Oxidation of light alkanes

A similar conclusion applies to a Mg-V-O catalyst in which Mg3(V04)2 is the active component. The relative rates of reaction for different alkanes on this catalyst follow the order ethane < propane < butane 2-methylpropane < cyclohexane (Table I) [12-14]. This order parallels the order of the strength of C-H bonds present in the molecule, which is primary C-H > secondary C-H > tertiary C-H. Ethane, which contains only primary C-H bonds, reacts the slowest, whereas propane, butane, and cyclohexane react faster with rates related to the number of secondary carbon atoms in the molecule, and 2-methylpropane, with only one tertiary carbon and the rest primary carbons, reacts faster than propane which contains only one secondary carbon. Similar to a Mg-V-O catalyst, the relative rates of oxidation of light alkanes on a Mg2V207 catalyst follow the same order (Table I). 

This paper summarized our current understanding of the factors that determine selectivity for dehydrogenation versus formation of oxygen-containing products in the oxidation of light alkanes. From the patterns of product distribution in the oxidation of C2 to C6 alkanes obtained with supported vanadium oxide, orthovanadates of cations of different reduction potentials, and vanadates of different bonding units of VO in the active sites, it was shown that the selectivities can be explained by the probability of the surface alkyl species (or the... 

Frusteri and co-workers648-651 have evaluated the activity of Nafion-based membranes in the oxidation of light alkanes. The membranes were prepared by depositing a... 

This paper is an attempt to summarize the situation with respect to the selective catalytic oxidation of light alkanes using heterogeneous catalysts. Methane oxidation reactions and the oxidation of butane to maleic anhydride will only be alluded to occasionally, because they have been reviewed in detail in a large number of papers. 

A very large amount of work has been devoted in the past to the oxidation of olefins ("allylic" oxidation to unsaturated aldehydes) and butane (to maleic anhydride). This has led to the development of ideas and concepts which are quite naturally used in the new investigations concerning light alkanes. It is necessary to examine these ideas and concepts and to evaluate in a critical way their potential for discovering or improving catalysts in the new field that oxidation of light alkanes constitutes. This will be done here shortly on the basis of classical books or articles [53,58-62]. 

We believe that supports could play a more important role in the oxidation of light alkanes than it did in allylic oxidation. But this role will be complex, and include better dispersion of the active phase, stabilisation of the selective phase, control of oxido-reduction, and/or facilitation of oxygen spillover. 

Contrary to the case of olefins, homogeneous catalytic oxidations of light alkanes occur at temperatures similar to those of the catalytic reaction. This certainly led to misinterpretation of supposedly catalytic data in certain cases. Two examples will illustrate the role of homogeneous reaction the oxidative dehydration of propane and the reactions of pentane with oxygen. 

These results question the validity of many previous results on catalytic oxidation of light alkanes. One should reassess the data concerning the relative reactivity of the various alkanes [105] and selectivity. 

Yamanaka, L, Hasegawa, S., and Otsuka, K. 2002. Partial oxidation of light alkanes by reductive activated oxygen over the (Pd-black + VO (acac) (2)/VGCF) cathode of H-2-O-2 cell system at 298 K. Applied Catalysis A General. 226, 305-315. 

Table 2. Maximum yields to the desired products in the oxidation of light alkanes.

Figure 4. Oxidation of light alkanes during O2-H2 cell reactions.

Active species and working mechanism of silica supported M0O3 and V2O5 catalysts in the selective oxidation of light alkanes... 

The aim of this paper is to provide a correlation between the catalytic pattern of differently loaded silica supported M0O3 and V2O5 catalysts in MPO and POD reactions with their surface and redox features in order to highlight the nature of the active surface species in the selective oxidation of light alkanes. 

The selective oxidation of light alkanes has attracted much attention because it represents a route to obtain more valuable organic compounds from low cost saturated hydrocarbons. 

Because of the global abundance of liquefied petroleum gas (LPG), interest in the potential use of ethane, propane, and butanes as sources of the corresponding alkenes or their derivatives is increasing [1]. In the last decade much progress has been made, particularly in the selective partial oxidation of light alkanes with molecular oxygen in gas phase [1,2]. For economic reasons, molecular oxygen is usually used as the primary oxidant[3]. 

Nevertheless, in spite of some difficulties, GRI-Mech signifies a new era in modeling of combustion and oxidation of light alkanes and other substances. The main principles of GRI-Mech serve as a basis for further widening the area of its application for related processes and substances (Curran, 2004). 

Sinev, M. Yu., Free radicals as intermediates in catalytic oxidation of light alkanes New opportunities, Res. Chem. Inter. 32, 205 (2006). 

The oxidation of light alkanes by air or O2 at supercritical temperatures and pressures was explored by Standard Oil in the mid-1920s [153]. Experiments were performed at the laboratory and then semicommercial plant level. The primary products were alcohols. For example, the oxidation of pentane was performed at supercritical conditions (240 °C, around 200 bar and a few mole per cent O2) and produced primarily C2-C3 alcohols and acids. However, the oxidation of heptane was performed at subcritical temperatures (225 °C) and produced primarily Cg-Cy alcohols. The change in selectivity was attributed to either the difference in phase or more likely the difference in temperature. Other commercial processes for the formation of alcohol denaturants or formaldehyde were reported in the same decade [154,155], but it is unclear whether those reactions were operated at supercritical pressures. Modem processes involving alkane oxidation are heterogeneously catalyzed and operated at sub-critical pressures [156]. 

Halogenated metalloporphyrins are effective catalysts for selective air oxidation of light alkanes [30] as well as of olefins [31], The postulated mechanism of the reaction (Scheme IX.2) [30c] is similar to those proposed for biological oxidation (by cytochrome P450 and methanemonooxygenase, see Chapter XI). 

Oxygen-Ion Transport Membrane and Its Applications in Selective Oxidation of Light Alkanes... 

The first section of this chapter gives a brief survey of major membrane concepts and different membrane reactor configurations. Membrane materials are discussed in the second section. The third section will present the recent development of OITM reactors for selective oxidation of light alkanes. 

P.E. Ellis and J.E. Lyons, Selective air oxidation of light alkanes catalysed by... 

Mechanistic Insights into Selective Oxidation of Light Alkanes by Transition Metal Compounds/Complexes... 

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