Oxidative dehydrogenation of ethylbenzene with CO2 for styrene production over porous iron-based catalysts

Porous iron-based catalysts with different promoters (Zr, Ti or Al) have been tested in oxidative dehydrogenation of ethylbenzene with CO2 for styrene production. The catalysts were characterized by X-ray diffraction (XRD), 57Fe-Mössbauer and Raman spectroscopy, temperature-programmed reduction (TPR) and N2 adsorption–desorption measurements, before and after the catalytic evaluation. The reactivity of iron-based catalysts toward styrene production was dependent on the structural and textural features of the solid as well as the nature of the promoter. α-Fe2O3 and rutile TiO2 present on FeTi were converted in situ into FeTiO3, Fe2TiO5 and FeTi2O5, and these phases revealed a high styrene yield (up to 50%) in the first stage of the reaction, but lower selectivity than that exhibited by their FeZr and FeAl counterparts. However, FeTi performed much better in terms of stability showing no tendency to sintering or phase transformation whereas the other solids suffered from hard carbon deposition.