Showing papers on "Partial oxidation published in 1989"

Partial oxidation of sewage sludge

Abstract: Municipal sanitary sewage sludge is disposed of by an improved partial oxidation process without polluting the environment. Aqueous slurries of sewage sludge are upgraded by hydrothermal treatment, preferably while being sheared, concentrated, and then mixed with a supplemental fuel, preferably coal. A pumpable aqueous slurry of sewage sludge-coal and/or petroleum coke is thereby produced having a greater total solids and heat content (HHV) as well as containing an increased amount of sewage sludge for reacting with free-oxygen containing gas in a free-flow partial oxidation gas generator. Hot quench water or steam produced by cooling the hot raw effluent stream of synthesis gas, reducing gas or fuel gas from the gasifier may provide heat for the hydrothermal step.

Catalytic partial oxidation of methane over barium metaplumbate BaPbO3: possible involvement of peroxide ion

Abstract: Although numerous metal oxides catalyze the oxidative dimerization of methane to higher hydrocarbons, the nature of the catalytically active sites is substantially unknown. Previous speculation that peroxide or superoxide ions are responsible for methane activation over Sm/sub 2/O/sub 3/ and over Na/sup +//MgO at high temperatures is supported by the fact that several simple peroxides, e.g., Na/sub 2/O/sub 2/, SrO/sub 2/, and BaO/sub 2/m can stoichiometrically oxidize methane. Here the authors shows, for the first time, the existence of peroxide ions on a complex metal oxide surface that catalyzes the oxidation of methane to C/sub 2/ hydrocarbons. They suggest that these peroxides may exist in a novel, through-bond isomer similar electronically to ozone.

A study of the mechanism of the partial oxidation of methane over rare earth oxide catalysts using isotope transient techniques

Abstract: The mechanism of the partial oxidation reaction of methane over three catalysts (Sm{sub 2}O{sub 3}, Li/Sm{sub 2}O{sub 3}, and Pr{sub 6}O{sub 11}) having a range of activities and product selectivities has been studied by using isotope transient techniques. The most important conclusions from this study are (1) that large amounts of CH{sub 4} are adsorbed on all working catalysts, (2) that the reaction takes place on a small number of very active catalyst sites and does not involve the adsorbed CH{sub 4}, (3) that gas-phase oxygen exchanges rapidly with the lattice oxygen atoms of the working catalysts, (4) that the rate of CH{sub 4} conversion is dependent on the rate of lattice oxygen exchange, and (5) that the carbon oxides are substantially formed by the secondary oxidation of the reaction products. A mechanism based on the formation and reactions of (O{sup {minus}}) species is proposed for the C{sub 2+} products, but a different form of activated oxygen appears to be responsible for the formation of the carbon oxides.

Partial oxidation of methane over oxide catalysts. Comments on the reaction mechanism

Abstract: A detailed investigation of the partial oxidation of methane to ethane and ethene is described. In particular a range of oxidants (O2, N2O, O3) have been reacted with a series of catalysts (MgO, Li/MgO, La2O3, Li/La2O3, Sm2O3 and Li/Sm2O3) and these studies have been utilized to investigate the reaction mechanism. Methane oxidation at conversions of ca. 1 % have indicated that ethene as well as ethane is a primary reaction product, but at higher conversions the major fraction of the ethene formed is via oxidative dehydrogenation of ethane in a secondary reaction. Based on this study a reaction mechanism is proposed and discussed. In line with previous studies the results from used of N2O as oxidant confirm that O–(s) is the oxidising species responsible for CH˙3 formation, from CH4, which on dimerisation yields ethane. In addition it is proposed that primary formation of ethene results from the interaction of methane with a different surface oxygen species (e.g. O2–2(s)). The oxides studied, which can be considered as broadly representative of the wide range of oxides utilised as catalysts, become active only at high temperatures ( 700 °C) and at such temperatures the gas phase nature of the overall reaction is dominant. The consequences of this observation are discussed with respect to the design of improved catalysts.

