CO2 hydrogenation to linear α-olefins on FeCx/ZnO catalysts: Effects of surface oxygen vacancies
Chen Wang, Jianli Zhang, Xinhua Gao, Qingxiang Ma, Subing Fan, Tiansheng Zhao
Abstract
Selective formation of hydrocarbons from CO 2 hydrogenation via the FTS pathway has been attracting interest. Oxygen vacancies (O v ) on the catalyst surface show a subtle role during CO 2 activation. Herein, the effects of O v on FeC x /ZnO catalysts are presented for CO 2 hydrogenation to linear α-olefins (LAOs). ZnO with surface O v of varied concentrations was firstly obtained using heated H 2 -treatment and used to support active FeC x phases. FeC x /ZnO with appropriate surface O v achieved CO 2 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 °C, FeC x /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 CH x species for chain growth. Excessive O v accelerated secondary hydrogenation and increased CH 4 .