as their dependence on the kind of additive, indicate that the decisive factor of photolysis in the absence of additives is the formation of the nitric oxide peroxyl radical, ONOO, formed by reaction of peroxynitrite with the primarily generated OH radical. The decay of ONOO is the source of O2 in this system. Nitric oxide, NO, the other fragment of this decay reaction, reacts with nitrogen dioxide, which is one of the primarily formed intermediates. The latter reaction is one of the pathways to the product nitrite, particularly in the alkaline range. The formation of NO during photolysis has been verified by electron spin resonance (ESR) spectroscopic detection of the nitroxide 1,1,3,3-tetramethyl-isoindolin-2-oxyl, the NO adduct to 7,7,8,8-tetramethyl-o-quinodimethane.
Of the three primary processes discussed in the literature, we conclude that reactions (1) and (2) occur with quantum yields of approximately 0.09 and 0.1 respectively NO3−+hv→NO2+O−(O−+H2O→OH+OH−)(1)NO3−+hv→ONOO−(2) It appears that none of the peroxynitrite anion is formed in a cage reaction through the recombination of the primary fragments from reaction (1). The primary process shown in reaction (3) is of relatively minor importance, with a quantum yield of no more than 0.001 NO3−+hv→NO2−+O(3)
In the presence of methanol (or propan-2-ol) and oxygen under acidic conditions, formaldehyde (or acetone) is formed in an amount equivalent to nitrite via peroxyl radical reactions (quantum yield of approximately 0.06 for both alcohols). In the alkaline range, the apparent formaldehyde quantum yield decreases with increasing pH, while formic acid is produced in increasing amounts. The formation of formic acid is ascribed to the reaction of peroxynitrite anion with photolytically generated formaldehyde. The acetone quantum yield does not decrease with increasing pH over the whole alkaline pH range.
In the presence of cyclopentane under oxygen-free conditions, apart from nitrite (and peroxynitrite when alkaline), the compounds nitrocyclopentane, cyclopentyl nitrate, cyclopentene, cyclopentanol and cyclopentanone are produced. The formation of the organic nitrogen compounds leads to an increase in the pH as photolysis proceeds. This pH shift is particularly pronounced in the neutral range.
TL;DR: A submitted manuscript is the version of the article upon submission and before peer-review as mentioned in this paper, while a published version is the final layout of the paper including the volume, issue and page numbers.
Abstract: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.
TL;DR: In this article, a direct methanol/oxygen solid polymer electrolyte fuel cell was demonstrated, which employed a 4 mg cm−2 Pt-Ru alloy electrode as an anode, a 4 cm −2 Pt black electrode as a cathode, and an acid-doped polybenzimidazole membrane as the solid polymers electrolyte.
Abstract: A direct methanol/oxygen solid polymer electrolyte fuel cell was demonstrated. This fuel cell employed a 4 mg cm−2 Pt-Ru alloy electrode as an anode, a 4 mg cm−2 Pt black electrode as a cathode and an acid-doped polybenzimidazole membrane as the solid polymer electrolyte. The fuel cell is designed to operate at elevated temperature (200°C) to enhance the reaction kinetics and depress the electrode poisoning, and reduce the methanol crossover. This fuel cell demonstrated a maximum power density about 0.1 W cm−2 in the current density range of 275–500 mA cm−2 at 200°C with atmospheric pressure feed of methanol/water mixture and oxygen. Generally, increasing operating temperature and water/methanol mole ratio improves cell performance mainly due to the decrease of the methanol crossover. Using air instead of the pure oxygen results in approximately 120 mV voltage loss within the current density range of 200–400 mA cm−2 .
TL;DR: In this paper, the pyrolysis of olive and grape bagasse has been studied with the aim of determining the main characteristics of the charcoals formed and the nature and quantity of gases and liquids produced.
Abstract: The pyrolysis of olive and grape bagasse has been studied with the aim of determining the main characteristics of the charcoals formed and the nature and quantity of gases and liquids produced. Variables investigated were temperature between 300 and 900°C and particle size between 0.4 and 2 mm diameter. Experiments were carried out in an isothermal manner. As a general rule, particle size does not exert any influence, whereas temperature is a very significant variable. Thus an increase in this variable yields an increase in the fixed carbon content, gases produced and, to a lesser extent, ash percentage. On the other hand, volatile material and solid yields decrease with increasing temperature. The principal gases generated are H2, CH4, CO and CO2, while among the liquid components the presence of methanol, acetone, furfuryl alcohol, phenol, furfural, naphthalene and o-cresol has to be highlighted. Heating values of both gas and solid phases were determined from gas composition and elemental carbon analysis. The quality of charcoals and heating value allow the conclusion that the most convenient temperature for the pyrolysis should be between 600 and 700°C, at which the production of liquids is at its maximum. Finally, a kinetic study of the pyrolysis, based on gas generation from thermal decomposition of residues, has been carried out. From this model, rate constants for the formation of each gas and their corresponding activation energies were determined.
