Heterogeneous catalysis methane oxidative coupling

The most widespread efforts made towards the achievement of selective oxidation of alkanes are targeted on methane, a principal constituent of natural gas f 6-8]. Activation of the very stable C-H bond of methane is a particularly demanding problem. One example in which this has been achieved on industrial scales is the Degussa process [9], Methane is coupled to ammonia by heterogeneous catalysis in order to produce HCN, an important fundamental material for industrial chemistry. An unsolved problem is the selective oxidation of methane to methanol a reaction that would convert the methane gas into a transportable liquid. In nature, monooxygenases have evolved. These are able to activate molecular oxygen and to... 

In industry many selective oxidations are carried out in a homogeneously catalyzed process. Heterogeneous catalysts are also applied in a number of processes, e.g. total combustion for emission control, oxidative coupling of methane, the synthesis of maleic acid from butanes, the epoxidation of ethylene. Here we focus upon heterogeneous catalysis and of the many examples we have selected one. We will illustrate the characteristics of catalytic oxidation on the basis of the epoxidation of ethylene. It has been chosen because it illustrates well the underlying chemistry in many selective oxidation processes. 

The initial work which promoted interest in conventional heterogeneous catalysis for methane coupling chemistry was first reported in 1982 [56]. In this work, the subject reaction was evaluated using 23 metal oxides supported on a-alumina over the temperature range 500-1000 °C. Methane and oxygen were, however, sequentially introduced into the reaction vessel, suggesting that the overall chemical reaction involved the general Mars-van Krevelen reaction sequence ... 

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