Methanol carboxylation over zirconium dioxide: Effect of catalyst phase composition on its acid-base spectrum and direction of catalytic transformations

The effect of ZrO2 calcination temperature on its structure and acid-base characteristics was investigated to elucidate their relation to catalytic behaviour in methanol carboxylation. Varying the calcination temperature causes changes in ZrO2 phase composition and acid-base characteristics. The base properties of ZrO2 play a prominent role in dimethyl carbonate synthesis. Strong base sites (E-CO2>78kJ/mol) are needed to activate C?(2). Tetragonal modification of zirconium dioxide has a higher basicity than the monoclinic. Thus, the greater the contribution of t-ZrO2 in the catalyst, the greater its ability to activate C?(2) and therefore result in higher catalytic activity for methanol carboxylation. DMC selectivity was determined by the ratio of catalyst base site to acid site concentration.