THE REGULARITIES IN THE INTERACTION OF ALKANES WITH CO2 ON OXIDE CATALYSTS

Catalytic oxidation of C-1-C-7 alkanes by CO2 as a non-traditional oxidant was studied on oxide catalysts. The supported manganese oxide catalysts are the most active, selective and stable. Methane is converted mainly into synthesis gas. Ethane and propane give products of oxidative dehydrogenation. In the case of C-4-C-7 alkanes at first direct dehydrogenation takes place and after that reverse water gas shift proceeds. Reactions of carbon dioxide with hydrocarbons were up to now still insufficiently studied. This is caused by small reactivity of both CO2 and hydrocarbons. The recent interest in carbon dioxide reactions is two-fold: 1) the necessity to fight against the so-called green-house effect and 2) the exhaustion of raw carbon material sources [1]. The CO2 molecule can be used a non-traditional oxidant. The best reducing agent for CO2 is hydrogen. It was shown [2] that methanol synthesis proceeds not by direct CO + H-2 interaction, but by preliminary CO transformation into CO2 (1) CO + H2O = CO2 + H-2 After that the interaction of CO2 with H-2 gives methanol (2) CO2 + 3H(2) = CH3OH + H2O But hydrogen is expensive. Hydrocarbons in the role of CO2 reductants are more attractive. The most intensively studied reaction of hydrocarbons with CO2 is methane conversion into synthesis gas (3) CH4 + CO2 = 2H(2) + 2CO The main difficulty encountered when this reaction is used for the practical process of synthesis gas production is coking of the metal catalysts [3-6]. We have studied C-1-C-7 interaction with CO2 over oxide catalysts [7-10] and it turned out that manganese oxides containing catalysts are effective both for methane transformation into synthesis gas and for C-2-C-7 alkanes dehydrogenation and oxidative cracking. What is especially important is that these catalysts are very stable during a long period without cake accumulation. This paper provides a review of our work in this field.