CO₂ hydrogenation activity of Ni-Mg-Al₂O₃ catalysts: Reaction behavior on NiAl₂O₄ and MgAl₂O₄

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.