Selective Hydrogenation of Hexanoic Acid to Hexanol Under Mild Conditions over Titania-Based Pt-Re Catalyst
The Pt-ReOx species (x ≤ 1) of atomic dispersion were formed and stabilized on the titania surface. Their size, charge and chemical composition were characterized by means of HRTEM/STEM with EDX mapping, XPS, FTIR. It was shown these centers with Re:Pt = 2 are highly active and selective in hydrogenation of carboxylic acid to alcohol under very mild conditions (T = 110 C, P = 50 bar). The reaction rate constant for hydrogenation of hexanoic acid increased linearly with Pt content. As for Ru-NPy pair in homogeneous pincer-type complexes, the neighboring Pt-O atoms form a similar pair capable to dissociate H2 heterolytically with generation of Pt hydride to hydrogenate the carbonyl group of acid. Indeed, the TOF (40 h-1) and selectivity (99%) are approaching those of homogeneous catalyst. The first order kinetic model described well the kinetic data obtained in a wide range of reaction conditions.