New Active and Selective Rh−REOx−Al2O3Catalysts for Ethanol Steam Reforming

Abstract

The effect of the addition of a wide range of rare earth elements (Sc, Y, La, Er and Gd) on the catalytic behavior of Rh/Al2O3 base catalyst in the ethanol steam reforming (ESR) reaction was investigated. Physical−chemical properties of Rh−REOx−Al2O3 materials have been evaluated by H2 chemisorption, XRD, BET, TPR, IR spectroscopy and TPO. It was established that the catalytic behavior of the Rh/Al2O3 base catalyst is widely improved by the promotion with rare earth (RE) elements. It has been shown that the RE elements do not have an important impact on the oxidation state and the dispersion of the metallic centers but greatly alter the acid−base properties of the support. It was demonstrated that the catalytic performances of Rh−REOx−Al2O3 catalysts are mainly due to the increase of the support basicity and to the rearrangement of acid sites. The presence of a new type of Lewis acid sites (LAS) of weak strength on Rh−REOx−Al2O3 materials leads to decrease the production of coke precursor (C2H4). Finally, the most basic support leads to the highest hydrogen yield and to the less stable coke.