Showing papers on "Partial oxidation published in 1997"

Micromachined Reactors for Catalytic Partial Oxidation Reactions

Abstract: Silicon-based microfabrication of a novel chemical reactor (microreactor) having submillimeter flow channels with integrated heaters, and flow and temperature sensors is described. The potential application of this reactor to partial-oxidation reactions is explored by using Pt-catalyzed NH 3 oxidation as a model reaction. Investigation of reactor behavior as a function of operating conditions shows that conversion and selectivity behavior of conventional laboratory reactors can be reproduced and demonstrates the feasibility of conducting chemical reactions in microfabricated systems. Ignition-extinction behavior is explored, along with high-temperature microreactor materials degradation. Potential applications and scale-up of microreactors are also discussed.

Novel catalysis of gold deposited on metal oxides

Abstract: Gold exhibits a unique catalytic nature and action when it is deposited as nanoparticles on a variety of metal oxides. Most reactions are noticeably structure sensitive over such supported gold catalysts. Typical examples obtained in Japan of the low-temperature catalytic combustion, partial oxidation of hydrocarbons, hydrogenation of carbon oxides and unsaturated hydrocarbons, reduction of nitrogen oxides, and so forth, are presented. Another line of advance is also introduced in the thin films of gold metal oxide composites, which are applicable to electrical and optical gassensing.

Dense perovskite membrane reactors for partial oxidation of methane to syngas

Abstract: The partial oxidation of methane to synthesis gas (syngas, CO + H2) was performed in a mixed-conducting perovskite dense membrane reactor at 850°C, in which oxygen was separated from air and simultaneously fed into the methane stream. Steady-state oxygen permeation rates for La1-xA′xFe0.8 Co0.2O3-δ perovskite membranes in nonreacting air/helium experiments were in the order of A′x = Ba0.8 > Ba0.6 > Ca0.6 > Sr0.6. Deep oxidation products were obtained from a La0.2 Ba0.8 Fe0.8 Co0.2 O3–δ disk-shaped membrane reactor without catalyst, with a 4.6% CH4 inlet stream. These products were further reformed to syngas when a downstream catalytic bed was added. Packing the 5% Ni/Al2O3 catalyst directly on the membrane reaction-side surface resulted in a slow fivefold increase in O2 permeation, and a fourfold increase in CH4 conversion. XRD, EDS, and SEM analyses revealed structure and composition changes on the membrane surfaces. Oxygen continuously transported from the air side appeared to stabilize the membrane interior, and the reactor was operated for up to 850 h.

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.

Thermally enhanced compact reformer

Abstract: A natural gas reformer (10) comprising a stack of thermally conducting plates (12) interspersed with catalyst plates (14) and provided with internal or external manifolds for reactants. The catalyst plate is in intimate thermal contact with the conducting plates so that its temperature closely tracks the temperature of the thermally conducting plate, which can be designed to attain a near isothermal state in-plane to the plate. One or more catalysts may be used, distributed along the flow direction, in-plane to the thermally conducting plate, in a variety of optional embodiments. The reformer may be operated as a steam reformer or as a partial oxidation reformer. When operated as a steam reformer, thermal energy for the (endothermic) steam reforming reaction is provided externally by radiation and/or conduction to the thermally conducting plates. This produces carbon monoxide, hydrogen, steam and carbon dioxide. When operated as a partial oxidation reformer, a fraction of the natural gas is oxidized assisted by the presence of a combustion catalyst and reforming catalyst. This produces carbon monoxide, hydrogen, steam and carbon dioxide. Because of the intimate thermal contact between the catalyst plate and the conducting plates, no excessive temperature can develop within the stack assembly. Details of the plate design may be varied to accommodate a variety of manifolding embodiments providing one or more inlets and exit ports for introducing, pre-heating and exhaust the reactants.

Partial oxidation of methane to syngas over nickel-based catalysts modified by alkali metal oxide and rare earth metal oxide

Abstract: The NiO/Al2O3 catalyst was modified by alkali metal oxide (Li, Na, K) and rare-earth metal oxide (La, Ce, Y, Sm) in order to improve the thermal stability and the carbon-deposition resistance during the partial oxidation of methane to syngas (POM) reaction at high temperature. The reaction performance, thermal stability, structure, dispersity of nickel and carbon-deposition of the modified NiO/Al2O3 catalyst and unmodified NiO/Al2O3 catalyst were investigated by a series of characterization techniques including flow-reaction, BET, XRD, CO chemisorption and TG analysis. The results indicated that the modification with alkali metal oxide and rare-earth metal oxide improves the dispersion of active component nickel and the activity for the POM reaction over the nickel-based catalysts, and enhances their thermal stability during high temperature reaction and the ability to suppress the carbon-deposition over the nickel-based catalysts during the POM reaction. The nickel-based catalysts modified by alkali metal oxide and rare-earth metal oxide have excellent POM reaction performance (CH4 conversion of 94.8%, CO selectivity of 98.1%, 2.7×104l/kg·h), excellent stability and carbon-deposition resistance.

