A theoretical study on n-butane isomerization on supported Fe/γ-Al2O3 and SO4/Fe/γ-Al2O3 model catalysts

This paper reports the results of computational characterization of Fe/γ-Al2O3 and SO4/Fe/γ-Al2O3 using a semiempirical method (extended Hückel like) to analyze different active sites and the resulting acidity of the supported metal species. We found that the more favourable species of oxidized supported Fe are the dimeric and dioxo ones on (1 1 0 C) and (1 0 0) planes of γ-Al2O3. The enhancement of acidity on Fe/γ-Al2O3 due to sulfate addition is favored mainly on monomeric FeO octahedral species, on (1 1 0 C) planes. The dehydration step of highly dispersed sulfated Fe species could produce strong Lewis acid (cationic)-basic pairs. The dehydrogenation of n-butane is more favourable with double-vacancies in sulfated-Fe species onto the (1 1 0 C) plane.