Patent•
22 Mar 1996TL;DR: In this paper, a method is provided to improve the quality of recycle of certain residues by modifying the separation of alkanes and alkane-like materials and carbonyl-containing impurities from the recycle during the manufacture of acetic acid by the carbonylation of methanol.
Abstract: A method is provided to improve the quality of recycle of certain residues by modifying the separation of alkanes and alkane-like materials and carbonyl-containing impurities from the recycle during the manufacture of acetic acid by the carbonylation of methanol. The improvement comprises partitioning the residues by the addition of water obtained from aqueous streams containing up to 50 wt.% acetic acid and which have been treated in a catalytic distillation unit to react the acetic acid with methanol to form recyclable methyl acetate and water and wherein the water is separated from the organics by distillation.
TL;DR: In this article, a vapor-feed direct methanol fuel cell based on a Nafion 117 solid polymer electrolyte was investigated, and the structure, surface, and morphology of the catalysts were investigated by X-ray powder diffraction, Xray photoelectron spectroscopy, and transmission electron microscopy.
Abstract: A vapor-feed direct methanol fuel cell based on a Nafion 117{reg_sign} solid polymer electrolyte was investigated. Pt-Ru/C and Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. The structure, surface, and morphology of the catalysts were investigated by X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Crystalline face-centered cubic phases were found in the Pt and Pt-Ru catalysts. The alloy composition in the Pt-Ru/C catalyst was different from the nominal composition, probably due to the formation of surface RuO{sub x} species, as indicated by X-ray photoelectron spectroscopy. Transmission electron microscopy observation showed an increase of the average particle size and particle agglomeration in the Pt-Ru/C catalyst compared to the Pt/C catalyst. The membrane/electrode assembly was prepared by using a paste process method. Scanning electron microscopy and energy dispersive X-ray analyses showed good adhesion of catalyst layers to the membrane and a homogeneous distribution of the ionomer inside the catalyst. AC-impedance and galvanostatic steady-state polarization techniques were used to investigate the electrochemical performance of the direct methanol fuel cell.
TL;DR: In this article, the effect of gold catalysts on CO removal from hydrogen was investigated in polymer electrolyte fuel cells using the reformed gas of methanol, showing that gold supported on manganese oxide is especially effective in the selective removal of hydrogen from hydrogen.
TL;DR: In this article, a new synthesis route of dimethyl carbonate (DMC) was found from carbon dioxide and methanol catalyzed by base catalysts and in the presence of CH 3 I promoter.
Abstract: The new synthesis route of dimethyl carbonate (DMC) was found from carbon dioxide and methanol catalyzed by base catalysts and in the presence of CH 3 I promoter.
TL;DR: Gold deposited on various oxides with high dispersion was found to be active for the hydrogenation of CO 2 at temperatures between 150 and 400°C and smaller gold particles gave higher methanol productivity per exposed surface area of gold as mentioned in this paper.
TL;DR: In this paper, a complete kinetic equation for describing the reaction catalyzed by Amberlyst 15 was developed, which can be used in the simulation and design of the catalytic distillation column for removing acetic acid from wastewater.
Abstract: Computer simulation showed that catalytic distillation is an attractive process for the removal of dilute acetic acid from wastewater. Selection of catalysts and kinetic data have been obtained for the design of the catalytic distillation column.
Kinetic measurements were conducted in a batch reactor. Methanol was added to the dilute acetic acid solutions and reacted with the acid in water to form methyl acetate and water. The reaction can be catalyzed by solid acid catalysts. It was found that Amberlyst 15 was an effective catalyst for this reaction. The effects of stirrer speed, reaction temperature, reactant concentration and catalyst loading on reaction rate were investigated. A complete kinetic equation for describing the reaction catalyzed by Amberlyst 15 was developed. This equation can be used in the simulation and design of the catalytic distillation column for removing acetic acid from wastewater.
TL;DR: In this paper, a solid-state ion exchange at 650°C was applied to elucidate the reaction mechanism for gas-phase oxidative carbonylation of methanol to make dimethyl carbonate and the ion-exchanged Cu(II)Y showed very little activity for the same reaction.
TL;DR: In this paper, first-principles calculations performed on periodic zeolite models to investigate the nature of methanol adsorption were performed and the vibrational spectra of the adsorbed species were compared to experimental results.
