Radiation-induced chemical reaction of methane in the presence of silica-aluminas in relation to the catalytic activity of molecular sieves

The radiation-induced chemical reaction of methane in the presence of four types of silica-alumina having different SiO2/Al2O3 ratios correlated to the solid acidity was carried out at 3000C, in relation to the catalytic activity of methane radiolysis of molecular sieves. The main products were hydrogen and low-molecular-weight hydrocarbons up to C5 and all the yields were significantly increased compared to the absence of solid. It was found that there is not a direct correlation between the product yields, alkene/alkane ratios and hydrocarbon distributions and Al2O3 content in silica-alumina. This indicates that the enhancement of product yields is not attributable to the solid acidity of silica-alumina. The order and the decrease with time of product yields were the same as those obtained for the molecular sieve 5A. Silica gel, which has not the acidic property, also showed higher catalytic activity. Accordingly, it is concluded that the sensitization of the product yields in the radiolysis of methane over molecular sieves is independent of its solid acidity. An attempt is also made to explain the catalytic activity of the molecular sieves in terms of the concept of energy transfer. (author)