Photo-Oxidation of Glycerol Catalyzed by Cu/TiO2

Abstract

In the present study, glycerol was oxidized by photocatalysis to glyceraldehyde, formaldehyde, and formic acid. Copper-doped TiO2 was synthesized by the evaporation-induced self-assembly approach and it was used as catalyst during the glycerol photo-oxidation reactions. The prepared mesoporous material exhibited high specific surface area (242 m2/g) and band gap energy reduction of 2.55 eV compared to pure titania (3.2 eV) by the synthesis method due to the presence of copper cations (Cu2+ identified by XPS). The catalyst showed only anatase crystalline phase with nanocrystals around 8 nm and irregular agglomerates below 100 μm. The selectivity and formation rate of the products were favored towards formaldehyde and glyceraldehyde. The variables studied were catalyst amount, reaction temperature, and initial glycerol concentration. The response surface analysis was used to evaluate the effect of the variables on the product’s concentration. The optimized conditions were 0.4 g/L catalyst, 0.1 mol/L glycerol, and temperature 313.15 K. The response values under optimal conditions were 3.23, 8.17, and 1.15 mM for glyceraldehyde, formaldehyde, and formic acid, respectively. A higher selectivity towards formaldehyde was observed when visible light was used as the radiation source. This study is useful to evaluate the best reaction conditions towards value-added products during the oxidation of glycerol by photocatalysis using Cu/TiO2.

Clarifying solvent effect during photocatalytic glycerol conversion on TiO2/GQD as selective photocatalyst

“…However, the gas products are mainly H 2 and CO 2 . This study focused on the total liquid and gas selectivity and the DHA/GA ratio as a common metric in photocatalytic glycerol oxidation, where it is important to improve the DHA selectivity as the most desirable product 46 . For the TiO 2 NPs sample, only 0.5% conversion was observed in the absence of H 2 O 2 and increased to 1.7% when the oxidant was added.…”

Mechanistic Understanding in Manipulating Energetics of TiO2 for Photocatalysis

“…When photon energy is equivalent to hv 2 , electrons excite the dopant’s electronic states. Cu-modified TiO 2 showed a bandgap reduction to 2.55–2.85 eV compared to ∼3.2 eV of pure TiO 2 , which can be utilized for visible light photocatalytic H 2 generation. − In Co 2+ doped TiO 2 , the formation of charge transfer channels to Co 2+ ions was identified as the main reason for suppressed recombination …”

Photocatalytic Biohydrogen Production Using ZnO from Aqueous Glycerol Solution with Aid of Simultaneous Cu Deposition

“…The holes reacted with water to form hydroxyl radicals (•OH) and proton ions (H + ) (Equation ( 9)). Based on literature reports [30][31][32], it was proposed that glycerol molecules were adsorbed on the surface of ZnO and reacted with the formed hydroxyl radicals to degrade into CO 2 and H + as shown in Figure 6. Since hydrogen atoms can generally be extracted by the hydroxyl radicals from hydroxylated carbon more effectively, relative to from non-hydroxylated carbon, the hydroxyl radicals are primarily reacted with alcohols to produce aldehyde, which is then further oxidized to produce carboxylic acid.…”