Glycerol as a Superior Electron Source in Sacrificial H₂ Production over TiO₂ Photocatalyst

Abstract

Biodiesel fuel (BDF) has gained much attention as a new sustainable energy alternative to petroleum-based fuels. BDF is produced by transesterification of vegetable oil or animal fats with methanol along with the co-production of glycerol. Indeed, transesterification of vegetable oil (136.5 g) with methanol (23.8 g) was performed under heating at 61°C for 2 h in the presence of NaOH (0.485 g) to produce methyl alkanoate (BDF) and glycerol in 83.7 and 73.3% yields, respectively. Although BDF was easily isolated by phase separation from the reaction mixture, glycerol and unreacted methanol remained as waste. In order to construct a clean BDF synthesis, the aqueous solution of glycerol and methanol was subjected to sacrificial H2 production over a Pt-loaded TiO2 catalyst under UV irradiation by high-pressure mercury lamp. H2 was produced in high yield. The combustion energy (ΔH) of the evolved H2 reached 100.7% of the total ΔH of glycerol and methanol. Thus, sacrificial agents such as glycerol and methanol with all of the carbon attached to oxygen atoms can continue to serve as an electron source until their sacrificial ability was exhausted. Sacrificial H2 production will provide a promising approach in the utilization of by-products derived from BDF synthesis