Transient oxidation of volatile organic compounds on aCuO/Al2O3 catalyst

Abstract: Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on aCuO/Al 2 O 3 catalyst. The volatile organic compounds (VOCs) were adsorbed on the alumina surface and diffused to the CuO to react. Lattice oxygen in CuO is active for deep oxidation, and as lattice oxygen is depleted, diffusion of lattice oxygen to the surface limits the rate of oxidation. Supported CuO dehydrogenates and oxidizes VOCs and the order of reactivity is: HCOOH > CH 3 OH > CH 3 COOH > C 2 H 5 OH > C 2 H 4 O. Nearly all the oxygen in CuO can be extracted by VOCs. In the absence of gas-phase O 2 , extraction of lattice oxygen limits the oxidation rates of acetaldehyde and acetic acid, but gas-phase O 2 rapidly replenishes the lattice oxygen. No less-reactive, partial oxidation products were detected.

Sustainable Ni/Ca1−xSrxTiO3 catalyst prepared in situ for the partial oxidation of methane to synthesis gas

Abstract: A series of mixed metal oxides of the compositions Ca1−xSrxTi1−yNiyO (x = 0–1.0, y = 0–1.0) were prepared by the citrate method, and was tested for the oxidation of CH4 to synthesis gas. Analytical results clearly showed the presence of Ca1−xSrxTi1−yNiyO perovskite structure, where Sr substituted all the Ca sites while Ni substituted the Ti sites in the range of y < 0.1. Among the catalysts tested, the compositions of x = y = 0.2 showed the highest activity. Either Ni species in the Ca0.8Sr0.2Ti1−yNiyO perovskite structure or NiO originally separated from the perovskite structure during the preparation was in situ reduced to Ni metal during the CH4 oxidation. The Ni metal thus formed showed high activity for synthesis gas production, where Ca0.8Sr0.2TiO3 perovskite has an important role as a carrier of the Ni catalyst. Three catalysts of the composition Ca0.8Sr0.2Ti1.0Ni0.2O were then prepared by citrate, impregnation and mixing methods. The highest activity was obtained with the citrate, followed by the impregnation of Ni on Ca0.8Sr0.2TiO3 perovskite. The catalyst prepared by the mixing method afforded no perovskite, resulting in low activity. The amount of coke formation over the Ni catalysts after the reaction for 150 h was as follows: citrate < impregnation ⪡ Niγ-Al2O3 as the comparison. Ca0.8Sr0.2TiO3 perovskite was effective as the carrier of the Ni catalyst for the partial oxidation of CH4 to synthesis gas. Ni/Ca0.8Sr0.2TiO3 prepared by the citrate method is the most sustainable against coke formation during the reaction. It is likely that the citrate method gave high Ni dispersion over the perovskite as well as strong metal-support interaction between Ni and the perovskite, resulting in both high activity and high sustainability against coke formation.

Rapid injection process and apparatus for producing synthesis gas (law 560)

Abstract: A novel injector/reactor apparatus and an efficient process for the partial oxidation of light hydrocarbon gases, such as methane, to convert such gases to useful synthesis gas for recovery and/or subsequent hydrocarbon synthesis. Sources of a light hydrocarbon gas, such as methane, and oxygen or an oxygen-containing gas are preheated and pressurized and injected through an injector means at high velocity into admixture with each other in the desired relating proportions, at a plurality of mixing nozzles which are open to the partial oxidation zone of a reactor and are uniformly-spaced over the face of the injector means, to form a gaseous premix having a pressure drop through the injector. The gaseous premix is injected in a time period which is less than 5 milliseconds, preferably at a velocity between about 25 to 1000 feet/second, into a partial oxidation reaction zone so that the gaseous premix reacts therein, to reduce the amounts of CO 2 , H 2 O and heat produced by the partial oxidation reaction and form, cool and recover a useful syngas.

