The catalytic conversion of methane to methanol and formaldehyde under mild conditions

Abstract

The oxidation of methane to produce methanol and formaldehyde is an important process since methanol is used directly as a fuel or can be converted to valuable products such as other transportable fuels , fuel additives, or chemicals . Methane oxidation will continue to receive attention because of the large amount of methane available to be upgraded and the demand, worldwide, for low cost transportation fuel. There are many ways to activate methane; Hunter and Gesser [ 1] discussed photochemical and electrochemical activation, laser-induced activation, and radiolysis, as well as catalytic activation. The right combination has yet to be discovered. Inorganic ceramic membranes were used as supports for the catalysts. Various sources of silica (tetraethoxysilane and fumed silica) were used to modify the membrane support for the introduction of silanol groups that participate in the chemical reaction to form different bonds. Silica is known to stabilise the membrane support and it was found that it also increased the surface area of the membrane support. Tetraethoxysilane (TEOS) was incorporated through the sol-gel technique and was found to be the best method for the introduction of silica upon the membrane support. The BET surface area of the membrane support increased from 2.4 to 12.6 and 4.5 m2/g upon modification with TEOS and fumed silica respectively. The surface of the silica-modified membrane support was grafted with chlorodimethylsilane (CDMS) and y-aminopropyltriethoxysilane (APTS) for the introduction of hydrolytically and thermally stable Si-O-Si bonds. This modification was followed by the deposition of the active metal centre.