Showing papers on "Syngas published in 1995"

Dense ceramic membranes for partial oxidation of methane to syngas

Abstract: Several perovskite-type oxides (ABO3) containing transition metals on the B-site show mixed (electronic/ionic) conductivity. These mixed-conductivity oxides are promising materials for oxygen-permeating membranes that can operate without electrodes or external electrical circuitry. Oxides in the system LaSrFeCoO permeate large amounts of oxygen, and extruded tubes of these materials have been evaluated in a reactor operating at ca. 850°C for direct conversion of methane into syngas (CO + H2) in the presence of a reforming catalyst. Methane conversion efficiencies of > 99% were observed, and some of the reactor tubes have been operated for over 1000 h. Membrane tubes were fabricated from calcined powders by a plastic extrusion technique. Ceramic powders in the LaSrFeCoO system were made by solid-state reaction of the constituent carbonates, oxides, and/or nitrates. The chemical-phase behavior of the ceramic powders with varying stoichiometries were studied by high-temperature in-situ X-ray diffraction (XRD) as a function of oxygen partial pressure. The sintered extruded tubes were also characterized by XRD and scanning electron microscopy.

Solid multi-component membranes, electrochemical reactor components, electrochemical reactors and use of membranes, reactor components, and reactor for oxidation reactions

Abstract: Solid membranes comprising an intimate, gas-impervious, multi-phase mixture of an electronically-conductive material and an oxygen ion-conductive material and/or a mixed metal oxide of a perovskite structure are described. Electrochemical reactor components, such as reactor cells, and electrochemical reactors are also described for transporting oxygen from any oxygen-containing gas to any gas or mixture of gases that consume oxygen. The reactor cells generally comprise first and second zones separated by an element having a first surface capable of reducing oxygen to oxygen ions, a second surface capable of reacting oxygen ions with an oxygen-consuming gas, an electron-conductive path between the first and second surfaces and an oxygen ion-conductive path between the first and second surfaces. The element may further comprise (1) a porous substrate, (2) an electron-conductive metal, metal oxide or mixture thereof and/or (3) a catalyst. The reactor cell may further comprise a catalyst in the zone which comprises a passageway from an entrance end to an exit end of the element. Processes described which may be conducted with the disclosed reactor cells and reactors include, for example, the partial oxidation of methane to produce unsaturated compounds or synthesis gas, the partial oxidation of ethane, substitution of aromatic compounds, extraction of oxygen from oxygen-containing gases, including oxidized gases, ammoxidation of methane, etc. The extraction of oxygen from oxidized gases may be used for flue or exhaust gas cleanup.

Failure mechanisms of ceramic membrane reactors in partial oxidation of methane to synthesis gas

Abstract: In the course of generating synthesis gas (H2, CO) from methane, we have observed two types of fractures occurring on the Sr(Co, Fe)Ox-type oxygen membrane reactors The first type occurred shortly after the reaction started and the second type often occurred days after the reaction To determine the causes of these fractures, we have examined the starting material and fractured membranes using a combination of X-ray diffraction and thermogravimetric analyses We found that the first type of fracture was the consequence of an oxygen gradient in the membrane, pointing from the reaction side to the air side This causes a lattice mismatch inside the membrane, leading to fracture The second type of fracture, however, was the result of a chemical decomposition We found that the Sr(Co, Fe)Ox-type membrane had been reduced to SrCO3, and elemental Co and Fe by the synthesis gas generated in the reaction The decomposition causes enormous expansion leading to a large crack along the axis of tube

Power plant with carbon dioxide capture and zero pollutant emissions

Abstract: The invention relates to a power plant including an air separation unit arranged to separate oxygen from air and produce a stream of substantially pure liquid oxygen; a gas turbine arranged to combust a fuel, e.g., natural gas, liquefied natural gas, or synthesis gas, in the presence of substantially pure oxygen gas and carbon dioxide gas, and to produce an exhaust gas comprising water and carbon dioxide; and a carbon dioxide removal unit arranged to recover carbon dioxide gas from the exhaust gas, recycle a portion of the recovered carbon dioxide gas for passage through the gas turbine, and liquefy the remainder of the recovered carbon dioxide gas for removal from the plant. In this new plant, the carbon dioxide removal unit is thermally integrated with the air separation unit by directing the stream of liquid oxygen from the air separation unit to the carbon dioxide removal unit to liquefy the remainder of the recovered carbon dioxide gas, the liquid oxygen thereby evaporating and forming cold oxygen gas which is directed to cool the recycled carbon dioxide gas prior to passage of the carbon dioxide gas through the gas turbine, and the oxygen gas is then directed to the gas turbine.

