Nickel-Doped CdZrO x /SAPO-34 with Enhanced CO 2 Activation and H 2 Spillover: Promoting Selective Light Alkane Formation with High Activity and Durability

With significant advances in alkane dehydrogenation in recent years, the direct CO 2 hydrogenation to light alkanes (ethane, propane, and butanes) over an oxide/zeolite (OXZEO) composite catalyst offers a pathway for light olefin production. Nevertheless, the existing CO 2 -to-alkanes conversion often relies on the strong acid sites in zeolite micropores for olefin hydrogenation, which tends to cause side reactions and coking. Herein, we discovered the Ni-doping on a CdZrO x catalyst not only enhanced the density of oxygen vacancy for efficient CO 2 activation but also promoted the H 2 dissociation and spillover capacity. When combined with SAPO-34 aluminophosphate with medium acidity, the NiCdZrO x (0.05)/SAPO-34(0.075) bifunctional system converted CO 2 and H 2 directly into light alkanes (C 2 0 –C 4 0 ) with an alkane-in-hydrocarbons selectivity of 81% and CO 2 conversion of 40% at 350 °C and 4 MPa, maintaining its stability for 100 h. In situ X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and density functional theory (DFT) calculations attributed the robust catalytic performance to a tailored reaction pathway: CO 2 and H 2 were efficiently activated on NiCdZrO x (0.05) to form a methanol intermediate, which then migrated to the moderately acidic SAPO-34 aluminophosphate and underwent a controlled methanol-to-olefins (MTO) reaction. The generation of active hydrogen species due to the strong hydrogen spillover effect of NiCdZrO x (0.05) drove the secondary hydrogenation of light olefins into corresponding alkanes. Moreover, the hydrogen spillover also effectively minimized the coke deposition in SAPO-34 micropores, thereby significantly promoting the catalytic activity and stability of CO 2 hydrogenation to light alkanes.