CO_2 hydrogenation activity of Ni-Mg-Al_2O_3 catalysts: Reaction behavior on NiAl_2O_4 and MgAl_2O_4

摘要

CO2 hydrogenation activity of nickel-magnesium-aluminum mixed oxide catalysts was investigated. As Ni concentration increased, CO2 conversion increased due to the increased active metal content and suppression of NiAl2O4 formation. Calcination temperature was found to affect the textural properties of catalysts and to decrease surface area and pore volume significantly. Therefore, catalysts calcined at a relatively low temperature showed high activity, while the particle strength slightly decreased with the reduced calcination temperature. The catalytic activity of reduced NiAl2O4 and MgAl2O4 spinel oxides for the hydrogenation of CO2 was also investigated. NiAl2O4 dissociated CO2 to C on reduced Ni, and increased CH4 selectivity. On the other hand, CO2 was not fully dissociated, and the CO intermediate was desorbed to produce gaseous CO on reduced MgAl2O4. Adding MgO suppressed the formation of NiAl2O4, but CH4 selectivity decreased due to the formation of MgAl2O4, indicating the amount of MgO added should be optimized depending on the product required.