Direct conversion of CO2 into alcohols using Cu-containing mordenite zeolite catalysts

Encapsulating metal nanoparticles inside microporous support materials, such as zeolites, effectively mitigates catalytic deactivation caused by sintering. However, different encapsulation methods may significantly affect catalytic activity and selectivity. In this study, we synthesized Cu-containing mordenite (MOR) zeolites using three distinct approaches: 1) the incipient wetness impregnation of MOR with 1 wt.% Cu (Na–Cu/MOR–IMP), 2) tetraethylenepentamine (TEPA)-assisted hydrothermal synthesis, where TEPA was used to stabilize Cu during MOR crystallization (Na–Cu/MOR–TEPA), and 3) solvent-free interzeolite transformation of Cu-containing Faujasite zeolite to Cu–MOR (Na–Cu/MOR–IZT). The prepared materials were tested as catalysts for the direct conversion of CO 2 and H 2 into alcohols in high-pressure autoclaves. We examined the effects of exchanging zeolite counterions with different alkali metals. At a H₂ partial pressure of 3 MPa, Na–Cu/MOR–IMP exhibited a CO₂ conversion of 7% and ethanol selectivity of 21%, while Na–Cu/MOR–TEPA and Na–Cu/MOR–IZT displayed improved selectivity (~34%) with a similar CO₂ conversion (8%). Notably, Cs-exchanged Cu–MOR catalysts demonstrated the highest ethanol productivity, reaching 34.59 mmol g⁻¹ h⁻¹ with an ethanol selectivity of 63% at 5 MPa H₂. These results highlight the effectiveness of Cu incorporation into MOR zeolites and significant impact of alkali metal promoters on catalytic performance.