The bifunctional oxygen carrier K/LayCoxFe1-xO3 for the production of C2–C4 olefins via CO2 hydrogenation

Abstract

Developing the bifunctional oxygen carrier with excellent oxygen mobility and catalytic activity is the key to chemical looping combustion coupled CO2 hydrogenation to light olefins. In this study, a series of K/LayCoxFe1-xO3 (x = 0, 0.2, 0.4, 0.6, y = 0.2, 0.4, 0.8) with oxygen vacancy-active metal dual active centers were constructed by the Co doping-La defect synergistic strategy to evaluate the oxygen release and catalytic performance. The results indicated that K/La0.4Co0.4Fe0.6O3 had high oxygen mobility, and its reduced state can be directly used for CO2 hydrogenation to light olefins (C2=-C4=). The selectivity of C2=-C4= was close to 30%, and the conversion rate of CO2 was 36%. Combined with various characterizations, the synergy of Co doping and La defects increased the oxygen vacancy and promoted the exsolved CoFe alloy under the reduction induction of chemical looping combustion. In situ DRIFTS reveals the dynamic equilibrium of the Formate-Methoxy mechanism and RWGS-FTS pathway. Oxygen vacancies are found to enhance the conversion of CO2 via the formate pathway, while metal active phases alter the product distribution by changing the evolution of intermediates. The Co7Fe3 and oxygen vacancy on K/La0.4Co0.4Fe0.6O3 promotes the formation of CHx∗ and C–C coupling through various intermediates, improving the selectivity of light olefins.