Radiation effects on methane in the presence of molecular sieves

Abstract

Product analysis has been carried out for the radiation-induced reaction of methane in the presence of molecular sieves (MS) 3A, 4A, 5A and 13X. Irradiation of methane over MS 4A selectively produces C₂ hydrocarbons, while the use of MS 5A leads to C₂ and C₃ hydrocarbons. The selectivity and yields of these hydrocarbons, however, decrease with irradiation time, owing to deposition of carbonaceous solid produced from methane on the surface of the molecular sieves. The carbonaceous solid is decomposed to low-molecular-weight hydrocarbons when irradiated in an H₂ atmosphere. Material balance estimated for the radiation-chemical reaction of argon containing 2 mol% methane over MS 5A reveals that the carbonaceous solid is highly abundant in carbon atoms. On the other hand, the formation of carbonanceous solids plays a less important role in the radiation-chemical reaction of methane in the presence of silica gel, which is found to exhibit greater activity for the formation of hydrocarbons than the molecular sieves.