Showing papers on "Methanol published in 1994"
TL;DR: The use of a supercritical phase, in which hydrogen is highly miscible, leads to a very high initial rate of reaction up to 1,400 moles of formic acid per mole of catalyst per hour as discussed by the authors.
Abstract: THE use of carbon dioxide as a starting material for the synthesis of organic compounds has long been a goal for synthetic chemists. The hydogenation of carbon dioxide to formic acid, methanol and other organic substances is particularly attractive, but has remained difficult. This route to formic acid has been described recently, based on the use of organometallic rhodium catalysts in dimethyl sulphoxideII and aqueous2 solvents. We report here the efficient production of formic acid in a supercritical mixture of carbon dioxide and hydrogen containing a catalytic ruthenium() phosphine complex. The use of a supercritical phase, in which hydrogen is highly miscible, leads to a very high initial rate of reaction up to 1,400 moles of formic acid per mole of catalyst per hour. The same reaction under identical conditions but in liquid organic solvents is much slower. Our results suggest that supercritical fluids represent a promising medium for homogeneous catalysis.
611 citations
TL;DR: In this paper, 13C-Methanol and 12C ethene were co-reacted over SAPO-34 in a flow system at 400°C using argon as a carrier (diluent) gas.
597 citations
TL;DR: In this article, the authors measured the kinetics of methanol electro-oxidation on well-characterized Pt-Ru alloy surfaces as a function of temperature and found that the activity of Ru towards the dissociative adsorption of Methanol is a strong function of the temperature.
Abstract: The kinetics of methanol electro-oxidation on well-characterized Pt-Ru alloy surfaces were measured in sulfuric acid solution as a function of temperature. The alloy surfaces were prepared in ultrahigh vacuum with the surface composition determined by low energy ion scattering. It was found that the activity of Ru towards the dissociative adsorption of methanol is a strong function of temperature. This change in the adsorptive nature of the Ru sites with temperature produced a variation in the optimum surface composition with temperature. The optimum surface had an Ru content which increased with increasing temperature, from close to [approximately]10 atomic percent (a/o) Ru at 25 C to a value in the vicinity of [approximately]30 a/o at 60 C. The shift in optimum composition with temperature was attributed to a shift in the rate-determining step from methanol adsorption/dehydrogenation at low temperature to the surface reaction between the dehydrogenated intermediate and surface oxygen at high temperature. The apparent activation energies were consistent with this change in the rate-determining step.
551 citations
TL;DR: In this paper, a liquid feed direct methanol fuel cell has been developed based on a proton exchange membrane electrolyte and Pt/Ru and Pt catalyzed fuel and air/O2 electrodes, respectively.
305 citations
TL;DR: The pyridinium ion was found to be a novel homogeneous catalyst for the reduction of CO 2 to methanol as discussed by the authors, and the reduction process proceeds at low overpotentials.
282 citations
TL;DR: In this article, the Nafion/H[sub 3]PO[sub 4] electrolyte has been evaluated with respect to water content, ionic conductivity and transport of oxygen, and methanol vapor.
Abstract: In developing advanced fuel cells and other electrochemical reactors, it is desirable to combine the advantages of solid polymer electrolytes with the enhanced catalytic activity associated with temperatures above 100 C. This will require polymer electrolytes which retain high ionic conductivity at temperatures above the boiling point of water. One possibility is to equilibrate standard perfluorosulfonic acid polymer electrolytes such as Nafion, with a high boiling point Bronsted base such as phosphoric acid. The Nafion/H[sub 3]PO[sub 4] electrolyte has been evaluated with respect to water content, ionic conductivity and transport of oxygen, and methanol vapor. The results show that at elevated temperatures reasonably high conductivity (>0.05 [Omega][sup [minus]1] cm[sup [minus]1]) can be obtained. Methanol permeability is shown to be proportional to the methanol vapor activity and thus decreases with increasing temperature for a given partial pressure. Comparisons and distinctions between this electrolyte and pure phosphoric acid are also considered.
258 citations
TL;DR: The rate of methanol synthesis over a Cu(100) single crystal from a 1 ∶ 1 mixture of CO2 and H2 has been measured at a total pressure of 2 bar and a temperature range of 483-563 K as discussed by the authors.
