The dependence of high catalytic performance on the tunable oxygen vacancy in the CZ(x)S/Zn-HZSM-5 bifunctional catalyst for alkylation of benzene and syngas

A bifunctional catalyst (CZ(x)S/Zn-HZSM-5) with tunable oxygen vacancy was prepared by coupling ceria-zirconia solid solution (CZ(x)S) and zinc-modified HZSM-5 zeolite (Zn-HZSM-5). The characterization results indicated that the formation of CZ(x)S by insertion of zirconia (Zr) atoms into cerium oxide (CeO2) could generate more oxygen vacancy due to the structural distortion. With the increasing of Zr content, the oxygen vacancy concentration on the surface of CZ(x)S increased as well, which reached a maximum for a Zr/Ce ratio of 4 and then decreased by further increase of Zr content. The dependence of oxygen vacancy concentration in the CZ(x)S/Zn-HZSM-5 bifunctional catalyst on their catalytic performance in the benzene alkylation with syngas was further investigated. The result exhibited that the oxygen vacancy was the site for CO activation, and the more oxygen vacancy, the better catalytic performance. The best catalytic activity, with a CO conversion of 33%, the benzene conversion of 30% and the total toluene and xylene selectivity of 92% was obtained over the bifunctional catalyst CZ(4)S/Zn-HZSM-5 with the highest oxygen vacancy concentration.