Highly stable Pt/CoAl2O4 catalysts in Aqueous-Phase Reforming of glycerol

Abstract

Pt/CoAl2O4 catalysts with small amounts of Pt (0.3 and 1 wt.%) were prepared by wet impregnation of platinum on cobalt aluminate (mole ratio Co/Al = 0.625). These catalysts were compared with monometallic Pt/alumina and cobalt aluminate counterparts. The physicochemical characteristics of the obtained materials were thoroughly analysed. The catalytic performance of the prepared assays was investigated in the Aqueous-Phase Reforming (APR) of glycerol for up to 100 h TOS, and in liquid phase Water-Gas Shift (WGS). It was concluded that the addition of Pt to cobalt aluminate resulted in a synergistic effect that promoted the reduction of both Pt and Co species, as well as cobalt dispersion, what increased the amount of exposed metallic sites. These effects were, however, sensitive to the amount of Pt loaded. The glycerol APR activity of bimetallic catalysts was very stable over 100 h TOS with conversion values above 99 %. Conversion to gas was also above 95 % during the whole operation. Contrarily, the counterpart monometallic catalysts suffered noticeable deactivation at above 70 h TOS. Also, WGS activity of bimetallic assays was higher than the monometallic counterparts. Addition of Pt to cobalt aluminate lowered selectivity to hydrogen, due to a higher CO hydrogenation activity. Examination of the spent catalysts showed better textural stability of the bimetallic samples, as well as much lesser formation of carbonaceous surface deposits. Nevertheless, oxidation and leaching of cobalt remains as the main drawback of bimetallic catalysts to be used in APR.