Roles Investigation of Promoters in K/Cu–Zn Catalyst and Higher Alcohols Synthesis from CO2 Hydrogenation over a Novel Two-Stage Bed Catalyst Combination System

Abstract

A novel two-stage bed catalyst combination system composed of a low-temperature RWGS catalyst and another high-temperature modified F–T synthesis catalyst was developed to higher alcohols synthesis from CO2 hydrogenation in this work. Firstly, the roles of K2O and ZnO promoters in Cu-based catalyst were investigated by N2 adsorption/desorption, XRD, H2-TPR, CO2-TPD and RWGS reaction test. Results showed that K2O plays a positive role in improving the CuO–ZnO interaction and ZnO acts as a support for promoting the dispersion of copper species and improving the unit surface area of copper metal. Well dispersed copper in contact with the surface of ZnO particles leads to the ideal performances for RWGS reaction accompanying with methanol synthesis over CuZn1.0K0.15 catalyst due to the synergetic promotion effect between K2O and ZnO promoters. Then, the optimization of loading mode and loading volume ratio of catalyst combination system was conducted. It was indicated that the higher alcohols can be effectively synthesized from CO2 hydrogenation over the optimal CZK(1.5)//CFCK(4.5) two-stage bed catalyst combination system due to the thermal coupling effect and product conversion coupling effect of these catalysts. The higher alcohols synthesis from CO2 hydrogenation was effectively conducted over the CZK(1.5)//CFCK(4.5) two-stage bed catalyst combination system due to the thermal coupling effect and product conversion coupling effect.