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[Display omitted] • The crystalline phases of ZrO 2 greatly influence the catalytic performance over Pd/In 2 O 3 catalysts. • Pd/In 2 O 3 /Mix-ZrO 2 catalyst with mixed ZrO 2 phases exhibits a high STY of methanol. • The large size of Pd nanoparticles favors H 2 dissociation and CO 2 /intermediates hydrogenation. • The number of medium basic sites and oxygen vacancies are vital for superior performance. The crystalline phases of support have great influence on their surface and structure properties. Therefore, adjusting the crystalline structure of heterogeneous catalysts imposes a significant impact on the catalytic performance. Herein, a suite of Pd/In 2 O 3 /ZrO 2 catalysts with different crystalline phases of ZrO 2 were prepared and evaluated for CO 2 hydrogenation to CH 3 OH using the same amount of metal loading. The activity data showed the distinct superior reactivity of Pd/In 2 O 3 /ZrO 2 catalyst used mixed monoclinic and tetragonal phases ZrO 2 (Mix-ZrO 2) as support as compared to respective single phase of monoclinic ZrO 2 (m-ZrO 2) and tetragonal ZrO 2 (t-ZrO 2). The catalysts are extensively characterized through BET, XRD, HRTEM, UV–vis, H 2 -TPR, CO 2 /H 2 -TPD and XPS. Combining the characterization results and activity data, the superior activity of Pd/In 2 O 3 /Mix-ZrO 2 catalyst can be correlated with large particle size of Pd nanoparticles, the concentration of oxygen vacancies, and the abundant medium basic sites, which were essential for activation of H 2 and inert CO 2 and enhancement of catalytic performance. The best-performing Pd/In 2 O 3 /Mix-ZrO 2 catalyst exhibited a remarkable reactivity with space time yield (STY) of 0.54 g methanol ·h−1·g cat −1 at 573 K and 5 MPa, and stability without noticeable deactivation after 100 h of time on stream, demonstrating its potential as catalyst used in CH 3 OH synthesis from CO 2 hydrogenation. [ABSTRACT FROM AUTHOR]

Advances in design concept of oxide-zeolite (OX-ZEO) bifunctional tandem catalysts have demonstrated its potential for highly enhanced selectivity and yield in CO 2 conversion by assigning CO 2 activation and C-C coupling to specific oxide and zeolite, respectively. However, the crystalline structural effects of oxides have not been thoroughly investigated. Here, ZnO/ZrO 2 with different ZrO 2 crystalline phases modulated by Li doping has been used as an oxide catalyst to combine with SAPO-34 as a bifunctional composite catalyst for CO 2 hydrogenation to light olefins. With the transformation of the support ZrO 2 crystalline phase from tetragonal phase to mixed crystalline phase in the catalyst, the CO 2 conversion and yield of target product light olefins were significantly improved. The best-performing ZnO/5Li-ZrO 2 catalyst exhibited a CO 2 conversion of 28.56%, light olefins selectivity of 82.00% with a yield of 8.77% along with good stability under the reaction conditions of 380 °C, 3 MPa, and 6000 mL/g/h. The characterization results by XRD, Raman, HRTEM, XPS and CO 2 -TPD confirmed that the highly enhanced catalytic performance was attributed to the strong interaction between the mixed crystal phase 5Li-ZrO 2 and ZnO, which generated a large number of oxygen vacancies for CO 2 activation. The results indicate that controlling the crystal phase of the oxide support is of prime importance in designing more active and selective oxide-zeolite bifunctional catalysts for high-efficiency CO 2 to light olefins conversion. [Display omitted] • The mixed ZrO 2 crystal phases boost the catalytic hydrogenation of the bifunctional tandem catalysts. • The ZnO/5Li-ZrO 2 -SAPO-34 tandem catalysts exhibits superior activity due to strong interaction between ZnO and 5Li-ZrO 2. • The ZnO/5Li-ZrO 2 catalysts possess a large number of oxygen vacancies and moderately basic sites. • The ZnO/5Li-ZrO 2 -SAPO-34 tandem catalysts exhibits high CO 2 conversion (28.56%) and light olefins yield (8.77%) at 380 °C. [ABSTRACT FROM AUTHOR]