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Influence of Support for Ru and Water Role on Product Selectivity in the Vapor-Phase Hydrogenation of Levulinic Acid to γ‑Valerolactone: Investigation by Probe-Adsorbed Fourier Transform Infrared Spectroscopy

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journal contribution
posted on 13.08.2018, 00:00 authored by Vijay Kumar Velisoju, Ganga Bhavani Peddakasu, Naresh Gutta, Venu Boosa, Manasa Kandula, Komandur V. R. Chary, Venugopal Akula
Ru supported on activated carbon, Al2O3, and MgO was assessed for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). Role of H2O on the hydrogenation activity of Ru was studied by probe-adsorbed diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy. Ru supported on activated carbon showed a maximum productivity of 1.18 kgGVL kgcatalyst–1 h–1 with an insignificant loss in the activity after 72 h of continuous operation in the presence of H2O. Using pure LA, GVL rate was decreased by an order of magnitude (0.12 kgGVL kgcatalyst–1 h–1) within 6 h of reaction time. The physicochemical characteristics of the catalysts were examined by temperature-programmed desorption of NH3, CO pulse chemisorption, H2-temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques. H2O-adsorbed DRIFT spectroscopic data revealed the reversible generation of surface −OH groups when aqueous LA was used as the substrate; consequently, Ru/C catalyst stability was also improved. Finally, on the basis of the kinetic and in situ spectroscopic data, a plausible surface-reaction mechanism is proposed for the vapor-phase LA hydrogenation to GVL in the presence of H2O over the carbon-supported Ru catalyst.