The photocatalytic H2 evolution by Pt-loaded TiO2 was examined using sacrificial agents such as 1,2-ethanediol, glycerol, erythritol, and arabitol, the carbons of which all have hydroxy groups. In these cases, almost complete decomposition of sacrificial agents into CO2 and H2O occurred. Moreover, the H2 evolution reached the maximum values estimated by their potentially electron-donating ability. On the other hand, smaller amounts of CO2 and H2 were evolved from 1,2,3-butanetriol, 1,2,4-butanetriol, and 1,2-butanediol, which had both continuous hydroxylated carbons and one or two non-hydroxy-substituted carbons, the inner continuous 2,3-butanediol, and the discontinuous 1,3- and 1,4-butanediols. In the cases of monools such as 2-butanol and 2-propanol, CO2 was not evolved at all. Thus, we found that the structure of sacrificial agents, more so than the potential electron-donating ability, is an important factor to evolve H2 efficiently.

Photocatalytic reaction was performed by irradiation of Pt-doped TiO2 in an aqueous solution of xylose acting as a sacrificial reagent to evolve hydrogen, whose amounts reached 8.6 equivalents to the xylose used.

Ethanol and pentose were produced from lignocellulosic napiergrass by the simultaneous saccharification and fermentation process (SSF) using hydrolytic enzyme and S. Cerevisiae. After the ethanol was removed, the pentose solution was subjected to photocatalytic hydrogen evolution with Pt-loaded TiO 2 under UV-irradiation. This process converted 100 g of napiergrass into 12.3 g of ethanol and 1.76 g of hydrogen whose total combustion energy of (∆H) was 615 kJ. This was close to the ∆H (639 kJ) of the pentose (13.6 g) and hexose (27.4 g) obtained by the cellulose-saccharification of 100 g of napiergrass.

Photocatalytic H 2 evolution was examined using Pt-loaded TiO 2 -photocatalyst in the presence of amines as sacrificial agents. In the case of amines with all of the carbon attached to the hetero-atom such as 2-aminoethanol, 1,2-diamonoethane, 2-amino-1,3-propanediol, and 3-amino-1,2-propanediol, they were completely decomposed into CO 2 and water to quantitatively evolve H 2 . On the other hand, the amines with both hetero-atoms and one methyl group at the β-positions (neighboring carbons) of amino group such as 2-amino-1-propanol and 1,2-diaminopropane were partially decomposed. Also, the photocatalytic H 2 evolution using amines without the hetero-atoms at the β-positions such as ethylamine, propylamine, 1-butylamine, 1,3-diaminopropane, 2-propylamine, and 2-butylamine was inefficient. Thus, it was found that the neighboring hetero-atom strongly assisted the degradation of sacrificial amines. Moreover, rate constants for H 2 evolution were compared among amines. In conclusion, the neighboring hetero-atom did not affect the rate constants but enhanced the yield of hydrogen evolution.

Biodiesel (BDF) has gained much attention as new sustainable energy alternative to petroleum-based fuels. In particular, BDF market has significantly increased in Europe to adhere energy and climate policies. Therefore, the increased BDF production requires new utilization of glycerol which is by product of BDF synthesis. We have focused on photocatalytic reforming using titanium oxide (TiO2) photocatalyst using glycerol as sacrificial agent (SaH). Recently we have found that SaH with all of the carbon attached oxygen atoms such as glycerol and methanol continued to serve as an electron source until their sacrificial ability was exhausted in photocatalyzed hydrogen evolution using a Pt-loaded TiO2 (Pt/TiO2) catalyst. Here we investigated the utilization of residual glycerol in BDF synthesis by photocatalytic reforming.BDF (methyl alkanoate) preparation by transesterification of commercially-available vegetable oil (136.5 g) was performed by heating with MeOH (23.8 g) in the presence of NaOH (0.485 g) at 61 ℃ for 2 h. After cooling, standard follow-up operation was performed as follows. The products were separated into a lower layer (Solution A) and an upper layer. The upper layer was washed with water and separated into a BDF layer and an aqueous washing solution (Solution B). Glycerol (10.4 g) was obtained from Solution A in 73.3% yield along with methanol (6.85 g). BDF (114.5 g) was isolated in 83.7% yield. Solution B contained methanol in 4.38 g. The residual glycerol and unreacted methanol were turned to hydrogen by TiO2-photocatalytic reforming of Solutions A and B using Pt/TiO2 (100 mg) in aqueous solution (150 mL) under irradiation by high-pressure mercury lamp. Hydrogen was evolved in 2.82 g and 0.28 g from Solutions A and B, respectively. The combustion energy (ΔH) of the evolved H2 corresponded to 100.8% based on the total ΔH of glycerol and methanol involved in Solutions A and B. Similar experiment was performed using pre-used vegetable oil. Hydrogen was recovered from Solutions A and B as 69.6% of ΔH. Presence of sodium alkanoate disturbed the hydrogen evolution.