FTIR studies on the selective oxidation and combustion oflight hydrocarbons at metal oxide surfaces Part3.—Comparison of the oxidation ofC3 organic compounds over Co3O4,MgCr2O4 and CuO

Abstract: Oxidation of the C 3 organic compounds propane, propene, acrolein, propan-2-ol and acetone has been investigated over three transition-metal oxide catalysts, Co 3 O 4 , MgCr 2 O 4 and CuO, in a flow reactor and using FTIR spectroscopy to study the adsorbed species. Co 3 O 4 and MgCr 2 O 4 are very active in propane and propene catalytic combustion. FTIR studies suggest that adsorbed isopropoxide species and adsorbed acetone and acetates are intermediates in propane oxidation while adsorbed acrolein and acrylates are intermediates in propene oxidation. Flow reactor studies support these hypotheses. It is suggested that the reaction rates in propane and propene total oxidation can be influenced, at low temperature, by the rate of oxidation of adsorbed acetate and acrylate intermediates, respectively. Co 3 O 4 and MgCr 2 O 4 are also active and quite selective catalysts for the oxy-dehydrogenation of propan-2-ol to acetone at low conversion, suggesting that the same oxygen species are involved in total and partial oxidation of organic compounds. CuO, as such, is not active in the adsorption and oxidation of C 3 hydrocarbons and oxygenates, at low temperature. At higher temperatures the reactants reduce the catalyst and catalytic activity starts. The oxidation state of the CuO x catalyst can be evaluated by IR studying the transmittance of the radiation upon different treatments.

System for production of high-purity hydrogen, process for production of high-purity hydrogen, and fuel cell system

Abstract: There is a system for producing high-purity hydrogen by reforming a hydrocarbon and/or an oxygen atom-containing hydrocarbon to form a reformed gas containing hydrogen and separating the hydrogen from said gas. The system includes a hydrocarbon source, a water source, an oxygen source, a vaporization chamber connecting with the hydrocarbon source, the water source and the oxygen source, and a reforming chamber provided with a catalyst for steam reforming and partial oxidation and a hydrogen-separating membrane. The reforming chamber is thermally connected with the vaporization chamber. A process for producing high-purity hydrogen includes heating a reforming chamber provided with a hydrogen-separating membrane, feeding, into the reforming chamber, hydrocarbon, steam and oxygen or air to give rise to steam reforming and partial oxidation therein to produce a reaction gas, and passing the reaction gas through the hydrogen-separating membrane to recover high-purity hydrogen. The heat possessed by the portion of the reaction gas not permeable into the hydrogen-separating membrane and the heat generated by the partial oxidation are utilized for the heating and reforming of the hydrocarbon, water and oxygen or air.

Rapid injection catalytic partial oxidation process and apparatus for producing synthesis gas (law 562)

Abstract: A novel injector/reactor apparatus and an efficient process for the partial oxidation of light hydrocarbon gases, such as methane, to convert such gases to useful synthesis gas for recovery and/or subsequent hydrocarbon synthesis. Sources of a light hydrocarbon gas, such as methane, and oxygen or an oxygen-containing gas are preheated and pressurized and injected through an injector means at high velocity into admixture with each other in the desired proportions, at a plurality of mixing nozzles which are open to the catalytic partial oxidation reaction zone of a reactor and are uniformly-spaced over the face of the injector, to form a reactant gaseous premix having a pressure drop through the injector. The gaseous premix is injected in a time period which is less than 5 milliseconds, at a velocity between about 25 to 1000 feet/second, into a reaction zone comprising a catalytic partial oxidation zone so that the gaseous premix reacts in the presence of the fixed catalyst arrangement to reduce the amounts of CO2, H2 O and heat produced by the partial oxidation reaction and form, cool and recover a useful syngas.

Enhancing Biological Treatability of Landfill Leachate by Chemical Oxidation

Abstract: Chemical oxidation for the partial oxidation of nonbiodegradable compounds has been used to enhance biotreatment. In this study, Fenton's reagent was used in batch mode to enhance the biological treatability of the leachate from an improperly managed municipal solid waste landfill. Removal of color by the oxidation process was also investigated. For this particular landfill leachate, the optimum H2O2 dose was found to be 1500 mg/L with the molar ratio of Fe2+/H2O2 being 0.08. Decolorization efficiency as high as 92.0% was achieved. For the removals of both organics and color in the leachate, the effective pH was in the vicinity of 3.5. Chemical sludge production increased with increasing Fe2+ dose at a fixed H2O2 dose. The ratio of BOD20/COD increased after the oxidation, which indicated that the Fenton oxidation could be effective prior to the biological process. Key words: Landfill; leachate; fenton; oxidation; organics; color

Two component-three dimensional catalysis

Abstract: This invention relates to catalytic reactor membranes having a gas-impermeable membrane for transport of oxygen anions. The membrane has an oxidation surface and a reduction surface. The membrane is coated on its oxidation surface with an adherent catalyst layer and is optionally coated on its reduction surface with a catalyst that promotes reduction of an oxygen-containing species (e.g., O 2 , NO 2 , SO 2 , etc.) to generate oxygen anions on the membrane. The reactor has an oxidation zone and a reduction zone separated by the membrane. A component of an oxygen containing gas in the reduction zone is reduced at the membrane and a reduced species in a reactant gas in the oxidation zone of the reactor is oxidized. The reactor optionally contains a three-dimensional catalyst in the oxidation zone. The adherent catalyst layer and the three-dimensional catalyst are selected to promote a desired oxidation reaction, particularly a partial oxidation of a hydrocarbon.

