Preparation of Fe-Zr catalyst by microwave-hydrothermal method and its catalytic performance for the direct synthesis of light olefins from CO hydrogenation

A series of Fe-Zr catalysts with different Fe₂O₃/ZrO₂ molar ratios were prepared using ZrO(NO₃)₂·2H₂O and Fe(NO₃)₃·9H₂O as raw materials by means of microwave-hydrothermal method. Then,the catalysts were promoted with potassium by impregnation. The samples were characterized by XRD,SEM,TEM and N₂ adsorption-desorption methods. The results showed that the catalysts prepared by microwave-hydrothermal method have a narrow particle size distribution,a lower BET specific surface area and a larger pore size compared with the traditional precipitation method. During the subsequent CO hydrogenation,it was shown that the product distribution was significantly improved with the addition of zirconium,and the suitable interaction between Fe-Zr and proper pore size were favorable for inhibiting the methane formation and enhance the olefin selectivity. With decreasing the Fe₂O₃/ZrO₂ molar ratio,the interaction between Fe and Zr was strengthened,and the olefin selectivity and productivity first increased and then decreased. An olefin to paraffin ratio of 4.86 and light olefin productivity of 62.57 g/m³ could be obtained with a Fe₂O₃/ZrO₂ molar ratio of 75：25 under conditions of H₂/CO=2,340 ℃,1.5 MPa and 1 000 h^-1.