Showing papers on "Methanol published in 1997"

A distributed reactivity model for sorption by soils and sediments. 7. Enthalpy and polarity effects on desorption under supercritical fluid conditions

Abstract: Mechanisms of phenanthrene desorption from five subsurface materials in supercritical carbon dioxide (SC CO2) were investigated by measuring isotherms in the presence of fixed quantities of a polar cosolvent (methanol) and by calculating desorption enthalpies from the temperature dependence of the isotherms. The addition of 7.4 mol % methanol to the SC CO2 phase resulted in 2−11-fold reductions in Freundlich capacity factors at 120 atm and 50 °C. The capacity reduction greatly exceeded that expected from the 21% increase in phenanthrene solubility accompanying cosolvent addition. Isotherms became more linear at 120 atm and 50 °C upon methanol addition for all sorbents except a shale sample. Solubility and organic carbon-normalized phenanthrene sorption capacities declined with increasing solvent polarity, in the order dry SC CO2 > methanol-amended SC CO2 > aqueous solution, and declined with sorbent organic carbon content. Sorption enthalpies from an ideal gas reference state ranged from −106 to −70 kJ/mo...

Photocatalytic destruction of VOCs in the gas-phase using titanium dioxide

Abstract: The gas-phase photocatalytic destruction of 17 VOCs over illuminated titanium dioxide was investigated using a plug flow reactor with the following experimental conditions: 200 ml min−1 flow rate, 23% relative humidity, 21% oxygen and an organic compound concentration range of 400–600 ppmv. At steady state, high conversion yields were obtained for trichloroethylene (99.9%), isooctane (98.9%), acetone (98.5%), methanol (97.9%), methyl ethyl ketone (97.1%),t-butyl methyl ether (96.1%), dimethoxymethane (93.9%), methylene chloride (90.4%), methyl isopropyl ketone (88.5%), isopropanol (79.7%), chloroform (69.5%) and tetrachloroethylene (66.6%). However, the photodegradation of isopropylbenzene (30.3%), methyl chloroform (20.5%) and pyridine (15.8%) was not so efficient. Carbon tetrachloride photoreduction was investigated in the presence of methanol as an electron donor. It was observed that the presence of methanol results in higher degradation rates. No reaction byproducts were detected for all VOCs tested under the experimental set-up and conditions described. Also, long-term conversion was obtained for all tested compounds. Catalyst deactivation was detected with toluene only, but the activity was restored by illuminating the catalyst in the presence of hydrogen peroxide. The capacity of the process to destroy different classes of volatile organic compounds present in the atmosphere was demonstrated.

Methanol oxidation as a catalytic surface probe

Abstract: The goal of this review is to present some aspects of the use of a test reaction, i.e., methanol oxidation, as a tool to characterize oxidation catalysts. The selectivity pattern and the formation rates of the reaction products are used to characterize both structural (dispersion) as well as chemical properties (acid-base and redox) on supported oxide catalysts, especially for molybdenum-based systems supported on silica and vanadia on titanium oxide. This highly sensitive technique which gives information on the catalytically active sites at the molecular level characterizes a catalyst at work and is particularly well-adapted to the study of supported catalysts.

Additives To Lower and Stabilize the Viscosity of Pyrolysis Oils during Storage

Abstract: The initial development of additives to stabilize the viscosity of biocrude during long-term storage has produced dramatic results. The additives investigated were ethyl acetate, methyl isobutyl ketone and methanol, acetone, methanol, acetone and methanol, and ethanol. These additives represent three chemical families, which all demonstrated the ability to drastically reduce the aging rate of biocrude, as defined by the increase in viscosity with time. Accelerated aging tests were run at 90 °C to screen the additives. The additives not only lowered the initial viscosity at 40 °C by half but also reduced the aging rate of a hot gas filtered pyrolysis oil made from hybrid poplar (NREL run 175) by factors of 1−18 compared to the original pure oil. With the best additive, methanol, at a 10 wt % level in the pyrolysis oil, the modified biocrude was still a single-phase liquid and still met the ASTM No. 4 diesel fuel specification for viscosity even after 96 h exposure to 90 °C. Based on the aging rate at 90 °C...

Synthesis of dimethyl ether (DME) from methanol over solid-acid catalysts

Abstract: The catalytic conversion of methanol to dimethyl ether (DME) has been studied over a series of solid-acid catalysts, such as γ-Al2O3, H-ZSM-5, amorphous silica-alumina, as well as titania modified zirconia. All the catalysts are active and selective for DME formation. The apparent activation energy for DME formation over γ-Al2O3 is ca. 25 kcal/mol, a value that increases to ca. 37 kcal/mol upon the addition of 23 Torr of H2O to the reagent. The rate of methanol dehydration decreases with increasing acidity (silica content) over the amorphous silica-alumina catalysts. Although H-ZSM-5 with Si/Al = 25 is the most active among the catalysts tested, the DME selectivity is only 20% at 280°C, a typical temperature used in the syngas-to-methanol process. An amorphous silica-alumina catalyst with 20 wt.-% silica content (SIRAL20) exhibits the best catalytic performance of those tested at 280°C.

