Showing papers on "Partial oxidation published in 1991"

Partial oxidation of methane to synthesis gas using carbon dioxide

Abstract: INCREASING concern about world dependence on petroleum oil has generated interest in the more efficient use of natural gas1–4. The conversion of methane to the common feedstock synthesis gas (carbon monoxide and hydrogen) by steam reforming is already well established5, and we have shown recently that yields of syn-thesis gas in excess of 90% can be obtained at moderate tem-peratures and ambient pressure by partial oxidation, with air or oxygen, over supported transition-metal catalysts6,7. The use of carbon dioxide as an oxidant for conversion of natural gas to synthesis gas is well established in steam reforming5, and is also known in CO2 reforming (for example, the Calcor process8,9), in which the use of excess CO2 yields mainly CO. In the present work, we describe an alternative catalytic strategy for CO2 reform-ing which gives excellent yields (90%) from a stoichiometric (1:1) feed of CO2 and CH4. Carbon deposition ('coking'), which is a hazard of CO2-reforming routes, is suppressed here by the use of catalysts based on platinum-group metals. We show that the exothermic partial oxidation of CH2 and the endothermic CO2-reforming reaction can be carried out simultaneously, thus introducing the possibility of tuning the thermodynamics of the process.

Oxidation kinetics of ammonia and ammonia-methanol mixtures in supercritical water in the temperature range 530-700.degree.C at 246 bar

Abstract: Oxidation of industrial chemical and metabolic wastes in a supercritical water medium is an effective method for the treatment and disposal of these materials. Partial oxidation of nitrogen-containing organics in supercritical water leads to the formation of ammonia, which is the rate-limiting step in the overall oxidation to nitrogen. In this study, the oxidation kinetics of ammonia and ammonia-methanol mixtures in supercritical water were experimentally determined in a packed and unpacked tubular plug flow reactor. The oxidation of ammonia was found to be partially catalyzed by the Inconel 625 (a nickel-chromium alloy) reactor walls. In the unpacked reactor, the activation energy was 38 kcal/mol over temperatures ranging from 640 to 700 °C. Oxidation of ammonia in the packed reactor gave an activation energy of 7.1 kcal/mol over the temperature range 530–680 °C and a reaction rate approximately 4 times larger than the tubular reactor data. A power law model and a catalytic model were tested, and the catalytic model was found to represent the data well. In experiments with ammonia-methanol mixtures, the oxidation of ammonia was unaffected by the presence of methanol for experiments conducted in the tubular reactor and retarded by the presence of methanol for packed bed experiments. These observations are consistent with the hypothesis that ammonia oxidation proceeds predominantly as a catalytic reaction in the packed bed reactor at the temperatures investigated. Competitive adsorption of methanol and ammonia reduces the oxidation rate of ammonia in the packed bed reactor. © 1991, American Chemical Society. All rights reserved.

Fuel cell system for transportation applications

Abstract: A propulsion system for a vehicle having pairs of front and rear wheels and a fuel tank. An electrically driven motor having an output shaft operatively connected to at least one of said pair of wheels is connected to a fuel cell having a positive electrode and a negative electrode separated by an electrolyte for producing dc power to operate the motor. A partial oxidation reformer is connected both to the fuel tank and to the fuel cell receives hydrogen-containing fuel from the fuel tank and water and air and for partially oxidizing and reforming the fuel with water and air in the presence of an oxidizing catalyst and a reforming catalyst to produce a hydrogen-containing gas. The hydrogen-containing gas is sent from the partial oxidation reformer to the fuel cell negative electrode while air is transported to the fuel cell positive electrode to produce dc power for operating the electric motor.

Promotion by Poisoning

Abstract: Summary Poisoning of metal catalysts may provide a tool for improving selectivity by affecting the concentrations of ensembles required by different reaction paths. This is illustrated by steam reforming on sulfur passivated nickel catalysts and the results are compared with observations for sulfided platinum-rhenium catalysts for catalytic reforming and for a chlorine poisoned palladium catalyst for partial oxidation of methane.

Catalytic conversion of methane to synthesis gas over europium iridate, Eu2Ir2O7: Anin situ study by x-ray diffraction and mass spectrometry

Abstract: The selective partial oxidation of methane over the europium iridium pyrochlore, Eu2Ir2O7, has been studiedin situ by using powder X-ray diffraction and mass spectrometry. At a temperature of 873 K and 1 atmosphere pressure, with a CH4∶O2 ratio of 2∶1 under argon dilution, high yields of synthesis gas are obtained. The pyrochlore structure of the iridate is modified during the initiation of the catalyst, giving an active solid that is shown to comprise particles of iridium metal, ∼ 30 A in diameter, supported on europium oxide, Eu2O3. The modification of the pyrochlore structure was monitored by X-ray diffraction, and the product gases were continuously analysed by mass spectrometry.

