One-step conversion of syngas to light olefins over bifunctional metal-zeolite catalyst

Light olefins (C₂–C₄) are fundamental building blocks for the manufacture of polymers, chemical intermediates, and solvents. In this work, we realized a composite catalyst, comprising Mn_xZr_y oxides and SAPO-34 zeolite, which can convert syngas (CO + H₂) into light olefins. Mn_xZr_y oxide catalysts with different Mn/Zr molar ratios were facilely prepared using the coprecipitation method prior to physical mixing with SAPO-34 zeolite. The redox properties, surface morphology, electronic state, crystal structure, and chemical elemental composition of the catalysts were examined using H₂-TPR, SEM, XPS, XRD, and EDS techniques, respectively. Tandem reactions involved activation of CO and subsequent hydrogenation over the metal oxide catalyst, producing methanol and dimethyl ether as the main reaction intermediates, which then migrated onto SAPO-34 zeolite for light olefins synthesis. Effects of temperature, pressure and reactant gas flow rate on CO conversion and light olefins selectivity were investigated in detail. The Mn₁Zr₂/SAPO-34 catalyst (Mn/Zr ratio of 1:2) attained a CO conversion of 10.8% and light olefins selectivity of 60.7%, at an optimized temperature, pressure and GHSV of 380 °C, 3 MPa and 3000 h⁻¹ respectively. These findings open avenues to exploit other metal oxides with CO activation capabilities for a more efficient syngas conversion and product selectivity.