Tandem catalysis over tailored ZnO-ZrO2/MnSAPO-34 composite catalyst for enhanced light olefins selectivity in CO2 hydrogenation

A ZnO-ZrO2 metal catalyst prepared by co-precipitation technique, physically combined with a modified zeolite (MeSAPO-34, Me = Zn, Zr, Mn) prepared by the hydrothermal synthesis in a granule stacking arrangement, was tested for direct CO2 hydrogenation to light olefins. XRD, CO2-TPD, NH3-TPD, FT-IR, SEM-EDS, N2 physisorption, HAADF and BET techniques were utilized to characterize the as-prepared catalysts samples. The series reaction phenomenon involved methanol synthesis on the ZnO-ZrO2 catalyst and methanol-to-light olefins synthesis over the MeSAPO-34 zeolite, which afforded an avenue for precise tailoring of the two different active sites individually. We reveal that the target product selectivity in this process can be optimized by the choice and amount of basic metal embedded into the zeolite ionic structure to tune the acidity of the molecular sieve and limit secondary hydrogenation reactions. The composite (13%ZnO-ZrO2/Mn0.1SAPO-34) realized a very high CO2 conversion of 21.3%, suppressed CO and CH4 selectivity below 43% and 4% respectively, attained a remarkable light olefins selectivity of 61.7% at 380 °C, 2 MPa, and GHSV = 4800 h−1. The catalyst synthesis approach coupled with the tandem reactions involved open more prospects to utilizing CO2 resources in green chemistry.