Method and system for combusting hydrocarbon fuels with low pollutant emissions by controllably extracting heat from the catalytic oxidation stage

Abstract: A method of combusting a hydrocarbon fuel includes mixing the fuel with a first air stream to form a fuel/air mixture having an equivalence ratio of greater than 1 and partially oxidizing the fuel by contacting it with an oxidation catalyst to generate a heat of reaction and a partial oxidation product stream. The partial oxidation product stream is mixed with a second air stream and completely combusted in a main combustor at a condition at which appreciable quantities of thermal NOx are not formed to generate an effluent gas stream, thereby generating an effluent gas stream containing decreased amounts of thermal and prompt NOx. A system for combusting a hydrocarbon fuel includes, in combination, means for mixing the fuel with a first air stream, a catalytic oxidation stage containing an oxidation catalyst, means for mixing the partial oxidation product stream with a second air stream, and a main combustor capable of completely combusting the partial oxidation product stream.

Simulation of methane partial oxidation over silica-supported moo3 and v2o5

Abstract: Microkinetic simulations have been carried out to describe the partial oxidation of methane over silica-supported molybdena and vanadia. The objective of this study was to formulate a physically reasonable reaction network to capture the basic aspects of the surface catalytic chemistry and to use this network to link methane oxidation kinetics with the kinetics observed for the oxidation of subsequent gaseous products, i.e., methanol, formaldehyde, and carbon monoxide. The most abundant reactive intermediates on the catalyst surface are suggested to be oxygen and hydroxyl groups. This reaction network successfully predicts the catalytic activities, selectivities, activation energies, and reaction orders observed over silica-supported molybdena and vanadia; and the microkinetic model also semiquantitatively explains the kinetic trends for related catalyst systems and is consistent with surface bonding energetics reported in the literature over various oxide catalysts. The microkinetic reaction network properly reduces to the more simple macrokinetic model reported previously for methane partial oxidation.

Shaped oxidation catalyst structures for the production of maleic anhydride

Abstract: Shaped oxidation catalyst structures containing catalytic material comprised of mixed oxides of vanadium and phosphorus which are useful for the production of maleic anhydride via the partial oxidation of nonaromatic hydrocarbons, particularly n-butane, in the vapor phase with molecular oxygen or a molecular oxygen-containing gas are provided. Such structures are characterized by exhibiting (a) a geometric volume of from about 30 percent to about 90 percent of that exhibited by the void space-free solid geometric form, (b) an external geometric surface area/geometric volume ratio of at least about 15 cm-1, (c) a bulk density of from about 0.4 g/cm3 to about 1.4 g/cm3, and (d) a mechanical resistance sufficient to maintain substantially the structural integrity of the shaped structure under handling and use conditions.

Phosphorous/vanadium oxidation catalyst

Abstract: An improvement in the oxidation catalyst used for the partial oxidation of n-butane and containing vanadium and phosphorus, zinc and lithium mixed oxides which comprises adding a molybdenum compound modifier in an amount of from about 0.005 to 0.025/1 Mo/V to the catalyst during the digestion of the reduced vanadium compound by concentrated phosphoric acid. The addition of Mo produces a catalyst which is very stable more active system and longer lived than the unmodified catalyst.

Process for oxidation of propane

Abstract: Disclosed is a process for the partial oxidation of propane to yield acrylic acid, propylene, acrolein and acetic acid by contacting propane in admixture with a molecular oxygen-containing gas in a reaction zone with an oxidic solid catalyst that 1) contains the components and proportions represented by the empirical formula Bi.sub.b Mo.sub.c V.sub.v A.sub.a D.sub.d E.sub.e O.sub.x wherein A is one or more of K, Na, Li, Cs and Tl, D is one or more of Fe, Ni, Co, Zn, Ce and La, E is one or more of W, Nb, Sb, Sn, P, Cu, Pb, B, Mg, Ca and Sr, a, d and e are each zero-10 b is 0.1-10 c is 0.1-20 v is 0.1-10 c:b is from 2:1 to 30:1 v:b is from 1.5:1 to 8:1 and 2) is made by performing a bismuth molybdate containing composition having at least 0.67 atoms of Mo per atom of Bi, before combining with any vanadium compound.