Abstract: The rate of methanol synthesis over a Cu(100) single crystal from a 1 ∶ 1 mixture of CO2 and H2 has been measured at a total pressure of 2 bar and a temperature range of 483–563 K. At these conditions the apparent activation energy is determined to be 69 kJ mol−1, and at 543 K the turnover rate is 2.7 × 10−4 (site s)−1. A kinetic model for the methanol synthesis is presented. Predictions from this model are in good agreement with the rates of methanol synthesis observed on real catalysts at industrial conditions.
222 citations
TL;DR: In this paper, the incorporation of silicon via direct synthesis into AlPO4-18 (AET), which has a framework structure related to, but crystallographically distinct from, that of the well-known solid acid catalyst SAPO-34, was investigated by a range of techniques.
Abstract: The incorporation of silicon via direct synthesis into AlPO4-18 (AET), which has a framework structure related to, but crystallographically distinct from, that of the well-known solid acid catalyst SAPO-34, was investigated by a range of techniques. Unlike the Si/(Si + Al + P) ratio (typically about 0.10) in SAPO-34, which can be varied only within a very narrow range under normal synthetic conditions, the Si/(Si + Al + P) ratio in SAPO-18 is tunable from 0 to 0.10 by varying the silicon content in the synthetic gel. Si-29 MAS NMR spectroscopy reveals that silicon substitutes for both phosphorus and aluminum in SAPO-18, whereas in SAPO-34, silicon substitutes only for phosphorus. Infrared and H-1 MAS NMR spectroscopies and temperature-programmed desorption (TPD) of ammonia were used to examine the Bronsted acid sites borne by SAPO-18 samples. As expected, the concentration of Bronsted acid sites in all SAPO-18 samples is much less than that in SAPO-34. In contrast to the essentially neutral AlPO4-18, which catalyzes methanol conversion only to dimethyl ether, SAPO-18 catalytically converts methanol to light olefins with high activity and selectivity. The maximum conversion of methanol to ethene and propene reaches 80% with a 100% conversion of methanol to hydrocarbons. With an optimum framework composition, SAPO-18 retains its catalytic activity and selectivity longer than SAPO-34.
155 citations
153 citations
TL;DR: The rate of methanol synthesis over a Cu(100) single crystal from a binary mixture of CO2 and H2 has been measured for total pressures of 1-4 bar, various gas compositions ranging from CO2:H2 ratios of 4:1 to 3:17 and a temperature range of 483-563 K.
151 citations
TL;DR: In this paper, simple alcohol esterification mixtures of D-glucaric acid were reacted with bis-primary diamines in a polar solvent, typically methanol, to produce the polyamides.
Abstract: Convenient procedures are described for the preparation of hydroxylated nylons (polyhydroxypolyamides) from D-glucaric acid. The procedures, which do not require protection/deprotection of carbohydrate hydroxyl groups, can be used to make a variety of polymers with a range of properties from D-glucaric acid. Simple alcohol (e.g. methanol or ethanol) esterification mixtures of D-glucaric acid (from oxidation of D-glucose) were reacted with bis-primary diamines in a polar solvent, typically methanol, to produce the polyamides. D-Glucaric acid esterification mixtures contain varying amounts of dialkyl D-glucarate, alkyl D-glucarate 1,4-lactone, and alkyl D-glucarate 6,3-lactone
TL;DR: In this article, the coverage of oxygen formed on the surface of catalysts during methanol synthesis from CO2 has been measured for copper-based catalysts including various metal oxides using a method called reactive frontal chromatography.
Abstract: The coverage of oxygen formed on the surface of catalysts during methanol synthesis from CO2 has been measured for copper-based catalysts including various metal oxides using a method called reactive frontal chromatography (RFC). An excellent correlation between the specific activity for methanol synthesis and the oxygen coverage (θ) was obtained, where the activity increased linearly with oxygen coverage atθ 0.18. The results strongly indicate that the support effect or addition of metal oxides revealed in methanol synthesis over copper catalysts is ascribed to the ratio of Cu+ to Cu0 on the surface of copper particles.
TL;DR: The reaction of H atoms with solid CO molecules was studied in this article, where the solid CO film deposited on the cold head of the cryocooler was reacted with H atoms by spraying the plasma-activated hydrogen gas over the surface of the sample.
TL;DR: In this article, a high-pressure (20 MPa) and high-temperature (350 o C) liquid water processing environment was used to treat various wastewaters and model compounds.
