An Experimental and Theoretical Study of Glycerol Selective Oxidation to 1,3-Dihydroxyacetone Via Bimetallic Platinum-Bismuth Catalysts

It is important to utilize glycerol, the main by-product of biodiesel production, to manufacture high value-added chemicals such as 1,3-dihydroxyacetone (DHA). In our prior work, a series of optimized Pt-Bi catalysts was prepared for selective oxidation of glycerol to DHA. The catalytic mechanism, however, remained unclear. In the present work, both experimental and theoretical approaches were used to reveal the DHA formation mechanism. Specifically, the performance of five different catalysts (Pt-Bi/AC, Pt-Bi/ZSM-5, Pt/MCM-41, Pt-Bi/MCM-41 and Pt/Bi-doped MCM-41) was investigated experimentally and Pt-Bi/MCM-41 exhibited the highest DHA yield. Using a periodic slab-model density functional theory (DFT), computations were made to obtain energy barriers of elementary steps, reaction pathways and Bi effect as an additive to Pt catalyst. Both the experimental and calculated kinetic results show that for high DHA selectivity, Bi should be placed on top of Pt, rather than inside or below Pt or in the support skeleton. The promoter effects of Bi were identified for the DHA formation mechanism. The results demonstrate that the Bi species on the Pt surface is necessary and efficient to selectively convert glycerol to DHA.