Direct oxidation of methane-to-methanol

Direct oxidation of methane to methanol is an obvious dream reaction ... 

The Active Oxygen for Direct Oxidation of Methane to Methanol in the Presence of Hydrogen... 

One widely known example of such ineffective attempts is the direct oxidation of methane-to-methanol (DOMM) (see Arutyunov and Krylov, 1998 and literature cited therein). Whereas at atmospheric or somewhat higher pressures the introduction of catalysts (or homogeneous promoters) accelerates the process and increases product (mainly formaldehyde) yield to some extent, at increasing pressures their efficiency sharply drops. As a result, the methanol yield cannot be increased by any means above the level attainable in high-pressure homogeneous oxidation. 

It would be highly desirable to be able to convert methane directly into value-added products, most importantly into methanol by direct oxidation with oxygen at low temperatures and pressures. Selective direct oxidation of methane to methanol would allow plants to be built at the sources of methane, thereby elimi-... 

The base model of the direct oxidation of methane to methanol, proposed in [28d, 3 Id], takes into account all the main reliably established elementary reactions that play a significant role at high pressures and moderate temperatures, including heterogeneous destruction of radicals and peroxides on the reactor surface. This mechanism and parameters of its stages are presented in Table II.7. 

The direct oxidation of methane to methanol or formaldehyde has been a dream reaction for a long time [537]. Attempts include gas-phase reaction, catalytic reactions, and use of other oxidants than air. Selectivities may be high, but at a lower conversion per pass resulting in yields being inferior for industrial use. 

In recent years alternative methanol synthesis technologies have been tested in research and development, for example, methanol synthesis in liquid-phase reactions or the direct oxidation of methane to methanol. 

On the other hand, an alternative to gas-phase heterogeneous catalysis has been the use of metal complexes in the presence of sulfuric acid. However, this method currently presents some important drawbacks. Schiith and co-workers have developed a solid catalyst for the direct oxidation of methane to methanol, over several... 

The direct oxidation of methane to methanol has shown only limited success. The process would be very economical if it could achieve 80% selectivity at 80% conversion, based on Catalytica s evaluation. The development of selective catalysts and effective reaction processes is challenging. Bioprocessing that has potential for high selectivity is also worth further research. 

The catalytic reactions of methane reforming to syngas, oxidative coupling of methane to ethane and ethylene, direct oxidation of methane to methanol and formaldehyde occur at relatively high temperatures, 400—1000 °C, i.e., can be qualified as high-temperature catalytic oxidation processes. Numerous studies of these reactions, different in many ways, showed, however, that they have a number of common features, the most important of which are ... 

This combination of the properties of methanol-coal fuel makes the joint utilization of coalbed methane and coal waste on the basis of small-tonnage process of direct oxidation of methane to methanol an attractive option (Fig. 11.28). 

Thus, despite a great diversity of conditions for the oxidative conversion of methane, there are three basic t)2pes of processes and the respective products of oxidative conversion of methane the direct oxidation of methane to methanol (DMTM), CX2M, and partial oxidation to S5mgas (POM). To gain deeper insights into the prospects of the DMTM, let us, at least briefly, consider the potentialities and perspectives of other processes of oxidative conversion of natural gas. 

Fujimoto K, Sekine Y. Low temperature direct oxidation of methane to methanol. In De Pontes M, Espinoza RL, Nicolaides CP, Scurrell MS, editors. Natural gas conversion IV. Studies in surface science and catalysis, vol. 107. Elsevier Science B.V 1997. p. 63—6. 

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