Boosting CO2 hydrogenation efficiency for methanol synthesis over Pd/In2O3/ZrO2 catalysts by crystalline phase effect

Abstract

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/In2O3/ZrO2 catalysts with different crystalline phases of ZrO2 were prepared and evaluated for CO2 hydrogenation to CH3OH using the same amount of metal loading. The activity data showed the distinct superior reactivity of Pd/In2O3/ZrO2 catalyst used mixed monoclinic and tetragonal phases ZrO2(Mix-ZrO2) as support as compared to respective single phase of monoclinic ZrO2(m-ZrO2) and tetragonal ZrO2(t-ZrO2). The catalysts are extensively characterized through BET, XRD, HRTEM, UV–vis, H2-TPR, CO2/H2-TPD and XPS. Combining the characterization results and activity data, the superior activity of Pd/In2O3/Mix-ZrO2 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 H2 and inert CO2 and enhancement of catalytic performance. The best-performing Pd/In2O3/Mix-ZrO2 catalyst exhibited a remarkable reactivity with space time yield (STY) of 0.54 gmethanol·h−1·gcat−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 CH3OH synthesis from CO2 hydrogenation.