CO2 hydrogenation to olefins on supported iron catalysts: Effects of support properties on carbon-containing species and product distribution

Catalytic utilizing of CO2 into valuable olefins on Fe-based catalysts is a feasible way to mitigate the pressure of carbon neutrality. Herein, by investigating the effects of support (SiO2, Al2O3, CNT, and ZrO2) on the structure and catalytic performance of iron catalysts, we have found that ZrO2 supported catalysts are more beneficial to olefin selectivity and chain growth. The optimization catalytic performance of FeNa/ZrO2 displays C-2-C-7 olefin selectivity of 68.2% (O/P = 8.0) with a space time yields (111.4 g Kg(cat)(-1) h(-1)) at X-CO2 = 32.7%, 320 degrees C, 2.0 MPa, CO2/H-2/Ar = 1:3:3, and 9000 mL g(-1)h(-1). Characterizations show that the support regulates the composition of the iron oxide phase and the iron carbide phase and induces to form the highest content of Fe5C2 on the spent FeNa/ZrO2, which is probably caused by the carbon rich surface and lower disorder of carbon species. Besides, the higher intensity of CO2 and CO adsorption and lower intensity of H-2 adsorption is confirmed on the surface of the FeNa/ZrO2 catalysts, leading to a higher ratio of C/H on the surface of the spent catalysts and consequently inhibiting the hydrogenation of olefins. Therefore, the O/P is 8 times as many as that on the FeNa/SiO2 and FeNa/Al2O3. Understanding the effect of support on CO2 hydrogenation to olefins over iron-based catalysts would be significant for precisely designing new catalysts.