Effect of Iron Promoter on Structure and Performance of K/Cu–Zn Catalyst for Higher Alcohols Synthesis from CO2 Hydrogenation

Abstract

Effect of iron promoter on the microstructures of K/Cu–Zn catalyst was investigated by N2 adsorption/desorption, X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM) and H2 temperature programmed reduction (H2-TPR). Higher alcohols synthesis (HAS) from CO2 hydrogenation was performed in a fixed-bed reactor under the conditions of T = 300 °C, P = 6.0 MPa, GHSV = 5,000 h−1 and H2/CO2 = 3. These characterization results showed that incorporation of iron into the K/Cu–Zn catalyst resulted in increase of BET surface area and dispersion of catalyst particles. Especially, medium iron addition facilitated the synergistic effect between Cu–Fe and Zn–Fe interactions, improved the reduction of catalyst and increased the amounts of dispersed copper and iron carbides active centers. In the HAS reaction, the conversion of CO2, the space time yield and selectivity of C2+OH increased first and then decreased as the increase of iron concentration. Among these iron-promoted K/Cu–Zn catalysts, the CuZnFe0.5K0.15 catalyst with a Fe/(Cu + Zn + Fe) ratio of 0.2 exhibited the highest alcohol selectivity of 36.67 wt% with a high C2+OH/C1OH of 6.76, which can be radically attributed to the especial morphology and optimum reduction degree. The incorporation of medium iron promoter into the K/Cu-Zn catalyst improved obviously the catalytic performances of higher alcohols synthesis from CO2 hydrogenation .