Electrochemical investigations on carbon supported palladium catalysts

Abstract: Highly dispersed palladium catalysts on carbon were prepared by reduction of their salts with various reducing agents. The crystallite parameters and metal surface area were evaluated by XRD and electrochemical techniques. The electrochemical activity for the oxidation of hydrogen, methanol, formaldehyde and ethylene glycol and reduction of oxygen was evaluated in alkaline solutions by making PTFE bonded carbon electrodes. The electrochemical activity was correlated with the catalyst properties. Pd dispersed catalysts on carbon supports exhibit high activity for the oxidation of hydrogen and ethylene glycol in alkaline medium. Their electrochemical activity is dependant upon the crystallite properties like surface area, dispersion and crystallite size. For oxygen reduction reaction, the activity can be increased by alloying with other elements.

Partial oxidation of methanol to produce hydrogen over CuZn-based catalysts

Abstract: In this work CuZnO and Cu/ZnO/Al2O3 catalysts have been studied for the partial oxidation of methanol with oxygen to produce hydrogen. These CuZn based catalysts showed high activity for the partial oxidation of methanol and it was found that the catalytic activity is directly related to the copper metal surface area. In the series CuZn with copper relative content of 20–70 wt%, the catalyst Cu40Zn60 (Cu 40 wt% and Zn 60 wt%) which showed the highest copper area gave the best results for the partial oxidation of methanol. The activation energies and TOF (turnover frequencies) varied with the CuZn catalyst composition. For catalysts with low copper loading very high Ea and TOF were obtained (for Cu30Zn70 Ea=482 kJ/mol and TOF ca. 200 min−1 at 497–499 K) whereas for higher copper contents the Ea and TOF decreased tending to constant values (for Cu70Zn30 Ea=71 kJ/mol and TOF=160 min−1 at 497–499 K). These results are discussed in terms of a possible effect of the CuZnO interaction which depends on the catalyst composition. Catalytic experiments with Cu40Zn55Al5 (Cu 40 wt%, Zn 55 wt% and Al 5 wt%) showed that the presence of aluminium has an inhibiting effect producing slightly lower methanol conversion. On the other hand, higher selectivities for H2 and CO2 were obtained with only traces of the undesirable carbon monoxide. Moreover, the Al is very important for catalyst stability and life-time experiments showed that Cu40Zn55Al5 is stable during the partial oxidation of methanol with no significant change in activity and selectivity even after 110 h operation at 503 K. The catalyst Cu40Zn60 with no Al, deactivates rapidly after 20 h reaction at 503 K. Experiments using N2O as oxidant showed higher activity to convert methanol but producing large amounts of H2O and CO. The impregnation of catalyst with Na produced similar effect increasing the selectivity for H2O and CO. The results presented seem to indicate that the copper metal is active for partial oxidation of methanol to H2 and CO2 whereas Cu+1 favour the formation of H2O and CO. Cu+2 as CuO shows very low activity for methanol conversion producing only CO2 and H2O.

System and process for producing biodiesel fuel with reduced viscosity and a cloud point below thirty-two (32) degrees fahrenheit

Abstract: Triglycerides are reacted in a liquid phase reaction with methanol and a homogeneous basic catalyst. The reaction yields a spatially separated two phase result with an upper located non-polar phase consisting principally of non-polar methyl esters and a lower located phase consisting principally of glycerol and residual methyl esters. The glycerol phase is passed through a strong cationic ion exchanger to remove anions, resulting in a neutral product which is flashed to remove methanol and which is reacted with isobutylene in the presence of a strong acid catalyst to produce glycerol ethers. The glycerol ethers are then added back to the upper located methyl ethyl ester phase to provide an improved biodiesel fuel.

Electrocatalytic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carbon substrates

Abstract: To achieve methanol fuel cell electrodes allowing a high catalyst use, thin layers of various carbon powders and recast Nafion® were electrochemically plated with platinum. The resulting Pt deposits were characterized by hydrogen and carbon monoxide electrosorption, as well as by transmission electron microscopy. Methanol oxidation was then carried out using cyclic voltammetry. The influence of the amount of carbon surface oxides and the effect of Pt specific surface area on the Pt catalytic activity were thus investigated.

