Unraveling the role of reducing atmospheres on Fe-Zn-Al catalysts for highly selective carbon dioxide hydrogenation to light olefins

This study investigates the carbon dioxide (CO2) hydrogenation performance of Fe-Zn-Al catalysts pretreated under four distinct reducing atmospheres (H2, H2/N2, H2/CO, and CO/N2), elucidating their impact on CO2 conversion, CO selectivity, and light olefins selectivity. Combined with the characterization results, it was found that various catalyst components were obtained after activation in different atmospheres, but Fe5C2 was observed in all the catalysts after the CO2 hydrogenation reaction. The catalytic performance is intricately linked to the type of surface species produced after reduction and the Fe5C2 content. In a comparative perspective, the catalytic activity of the same catalyst in the four atmospheres followed the sequence H2>H2/N2>CO/N2>H2/CO. Notably, catalyst pretreatment with H2 yielded the highest CO2 conversion rate at 31.6 % and light olefins selectivity at 40.2 %. These results can be attributed to the highest electron density detected by XPS for the iron species on the spent catalyst and to the largest concentration of Fe5C2 formed during the reaction in the hydrogen reduced sample. •The synthesis of iron-zinc-aluminum catalysts utilizes environmentally friendly and low-cost deionized water as a solvent.•The impact of several reducing atmospheres on the performance of iron-zinc-aluminum catalysts was comparatively studied.•The structural characteristics of the catalyst, both before and after the reaction, were investigated.