Carbon dioxide and carbon monoxide hydrogenation over gold supported on titanium, iron, and zinc oxides

Abstract: Gold deposited on TiO2, Fe2O3, ZnO and ZnFe2O4 with high dispersion was found to be active for the hydrogenation of both carbon dioxide and carbon monoxide at temperatures between 150 and 400°C. Over the above catalysts, methanol was produced more readily from carbon dioxide than from carbon monoxide. In particular, Au/ZnO and Au/ZnFe2O4 showed high methanol selectivities from carbon dioxide, which were comparable to those obtained for copper catalysts. As for methanol synthesis from carbon monoxide, only Au/ZnO gave appreciable yields with similar selectivity as copper catalysts. The comparison between experimental and thermodynamic data proved that over all the catalysts except for Au/TiO2 three reactions, namely between carbon dioxide and methanol, carbon monoxide and methanol, carbon dioxide and carbon monoxide, simultaneously reached equilibria at temperatures above 300°C and that the methanol yield decreased with further increase in temperature. Hydrocarbons were formed at high temperatures and the resulting water was also involved in the above equilibria. As a main hydrocarbon product, methane was obtained much more selectively from carbon dioxide than from carbon monoxide. Ethane and propane were also produced from carbon dioxide and carbon monoxide over gold supported on reduced iron oxides.

Removal of carbon dioxide from gas streams

Abstract: Carbon dioxide is removed from a gas stream by passing the gas stream through a bed of natural or synthetic clinoptilolite or their chemically-modified derivatives. The process is particularly advantageous when applied to the removal of ppm levels of carbon dioxide from gas streams at temperatures above 20° C.

An investigation on the reaction mechanism for the partial oxidation of methane to synthesis gas over platinum

Abstract: The partial oxidation of methane to synthesis gas has been investigated by admitting pulses of pure methane, pure oxygen and mixtures of methane and oxygen to platinum sponge at temperatures ranging from 973 to 1073 K. On reduced platinum the decomposition of methane results in the formation of surface carbon and hydrogen. No deposition of carbon occurs during the interaction of methane with a partly oxidised catalyst. Oxygen is present in three different forms under the conditions studied: platinum oxide, dissolved oxygen and chemisorbed oxygen species. Carbon monoxide and hydrogen are produced directly from methane via oxygen present as platinum oxide. Activation of methane involving dissolved oxygen provides a parallel route to carbon dioxide and water. Both platinum oxide and chemisorbed oxygen species are involved in the oxidation of carbon monoxide and hydrogen. In the presence of both methane and dioxygen at a stoichiometric feed ratio the dominant pathways are the direct formation of CO and H2 followed by their consecutive oxidation. A Mars-van Krevelen redox cycle is postulated for the partial oxidation of methane: the oxidation of methane is accompanied by the reduction of platinum oxide, which is reoxidised by incorporation of dioxygen into the catalyst.

Energy efficient methane-to-syngas conversion with low H2/CO ratio by simultaneous catalytic reactions of methane with carbon dioxide and oxygen

Abstract: By simultaneous reactions of methane with CO2 and O2 over NiO-CaO catalyst under certain reaction conditions, it is possible to convert methane into syngas with low H2/CO ratio (1

Fuel cell generator and method of the same

Abstract: The fuel cell generator system of the present invention effectively cancels catalyst poisoning in fuel cells so as to improve the performance of fuel cells. In the fuel cell generator system of the invention, a carbon monoxide sensor is arranged in the middle of a gaseous fuel supply conduit, which connects fuel cells with a reformer for converting methanol and water to a hydrogen-rich gaseous fuel. An electronic control unit of the fuel cell generator system reads the carbon monoxide sensor to input a concentration of carbon monoxide D included in the gaseous fuel (step S250). When the carbon monoxide concentration D obtained is greater than a preset level D0, the electronic control unit increases the air flow fed to a partial oxidizing unit of the reformer (step S270). This accelerates the reaction in the partial oxidizing unit for oxidizing carbon monoxide to carbon dioxide, thereby lowering the concentration of carbon monoxide included in the gaseous fuel.

