Au/Pt/TiO sub(2) catalysts prepared by redox method for the chemoselective 1,2-propanediol oxidation to lactic acid and an NMR spectroscopy approach for analyzing the product mixture

• Published in: Applied catalysis. A, General Vol. 491; pp. 170 - 183
• Main Authors: Redina, Elena, Greish, Alexander, Novikov, Roman, Strelkova, Anastasiya, Kirichenko, Olga, Tkachenko, Olga, Kapustin, Gennady, Sinev, Ilya, Kustov, Leonid
• Format: Journal Article
• Language: English
• Published: 05.02.2015
• Subjects: Bimetals; Catalysis; Catalysts; Gold; Lactic acid; Nuclear magnetic resonance; Oxidation; Platinum; Titanium dioxide
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2014.11.039

1,2-propanediol obtained from the waste glycerol is the most prominent substrate to produce lactic acid (LA) through the sustainable "green" catalytic oxidative route. We showed that bimetallic Au/Pt/TiO sub(2) catalysts that could be easily prepared by the redox reaction with preadsorbed hydrogen possessed a high activity in the formation of lactic acid from 1,2-propanediol through selective primary hydroxyl group oxidation by an oxygen-air mixture or an air. The most efficient catalyst with the highest TON value was the sample with the lowest Au content. Even the addition of 0.025 wt.% of gold to the 1%Pt/TiO sub(2) catalyst by the redox method resulted in the enhanced 1,2-propanediol conversion up to 96% with the 91% selectivity to LA. The high oxidation activity of the Au/Pt/TiO sub(2) catalysts was ascribed to the strong interaction between the two metals in Au/Pt bimetallic particles and between the bimetallic particles and the support, which was proved by X-ray photoelectron spectroscopy (XPS) analysis, Fourier transform infrared spectroscopy of adsorbed CO (DRIFTS) technique, and temperature programmed reduction method (TPR-H sub(2)). The reaction products were identified and analyzed with the use of 1D and 2D nuclear magnetic resonance spectroscopy (NMR) methods, which also allowed suggesting a plausible up-to-date scheme of 1,2-propanediol catalytic oxidation.