Novel catalyst configuration to boost the yield of longer hydrocarbons from methanol-mediated CO2 hydrogenation

Abstract

Various C1 feedstocks and lower hydrocarbons (C2-C4) can be produced from CO2 hydrogenation, which is an important way to utilize excess CO2 and provide alternative fuel options for dwindling fossil fuels. Herein, a novel two-bed catalytic system was developed to increase the yield of liquid range hydrocarbons, where the first catalytic bed was composed of In2O3-ZrO2 (13 wt. In %)/HZSM-5 and the second bed was a desilicated HZSM-5 placed downstream from the first bed. A maximum hydrocarbon selectivity was found to be about 86% with 7.2% CO2 conversion at 533 K, while conversion increased up to 19.3% with 71.2% hydrocarbon selectivity at 623 K while keeping the pressure at 4.0 MPa. The selectivity of longer liquid range hydrocarbons (C8-C12) was increased from 29.2% to 42.4% using the oligomerization process in which the produced lower olefins from the first bed were oligomerized to enhance the liquid range hydrocarbon over desilicated HZSM-5. Additionally, a comparative study was carried out to examine the effect of desilication over HZSM-5 having different silica-to-alumina ratios of 24 and 59. Moreover, detailed characterizations were carried out before and after the desilication of the HZSM-5 to correlate catalytic activities with physical and chemical properties of the catalysts. The results suggest that a two-bed catalytic system is a promising option to increase the yield of liquid range hydrocarbons from methanol-mediated CO2 hydrogenation while there was a negligible effect on CO2 conversion due to the second bed.