Oxidation Of Light Alkanes Research Articles

Selective oxidation of light alkanes over Mo-based oxide catalysts

A highly reduced Keggin-type heteropolymolybdophosphate, H3PMo12O40(Py), which was formed by the heat-treatment of pyridinium salt of H3PMo12O40, can catalyze the propane oxidation to acrylic acid and acetic acid selectively. We propose a possible reaction mechanism for alkane oxidation, where protons and electrons on the reduced H3PMo12O40 catalyst cooperate for activating molecular oxygen to form electrophilic oxygen species for alkane oxidation. It is also reported that Anderson-type heteropolycompounds linked with vanadyl cations VO2+ were able to be synthesized by hydrothermal reaction and showed good catalytic activity for the ethene oxidation to acetic acid.

Vanadium–molybdenum phosphates supported by TiO2 for ethane oxidation to acetic acid: a correlation between the local environment of vanadium and the reactivity

Different complementary physicochemical tools have been used to explain the improvement of the catalytic performances for ethane oxidation into acetic acid induced by the addition of molybdenum as phosphate to vanadium phosphate deposited on TiO2-anatase, at a coverage below the monolayer. Electron microscopy techniques have shown that the elements are dispersed on the support. Electron spin resonance, laser Raman and UV-visible spectroscopies have evidenced that the short range order around vanadium is modified by the presence of molybdenum. 51V NMR has shown that molybdenum favours the octahedral symmetry of vanadium. The acidic properties of the catalyst are improved by the adding effect of molybdenum and by the addition of water. This should explain a better desorption of acetic acid and the improvement of the corresponding yield. This confirms the importance of the atomic environment of vanadium-based oxides to control the mild oxidation of light alkanes.

Selective oxidation of light alkanes: interaction between the catalyst and the gas phase on different classes of catalytic materials

Some aspects concerning the chemistry of oxidative transformation of paraffins catalyzed by different classes of materials are examined. Attention is given mainly to: (i) the role of the redox properties of transition metal oxide-based systems, and (ii) the contribution of radical-type, homogeneous and heterogeneously-initiated homogeneous reactions over nonreducible metal oxide catalysts. Technological solutions aimed at the control of oxidizing properties of the catalyst are also examined.

Partial oxidation of light alkanes by NO x in the gas phase

Partial oxidations of CH 4, C 2H 6, C 3H 8, and iso-C 4H 10 with O 2 were promoted by addition of NO in the gas phase. The addition of NO increased the conversion rate of alkanes and decreased the initiation temperatures for the reactions. Moreover, selectivities and yields to oxygenates, aldehydes, ketones and alcohols, were remarkably improved by the addition of NO. The maxima of one-pass yields of oxygenates were 7% for CH 4, 11% for C 2H 6, 13% for C 3H 8, and 29% for iso-C 4H 10. It is suggested that NO 2 produced from NO and O 2 is the initiator for the oxidation of light alkanes. Alkyl nitrite was proposed as the reaction intermediate for the formation of oxygenates. The alkyl nitrite decomposes into oxygenates and NO that works as catalyst for the activation of O 2 and the oxidation of alkanes.

Azide promotion of alkane oxidations catalyzed by metal complexes in solution

The oxidation of light alkanes catalyzed by metal complexes in solution is promoted by Group 1 metal azides. Yields of oxygenated reaction products are greatly enhanced when catalytic amounts of azides are added to the reaction mixture. The addition of sodium azide to oxidations catalyzed by transition metal acetylacetonates, heteropolyacids, polyoxometallates, phthalocyanines, bis-(pyridylimino)isoindolines, porphyrins and Schiff bases significantly enhances rates of low-temperature catalytic oxidation reactions in the liquid phase. Earlier work showed that Cr(III), Mn(III), Fe(III) and Co(III) complexes of electron-deficient macrocyclic complexes exhibited remarkable catalytic activity for oxidizing light alkanes. Such complexes bearing axial azide ligands were far more active than their axial chloride or acelate counterparts.

Coordination Symmetry and Reduction Features of V Ions in V2O5/SiO2Catalysts: Relevance to the Partial Oxidation of Light Alkanes

Coordination Symmetry and Reduction Features of V Ions in V2O5/SiO2Catalysts: Relevance to the Partial Oxidation of Light Alkanes

Partial Oxidation of Light Alkanes during O2-H2 Cell Reactions at Room Temperature

Abstract The partial oxidation of light alkanes (methane, ethane, and propane) has been carried out successfully by applying an O2-H2 cell at ambient temperature and atmospheric pressure. The conversion of alkanes increased in the order of CH4 < C2H6 < C3H8. The selectivity to useful oxygenates was the highest in the case of propane. The selectivity to acetone was higher than 65%.