Solid Ion Conductors in Heterogeneous Catalysis

Abstract: The electrochemical measurement of oxygen activity using ion-conducting solid electrolytes (λ-sensors) has become widely known, at least since the application of three-way catalysts in the postcombustion of exhaust gases from spark-ignition engines. However, the use of solid ion conductors is not limited to control devices. There are various other potential applications and numerous problems which can be studied: the formation of oxides in the course of catalytic reactions on metal surfaces, the improvement of selectivity and yield of catalytic reactions, such as the epoxidation of ethylene on silver catalysts and, finally, the cogeneration of electrical energy during oxidation reactions, such as the partial oxidation of methanol to formaldehyde.

Reactor for reforming hydrocarbon and process for reforming hydrocarbon

Abstract: A hydrocarbon-reforming reactor by a steam reforming reaction and a partial oxidation reaction, which comprises a chamber for feeding oxygen-containing gas, a chamber for feeding a mixture gas of hydrocarbon with steam and a chamber for heat exchange of reformed gas in this order from one side of the reforming reactor, and which further comprises a catalyst layer filled in a space between an inner tube having an opening to the chamber for feeding oxygen-containing gas and a reaction tube being so placed as to position the inner tube in its middle portion and having an opening to the chamber for feeding the mixture gas, and a process for producing reformed gas from hydrocarbon which comprises carrying out a steam reforming reaction in the catalyst layer on the side of the chamber for feeding the mixture gas of hydrocarbon with steam by feeding the mixture gas of hydrocarbon with steam to the catalyst layer from the chamber for feeding the mixture gas, carrying out a partial oxidation reaction and steam reforming reaction by feeding oxygen-containing gas fed into the inner tube through the chamber for feeding oxygen-containing gas to the catalyst layer through holes or slits provided in that part of the inner tube which is located opposite to the chamber for feeding the mixture gas, and allowing the resultant, reformed gas to move out of the reforming reactor from the reaction tube through the chamber for heat exchange of reformed gas.

Evidence for formation of gaseous methyl radicals in the decomposition of methoxide on oxygen-precovered Mo(110)

Abstract: Evidence of the unprecedented formation of gaseous methyl radicals from adsorbed methoxide is presented in this study. Previously, surface methoxide has been found to either form formaldehyde or decompose to CO and H{sub 2}. The observation of methyl radicals during decomposition of methanol on Mo(110) precovered with atomic oxygen is of significance to the study of the partial oxidation of methane over metal oxide catalysts, since the observed decomposition pathway of methanol is analogous to the reverse of methane oxidation.

Steady state and dynamic modelling of a packed bed reactor for the partial oxidation of methanol to formaldehyde i. model development

Abstract: Several levels of mathematical models involving one and two dimensions as well as single and multiple phases are used to predict the steady state and dynamic behavior of a packed bed reactor for the partial oxidation of methanol to formaldehyde. Parametric sensitivity is examined for several heat and mass transfer parameters, kinetic parameters, and operating conditions. Yield is compared for various models, and significant differences are observed between the one-dimensional and two-dimensional models. The dynamic behavior after step changes in the operating conditions is found to be qualitatively similar for different models.

Process for partial oxidation of a liquid or solid and/or a gaseous hydrocarbon-containing fuel

Abstract: Process for the partial oxidation of a liquid or solid and/or a gaseous fuel using a multi-orifice burner comprising a central channel and four concentric channels encircling the central channel. Liquid or solid fuel is supplied through the second concentric channel and the oxidizer is supplied through the first concentric channel and the third concentric channel. Hydrocarbon gas and/or moderator is supplied through the central channel and the fourth concentric channel. The supplies occur at specific mass flow distributions and velocities. The mass ratio of liquid or solid fuel to hydrocarbon gas ranges from 0 to 1.

