An investigation on AuPt and AuPt-Bi on granular carbon as catalysts for the oxidation of glycerol under continuous flow conditions

AuPt/AC and Bi modified AuPt/AC were prepared by impregnation using activated granular carbon as support followed by chemical reduction. The catalysts were characterized by means of Atomic Absorption Spectroscopy (AAS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalysts were evaluated in the base free glycerol oxidation at mild reaction conditions in a continuous flow fixed bed reactor. Experimental parameters, such as, contact time (Liquid Hourly Space Velocity: LHSV), temperature and O2 flow have been varied in order to evaluate catalytic performance in terms of activity, selectivity and long-term stability. Under optimized reaction conditions AuPt/AC showed a high selectivity to glyceric acid (68.3%) whereas Bi-AuPt/AC promoted the oxidation of the secondary alcohol giving a selectivity to dihydroxyacetone (DHA) of 48.1% at 28% conversion, one of the most promising values reported in the current literature. Long-term catalytic performance was carried out for 80 h and revealed a reasonable good stability of AuPt/AC against deactivation and leaching, whereas structural modification and subsequent changes in the catalytic reactivity were envisaged for Bi-AuPt/AC catalyst.