Photocatalytic Reforming of Glycerol over Gold and Palladium as an Alternative Fuel Source

Abstract

The photocatalytic reforming of glycerol to hydrogen over palladium and gold modified TiO 2 catalysts is reported. The rate of hydrogen production exceeds that measured for the photoreforming of methanol over both catalysts with the palladium catalyst performing approximately four times better than the gold. The reaction occurs under ambient conditions and neither system suffered from poisoning after extensive testing. This therefore offers a potentially attractive route by which one of the major waste products from the manufacture of biodiesel can be converted into a useful product.

Hydrogen Production by Photoreforming of Renewable Substrates

“…In methanol and glycerol reforming all the carbon atoms possess alphahydrogen; thus, complete dehydrogenation occurs on Pd, leaving absorbed CO on the surface, and converting all the hydrogen atoms into H 2 with a rate for glycerol PR ca. twice 8 ISRN Chemical Engineering than for methanol [13]. As mentioned above [109], the semiconductor plays an active role in the further oxidation of CO to CO 2 , thus regenerating an active site.…”

“…In aqueous solution other powerful oxidizing agents may be formed from surface adsorbed water, such as hydroxyl radicals and superoxide anions (O 2 − ) which are able to oxidize and mineralize almost all organic pollutants yielding CO 2 . As a matter of fact, PR is a much less explored route for obtaining H 2 from oxygenates, such as alcohols, or from biomass extracts and wastes [13,36,37].…”

“…0.5 wt% Pt/TiO 2 was tested for glycerol PR in aqueous solution, increasing the H 2 production rate by one order of magnitude with respect to pure water [38]. Other examples of glycerol PR over Pd/TiO 2 and Au/TiO 2 were proposed in [13], though the catalysts were sensitive to UV light only. Visible light was efficiently harvested by Fu and Lu [191], who used heteropolytungstate/TiO 2 catalysts.…”

“…PR is also thermodynamically more feasible than WS [10]. After a pioneering study in 1980 [11], the attention was more recently focused mostly on the PR of methanol, the simplest molecule, and a few examples of PR of compounds really obtainable from biomass can be found, for example, ethanol, glycerol [12][13][14], glucose, sucrose [14], starch and wood [11], and sewage sludge [15]. Glucose and cellulose were also processed with homogeneous catalytic processes [16].…”

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

“…2) and then upon two electron injections (through a-oxy radical [18,25]) acetaldehyde is formed. The hydrogen ions released through this process are reduced to one hydrogen molecule [27,28]. Reactions 1-4 represent these steps.…”