Metal cation exchange with zeolitic acid sites modulates hydrocarbon pool propagation during CO2 hydrogenation

We demonstrate that the exchange of zeolitic Brønsted acid sites (BASs) with cations from metal oxides plays a pivotal role in the propagation of hydrocarbon pools (HCPs) during CO₂ hydrogenation. We probed the likelihood of In₂O₃, ZnZrO_x, and Cr₂O₃ migration and their cation exchange with BASs of a silicoaluminophosphate, SAPO-34, by integrating them at nanoscale proximity (∼1,400 nm). Analysis with NH₃ temperature-programmed desorption and transmission Fourier transform infrared spectroscopy showed ion exchange of BASs with In^δ+ and Zn^δ+ but not for Cr^δ+. We measured the C₃/C₂ hydrocarbon ratio (indicating relative propagation of olefin to aromatic cycles) and paraffin-to-olefin ratio, which revealed that In^δ+ species inhibited HCPs inside the channels of SAPO-34, while Zn^δ+ species enhanced hydrogen transfer and secondary hydrogenation. Combining reactivity data with occluded hydrocarbon analysis and ¹³C solid-state nuclear magnetic resonance spectroscopy, we show that ion-exchanged species affect HCP propagation. Overall, our work provides insights for the rational integration of bifunctional catalysts.