CO2 hydrogenation to light olefins over Fe-Co/K-Al2O3 catalysts prepared via microwave calcination

This study evaluates the effects of microwave calcination on Fe-Co/K-Al2O3 catalysts for CO2 hydrogenation to light olefins, comparing microwave-treated samples at various power settings (700 W, 616 W, 511 W and 364 W) with a traditionally calcined counterpart. The lowest power setting results in incomplete precursor decomposition, adversely affecting Fe, K, and Al2O3 interactions. At medium power, though decomposition improves, Fe2O3 aggregates due to poor dispersion. Medium-high power produces rod-shaped structures with enhanced Fe and K contact, while the highest setting increases Fe2O3 particle size and Fe-K species content to 35.4%, still below the 37.9% observed in the traditional catalyst. Significantly, the formation of Fe-C species (Fe5C2) correlates positively with Fe-K interactions, enhancing the olefins to paraffins ratio. Additionally, the role of Fe3O4 is vital, providing the highest light olefins yield (24.5%) at an optimal Fe-C/Fe3O4 ratio of 0.34 in the medium-high power sample. Compared to the traditional catalyst, which declines significantly in CO2 conversion and olefin yield due to carbonaceous deposits over time, the medium-high power catalyst shows stable performance and reduced coke formation. Moreover, microwave calcination slashes energy consumption by over 99%, underscoring its potential for more sustainable and efficient catalyst preparation.