Showing papers on "Partial oxidation published in 1981"

Substoichiometric combustion of low heating value gases

Abstract: The combustible component of a gas stream of low heating value is combusted using less than a stoichiometric amount of oxygen with minor production of carbon monoxide due to the use of an oxygenation catalyst comprising at least three metals in a perovskite-type crystal structure. This combusted gas can be directly vented to the atmosphere after energy has been extracted from it for a useful purpose.

Moessbauer spectroscopic study of passivated small particles of iron and iron carbide

Abstract: Moessbauer spectra have been recorded at room, liquid-N/sub 2/, and liquid-He temperatures for iron supported on silica after calcination, reduction, and carburization. Passivation, i.e., exposure to air, of reduced iron resulted in partial oxidation to ..beta..-FeOOH. Carburization at 300/sup 0/C in 3H/sub 2/:CO produced a mixture of chi-Fe/sub 5/C/sub 2/ and epsilon'-Fe/sub 2/ /sub 2/C in agreement with previous workers. Passivation of these carbides resulted in partial oxidation to either ..gamma..-FeOOH or an amorphous iron gel. These experiments emphasize the great potential for error if the study of these materials is confined to room-temperature spectra.

Catalytic oxidation of cycloparaffins

Abstract: A process is disclosed for the catalytic oxidation of a cycloparaffin, e.g., cyclohexane, to partial oxidation products thereof, especially for the production of mixtures of cycloalkanols and cycloalkanones. In the process, molecular oxygen, usually in the presence of an inert gas, is introduced into the cycloparaffin at elevated pressure and a temperature of 130°-180° C., in the presence of an oxidation catalyst comprising a heavy metal compound along with an N-heterocyclic compound. The heavy metal of the heavy metal compound may be cobalt, vanadium, manganese, copper, iron or nickel. The heavy metal compound may have ligands of alkanoate, dialkylphosphate, dicycloalkylphosphate or alkylcycloalkylphosphate. The N-heterocyclic compound may be dipyridyl, pyrimidine, pyrazine, pyridine and pyridine substituted with --CN, --R, and/or --OR where R is alkyl. A preferred catalyst is cobalt bis[di(2-ethylhexyl)phosphate] in combination with pyridine.

Methanol oxidation over vanadium-containing model oxide catalysts. Influence of charge-transfer effects on selectivity

Abstract: Model vanadium-containing catalysts [α-Al2–xVxO3(x= 0–0.2), TixV1O2–x(x= 0–0.2) and SnxV1–xO2(x= 0–0.2)] have been studied to discover the extent to which conductivity or electron-exchange effects are important in determining catalyst selectivity in the oxidation of methanol. By cross-comparison of the catalytic behaviour and solid-state data for the three catalyst systems it is concluded that the high selectivity to partial oxidation products is correlated with relatively facile electron exchange between active-site cations. The host lattice is shown to have an important role in that the “electronic isolation” of the active sub-lattice seems to be important.

Analysis of the factors affecting selectivity in the partial oxidation of benzene to maleic anhydride. Part 1.—Detailed kinetics of maleic anhydride adsorption

Abstract: The adsorption of maleic anhydride on a vanadium pentoxide–molybdenum trioxide catalyst has been studied using the transient techniques of temperature programmed desorption and gas adsorption chromatography. The desorption spectra obtained over a range of adsorption temperatures show two peaks having maxima at between 220 and 250 °C and 340 and 350 °C. Solution of the Redhead equation for an assumed value of 1013 s–1 for the desorption A-factor at the peak maxima gave desorption energies of between 138 and 148 kJ mol–1 and 171 and 181 kJ mol–1. In spite of the high dosages used (ca. 107 Langmuirs), the surface coverages never exceeded 6 × 1012 sites (molecules) cm–2 with the number of high energy sites remaining constant at 3 × 1012 sites cm–2 over the large range of adsorption temperatures; it is inferred that these sites are a defect property of the mixed oxide. The gas adsorption chromatographic peak shapes are also analysed in terms of two adsorption bonds from which the heats of adsorption of 79.9 and 104.2 kJ mol–1 are derived. The adsorption of maleic anhydride on the mixed oxide catalyst is therefore seen to be activated, having adsorption activation energies of 63 and 71 kJ mol–1. These not inconsiderable heats of adsorption and desorption activation energies imply the possibility of product inhibition in the selective oxidation of benzene to maleic anhydride.

