Oxidation of Glycerol with H2O2 on Lead-Promoted Pd/Al2O3 Catalysts

MARÍA L. FAROPPA; JUAN J. MUSCI; MARÍA E. CHIOSSO; CLAUDIA G. CAGGIANO; HERNÁN P. BIDEBERRIPE; JOSÉ L. GARCÍA FIERRO; GUILLERMO J. SIRI; MÓNICA L. CASELLA

Lisboa

Congreso; 2nd EuCheMS Congress on Green and Sustainable Chemistry; 2015

EuCheMS

The heterogeneous catalytic oxidation of glycerol is presented as an environmentally friendly alternative to obtain one or more of its oxidation products preferentially [1]. This process provides an opportunity to generate high value-added products with good selectivity and under mild experimental conditions, although there are still some practical problems in the utilization of different catalytic systems regarding their activity and deactivation phenomena [2]. It has been suggested that the addition of a second metal (less active) such as Bi, Pb or Sn onto platinum or palladium catalysts could lead to an improvement in their catalytic performance. As a contribution, in the present work, we prepared alumina-supported Pd catalysts modified with different amounts of lead. The catalysts were characterized by transmission electron microscopy, temperature-programmed reduction and X-ray photoelectron spectroscopy, and their activity and selectivity in the aqueous-phase oxidation of glycerol was evaluated, using H2O2 as oxidizing agent. The catalysts with different contents of Pb showed different levels of activity. With the monometallic catalyst, a 5% conversion of glycerol was obtained, while with PdPb0.25, PdPb1.00 and PdPb1.60 catalysts, conversions of 23.7, 43.2 and 32.6%, respectively, were achieved. Concerning selectivity, the monometallic catalyst gave 96.3% of glycolic acid, indicative of the preferential oxidation of the secondary alcohol. The most active catalyst (PdPb1.00) gave a selectivity to glyceric acid of 59.5%. This behavior was attributed to a change in the architecture of the catalytic site, which weakens the adsorption of the initially formed dihydroxyacetone, favoring its subsequent oxidation.