Methanol synthesis from CO2 and H2 over Pd/ZnO/Al2O3: Catalyst structure dependence of methanol selectivity

Abstract CO 2 hydrogenation to methanol was investigated over Pd/ZnO/Al 2 O 3 , focusing on the influence of the preparation method, reduction temperature and Pd loading on the catalytic performance. The structure of each catalyst was thoroughly examined using various techniques. The results indicated that the methanol selectivity depended on the content of PdZn alloy, which changed dynamically with varying the preparation methods and pretreatment procedures of the catalysts. More specifically, the ratio of PdZn/Pd 0 in the bimetallic compound increased with the rise of the reduction temperature, which eventually led to the increase of methanol selectivity. Additionally, the EXAFS results revealed the presence of ZnO x modified Pd species when the Pd loading was decreased to be lower than 2 wt%. However, the CH 3 OH selectivity remained almost identical when the reactions were conducted under similar CO 2 conversions. Therefore, we conclude that both the PdZn alloy and Pd modified by ZnO x islands are the active sites for methanol synthesis from CO 2 hydrogenation.