The oxidative coupling of methane on chlorinated Lithium-doped magnesium oxide

Abstract: The incorporation of chloride ions into Li-doped MgO, via a sol–gel process results in a stable and active catalyst that is capable of converting methane to ethylene through a series of partial oxidation reactions.

Rate equations of solid-catalyzed reactions

Abstract: Rate Equations of Solid-Catalyzed Reactions, edited by Mezaki and Inoue, contains a comprehensive compilation of kinetic rate expressions for a large number of relevant catalytic reaction systems. Mezaki and Inoue should be commended for their effort. For the practicing catalytic engineer the book should serve as a quick reference guide for assessing the functional dependence of rate on various operating conditions for a catalytic reaction system of interest. Even in this age of computer-aid literature searches this book should reduce the typically large activation barrier and search time associated with locating kinetic rate expressions for a particular reaction system. It is a recommended reference book for all whom are involved in the business of catalytic reactions. However, its format is not amenable for teaching. The book is structured according to the reaction system type. Chapter (1) focuses on synthesis (e.g., of sulfur trioxide, ammonia, methanol), (2) on hydrogenations (e.g., of carbon monoxide, carbon dioxide, ethylene, cyclohexene), (3) on hydrogenolysis (of low molecular weight alkanes such as ethane and/or pentane), (4) on hydrocracking (of higher molecular weight components such as n-hexane and n-dodecane), (5) on dehydrogenation (e.g., of ethanol, ethane, cyclohexane), (6) on complete oxidation (e.g., of hydrogen, carbon monoxide, alkanes,more » and olefins), (7) on partial oxidation (e.g., of methanol, ethylene, xylenes, and ammonia), (8) on isomerization (e.g., of methane, ethane, and cyclohexane), (10) on decomposition of ammonia and nitric oxide, (11) on dehydration of various alcohols, (12) on cumene cracking, and (13) on other key reactions such as water-gas shift and nitric oxide reduction.« less

The partial oxidations of cyclohexane and benzene on the FeCl sub 3 -embedded cathode during the O sub 2 -H sub 2 fuel cell reactions

Abstract: Activation and partial oxidations of cyclohexane and benzene occur at ambient temperatures on cathodes containing various metal chlorides during O{sub 2}-H{sub 2} fuel cell reactions. Among the metal chlorides embedded in graphite cathodes, FeCl{sub 3} was the most effective for enhancing the partial oxidation of cyclohexane into cyclohexanol and cyclohexanone. This cathode was also effective for the hydroxylation of benzene to phenol. The effects of various kinetic factors on the rate of oxidations of cyclohexane and benzene have been examined. The kinetic results have been explained in terms of the reaction mechanism proposed. In this paper it is suggested that the activation and partial oxidation of cyclohexane and aromatics are initiated by an active oxygen, O*, generated on the iron cations at the cathode due to the reduction of dioxygen during the O{sub 2}-H{sub 2} fuel cell reactions. Experiments using H{sub 2}O{sub 2} as the oxidant have indicated that the H{sub 2}O{sub 2} cannot be a precursor of the active oxygen O*. The product distribution observed in the oxidation of toluene implies that the O* has a character more electrophilic than OH radicals.

Partial oxidation of olefins: conversion of isobutene to tert-butyl alcohol on oxygen-covered rhodium (111)

Abstract: The selective oxidation reactions of isobutene on oxygen covered Rh(111) have been investigated by temperature programmed reaction and X-ray photoelectron spectroscopies.

Low NOx combustion piloted by low NOx pilots

Abstract: An improved method of burning a hydrocarbon fuel in a combustion system includes burning the fuel in a main burner under fuel-lean conditions to produce a main flame and burning a low heating value fuel in a pilot burner to stabilize the main flame and limit the amount of NOx produced in the pilot burner. The pilot fuel can inherently have a low heating value, can be diluted high heating value fuel, or can be made by partially oxidizing a high heating value fuel. An improved combustion system for burning a hydrocarbon fuel with limited NOx emissions has a main burner (2), a pilot burner (10), and a partial oxidation stage (4) capable of converting a high heating value fuel to a low heating value fuel in a partial oxidation reaction. The system also has means for burning the low heating value fuel in the pilot burner. The system can include means (16) for removing heat from the partial oxidation stage or low heating value fuel to lower the temperature of the pilot flame.