Process for producing light olefins from crude methanol

Abstract: A process is disclosed for the production of light olefins from a hydrocarbon gas stream by a combination of reforming, oxygenate production, and oxygenate conversion wherein a crude methanol stream--produced in the production of oxygenates and comprising methanol, light ends, and heavier alcohols--is passed directly to the oxygenate conversion zone for the production of light olefins. Furthermore, the combination provides the synergy for increased catalyst life and reduced water treatment costs by recycling by-product water produced in the oxygenate conversion zone to provide water to the syngas production zone. The advantage of this integration is the elimination of costly methanol separation and purification steps which result in the overall reduction in the costs of producing the light olefins. Other advantages include the reduction in catalyst cost in the oxygenate production zone by the reduction in the catalyst selectivity by the extension of catalyst life in the oxygenate production zone. In addition, a portion of the by-product water can be combined with a propylene stream to provide a high octane blending component for gasoline. The propylene and butylene fractions produced by the above integrated scheme are further converted to high octane ether and other high value products.

Light alkenes from syngas via dimethyl ether

Abstract: A new route, named the SDTO method, for the synthesis of light alkenes from syngas is proposed. The method consists of the conversion of syngas to dimethyl ether, followed by the conversion of dimethyl ether to light alkenes. Catalysts for the two reactions have been developed. For the first reaction, the catalyst was synthesized by combining a methanol synthesis catalyst with λ-Al2O3 or zeolites, which possess both metallic and acidic functions. The conversion of the reaction is much higher than that of the methanol synthesis reaction. Suitable reaction conditions are: 210–280°C; P>.0MPa and gas hourly space velocity (GHSV) 6 h−1 or line velocity of MeOH> 15, the selectivity for ethylene and total light alkenes are ca. 60 and ca. 90, respectively (conversion= 100%). The stability of the modified SAPO-34 catalyst has been tested under severe conditions. The results from the serial connection of the two conversion steps without any separation show that the yield of C2=–C4= alkenes could be > 100 g/(m3 syngas).

Methane conversion by an air microwave plasma

Abstract: Activation of methane is carried out by means of an air microwave plasma (2.45 GHz). The experiments cover the absorbed microwave power range 350–650 W (20–50 W cm3 with 17–62%, of methane in the gas mixture, with pressures of 10–66 mbar and flow rates of 140‐700 ml min1. Methane, dioxygen, and dinitrogen consumptions as well as C2 hydrocarbons, carbon monoxide, and dihydrogen yields are analyzed hr gas chromatography. The distance of methane addition from the end of the discharge plays an important role in the composition and the concentration of the products obtained. This distance mainly determines the energy concentrated in the active species of the plasma when they react with methane. A kinetic mechanism jar the activation and decay of inethane and for the formation of C2 hydrocarbons and carbon monoxide is discussed based on the experimental results and kinetic data in the literature.

Pretreatment effect studies with a precipitated iron Fischer-Tropsch catalyst

Abstract: A doubly promoted precipitated iron catalyst (100 Fe/0.3 Cu/0.8 K by mass) was characterized after different pretreatment conditions and after Fischer-Tropsch (FT) synthesis in a fixed bed reactor. The BET surface area of the catalyst decreased markedly after pretreatments with hydrogen, carbon monoxide and synthesis gas (HCO 0.67 and 2). Calcined catalyst was in the form of α-Fe2O3, which was converted to either metallic iron (α-Fe) or a mixture of α-Fe and Fe3O4 after hydrogen reductions. During FT synthesis the α-Fe was carburized to iron carbides (χ-carbide or ϵ′-carbide) or oxidized to Fe3O4. After carbon monoxide or syngas pretreatments, the χ-carbide was the most dominant phase. During FT synthesis this carbide was partially or completely converted to ϵ′-carbide, Fe3O4, and/or FeCO3. Hydrogen reductions resulted in stable or increasing catalyst activity with time on stream and the reduction conditions had a strong effect on the subsequent catalyst activity. The carbon monoxide and syngas pretreated catalysts deactivated with time. The hydrogen reduced catalysts produced more methane and gaseous hydrocarbons than the carbon monoxide or the syngas pretreated catalysts, and favored secondary hydrogenation and isomerization reactions.