Abstract: The methanol to gasoline (MTG) conversion process, using a zeolite catalyst, is of major commercial importance. However, the first step of the reaction, involving methanol adsorption on the zeolite catalyst, is still not well understood. This paper describes first-principles calculations performed on periodic zeolite models to investigate the nature of methanol adsorption. We have examined a number of possible geometries for this adsorption and found that the nature of the adsorbed species can depend on the particular zeolite structure. In more open ring structures, as found in chabazite, the stable form of methanol is found to be protonated, in contrast to results of previous calculations on cluster models. However, in the sodalite structure methanol is found to be simply physisorbed. The vibrational spectra of the adsorbed species have been studied and compared to experimental results. It is found that both chemisorbed methanol and physisorbed methanol give strongly red-shifted O−H stretching frequencie...
TL;DR: In this article, the electro-oxidation of formic acid was studied in a directoxidation polymer-electrolyte fuel cell at 170 C using real-time mass spectrometry.
Abstract: The electro-oxidation of formic acid was studied in a direct-oxidation polymer-electrolyte fuel cell at 170 C using real-time mass spectrometry. The results are compared with those obtained for methanol oxidation under the same conditions. Formic acid was electrochemically more active than methanol on both Pt-black and Pt-Ru catalysts. The polarization potential of formic acid oxidation was ca. 90 to 100 mV lower than that of methanol. The oxidation of formic acid was dependent on the water/formic acid mole ratio. The best anode performance was obtained using a water/formic acid mole ratio of {approximately}2. In addition, Pt/Ru catalyst was more active than Pt-black for formic acid oxidation. The mass spectrometric results showed that CO{sub 2} is the only reaction product of formic acid oxidation. The results are discussed in terms of possible formic acid oxidation mechanisms.
TL;DR: In this paper, the influence of surface oxides of the activated carbon was experimentally studied on the adsorption characteristics of eleven different gases or vapors, including cyclohexane, benzene, 2-propanol and 2-butanol, and it was found that the isotherms on the carbon oxidized by HNO3 were much lower than those on the original carbon except in the low partial pressure range.
TL;DR: In this paper, it was shown that the active phase for methanol dehydration is fine crystallites of CuO/ZnO/γ-Al2O3 and that the most active dehydration catalyst is Na2CO3.
Abstract: Based on the knowledge of the mechanisms of methanol synthesis and methanol dehydration, it was predicted that if the dispersion of CuO/ZnO/γ-Al2O3 in hybrid catalysts for direct synthesis of dimethyl ether from synthesis gas was enhanced, the formation rate of dimethyl ether would be increased. In order to justify the prediction, five preparation methods, including two mechanical mixing ones and three co-precipitation ones were used to prepare the catalysts. It was found that co-precipitation impregnation and co-precipitation of Cu/Zn by NaAlO2 provided the catalyst with the highest activity and co-precipitation of Cu/Zn/Al by Na2CO3 resulted in the worst catalyst. Combined with the XRD results it is deduced that the active phases for direct synthesis of dimethyl ether from synthesis gas are highly-dispersed fine crystallites of CuO/ZnO/γ-Al2O3. Calcination temperature of the precursor of γ-alumina used in the methods of mechanical mixing was also studied. It was found that a calcination temperature of 550°C brought about the most active dehydration catalyst with the largest surface area and nearly pure γ-alumina of poor crystallinity. So it might be concluded that the active phase for methanol dehydration is fine crystallites of γ-alumina.
TL;DR: In this paper, the dynamics of CO and CO2/hydrogen reactant mixtures over both the prereduced and unreduced catalyst with the aim of acquiring information on the methanol synthesis mechanism.
Abstract: Hydrogenation reactions occurring on the surface of a copper/zirconia (Cu:Zr = 30:70 atom %) catalyst, which had previously been loaded by adsorption of formic acid, CO, and CO2, have been studied by means of in situ diffuse reflectance FTIR spectroscopy Besides characterizing the reactivity of adsorbates, the dynamics of CO and CO2/hydrogen reactant mixtures has been monitored over both the prereduced and unreduced catalyst, with the aim of acquiring information on the methanol synthesis mechanism Surface formates, which have previously been identified as intermediates in the catalytic reduction of carbon oxides yielding methane, appear to be spectator species in methanol synthesis over ZrO2 supported catalysts The latter synthesis, when using CO2 as the reactant, starts from surface carbonate, which is first reduced to yield adsorbed carbon monoxide and water The desired methanol product is generated via surface-bound formaldehyde and methoxy species