CO2 hydrogenation to linear α-olefins on FeCx/ZnO catalysts: Effects of surface oxygen vacancies

Selective formation of hydrocarbons from CO2 hydrogenation via the FTS pathway has been attracting interest. Oxygen vacancies (O-v) on the catalyst surface show a subtle role during CO2 activation. Herein, the effects of O-v on FeCx/ZnO catalysts are presented for CO2 hydrogenation to linear alpha-olefins (LAOs). ZnO with surface O-v of varied concentrations was firstly obtained using heated H-2-treatment and used to support active FeCx phases. FeCx/ZnO with appropriate surface O-v achieved CO2 conv. of 48.86% with LAOs sel. of 49.38% and C-1 product below 10%. Characterizations confirmed that the O-v concentration exhibited a positive correlation with the interaction between the iron species and ZnO. With H-2-treatment of ZnO at 500-600 degrees C, FeCx/ZnO-T showed 26-33% O-v in all the oxygen species, which increased the surface C/H ratio and promoted the formation of the key intermediate HCOO- and CHx species for chain growth. Excessive O-v accelerated secondary hydrogenation and increased CH4.