Chromic titanate catalysts for high‐melt‐index polyethylene by the particle‐form process

Abstract: A novel thermal activation procedure for ethylene polymerization catalysts made from silica, a chromium compound, and a titanium ester greatly increases the melt index of the polyethylene product under commericla polymerization conditions in comparison with conventional air activation. The novel activation has two steps. The first is heating under a reducing gas atmosphere (N2 + CO). The second step is partial oxidation at a lower temperature for a shorter time. The size of the melt index increase is related to the average oxidation number of the chromium, but oxidized chromium can be reduced and the effect persists with less intensity. Additionally, the magnitude of the effect is dependent upon gas flow rates during activation and prior chemical and thermal history of the chromium–silica combination. Since titanium is required for the two-step activation to be effective in increasing melt index, titanium atoms have a critical influence on the catalyst active sites. An experiment with tetraethoxysilane added to the catalyst shows that titanium and chromium atoms must be next nearest neighbors (separated by oxygen atoms).

Analysis of the factors affecting selectivity in the partial oxidation of benzene to maleic anhydride. Part 2.—Detailed kinetics of benzene adsorption and surface reaction

Abstract: The kinetics of the oxidation of benzene to maleic anhydride over a vanadium pentoxide–molybdenum trioxide catalyst have been studied using a combination of transient techniques. Temperature programmed desorption (t.p.d.) has shown (i) the existence of a weakly-bound molecular oxygen species having a desorption activation energy of between 105 and 113 kJ mol–1 and (ii) that the adsorption of benzene is heteroenergetic having three sets of desorption activation energies of between 97.9 and 104.2 kJ mol–1, 107.9 and 119.2 kJ mol–1 and 130.5 and 133.5 kJ mol–1. (As before, these desorption energies are obtained by solution of the Redhead equation for the peak maximum temperature for an assumed 1013 s–1A-factor.) In spite of the high benzene dosages used in these studies (ca. 3 × 1010 Langmuir, 1 Langmuir = 1.33 × 10–4 N m–2 s) the total coverages by these sites never exceeded 4 × 1011 cm–2, suggesting that they are an intrinsic defect property of the catalyst.Temperature programmed reaction spectroscopy (t.p.r.s.) has shown that (i) the overall oxidation of benzene to maleic anhydride is rate limited in the desorption of the product, the desorption activation energies of the reactively produced maleic anhydride (in the ranges 143.5–148.1 kJ mol–1 and 166.1–169.9 kJ mol–1) being identical to those obtained for pre-adsorbed maleic anhydride, (ii) the activation energy for the surface oxidation of the adsorbed benzene to adsorbed maleic anhydride is low, having a value of 31.4 kJ mol–1, (iii) the reactively produced maleic anhydride occupies the site upon which its precursor, benzene, was chemisorbed, inhibiting further benzene adsorption on that site and (iv) from the population distribution of the adsorbed maleic anhydride on the energetically heterogeneous surface, it was formed at the benzene adsorption temperature (50 °C).The immobility of the adsorbed maleic anhydride suggests that the oxygen is transported to the adsorbed benzene, which in combination with the low surface oxidation activation energy appears to preclude the involvement of lattice oxygen in this step, inferring that the oxidant is a mobile chemisorbed species, possibly the weakly bound molecular state seen in the t.p.d. experiments.Gas adsorption chromatography (g.a.c.) shows the heats of adsorption of benzene to be low, 58.6 and 69.5 kJ mol–1, the latter heat being a composite of two heats which cannot be resolved. The maximum number of sites available for benzene adsorption is only 2.7 × 1012 cm–2 of which 97.5% have a heat of adsorption of 58.6 kJ mol–1. Benzene adsorption is therefore weakly activated.

Partial oxidation of propene over U.V.-irradiated vanadium oxide supported on silica

Abstract: Photocatalytically inactive V2O5 became highly active for the oxidation of propene when supported on SiO2, and aldehydes were selectively formed even when the levels of conversion of propene were high.

