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

Boehmite, gamma-AlO(OH), recovered from aluminium dress tailings (ADT) and steel-pickling-chemical waste (SPW) were used to prepare 1-10 wt.% FeOx/Al2 O3 catalysts. Surface and bulk properties of the catalysts were characteriz ed by nitrogen sorptometry, thermogravimetry (TG) of adsorbed pyridine, X-r ay photoelectron spectroscopy and X-ray powder diffractometry. The results have shown the catalysts to consist of highly dispersed alpha-Fe2O3 particl es on high-surface area gamma-Al2O3, but cannot exclude the coexistence of monolayer species of Fe(II)-O and/or Fe(III)-O, as well as Fe(III) incursio ns into the support bulk structure. Activity tests of the catalysts towards ethanol dehydration (at 140-250 degrees C) in the gas phase, have revealed that increasing amounts of supported FeOx species could turn gamma-Al2O3 f rom being diethyl ether selective to ethene selective, without changing its originally high dehydration activity towards the alcohol, Consequent modif ications of the surface acid site density have been correlated to observed changes in the alcohol dehydration rate. Hence, the switching of the cataly st selectivity to ethene formation has been suggested to follow suppression (or elimination) of bi-molecular reaction mechanism necessary for ether fo rmation due to Fe(III) incursion into the support, and/or ether decompositi on on Fe2O3 particles. (C) 2000 Elsevier Science B.V. All rights reserved.