Theoretical Study of the Mechanism of Surface Methoxy and Dimethyl Ether Formation from Methanol Catalyzed by Zeolitic Protons

Abstract: Density functional theory is used to study the zeolite acid catalyzed methanol dehydration to dimethyl ether. Three different reaction pathways are proposed. In the first, methanol adsorption and surface methoxy species formation are the initial elementary steps for this reaction. Subsequent dimethyl ether formation by reaction of a new methanol molecule with the surface methoxy species takes place. The second path involves the simultaneous adsorption and activation of two methanol molecules with formation of dimethyl ether and water in one step. The third path involves also the simultaneous adsorption and activation of two methanol molecules. The difference is that, like in the first path, initially a methoxy surface species will be formed from dehydration of one of the methanol molecules, and this will be followed by dimethyl ether formation. The second path appears to be the preferred route for dimethyl ether formation, since its activation barrier is lower than the other two paths. The effect of makin...

Economic route for natural gas conversion to ethylene and propylene

Abstract: Publisher Summary The major component of natural gas is methane, which can be converted into methanol. Methanol is an important industrial intermediate in the manufacture of a number of products such as formaldehyde, acetic acid, and methyl tertiary butyl ether (MTBE). Methanol can also be used as a transportation fuel, but its use has been limited because of its other properties, such as its high water solubility and its blending vapor pressure. Natural gas can be converted to olefins with the help of GTO process. The first step in the process is the conversion of natural gas to methanol followed by the UOP/Hydro methanol to olefins (MTO) process using UOP's unique silicoaluminophosphate (SAPO)-34 catalyst. The primary products are ethylene and propylene. The processes most widely used in the conversion of natural gas to methanol include (1) ICI low-pressure methanol process, (2) Lurgi two-step reforming, and (3) Haldor Topsoe two-step reforming process.

Iron complexes in zeolites as a new model of methane monooxygenase

Abstract: Iron complexes in the ZSM-5 zeolite matrix (α-centers) are shown to perform single-turnover cycles of methane oxidation to methanol at room temperature when nitrous oxide is used as a source of oxygen. The origin of carbon and oxygen in the product methanol was traced using13C and18O isotopes. Probable structure of α-sites as well as mechanistic features of the reaction allow to consider this system as a first successful model of methane monooxygenase.

Method of and apparatus for refroming fuel and fuel cell system with fuel-reforming apparatus incorporated therein

Abstract: Methanol supplied as a raw fuel is mixed with water, vaporized in an evaporator 24, and supplied to a reformer 22 as a raw fuel gas. The reformer 22 also receives a supply of the compressed air from an air tank 36. The raw fuel gas is mixed with the compressed air in the reformer 22. An oxidation reaction of methanol supplied as the raw fuel proceeds in the reformer 22 to generate hydrogen and carbon dioxide, while a steam reforming reaction of methanol simultaneously proceeds in the reformer 22 to generate hydrogen and carbon dioxide. The amount of heat required for the endothermic reforming reaction can be supplied by the oxidation reaction of methanol. No external heat source is accordingly required in the reformer 22 to supply the heat required for the reforming reaction.

Preparation of superabsorbent polymers by crosslinking acrylic acid and acrylamide copolymers

Abstract: High water-absorbent copolymers comprising acrylic acid (AA) and acrylamide (AM) were prepared in the presence of a crosslinking agent, monofunctional aldehyde, by a solution polymerization technique using a redox initiation system. Such copolymers have very high water absorbency and absorbing kinetics to the distilled water. The copolymer formed which absorbed about 900 g water/g dry copolymer was used to study the influence of sodium chloride on the absorption capacity at 24°C. The swelling of this copolymer was studied in alcohol/water mixtures of increasing alcohol content at 294, 304, and 314 K. The main transition for ethanol/water and methanol/water mixtures is a rapid decrease of the retention capacity of the copolymer at 50–60 vol % ethanol and 55–65 vol % methanol, respectively. Swelling in distilled water at different temperatures (T) and the effect of solvent composition were also studied. Among the variables examined were initiator concentration, polymerization temperature, and amount of AM in the copolymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1345–1353, 1997

Theoretical study of C-C bond formation in the methanol to gasoline process

Abstract: Density functional theory is used to study one of the most successful routes to the production of synthetic fuels, the conversion of methanol to gasoline (MTG process) with an acidic zeolite. With ...

