Cu-Zr/SiO2 catalysts featured by different Cu-Zr-Si coordinations for ethanol conversion to 1,3-butadiene

Catalytic upgrading of bio-ethanol to 1,3-butadiene (1,3-BD, ETB) is a renewable and low-carbon technology for the bulk chemical production. Exploring robust catalysts and getting in-depth understanding of the relationship between the structure of catalytic sites and reaction selectivity are of great significance for ETB process applications. In this study, we constructed a robust Cu-Zr/SiO2 catalyst by an ammonia evaporation and post-impregnation method. Over the optimal 2%Cu-8%Zr/SiO2 catalyst, superior performance of 69.6% 1,3-BD selectivity and 71.2% ethanol conversion were obtained. Systematic characterizations revealed that three types of Cu-Zr-Si active sites were probably constructed on the Cu-8%Zr/SiO2 catalysts as varying the Cu loadings from 0.5-20%, affording greatly different activity and selectivity in the ETB process. The 1,3-BD productivity over the (SiO)2(CuO)Zr-OH sites was 8.2 and 77.2 times higher than that of (CuO)2-Zr-(OSi)2 and Cu-(O)2-Zr-(OSi)2 sites, respectively, attributed to the high activities and good balance among the reactions of dehydrogenation, aldol condensation, and MPVO reduction.