Partial oxidation of methane on potassium-promoted WO 3/SiO 2 and on K 2WO 4/SiO 2 catalysts

Abstract

The partial oxidation of methane to formaldehyde or ethane and ethylene was studied on K 2WO 4 deposited on various supports, on potassium-promoted WO 3/SiO 2 and for comparison on WO 3/SiO 2 in a fixed-bed continuous-flow reactor at 860–923 K using O 2 as oxidant. The catalysts were characterised by Raman, XP spectroscopy and TPR method. It was found that the original structure of potassium tungstate remained on K 2WO 4/SiO 2, whereas K 2W 2O 7 was very likely formed on K+WO 3/SiO 2. The main products of the reaction besides the carbon oxides were HCHO on WO 3/SiO 2 while on K-containing samples mainly the C 2 hydrocarbons were formed. The product distribution of the oxidation reaction was markedly influenced by the nature of the support. The highest activity was measured for alumina-supported catalyst. In this case, however, only traces of partially oxidised products were formed. Formaldehyde, in a larger quantity, was produced on WO 3/SiO 2 but C 2 in higher selectivity on K 2WO 4/SiO 2 was formed. A possible mechanism for the oxidative conversion of methane is also discussed.