Surface supported cobalt catalysts, process utilizing these catalysts for the preparation of hydrocarbons from synthesis gas and process for the preparation of said catalysts

Abstract: A supported particulate cobalt catalyst is formed by dispersing cobalt, alone or with a metal promoter, particularly rhenium, as a thin catalytically active film upon a particulate support, especially a silica or titania support. This catalyst can be used to convert an admixture of carbon monoxide and hydrogen to a distillate fuel constituted principally of an admixture of linear paraffins and olefins, particularly a C10+ distillate, at high productivity, with low methane selectivity. A process is also disclosed for the preparation of these catalysts.

Photosynthesis of CH4 at a TiO2 surface from gaseous H2O and CO2

Abstract: UV irradiation of the gas/solid interface of microcrystalline TiO2 in the presence of water and carbon dioxide in the gas phase at 343 K leads to photoreduction of carbon dioxide to form carbon monoxide, hydrogen and methane.

Gasification process combined with steam methane reforming to produce syngas suitable for methanol production

Abstract: An improved method for the production of stoichiometric ratioed syngas comprises partially oxidizing a gaseous feedstock containing substantial amounts of methane in a gasifier to produce a hot synthesis gas stream that is passed in indirect heat exchange through a steam reforming catalytic reactor. A portion of the steam reforming reaction products are mixed with the cooled gasifier synthesis gas stream exiting the steam reforming catalytic reactor to form a combined synthesis gas stream, called a "stoichiometric ratioed synthesis gas." The stoichiometric ratioed synthesis gas stream can then be passed into a methanol synthesis unit at substantially the specifications for optimal methanol production with little or no external compression. In a second embodiment the gasifier unit is arranged and operated in parallel with a primary steam reformer unit. The respective synthesis gas streams exiting each unit are combined to form a combined synthesis gas stream that undergoes oxidation in a secondary catalytic reformer unit to form a stoichiometric ratioed synthesis gas that requires minimal external compression before being converted to methanol.

Hydrogen generation process

Abstract: A process for the production of hydrogen that purifies a synthesis gas stream, containing hydrogen, carbon monoxide and combustibles, in a PSA unit. The PSA unit produces at least three streams: a substantially pure hydrogen product stream, a combustible-rich first tail-gas stream, and a carbon dioxide-rich second tail gas stream.

Catalytic oxidation of hydrocarbons and alcohols by carbon dioxide on oxide catalysts

Abstract: The great interest displayed lately in heterogeneous catalytic reactions of carbon dioxide is caused by two reasons: (1) the necessity to fight the greenhouse effect and (2) the exhaust of carbon raw material sources. Reactions of oxidative transformation of organic compounds of different classes (alkanes, alkenes, and alcohols) with a nontraditional oxidant, carbon dioxide, were studied on oxide catalysts Fe-O, Cr-O, Mn-O and on multicomponent systems based on manganese oxide. The supported manganese oxide catalysts are active, selective, and stable in conversion of the CH[sub 4] + CO[sub 2] mixture into synthesis gas and in oxidative dehydrogenation of C[sub 2] [minus] C[sub 7] hydrocarbons and the lower alcohols. Unlike metal catalysts manganese oxide based catalysts do not form a carbon layer during the reaction.

Processes for the conversion of methane to synthesis gas

Abstract: A method of converting a reactant gas mixture of CO 2 , O 2 and CH 4 comprises contacting the reactant gas at 750°-850° C. with a solid catalyst, which is a d-block transition metal or oxide such as a group VIII metal on a metal oxide support such as alumina, and which selectively converts the reactant gas into a product gas mixture comprising H 2 and CO.