Strongly acidic SSZ-13 zeolite boosts high-space-velocity CO2-to-light olefin conversion via synergistic bifunctional catalysis

Abstract

The direct conversion of CO₂ to light olefins has gained significant attention in C1 chemistry. Compared to the modified Fischer–Tropsch synthesis route (CO₂-FTO), the oxide–zeolite (OXZEO) composite catalytic system—which integrates methanol synthesis with methanol-to-olefin (MTO) reaction—has demonstrated superior light olefin selectivity. Nevertheless, conventional OXZEO systems employing silicoaluminophosphate (SAPO) zeolites face serious limitations due to their inherent weak acidity, requiring relatively low space velocities for effective MTO catalysis and resulting in suboptimal light olefin space-time-yield (STY). We developed a bifunctional ZnZrO_x/H-SSZ-13 system where CO₂ hydrogenates to methanol on ZnZrO_x, then rapidly converts to olefins on the strongly acidic zeolite. Crucially, the strong acidity of the SSZ-13 zeolite enables effective methanol conversion even at elevated space velocities. This system achieved 7.50 mmol g_cat⁻¹ h⁻¹ light olefin STY under a low reaction pressure of 1 MPa and a high gas-hourly-space-velocity (GHSV) of 21 000 mL g_cat⁻¹ h⁻¹, with 82.6% light olefin selectivity. This work highlights the critical synergy between tailored acid strength of the zeolite component and reaction conditions in advancing CO₂-to-olefin catalysis.