Effect of acidity and oxygen vacancy in Mn loaded SAPO-34 on CO2 hydrogenation to light olefin

In this paper, the interaction between metal catalyst and Mn-doped molecular sieve was proposed as a strategy to regulate the metal valence which influences acidic sites and promotes carbon dioxide adsorption during CO2 hydrogenation reaction. The ZnO-ZrO2/4%MnSAPO-34 catalyst displayed a stronger CO2 adsorption capacity and improved activity compared to the unmodified ZnO-ZrO2/SAPO-34 catalyst. Physical and chemical properties of the tested catalysts were explored using XRD, SEM-EDS, FT-IR, TEM, CO2-TPD, NH3-TPD and XPS. By fine tuning the Mn amount on SAPO-34 catalyst, the acidity which plays a crucial role in the selectivity of the light olefins, was controlled. Optimized conditions such as influence of catalyst composition and reaction temperature were also investigated. At 380 °C, 2.0 MPa, GHSV = 2400 h−1 and ZnO-ZrO2 to MnSAPO-34 mass ratio of 1, the selectivity of light olefins reached 83.2%, with a CO2 conversion of 17.3%.