Reaction of preadsorbed methane with oxygen over magnesium oxide at low temperatures

Abstract: Partial oxidation by O2 of methane, which had previously been adsorbed at room temperature on MgO pretreated at 1123 K in vacuo, has been examined near room temperature by t.p.d., i.r. and e.s.r. spectroscopies and compared with a methanol adsorption system. The oxidation reaction of methane preadsorbed either in the dark or under u.v.-irradiation proceeds according to the same reaction mechanism, where low-coordination surface ions of MgO play an important role. Methane is adsorbed in a heterolytically dissociated form (CH–3+ H+), and then oxidized to a methoxide species, OCH–3(2), on the admission of O2 at room temperature. On heating under evacuation, OCH–3(2) is either decomposed into H2 and CO in the temperature range 495–535 K or further oxidized by coexisting O–2 into HCO–2 below 473 K. The HCO–2 formed gives either CO or bidentate CO2–3 at ca. 600 K. Another more stable methoxide species, OCH–3(1), is also sometimes formed eithere directly on room-temperature oxidation or through a transformation of the less stable species, OCH–3(2), on heating at ca. 500 K. Part of the OCH–3(1) present then decomposes into H2 and CO at 760 K and the rest changes into bidentate CO2–3. The CO2–3 species thus formed ultimately are desorbed as CO2 above 600–700 K.

Steady state and dynamic modelling of a packed bed reactor for the partial oxidation of methanol to formaldehyde ii. experimental results compared with model predictions

Abstract: Heterogeneous and pseudohomogeneous two-dimensional models are compared to steady state and dynamic experimental data from a packed bed reactor for the partial oxidation of methanol to formaldehyde over an iron oxide-molybdenum oxide catalyst. Highly effective parameter estimation software was used to fit selected model parameters to large sets of experimental data so as to obtain small residuals. Heat transfer parameters which were successful in matching data from experiments without reaction were not capable of fitting data from experiments with reaction, and it was necessary to increase the radial heat transfer for higher temperatures or reaction rates. Axial composition profile data was represented by estimating the preexponential factors and activation energy in a half-order redox rate expression for methanol oxidation. After some decline in catalyst activity, a time-varying axial catalyst activity profile was determined from the data. A redox-type rate expression for the oxidation of formal...

Selective partial oxidation of propane over metal phosphate catalysts

Abstract: Catalytic oxidation of propane was studied over metal phosphates using propane rich feed. Oxidation reached measurable rate at 620–700 K over the catalysts. Over Cu2P2O7, Ni2P2O7, and LaPO4, propene, acetaldehyde, and methanol were principal products and the sum of these selectivities reached 70–80 mol%. Maximum selectivity of acrolein, 11.5 mol%, was observed over Mn2P2O7. Selectivity of propene reached 50.7 mol% over Co2P2O7. Deep oxidation was dominant over Cr4(P2O7)3, (ZrO)2P2O7, and CePO4.

Role of surface atomic arrangements of well defined phosphates in partial oxidation and oxidative dehydrogenation reactions

Abstract: Various vanadium and iron phosphates have been synthesized and characterized physically before and after catalytic reaction has taken place Vanadium phosphate was used for butane oxidation into maleic anhydride and iron phosphate for isobutyric acid dehydrogenation to methacrylic acid Vanadium phosphate catalyst in its working state corresponds to a mixture of the pyrophosphate phase (VO)2P2O7 and a given VOPO4 phase (αII, β or δ) 31P MASNMR spectra showed that the most efficient catalysts contained VOPO4 entities in interaction with (VO)2P2O7, while an X-ray electronic radial distribution study showed that VOPO4 entities are present but not necessarily organized in sufficiently long-range order to be detected by classical X-ray diffraction The iron phosphates Fe2P2O7, FePO4 and Fe7(PO4)6 were transformed under catalytic reaction into Fe7(PO4)6 and an unknown phase The latter phase was tentatively assigned from Mossbauer spectroscopy to Fe6P6O23 with an Fe3+/Fe2+ ratio equal to two The best catalysts including the industrial catalyst were those containing the Fe6P6O23 phase A similarity has been found in the behaviour of vanadium and iron phosphates The best catalysts correspond to those which exhibit short- or long-range order between the reduced pyrophosphate phase and a more oxidized form as VOPO4 or Fe6P6O23 It is suggested that the ease of transformation of two PO4 groups, at least locally, into one P2O7 group is the clue to obtaining an efficient catalyst This is a case of topotactic transformation

