A Comprehensive Study on Carbon Dioxide Reforming of Methane over Ni/γ-Al2O3Catalysts

Carbon dioxide reforming of methane into syngas over Ni/γ-Al2O3 catalysts was systematically studied. Effects of reaction parameters on catalytic activity and carbon deposition over Ni/γ-Al2O3 catalysts were investigated. It is found that reduced NiAl2O4, metal nickel, and active species of carbon deposited were the active sites for this reaction. Carbon deposition on Ni/γ-Al2O3 varied depending on the nickel loading and reaction temperature and is the major cause of catalyst deactivation. Higher nickel loading produced more coke on the catalysts, resulting in rapid deactivation and plugging of the reactor. At 5 wt % Ni/γ-Al2O3 catalyst exhibited high activity and much lesser magnitude of deactivation in 140 h. Characterization of carbon deposits on the catalyst surface revealed that there are two kinds of carbon species (oxidized and −C−C) formed during the reaction and they showed different reactivities toward hydrogenation and oxidation. Kinetic studies showed that the activation energy for CO production in this reaction amounted to 80 kJ/mol and the rate of CO production could be described by a Langmuir−Hinshelwood model.