Gold as a low-temperature oxidation catalyst: factors controlling activity and selectivity

Abstract: Publisher Summary Researchers have found remarkably high catalytic activity in the low-temperature oxidation of CO with some supported gold catalysts prepared by coprecipitation. This chapter discusses the major factors that determine catalytic activity and selectivity in supported gold catalysts. The catalytic activity and selectivity of gold for oxidation can be widely tuned by control of three major factors; selection of type of metal oxide supports, size of the gold particles, and control of the contact structure of the gold particles with the supports. These factors are markedly influenced by the preparation method. Gold supported on metal oxides and hydroxides has been prepared by several different methods and tested for CO oxidation and partial oxidation of propylene. Coprecipitation, deposition-precipitation, and chemical vapor deposition methods are especially effective for depositing gold as nanoparticles with diameters smaller than 5 nm and with strong interaction with the supports. It has been found that over very much dispersed gold catalysts, CO oxidation can take place even at −77°C and propylene oxide can be selectively produced at temperatures around 100°C. For CO oxidation over gold supported on metal oxides, the catalytic activity is almost insensitive to the type of metal oxide support, but strongly depends on the strength of interaction with the supports.

Partial oxidation of methane over aNi/BaTiO3 catalyst prepared by solid phasecrystallization

Abstract: Ni/BaTiO 3 catalyst has been prepared by solid phase crystallization (SPC) and used successfully for partial oxidation of CH 4 into synthesis gas at 800°C. In the SPC method, Ni/BaTiO 3 catalyst is obtained in situ by the reaction of starting materials with nickel species homogeneously incorporated in the structure. For the starting reagents, materials of two compositional types were employed i.e., perovskite structures BaTi 1-x Ni x O 3- δ (0⩽x⩽0.4) and stoichiometric structures, BaTiO 3 , Ba 2 TiO 4 and BaTi 5 O 11 , with 0.3NiO. The starting materials were tested for oxidation of CH 4 by increasing the reaction temperature from room temperature to 800°C. The catalysts showed the highest activity for synthesis gas formation around 800°C, and the highest value was obtained at a composition of x=0.3 in the former catalysts. Among the latter catalysts, the highest activity was observed over BaTiO 3 ·0.3NiO, which was more active than BaTi 0.7 Ni 0.3 O 3-δ . On the both catalysts, nickel species originally incorporated in the structure were reduced to the metallic state during the reaction. The BaTiO 3 ·0.3NiO catalyst was further tested for 75 hours at 800°C with no observable degradation and negligible coke formation on the catalyst. Thus, Ni/BaTiO 3 prepared in situ from the perovskite precursor, i.e., by the SPC method, was the most active and resistant to coke formation and deactivation during the reaction. This may be due to well dispersed and stable Ni metal particles over the perovskite, where the nickel species thermally evolve from the cations homogeneously distributed inside an inert perovskite matrix as the precursor.

Selective Oxidation of Ethane Using the Au|YSZ|Ag Electrochemical Membrane System

Abstract: The catalytic conversion of ethane to acetaldehyde on an inert gold electrode has been studied using the electrochemical membrane reactor with yttria-stabilized zirconia (YSZ) solid electrolyte at 475 C. On applying a direct current to the reaction cell, 5% ethane in N{sub 2}, Au|YSZ|Ag, 100% O{sub 2}, acetaldehyde was formed and the formation rate increased linearly with increasing current. Selectivities to acetaldehyde and carbon dioxide were 45 and 55%, respectively. The addition of oxygen to the ethane-mixed gas in the anode space did not affect the acetaldehyde formation. The use of YSZ powder as a fixed bed catalyst under the mixed gas flow of ethane and oxygen at 450 to 600 C resulted in the formation of carbon monoxide, carbon dioxide, and ethene. Even the use of N{sub 2}O instead of oxygen resulted in no formation of acetaldehyde. Hence, it is likely that partial oxidation of ethane to acetaldehyde was carried out by the oxygen species transferred electrochemically through the YSZ which appeared at the gold-YSZ-gas triple-phase boundary. From the results of ethanol oxidation over the Au|YSZ|Ag system, the following mechanism was proposed: ethane is dehydrogenated to an ethyl radical, then converted to ethoxide, and finally to acetaldehyde by themore » oxygen species transferred through the YSZ.« less