Molybdenum carbides and carbonaceous carbons on Mo/Al-FSM16 for methane conversion

Abstract

The catalytic activity of 12.0 wt.% Mo/Al-FSM16 (Si/Al=30) was related to the Mo carbides and carbonaceous carbons during CH 4 conversion at 973 K. The material had been carburized during the temperature-programmed reaction with 20% CH 4/H 2 at 973 K, with and without purging in He. The temperature-programmed surface reaction and X-ray diffraction analysis showed that the carburized catalysts consisted of Mo carbides (α-Mo 2C 1− x , β-Mo 2C, and η-Mo 3C 2) and carbonaceous carbons (pyrolytic and graphitic carbons). The purging treatments of the carburized catalysts at 973 K for 1 or 2 h lowered the activity, due to a decrease in the carbonaceous carbon releases of C 2H 2, C 2H 4, CO 2, and H 2O and due to the Mo carbides changing to other forms. The CH 4 conversion was responsible for η-Mo 3C 2 conjugation to pyrolytic carbons, which played the role of the intermediate species. The IR study revealed that CH 2 and CH 3 species were formed as the intermediates of the pyrolytic species for CH 4 formation. The pulse experiments of C 2H 4, C 2H 6, C 3H 8, and C 4H 8 showed that hydrogen was readily formed through the adsorbed C 2H 4 and C 3H 8 species as intermediates and that benzene was formed through the adsorbed C 4H 8 species.