Trickle-Bed Reactor Studies for Selective Oxidation of Glycerol to Dihydroxyacetone Over Pt-Bi/C Catalyst

Increase in the production of biodiesel has resulted in an oversupply of glycerol, the primary byproduct which forms in a 1:10 ratio with biodiesel.  An effective utilization of glycerol (currently ~$0.02/lb) by conversion to the higher value chemical dihydroxyacetone (DHA; currently ~$20/lb) will enhance the economics of biodiesel production.  Recently, we have developed a catalyst (3%Pt, 0.6% Bi on activated carbon) capable of selective oxidation of glycerol to DHA at high yield (>40%) in a semi-batch reactor [1].  Development of a continuous-flow process, however, is necessary to increase production.  Towards this end, a trickle-bed reactor has been used with cocurrent downflow of oxygen and aqueous glycerol solution over a packed bed.  An optimization of the feed solution pH and concentration as well as reactor temperature and pressure will be presented.  Additionally, the effects of gas and liquid flowrates will be discussed in light of hydrodynamic characteristics of trickle-bed reactors for foaming liquids. The development of a continuous-flow process for conversion of glycerol to DHA increases the economic viability of biodiesel production, while also providing insight into the behavior of trickle-bed reactors.

[1] Hu, W., Knight, D., Lowry, B., Varma, A. Selective Oxidation of Glycerol to Dihydroxyacetone over Pt-Bi/C Catalyst:  Optimization of Catalyst and Reaction Conditions. Ind. Eng. Chem. Res. 2010, 49 (21), 10876-10882.