Effect of N- and B-doped carbon-loaded Ce-Zr composite oxide catalysts on the anisole acetylation reaction

Herein, a series of Ce-Zr composite oxides with different Ce-Zr molar ratios were prepared and used to catalyze the acetylation of anisole and acyl chloride, in which Ce2ZrOx catalyst showed the best performance with 63.7% para-methoxyacetophenone (p-MAP) yield. Next, N-doped carbon supported Ce2ZrOx (CN-Ce2ZrOx) catalyst exhibited better catalytic performance than B-doped one (CB-Ce2ZrOx), the former gave 79.6% p-MAP yield, which is a much higher than the latter's yield of 25.2%. The presence of B induces the transfer of some electrons from Zr to Ce, which reduces Lewis acidic sites of Ce species, and then the ability of Ce species as active sites to adsorb reactants becomes weaker, thus reducing the catalytic activity. The presence of N pushes some electrons of Ce to Zr, this enhances the Lewis acidity of Ce species, and the ability of Ce species as active sites to adsorb reactants becomes stronger, thereby enhancing the catalytic activity. In addition, N doping brings more oxygen vacancies as acidic sites, thus further improving the catalytic activity. Kinetic studies indicate that CN-Ce2ZrOx catalyst obtains a lower activation energy, thus improving reaction rate. Density functional theory (DFT) calculations reveal that CN-Ce2ZrOx catalyst reduces adsorption energy barriers of reactants and increases the catalytic activity.