The mechanism of the partial oxidation of methane

Abstract: The principal characteristics of the homogeneous and heterogeneous-catalytic conversion of methane into condensation products (C2 and C3 hydrocarbons) and partial oxidation products (methanol and formaldehyde) are considered. Data are presented concerning the most effective catalysts and data relating to the mechanism of the activation of methane on oxide and oxide halide catalysts, the nature of the active centres, and the kinetics of the partial oxidation of methane are analysed. It is shown that the oxidative condensation of methane in the presence of the catalysts considered is a heterogeneous-homogeneous process, which imposes special requirements in its practical realisation. The bibliography includes 118 references.

Oxidation of methane to methanol

Abstract: A marked improvement in yield, in selectivity or in both is obtained in the synthesis of methanol by the homogeneous direct partial oxidation of natural gas or other source of methane when the reactor space is filled with inert, refractory inorganic particles.

Partial oxidation of methane over Y1Ba2Cu3O6+x-zFz

Abstract: In this communication we report our study on using high-temperature superconductors as partial oxidation catalysts. We have also investigated fluorinated superconducting materials, since the presence of a strong oxidizing agent should favor partial oxidation selectivities.

Selective oxidation of propane to acrolein over Ag-doped bismuth vanadomolybdate catalysts

Abstract: Acrolein was formed as a major product in the partial oxidation of propane using molecular oxygen over Ag-doped bismuth vanadomolybdate catalysts having a scheelite structure.

Infrared study of the adsorption of ethanoic acid, acrylic acid, acetone, acrolein and propene–NO mixtures on Rh/SiO2 catalysts

Abstract: Infrared spectra of the adsorbed products of reaction of propene and NO over Rh/SiO2 are compared with spectra of adsorbed acetone, acrolein, acrylic acid and ethanoic acid. Acetone and acrolein formed hydrogen bonds with surface silanol groups and underwent decomposition on rhodium to give rhodium carbonyl species. The carboxylic acids also gave rhodium carbonyl species, but for ethanoic acid this only occurred at high temperature. Both acids were adsorbed on silica either through chemisorption giving a surface ester or as a weakly held dimer. Heat treatment of Rh/SiO2 in propene/NO mixtures gave acrylic acid as the dominant partial oxidation product. However, addition of propene before NO to the reaction system led to the generation of a surface poison which inhibited the oxidation of propene.

Partial oxidation of ethane over boron oxide added catalysts

Abstract: B2O3–Al2O3, B2O3–MgO, B2O3–La2O3, and B2O3–P2O5 are selective catalysts for the partial oxidation of ethane. Among these catalysts, B2O3(30wt%)-added Al2O3 showed the highest catalytic activity in the formations of acetaldehyde (yield 1.03%) and ethylene (14.6%). Acetaldehyde is formed not via ethylene but directly from ethane. The formations of ethylene and acetaldehyde occur on different active sites.

Conversion of methane

Abstract: A mixture of organic compounds comprising a major amount of liquid hydrocarbons, mostly aromatic, is formed by the direct partial oxidation of methane in the presence of a ZSM-5 catalyst. The reaction conditions are substantially the same as those required for the direct homogeneous partial oxidation to methanol. However, liquid hydrocarbon formation depends on the presence of a small amount of an impurity such as propane or propylene in the feed; in the absence of such, only methanol is formed. With such modifier present, controls of reaction parameters, e.g., temperature, permits synthesis of both methanol and liquid hydrocarbons in desired proportions. Properly processed natural gas can serve to provide methane and at least part of the reaction modifier.

Electrocatalytic oxidative dimerization of methane

Abstract: A solid oxide fuel cell and process for direct conversion of natural gas into DC electricity concurrently with the electrocatalytic partial oxidation of methane to C 2 hydrocarbon species C 2 H 4 , C 2 H 6 , and minor amounts of C 2 H 2 .