Effect of crystal structure of ZrO₂ catalyst on isobutene synthesis from CO hydrogenation

ZrO₂ catalysts with different crystal structures show different catalytic performance in isobutene synthesis from CO hydrogenation reaction. Although monoclinic ZrO₂ has the best catalytic performance in isobutene synthesis from syngas, its isosynthesis active sites are still not well understood. To better understand the critical parameters that influence syngas to isobutene reactions over ZrO₂ catalysts, we prepared a series of ZrO₂ catalysts with distinct crystal structures and investigated their catalytic performance of CO hydrogenation to isobutene. Compared with tetragonal and amorphous ZrO₂ catalysts, there are more coordinatively unsaturated Zr and O sites on the surface of monoclinic ZrO₂ catalyst. The coordinatively unsaturated Zr sites are the active sites of CO adsorption and activation, which is beneficial to CO conversion. The coordinatively unsaturated O sites provide more basic sites for isobutene formation. Furthermore, the coordinatively unsaturated Zr and O sites on monoclinic ZrO₂ catalyst surface may inhibit electron transfer to formate species formed during reaction, resulting in weak adsorption on catalyst surface of formate species. The weakly adsorbed formate species on the surface of monoclinic ZrO₂ catalyst is favorable for the synthesis of isobutene from CO hydrogenation reaction.