Process for the production of gas mixtures containing hydrogen and carbon monoxide via the endothermic partial oxidation of organic compounds

Abstract: An improved process for the production of a gas mixture containing hydrogen and carbon monoxide by endothermal partial oxidization of an organic compound with steam and/or carbon dioxide is disclosed wherein at least a portion of the heat required for the partial oxidation is obtained by direct heat exchange with products obtained from the gasification of a carbonaceous ash-forming fuel with oxygen in the presence of steam.

Alumina catalyst carrier for partial oxidation and prepatation thereof

Abstract: PURPOSE: To obtain a carrier having large specific surface area, high strength and uniform fine power distribution, as the alumina catalyst carrier for partial oxidation, by compounding an inorg. binder in a specific low soda alumina secondary particle being a main aggregate material. CONSTITUTION: In an almost spherical low soda alumina particle comprising α- alumina crystal with a particle size 1W5μ and having an average particle size 30W50μ as a main aggregate material, mullite type inorg. binder is compounded in an amount 1W15wt% on the basis of the total amount to obtain the alumina catalyst carrier for partial oxidation having a specific surface area of 1W2m 2 /g. This carrier is an excellent one having a relatively high specific surface area, high strength and uniform fine pore distribution. COPYRIGHT: (C)1982,JPO&Japio

Propane Oxidation Over Mixed Metal Oxides: Perovskites, Trirutiles and Columbites

Abstract: Two approaches were tried and found to be effective to synthesize catalysts that were active for the partial oxidation of propane. A model system with controllable defects was studied. A series of perovskites were found to be active if both bismuth atoms and vacancies were present simultaneously on the “A” site. Second, we found that substitution and stabilization of vanadium (+IV) into ternary rutile related structures provided a means of producing catalytically active phases. The activity decreased from 500 to 350°C. The selectivity was somewhat different for the perovskite and trirutile catalysts; the selectivity changes with decreasing temperature. The perovskites showed activity that was similar to scheelites containing Bi and vacancies on the high coordinate site. The vanadium catalysts were more active in producing partially oxidized products with less than three carbons. An unexpected increase in activity was seen between 425 and 400°C.

Preparation of methanol and formaldehyde by partial oxidation of methane

Abstract: PURPOSE: To prepar the titled compound in high yield, by the direct catalytic partial oxidation of methane with an oxidizing agent generating oxygen anion radical, using a molybdenum oxide as a catalyst. CONSTITUTION: Methanol and formaldehyde are obtained by reacting methane with an oxidizing agent capable of easily generating oxygen anion radical, e.g. dinitrogen monoxide, nitrogen monoxide, etc. in the presence of an oxidation catalyst comprising an oxide of molybdenum. The oxidation catalyst is prepared by supporting an oxide of molybdenum on a carrier such as silica, alumina, etc. by impregnation, equilibrium adsorption, etc., drying the mixture at 100W200°C, and calcining in air at 350W700°C. The ratio of the molybdenum oxide (in terms of oxide) to the carrier is preferably 0.5W6wt%. The amount of the oxidizing agent is 0.05W10mol, preferably 0.5W5mol per 1mol of methane. COPYRIGHT: (C)1983,JPO&Japio

Method for enhancing the ignition performance of dialkoxyalkanes used as diesel fuel, in particular 1,1-diethoxyethane

Abstract: The ignition performance of dialkoxyalkanes, used as diesel fuel, of the formula in which R1 and R2 are hydrogen or alkyl radicals having up to 3 C atoms, and R3 and R4 are alkyl radicals having up to 4 C atoms, can be enhanced by partial oxidation with an oxygen donor; it is sufficient in this case if a part of the dialkoxyalkane of 0.5 to 3% by weight, calculated as H2O2, is oxidised. Preferably, 1,1-diethoxyethane is oxidised. The preferred oxidising agents are ozone-containing oxygen, air with UV irradiation and especially H2O2.

Improvements in or relating to coal gasification process

Abstract: A process for gasifying a carbonaceous fuels to produce carbon monoxide, hydrogen and methane in which a first stream of carbonaceous material is gasified in a high temperature partial oxidation zone (2) without bed formation the mineral matter content of the fuel being removed as molten slag. A second stream of carbonaceous material is entrained/fluidised in a rapid mixing (10) zone by the upflowing products from the partial oxidation zone and circulating char from a surrounding annular fluidised bed zone (11), the latter being fluidised by the addition of an appropriate agent.

