Recovery of ethene-selective FeOx/Al2O3 ethanol dehydration catalyst from industrial chemical wastes Original Research Article

Boehmite, γ-AlO(OH), recovered from aluminium dross tailings (ADT) and steel-pickling chemical waste (SPW) were used to prepare 1–10 wt.% FeOx/Al2O3 catalysts. Surface and bulk properties of the catalysts were characterized by nitrogen sorptometry, thermogravimetry (TG) of adsorbed pyridine, X-ray photoelectron spectroscopy and X-ray powder diffractometry. The results have shown the catalysts to consist of highly dispersed α-Fe2O3 particles on high-surface area γ-Al2O3, but cannot exclude the coexistence of monolayer species of Fe(II)–O and/or Fe(III)–O, as well as Fe(III) incursions into the support bulk structure. Activity tests of the catalysts towards ethanol dehydration (at 140–250°C) in the gas phase, have revealed that increasing amounts of supported FeOx species could turn γ-Al2O3 from being diethyl ether selective to ethene selective, without changing its originally high dehydration activity towards the alcohol. Consequent modifications of the surface acid site density have been correlated to observed changes in the alcohol dehydration rate. Hence, the switching of the catalyst selectivity to ethene formation has been suggested to follow suppression (or elimination) of bi-molecular reaction mechanism necessary for ether formation due to Fe(III) incursion into the support, and/or ether decomposition on Fe2O3 particles.