Effective conversion of CO2 into light olefins along with generation of low amounts of CO

Abstract

Indium-based oxide/zeolite bifunctional catalyst has been shown to be potential for conversion of CO2 into C2=-C4=. However, this type of catalyst generates large amounts of CO with selectivity ≥ 55 %. Thus, a new type of InCeZrOx(n)/H-SAPO-34(x) composite is fabricated here for catalyzing CO2 hydrogenation to light olefins, and its catalytic mechanism is investigated by combining in situ spectroscopy and isotope-labeled experiments. Upon optimization of In content incorporated in CeZrOx, the coupling manner of InCeZrOx with H-SAPO-34 and reaction conditions, this composite gives comparable C2=-C4= yield to previously reported catalysts but a much lower CO selectivity (9.7 %) as a result of C2=-C4= selectivity in hydrocarbons reaching 93.6 %, while those of CH4 and C20-C40 as low as 1.9 % and 2.4 %, respectively. Various characterization and designed experiment results reveal that incorporation of appropriate amounts of In in CeZrOx generates more oxygen vacancies that promotes CO2 activation to form formate and methoxy intermediates at low temperature and pressure, whereas addition of more In species causes some to migrate onto H-SAPO-34(x) and poison acid sites, which leads to quick deactivation of catalysts.