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Highly selective/enantioselective pt-ReOx/C catalyst for hydrogenation of L-malic acid at mild conditions

Journal of Energy Chemistry 2018年第3期27卷 903-912页

作者： Bair S.Bal'zhinimaev Eugene A.paukshtis alexey p.suknev Nikita V.Makolkin Boreskov Institute of Catalysis SB RA5 Prospect Akademika Lavrentieva5Novosibirsk 630090Russia

The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized（Re2＋）. The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs（ca. 50 h-1）, selectivities（ca. 99%）and stability of pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions（T = 90–130 ℃）. Taking into account that（i） hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and（ii） association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically（ee 〉 99%） pure（S）-3-hydroxy-γ-butyrolactone and（S）-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XpS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.

关键词： L-malic acid Hydrogenation Enantioselectivity platinum Rhenium Atomic dispersion

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The nature of active sites in pt–ReO_X/TiO_2 catalysts for selective hydrogenation of carboxylic acids to alcohols

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Journal of Energy Chemistry 2015年第5期24卷 646-654页

作者： alexey suknev Vladimir Zaikovskii Vasily Kaichev Eugenii paukshtis Ekaterina Sadovskaya Bair Bal'zhinimaev Boreskov Institute of Catalysis SB RAS Novosibirsk State University

The highly dispersed pt-ReOx （x _〈 1 ） sites ca. 0.5 nm in size were formed via a successive and strong inter- action 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 ℃, 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-ReOx 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.

关键词： Selective hydrogenation Hexanoic acid Hexanol platinumRhenium Nanoparticles

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