(22b) Photocatalytic Reaction of Glycerol and Glycerol Degradation Products Using Metal-Loaded Titanium Dioxide

The photocatalytic reaction of dilute aqueous solutions of glycerol, acetic acid and methanol in the presence of a metal-loaded titanium dioxide catalyst under solar simulating lights was investigated.  Surface deposits of precious metals, such as Pt, Au, Ni, Pd, have been used to enhance photocatalytic reactions, however, this work examined the performance of copper on titanium dioxide.  Reaction with glycerol produced hydrogen and carbon dioxide at maximum rates of 7.4 and 2.6 μmol/L·min, respectively.  The reaction had a high initial selectivity for hydrogen which decreased as the reaction progressed. Catalyst metal loading, temperature, and pH effects were tested.  Acetic acid and methanol were identified as products from the glycerol reaction as well.  Photoreaction of acetic acid gave the lowest hydrogen production rate and yielded a mixture of methane, hydrogen and carbon dioxide, with an initial equal molar production of carbon dioxide and methane that transitioned to low methane production at extended reaction times.  Photoreaction of methanol yielded hydrogen and carbon dioxide with the best selectivity for hydrogen production.  All substrates generated significant amounts of formaldehyde.  Copper leached into the aqueous solution to various extents, depending strongly on the solution pH, and contributed to reduced reaction rates with time.