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

Abstract

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.