High Conversion of Syngas to Ethene and Propene on Bifunctional Catalysts via the Tailoring of SAPO Zeolite Structure

Direct conversion of syngas to light olefins using bifunctional catalysts containing both oxides and zeolites represents a promising alternative in comparison with Fischer-Tropsch synthesis. It is still a great challenge to achieve highly selective production of ethylene and propylene at a satisfying CO conversion for potentially industrial applications. Here, we report that a high selectivity to ethylene and propylene can be achieved by tailoring silicoaluminophosphate zeolite structure and acid site strength. By comparing bifunctional catalysts composed of ZnCr oxide and different zeolites with 8-membered ring openings, we achieve the total selectivity of 76.4% in ethylene and propylene at a CO conversion as high as 38.2% by catalysts containing SAPO-17 zeolite (ERI framework). The detailed hydrocarbon distribution is nearly identical to that in the methanol-to-olefins reaction. The high selectivity can be rationalized due to both smaller 8-membered ring openings and the weaker Brønsted acid strength of SAPO-17 zeolites.