Unraveling the hydrogen spillover in tandem propane dehydrogenation and reverse water gas shift reaction.

Abstract

The integration of CO₂ into the dehydrogenation of propane (PDH) holds significant promise for both propylene production and greenhouse gas utilization. However, a pivotal challenge lies in mitigating the undesirable dry reforming of propane (DRP), which diminishes propylene selectivity compared to direct PDH processes. Herein, we describe a coupled process that integrates PDH with reverse water gas shift (RWGS) using a tandem catalytic system. The PtSn/Al₂O₃ analogue performs the dehydrogenation reaction, while an adjacent defective CeO_x/Al₂O₃ at nanoscale acts as the hydrogenation sites for CO₂. Catalysis and kinetic studies demonstrate the in-situ removal of hydrogen from PtSn/Al₂O₃ to adjacent CeO_x/Al₂O₃, facilitated by CO₂, shifts the quasi-equilibrium of PDH towards propylene production, while suppressing the competitive DRP side reaction. This hydrogen spillover-mediated coupling mechanism enables superior propylene selectivity of ~98.8%, along with high CO₂ (~43.9%) and propane conversion (~44.2%) at 550 °C, outperforming direct PDH (~40.6%). Analysis of CO₂ footprint indicates the PDH-RWGS tandem process has the potential for carbon utilization to mitigate detrimental CO₂ emissions.