Highly active ternary oxide ZrCeZnOx combined with SAPO-34 zeolite for direct conversion of syngas into light olefins

Direct conversion of syngas into light olefins over bifunctional catalysts (metal oxide and zeolite) has attracted great attention in recent years. For this reaction, the adsorption and activation of CO and H2 occur on metal oxide surface, thus the design of metal oxide is crucial. In this study, ternary oxides ZrCeZnOx with various CeO2 contents were prepared by parallel coprecipitation method, and SAPO-34 zeolite (Si/Al = 0.125) was hydrothermally synthesized. The metal oxides were characterized by XRD, BET, TEM, SEM, XPS, CO-TPD, H2-TPD, TGA and in-situ DRIFTS. The addition of CeO2 into Zr-Zn oxide shifted the diffraction peaks to lower values, and formed the Ce0.5Zr0.5O2 solid solution as the Zr/Ce/Zn atomic ratio reached 4/4/1. As the CeO2 content rose, the BET surface area increased while the metal oxide particle size decreased. Moreover, the addition of CeO2 greatly enhanced the concentration of oxygen vacancies and the adsorption ability of CO and H2. The in-situ DRIFTS confirmed that CH3O* was the intermediate. By optimizing the reaction conditions, ZrCeZnOx/SAPO-34 catalyst exhibited high CO conversion of 25.6 % and light olefins selectivity of 78.6 %. This study will contribute to the design of metal oxide for bifunctional catalyst for light olefins synthesis.