Indium-containing ZSM-5 catalyst for methylation of benzene: effect of silica/alumina rations and reaction conditions

Abstract

Catalytic conversion of methane to higher hydrocarbons is an attractive route for the utilization of methane. One possible way to convert methane is the direct methylation of benzene by methane in the presence of a catalyst. Indium-containing ZSM-5 catalyst has exhibited an ability to activate methane and convert benzene into toluene and xylenes. In this study, indium-containing ZSM-5 catalysts were prepared with varying SiO₂/Al₂O₃ molar ratios. The catalysts were characterized by temperature program reduction, temperature program desorption, X-Ray diffraction and UV-vis spectrophotometry. The In/HZSM-5 catalysts were treated in a hydrogen atmosphere prior to the reaction at 700 ºC, this temperature was confirmed by the temperature program reduction method. Direct methylation could be achieved if oxygen was fed along with the feed at a reaction temperature of 350 ºC. The effect of the reaction parameters; indium to aluminum ratio 1.0, methane to benzene feed ratio 104 and space velocity 2.8 h¯¹provided benzene conversion of 3% and greater than 95% toluene selectivity. SiO₂/Al₂O₃ molar ratios (23, 30, 50, 80 and 280) were also investigated and found that the highest benzene conversion was provided by a SiO₂/Al₂O₃ molar ratio of 50.