The nature of active sites in Pt-ReO_X/TiO₂ catalysts for selective hydrogenation of carboxylic acids to alcohols

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• 作者：Alexey Suknev^a ; Vladimir Zaikovskii^a ; ^b ; Vasily Kaichev^a ; ^b ; Eugenii Paukshtis^a ; ^b ; Ekaterina Sadovskaya^a ; ^b ; Bair Bal'zhinimaev^a ; ^{balzh@catalysis.ru" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Selective hydrogenation ; Hexanoic acid ; Hexanol ; Platinum ; Rhenium ; Nanoparticles
• 刊名：Journal of Energy Chemistry
• 出版年：2015
• 出版时间：September 2015
• 年：2015
• 卷：24
• 期：5
• 页码：646-654
• 全文大小：1677 K

文摘

The highly dispersed Pt–ReO_X (x ≤ 1) sites ca. 0.5 nm in size were formed via a successive and strong interaction of the Re precursor with titania and then of the Pt complex with deposited low-valent rhenium oxide clusters. The size, charge and chemical composition were characterized by means of HRTEM/STEM with EDX mapping, XPS, and FTIRS. These sites with Re/Pt = 2 were shown to be highly active and selective in the hydrogenation of carboxylic acid to alcohol under very mild conditions (T = 130 °C, P = 50 bar). The reaction rate constant for the hydrogenation of hexanoic acid increased linearly with the Pt content. As for the homogeneous pincer-type Ru-organic complexes, the active Pt–ReO_X sites can dissociate heterolytically the molecular hydrogen with the formation of hydroxyl groups and Pt hydride for hydrogenation of the carboxylic group. Indeed, TOF of 20 h⁻¹ and selectivity of 98%–99% are approaching the values typical of homogeneous catalysts. The first order kinetics described well the experimental data obtained in a wide range of reaction conditions.