(655e) Visualizing the Effect of Reaction Parameters and Catalyst Configuration for Tandem Hydrogenation of CO2 to Gasoline-Range Hydrocarbons
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
CO2 Upgrading IV: Alternative Approaches II
Monday, November 6, 2023 - 4:42pm to 5:00pm
Tandem hydrogenation of CO2 to C5+ hydrocarbons is an attractive solution for mitigating CO2 emissions while producing drop-in replacements for fossil-derived products. This could be achieved by coupling two reactions in the same reactor, which involves the transfer of key reaction intermediates from one system to another. Recent studies show that In2O3 combined with HZSM-5 converts CO2 to gasoline range (C5+) hydrocarbons through a two-step process in which CO2 and H2 produce methanol over In2O3 and then methanol is dehydrated and coupled over HZSM-5 to form hydrocarbons. However, the low conversion and selectivity to C5+ hydrocarbons demand a more detailed investigation of the catalytic process to improve hydrocarbon selectivity and catalyst design. Herein, we elucidate how the selection of reaction parameters (temperature, pressure, GHSV) and catalyst configuration can influence the selectivity of hydrogenation products. We demonstrate the optimal reaction conditions required to suppress reverse water gas shift and methanation reaction to increase C5+ selectivity. We investigate the effect of the integration manner of In2O3 and HZSM-5 on hydrocarbon distribution by changing the spacing of their active sites. We observe that increasing the proximity from the millimeter scale to the micro-scale increases C5+ selectivity from 2% to 55%. However, nano-scale proximity yields mostly methane (70%) and no C5+ hydrocarbon. Characterization of the fresh and spent catalysts with ammonia TPD reveals that in nano-scale proximity the acidity of HZSM-5 decreases. Hence, we hypothesize that migration of In ion to zeolite driven by the harsh reaction conditions could passivate zeolite in nanoscale proximity. To further investigate, we intentionally passivate HZSM-5 with Na+ to evaluate catalytic activity at micro-scale proximity, which yields mostly methane similar to the nano-scale arrangement of In2O3 and HZSM-5. To conclude, the selectivity of hydrogenation products can be steered by the selection of reaction parameters and proximity of catalyst components.
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