Method for the production of synthesis gas

Abstract: Crude gas obtained through partial oxidation of carbon-containing material is subjected to catalytic conversion in an apparatus containing a moistening-demoistering system connected by means of a combined water circulation. To reduce the required amount of steam and process heating, a partial stream of water coming from the moistener is branched off, heated by indirect heat exchange with converted, hot synthesis gas, and then united with the partial stream of water coming from the demoistener for re-delivery to the moistener.

Metal catalyst without carrier for the partial soot-free oxidation of liquid hydrocarbons with air

Abstract: For the soot-free production of a fuel gas mixture containing carbon monoxide, hydrogen and gaseous hydrocarbons by partial oxidation of liquid hydrocarbons with air, with air numbers below 0.3 and temperatures between 600 DEG and 800 DEG C., a metal catalyst is employed according to the invention, which is prepared by forming shaped bodies composed of an aluminum alloy which contains 15 to 35 wt. % silicon, and subjecting the shaped bodies for at least 10 hours at temperatures between about 600 DEG and about 800 DEG C. to an oxidizing atmosphere and for at least 10 hours at temperatures between about 600 DEG and about 800 DEG C. to gaseous or gasified hydrocarbons for the partial conversion of the aluminum in the shaped body to alpha -Al2O3 and for the partial conversion of the silicon in the shaped body to beta -SiC, respectively.

A preliminary study of the influence of alkali-metal promoters on the selectivity and activity of vanadium catalysts in the oxidation of naphthalene

Abstract: The oxidation of naphthalene over vanadia catalysts promoted by alkali- metal sulfates was studied in the temperature range 400-440°C. The effects of SO3 levels and alkali-metal sulfate promoter type on catalyst activity and selectivity were investigated in laboratory fixed-bed reactors employing integral conversions. The relative promoting abilities of the alkali metals sodium, potassium, rubidium and caesium were investigated with laboratory catalyst preparations. Alkali metals of higher atomic number favoured selectivity to partial oxidation products with an associated loss in overall activity.

Partial oxidation syngas can help improve refining economics

Abstract: The chemistry of gasification of heavy feedstocks by partial oxidation and the operating characteristics of the partial-oxidation gasifier without soot recycling have already been reported. A flow scheme and equipment for a process embodying soot recycling practiced in all the modern Texaco-licensed plants using liquid feeds are described. Gasification data are presented for vacuum residue, solvent deasphalter bottoms, H-Oil residue, and a commercial heavy oil fraction. Effects of soot recycling, gasification pressure, and of feed stream/oil ratio on the process are all evaluated. Partial oxidation plants now being constructed or planned for construction are mentioned. (BLM)

Highhtemperature treatment of hydrocarbonncontaining material

Abstract: PURPOSE:To prevent the deposition of solid carbon and to improve productivity, by a method wherein when a high-temprature treatment such as thermal cracking of hydrocarbons is carried out, the surface of an apparatus made of Ni-contg. steel, where the apparatus is contacted with hydrocarbons, is coated with a heat-resistant material which does not contain nickel. CONSTITUTION:When thermal cracking, steam reforming or partial oxidation of hydrocarbons is conducted by subjecting the hydrocarbons alone or together with an ancillary raw material such as steam or oxygen-contg. gas and reaction products such as H, CO and CO2 to a heat treatment at 500 deg.C or higher, the surface of a reaction apparatus made of Ni-contg. steel, where the apparatus is contacted with the hydrocarbon, is coated with a heat-resistant material which does not contain nickel, and then the above heat treatment is carried out. Examples of the heat- resistant materials are (A) steel which does not contain nickel, (B) metal alone such as Ti, Co, Cr or Fe or alloy composed of at least two metals seleted from Ti, Co, Cr and Fe, (C) alloy obtd. adding Al or Al and Si to the above steel (A), or the metal or the alloy of the above (B), (D) alloy composed of Ti and Nb or Cr and Cu, and (E) alumina, TiO2, SiO2, SiC, BN, Cr2O3 or silicon nitride.