Selective partial oxidation of light alkanes over alkali-ion-modified silica-supported vanadium oxides excited with visible light

Alkali-ion (Na+, K+, and Rb+)-modified V2O5/SiO2 irradiated with visible light catalyzes the partial oxidation of 2-methylpropane to form mainly propanone and 2-methylpropan-2-ol. The addition of alkali ions to V2O5/SiO2 is essential to generate the active site that can be excited with visible light. It is confirmed that there are two types of reaction paths for the formation of 2-methylpropan-2-ol.

Dynamic processes on vanadium phosphorous oxides for selective alkane oxidation

The use of complementary physicochemical tools (XRD, Raman spectroscopy, XPS, 31P NMR, and electron microscopy techniques), sometimes used in in situ conditions has allowed to evidence the dynamic processes occurring during the oxidation of light alkanes on the vanadium phosphorus oxide (VPO) system. The transformations of the VPO system in the course of the oxidation of n-butane to maleic anhydride and of the oxidation of propane to acrylic acid are contrasted in connection with the evolution of the catalytic performances.

ALKANE PARTIAL OXIDATION

Direct partial catalytic oxidation of alkanes to commercial chemicals has received a boost from a microsecond reactor under development at the University of Minnesota, Minneapolis. The reactor can convert n -butane to formaldehyde and olefins in high yield, with high selectivity [ Science , 271, 1560 (1996)]. Developed by professor of chemical engineering Lanny D. Schmidt and graduate student Duane A. Goetsch, the reactor employs a 90% platinum- 10% rhodium gauze catalyst inside a quartz tube less than 2 cm in diameter. The room-temperature alkane gas heats rapidly to 800 °C as it flows past the gauze. The product gases are then rapidly thermally quenched before they can be totally oxidized to carbon dioxide and water. Catalytic partial oxidation of light alkanes, particularly those in natural gas, has always attracted commercial interest. The problem has been to control nonselective reactions that produce mostly carbon oxides. The microsecond reactor provides the necessary kinetic controls to stop the re...

Selective heterogeneous oxidation of light alkanes. What differentiates alkane from alkene feedstocks?

Some aspects of the reactivity of vanadyl pyrophosphate catalysts inn-butane andn-pentane oxidation and propane ammoxidation are discussed in order to illustrate differences and peculiarities of the catalysts for the selective oxidation of alkanes in comparison to the catalysts for the selective oxidation of alkenes. The formation of alkenes as reaction intermediates, the catalytic and mechanistic differences in alkane and alkene conversion, their different effects in changing the active surface configuration, the relationship between surface concentration of adspecies and catalytic behavior, and the problem of the surface isolation of the active intermediates are discussed. Some brief economic considerations about the advantages of the various processes of alkane oxidation as compared to alkene or aromatic oxidation are also given.

ChemInform Abstract: Selective Air Oxidation of Light Alkanes Catalyzed by Activated Metalloporphyrins. The Search for a Suprabiotic System

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Thin-layer supported nafion catalysts for the partial oxidation of light alkanes

Thin-layer carbon supported Nafion-H catalysts were found to be active and highly selective for the partial oxidation of C1–C3 alkanes under mild conditions and in the presence of aqueous H2O2. A three phase catalytic membrane reactor (3PCMR) has been used.

Selective air oxidation of light alkanes catalyzed by activated metalloporphyrins - the search for a suprabiotic system

Halogenated metalloporphyrins have been examined as catalysts for the air oxidation of propane and isobutane at low temperature. Room temperature oxidation of isobutane with air gives > 13,000 turnovers with > 90% selectivity to tert -butyl alcohol.

Étude chimique et cinétique de l'oxydation homogène en phase gazeuse d'alcanes légers. I. Isobutane

A literature survey on the homogeneous gas-phase oxidation of light alkanes shows that despite a rather high number of papers there are still, even in the case of isobutane, an important number of unresolved questions, which makes the writing of a reaction scheme rather difficult. To obtain more reliable experimental data, we have studied the homogeneous gas-phase oxidation of isobutane in a conventional static system, at 310 and 340 °C and subatmospheric pressure. This investigation is chiefly aimed at identifying and measuring the major primary products of the reaction. A chain radical scheme based on the primary products and on estimation of the rate constants of the elementary steps by the methods of Thermochemical Kinetics is put forward to interpret our experimental results. Two major reaction routes appear, one corresponding to the formation of isobutene and the other to the formation of isobutene oxide. The conclusions of the present investigation and suggestions for further developments are also mentioned. Keywords: oxidation, chemical kinetics, reaction mechanism, isobutane.