Effects of zirconia promotion on the activity of Cu/SiO2 for methanol synthesis from CO/H2 and CO2/H2

Abstract: The effect of zirconia promotion on Cu/SiO2 for the hydrogenation of CO and CO2 at 0.65 MPa has been investigated at temperatures between 473 and 573 K. With increasing zirconia loading, the rate of methanol synthesis is greatly enhanced for both CO and CO2 hydrogenation, but more significantly for CO hydrogenation. For example, at 533 K the methanol synthesis activity of 30.5 wt% zirconia-promoted Cu/SiO2 is 84 and 25 times that of unpromoted Cu/SiO2 for CO and CO2 hydrogenation, respectively. For all catalysts, the rate of methanol synthesis from CO2/H2 is higher than that from CO/H2. The apparent activation energy for methanol synthesis from CO decreases from 22.5 to 17.5 kcal/mol with zirconia addition, suggesting that zirconia alters the reaction pathway. For CO2 hydrogenation, the apparent activation energies (~12 kcal/mol) for methanol synthesis and the reverse water-gas shift (RWGS) reaction are not significantly affected by zirconia addition. While zirconia addition greatly increases the methanol synthesis rate for CO2 hydrogenation, the effect on the RWGS reaction activity is comparatively small. The observed effects of zirconia are interpreted in terms of a mechanism which zirconia serves to adsorb either CO or CO2, whereas Cu serves to adsorb H2. It is proposed that methanol is formed by the hydrogenation of the species adsorbed on zirconia.

On‐Line FTIR Spectroscopic Investigations of Methanol Oxidation in a Direct Methanol Fuel Cell

Abstract: A real-time Fourier transform infrared spectroscopy (FTIRS) analysis of the products of methanol oxidation in a prototype direct-methanol fuel cell operating at high temperatures (150 to 185 C) is reported here. The methanol oxidation products on platinum black and platinum-ruthenium catalyst surfaces were determined as a function of the fuel cell operating temperature, current density, and methanol/water mole ratio. Neither formaldehyde nor formic acid was detected in anode exhaust gas at all cell operating conditions. The product distributions of methanol oxidation obtained by on-line FTIRS are consistent with previous results obtained by on-line mass spectroscopy under similar conditions. With pure methanol in anode feed, methanaldimethylacetal was found to be the main product, methyl formate and CO{sub 2} were also found. However, when water was present in the anode feed, the main product was CO{sub 2}, and the formation of methanal-dimethylacetal and methyl formate decreased significantly with increase of the water/methanol mole ratio. Increase of cell operating temperature enhanced the formation of CO{sub 2} and decreased the formation of methanaldimethylacetal and methyl formate. Pt/Ru catalyst is more active for methanol oxidation and has a higher selectivity toward CO{sub 2} formation than Pt-black. Nearly complete methanol oxidation, i.e., the product was almostmore » exclusively CO{sub 2}, was achieved using a Pt/Ru catalyst and a water/methanol mole ratio of 2 or higher in the anode feed at a temperature of 185 C or above.« less

Potential Dependence of the Yield of Carbon Dioxide from Electrocatalytic Oxidation of Methanol on Platinum(100)

Abstract: The yield of complete oxidation product (CO2) from electrocatalysis of methanol on a Pt(100) electrode in perchloric acid electrolyte at room temperature was determined by combined measurements of chronoamperometry and linear sweep voltammetry. The fractional yield of CO2 was zero over a potential range of 0.35−0.45 VRHE and increased monotonically to unity over the potential range of 0.5−0.65 V. The results may be explained by a simple parallel mechanism, in which methanol oxidizes directly to CO2, or by a complex serial mechanism, in which the overpotential for CO oxidation is reduced by solution phase methanol.

A Highly Catalytic Bimetallic System for the Low-Temperature Selective Oxidation of Methane and Lower Alkanes with Dioxygen as the Oxidant

Abstract: This report describes a highly catalytic bimetallic system for the low temperature selective oxidation of methane, ethane, and butane with dioxygen as the oxidant. The catalytic system consists of a mixture of copper chloride and metallic palladium and operates in a 3:1 mixture (v/v) of trifluoroacetic acid and water in the presence of dioxygen and carbon monoxide. Methane was selectively converted to methanol. The dependence of the reaction rate on the partial pressure of methane was measured, and saturation kinetics was observed. The dependence of the rate on the partial pressure of carbon monoxide was measured at two different pressures of methane, and a first-order dependence on the partial pressure of carbon monoxide was observed in both instances. The activation parameters for the overall reaction were obtained under the reaction conditions when the rate was first order in both methane and carbon monoxide. The values obtained were A = 2 × 104 s-1 and Ea = 15.3 kcal mol-1. Both C−H and C−C cleavage p...

Methanol oxidation over vanadia-based catalysts

Abstract: The literature data on the behavior of vanadia-based cataysts in the oxidation of methanol are briefly reviewed. The potential of vanadia-titania catalysts for the production of methyl formate through methanol oxidation is outlined, and mechanistic and technical features of this process are discussed.