Abstract: A high-pressure (20 MPa) and high-temperature (350 o C) liquid water processing environment was used to treat various wastewaters and model compounds. Organics were converted to methane and carbon dioxide in the presence of a fixed bed of nickel or ruthenium catalyst. Nitrates were destroyed by reaction with methanol in the presence of a nickel catalyst. Noncatalytic hydrolysis of carbon tetrachloride and chloroform was also demonstrated. Three scales of continuous-flow reactors were used in these tests. Extended tests to demonstrate catalyst lifetimes were also performed. Several examples of test results with actual industrial waste streams showed that this process can be effectively used with appropriate catalysts to clean wastewater and recover waste organics as useful fuel gas
TL;DR: Ethanol was found to be considerably more readily available as a carbon source for denitrification than was methanol, and an efficient denitrify with ethanol was established in a short time, while den itrification with meethanol required a substantial adaptation time and never showed the same stability as denitrified with ethanol.
TL;DR: In this article, the role of enzyme and mediator in these reduction processes is discussed in detail, and successful attempts have been made to reduce carbon dioxide to methanol with cooperative assistance of FDH and MDH in the presence of PQQ as the electron mediator.
Abstract: Electrolysis at potentials between -0.7 and -0.9 V vs SCE of carbon dioxide-saturated phosphate buffer solutions (pH7) containing formate dehydrogenase (FDH) and either methyl viologen (MV[sup 2+]) or pyrroloquinolinequinone (PQQ) as an electron mediator yielded formate with current efficiencies as high as 90%. The enzyme was durable as long as the electrolysis was carried out in the dark. Electrolysis of phosphate buffer solutions containing sodium formate in the presence of methanol dehydrogenase (MDH) and MV[sup 2+] at -0.7 V vs SCE yielded formaldehyde if the concentration of the enzyme used was low, whereas both formaldehyde and methanol were produced for relatively high concentrations of the enzyme where the methanol production began to occur when the formaldehyde produced accumulated. The use of PQQ in place of MV[sup 2+] as the electron mediator exclusively produced methanol alone after some induction period in the electrolysis. On the basis of these results, successful attempts have been made to reduce carbon dioxide to methanol with cooperative assistance of FDH and MDH in the presence of PQQ as the electron mediator. The role of enzyme and mediator in these reduction processes is discussed in detail. 34 refs., 10 figs., 2 tabs.
TL;DR: The palladium-catalyzed reaction of 2-alkynylbenzamides gave 3-alkylidenisoindole derivatives as discussed by the authors, which is the same as 3-carboxylates.
TL;DR: In this article, the surface molybdenum oxide species is assigned to an isolated, highly distorted octahedral mono-oxo Mo structure, which is independent of the preparation methods used in the present study.
TL;DR: In this article, a comparison between ammonia and methanol, applied indirectly in a hydrogen/air fuel cell, is presented, focusing on the specific energy of the carburants (amount of electricity produced per mass of fuel), specific energy corrected for the mass and volume of the tank, and overall energy efficiency.
TL;DR: The synthesis of cellular building blocks starts with the central anabolic intermediate acetyl-CoA which, in autotrophic methanogens, is synthesized from two molecules of CO2 in a linear pathway.
Abstract: Methanogenic archaea convert a few simple compounds such as H2 + CO2, formate, methanol, methylamines, and acetate to methane. Methanogenesis from all these substrates requires a number of unique coenzymes, some of which are exclusively found in methanogens. H2-dependent CO2 reduction proceeds via carrier-bound C1 intermediates which become stepwise reduced to methane. Methane formation from methanol and methylamines involves the disproportionation of the methyl groups. Part of the methyl groups are oxidized to CO2, and the reducing equivalents thereby gained are subsequently used to reduce other methyl groups to methane. This process involves the same C1 intermediates that are formed during methanogenesis from CO2. Conversion of acetate to methane and carbon dioxide is preceded by its activation to acetyl-CoA. Cleavage of the latter compound yields a coenzyme-bound methyl moiety and an enzyme-bound carbonyl group. The reducing equivalents gained by oxidation of the carbonyl group to carbon dioxide are subsequently used to reduce the methyl moiety to methane. All these processes lead to the generation of transmembrane ion gradients which fuel ATP synthesis via one or two types of ATP synthases. The synthesis of cellular building blocks starts with the central anabolic intermediate acetyl-CoA which, in autotrophic methanogens, is synthesized from two molecules of CO2 in a linear pathway.
TL;DR: In this paper, a coprecipitated Cu-ZrO2 catalysts were found to show higher selectivity to methanol in CO2 hydrogenation than conventional ZnO catalysts.