Catalyst and process development for hydrogen preparation from future fuel-cell feedstocks. Final report, October 1, 1978-June 30, 1981

Abstract: The objective of this contract was to develop and demonstrate processes for the production of gaseous fuel cell feeds from high sulfur distillate fuels. The processes considered and studied in this program were high temperature steam reforming with hydrogen recycle, catalytic partial oxidation, and autothermal reforming. Even with hydrogen recycle, high temerature steam reforming of No. 2 oil proved to be dfficult due to carbon formation in the preheat section. Several steam reforming catalysts were evaluated during this phase of the program. (WHK)

Recovery of particles rich in carbon from aqueous suspensions containing same

Abstract: Unconverted char in a mixture of particles formed in the partial oxidation of an ash-containing solid fuel is recovered by grinding the mixture and subjecting the ground material to froth flotation

Oxidation of ethylene over silver: adsorption, kinetics, catalyst

Abstract: Selective oxidation of ethylene to ethylene oxide over supported silver catalysts is not only one of the very few uses of that element as n catalyst of industrial importance, it also has been the basis for the manufacture of an important chemical intermediate that underlies the large glycol industry as well as the manufacture of a varied array of solvents and related chemical materials, The chemical reactions offer a classical example of selectivity for partial oxidation to ethylene oxide versus complete combustion to carbon dioxide and water.

Investigation of Catalytic Reactions of Ethanol Proceeding on Oxidic Clusters of Vanadium on Aerosil Using a Transient Response Method

Abstract: On an oxidic vanadium cluster catalyst the rates of the partial oxidation and dehydration of ethanol have been studied by the transient response technique. The results with respect to oxidation are in agreement with a reduction-reoxidation mechanism, the decomposition of a stable surface compound being the limiting step of the reaction. In absence of oxygen in the gas phase de-hydrogenation of ethanol seems to be possible on the reduced catalyst.

Process for the catalytic treatment of crude gas produced by partial oxidation

Abstract: A process for removing nitric oxides and also SO2 and oxygen traces from the crude gas product of partial oxidation (gasification) of carbon- containing feedstocks is characterised by treating the crude gas with a catalyst containing sulphidic iron. The catalyst may be a sulphidised mixture of iron and chromium oxides, or a sulphidised Fe III hydroxide-containing material.

Catalytic Activity and Deactivation Mechanisms of Supported NiO in CH4 Oxidation

Abstract: The partial oxidation of CH4 was studied using a commercial Ni/α-Al2O3 catalyst. The results show that two operating regimes can be maintained: a low-conversion regime where CO2 and H2O are formed and a high-conversion regime where CO, CO2, H2 and H2O are formed. The latter regime is established by "catalytic light-off" which among other conditions depends on temperature, feed composition and catalyst activity. Prior to light-off, the catalyst is in the NiO form. Following light-off, the catalyst is in NiO form near the inlet and metallic form further downstream. A series of NiO/α-Al2O3, and NiO/ZrO2 catalysts were prepared by impregnation and calcination in air between 750 and 1050°C. These catalysts were characterized by the BET method, O2 chemisorption, X-ray diffraction, electron microscopy and ESCA. Test analyses indicate that the supported NiO particles are made up of a large number of small crystallites which become more dispersed after reduction and reunite after oxidation. The activity of these catalysts for CH4 oxidation under pre-light-off conditions was found to decrease dramatically with increasing calcination temperature. However, the calcined catalysts can be reactivated by reduction in H2 prior to reaction. The change in activity is attributed mainly to the change in specific activity of NiO which is explained in terms of the change in excess oxygen content.

Moessbauer spectroscopic study of passivated small particles of iron and iron carbide

Abstract: Moessbauer spectra have been recorded at room, liquid-N/sub 2/, and liquid-He temperatures for iron supported on silica after calcination, reduction, and carburization. Passivation, i.e., exposure to air, of reduced iron resulted in partial oxidation to ..beta..-FeOOH. Carburization at 300/sup 0/C in 3H/sub 2/:CO produced a mixture of chi-Fe/sub 5/C/sub 2/ and epsilon'-Fe/sub 2/ /sub 2/C in agreement with previous workers. Passivation of these carbides resulted in partial oxidation to either ..gamma..-FeOOH or an amorphous iron gel. These experiments emphasize the great potential for error if the study of these materials is confined to room-temperature spectra.