Abstract: Coprecipitated Cu-ZrO2 catalysts were found to show higher selectivity to methanol in CO2 hydrogenation than conventional Cu-ZnO catalysts. Addition of ZnO to Cu-ZrO2 catalysts of Cu/ZrO2 = 1 (weight ratio) greatly enhanced the activity at lower temperatures, while keeping the high methanol selectivity of Cu-ZrO2 catalysts. A remarkable increase in the Cu dispersion with increased amount of added ZnO explains the increased activity at lower temperatures, while the reforming of methanol to CO is accelerated by ZnO at higher temperatures, leading to a lowered yield of methanol. It is suggested that ZrO2 rather than ZnO in the ternary systems plays a more effective role for the selective formation of methanol.
TL;DR: In this article, chemical equilibria of poly(oxymethylene) glycol formation in formaldehyde solutions in water (and deuterium oxide) and of the poly(oxide methylene) hemiformal formation in methanolic formaldehyde solution were studied.
Abstract: Reliable information on chemical equilibria in formaldehyde solutions is needed for the design of separation process for formaldehyde containing mixtures. Chemical equilibria of the poly(oxymethylene) glycol formation in formaldehyde solutions in water (and deuterium oxide) and of the poly(oxymethylene) hemiformal formation in methanolic formaldehyde solutions were studied by [sup 1]H and [sup 13]C-NMR spectroscopy. Overall formaldehyde mole fraction and temperature range from 0.06--0.19 mol/mol, 275--357 K for solutions in water and 0.17--0.50 mol/mol, 274--317 K for methanolic solutions. Chemical equilibrium constants are determined assuming ideal solution behavior. Results from [sup 1]H and [sup 13]C-NMR spectroscopy agree well. Chemical equilibria of the poly(oxymethylene) glycol formation do not depend on whether water or deuterium oxide is used. The new experimental results confirm only some of the literature data.
TL;DR: The effect of acid/base functional groups associated with platinized-carbon electrodes on their catalytic activity toward electro-oxidation of methanol in sulfuric acid electrolyte at 60-degrees-C is studied in this article.
Abstract: The effect of acid/base functional-groups associated with platinized-carbon electrodes on their catalytic activity toward electro-oxidation of methanol in sulfuric acid electrolyte at 60-degrees-C is studied Platinized-carbon electrodes with sm amounts of functional groups exhibit higher catalytic activity compared to those with large concentrations of acidic/basic surface functionalities The overpotential for methanol oxidation is minimum on electrodes of platinized carbons with pHzpc values between 6 and 7 An x-ray photoelectron spectroscopic study of various platinized carbons suggests that the acid/base surface functional-groups produce ample amounts of surface Pt-oxides and a consequent decrease in activity toward methanol oxidation
TL;DR: In this article, secondary and secondary alcohols are oxidised by H2O2 in the presence of titanium silicalite-1 to carbonylic compounds, and the reaction pattern is consistent with a process taking place essentially inside the zeolite channels.
TL;DR: Methylotrophic methanogens and acetogens were stimulated by cobalt additions, while the other trophic groups utilizing downstream intermediates, H2-CO2 or acetate, were largely unaffected and indicated that acetogens can outcompete methanogen only when reactor methanol and cobalt concentrations are high, provided enough inorganic carbon is available.
Abstract: Methanol is an important anaerobic substrate in industrial wastewater treatment and the natural environment. Previous studies indicate that cobalt greatly stimulates methane formation during anaerobic treatment of methanolic wastewaters. To evaluate the effect of cobalt in a mixed culture, a sludge with low background levels of cobalt was cultivated in an upflow anaerobic sludge blanket reactor. Specific inhibitors in batch assays were then utilized to study the effect of cobalt on the growth rate and activity of different microorganisms involved in the anaerobic degradation of methanol. Only methylotrophic methanogens and acetogens were stimulated by cobalt additions, while the other trophic groups utilizing downstream intermediates, H2-CO2 or acetate, were largely unaffected. The optimal concentration of cobalt for the growth and activity of methanol-utilizing methanogens and acetogens was 0.05 mg liter-1. The higher requirement of cobalt is presumably due to the previously reported production of unique corrinoid-containing enzymes (or coenzymes) by direct utilizers of methanol. This distinctly high requirement of cobalt by methylotrophs should be considered during methanolic wastewater treatment. Methylotroph methanogens presented a 60-fold-higher affinity for methanol than acetogens. This result in combination with the fact that acetogens grow slightly faster than methanogens under optimal cobalt conditions indicates that acetogens can outcompete methanogens only when reactor methanol and cobalt concentrations are high, provided enough inorganic carbon is available.
TL;DR: In this paper, the authors measured the gas-liquid solubilities of the solutes carbon monoxide, carbon dioxide, hydrogen, water, ethane, propane, pentane, hexane, methanol, ethanol, 1propanol, 1-butanol, 1 -pentanol, and 1-hexanol in the solvents tetraethylene glycol, hexadecane, octacosane, 1hexadecanol, and phenanthrene.
Abstract: At temperatures between 473 and 673 K and pressures between 2 and 10 MPa, synthesis gas can be converted toward methanol, fuel-methanol (a mixture of methanol and higher alcohols), or a mixture of hydrocarbons (Fischer-Tropsch synthesis), depending on the type of heterogeneous catalyst applied. The gas-liquid solubilities of the solutes carbon monoxide, carbon dioxide, hydrogen, water, ethane, propane, pentane, hexane, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol in the solvents tetraethylene glycol, hexadecane, octacosane, 1-hexadecanol, and phenanthrene were measured as a function of temperature. The solutes are all reactants or products relevant for synthesis gas conversion into alcohols and/or hydrocarbons. The solvents are seen as potentially attractive for synthesis gas conversion via gas-slurry processes. Experimental conditions varied between 293 and 553 K and 0.06 and 5.5 MPa, covering typical process conditions for synthesis gas conversion. The total set of experimental results consists of 1,533 gas-liquid solubilities divided over 60 binary systems. As far as the authors know hardly any of the gas-liquid solubilities from this set have been reported previously in the literature. Where literature data are available, a comparison is made with their data. This comparison always shows an agreement within the calculated experimental errors with an average deviationmore » of 7.6% and a maximal deviation of 15.0%.« less
TL;DR: The theoretically predicted 1 H shift of ammonia adsorbed on a zeolite cluster which containes two complete coordination spheres of O and Si around the central aluminum is 6.8 ppm.
Abstract: The theoretically predicted 1 H shift of ammonia adsorbed on a zeolite cluster which containes two complete coordination spheres of O and Si around the central aluminum is 6.8 ppm. It corresponds well to the data observed for a single adsorbed NH 4 + ion. The calculated 1 H chemical shifts of the two possible structure types, the neutral and the ion-pair complex, of a single adsorbed methanol molecule are 5.7 and 15.3 ppm, respectively. For complexes with a single water molecule these values are 4,5 and 12.7 ppm, respectively. Additional calculations on the ion-pair complex with a second adsorbed neutral methanol or water molecule indicate the formation of an oxonium species only for higher loadings on the BrOnsted sites
TL;DR: In this article, the oxidation of methanol and C1 molecules was investigated on platinum-modified polyaniline electrodes, and it was found that such electrodes are conducting even at 0.0 V vs RHE.
Abstract: The oxidation of methanol and C1 molecules was investigated on platinum-modified polyaniline electrodes. It was found that such electrodes are conducting even at 0.0 V vs RHE. They were found to have a higher electrocatalytic activity than bulk platinum electrodes. Moreover, the poisoning effect is drastically decreased as proved by in situ EMIRS studies which show no significant COads signal. Finally, kinetic results show that the methanol electrooxidation is first order with respect to methanol and that the main oxidation product is formaldehyde.
TL;DR: In this paper, a detailed chemical kinetic model has been developed that accurately describes pyrolysis, ignition and oxidation of many small hydrocarbon fuels over a wide range of experimental conditions.
TL;DR: The antioxidative effects of methanol extracts of crude drugs were estimated by an electrochemical method and it was clear that substances oxidized at lower potentials had stronger radical scavenging effects than those oxidizing at higher potentials.
Abstract: The antioxidative effects of methanol extracts of crude drugs were estimated by an electrochemical method because there are many electrochemically-active substances in natural antioxidants. Twelve kinds of crude drugs, which had been reported to exhibit strong activity in an antioxidative test based on the air oxidation of linoleic acid, were studied. The oxidative capacity calculated from voltammograms of their methanol extracts were compared and examined together with data on their radical scavenging effects. The results showed that the electrochemical behavior in most cases correlated with the radical scavenging effect. Crude drugs which had clear oxidative peaks below +1.2 V and a large oxidative capacity were suggested to have strong radical scavenging effects. It was clear that substances oxidized at lower potentials had stronger radical scavenging effects than those oxidized at higher potentials. Therefore, this electrochemical method can be considered as a rapid and simple method for estimating the antioxidative effects as a radical scavenger.