Highly Selective Oxidation of Ethyl Lactate to Ethyl Pyruvate Catalyzed by Mesoporous Vanadia-Titania

Wei Zhang; Giada Innocenti; Paula Oulego; Vitaly Gitis; Haihong Wu; Bernd Ensing; Fabrizio Cavani; Gadi Rothenberg; N Raveendran Shiju

doi:10.1021/acscatal.7b03843

Highly Selective Oxidation of Ethyl Lactate to Ethyl Pyruvate Catalyzed by Mesoporous Vanadia-Titania

ACS Catal. 2018 Mar 2;8(3):2365-2374. doi: 10.1021/acscatal.7b03843. Epub 2018 Jan 9.

Authors

Wei Zhang¹, Giada Innocenti^{2

3}, Paula Oulego⁴, Vitaly Gitis⁵, Haihong Wu⁶, Bernd Ensing¹, Fabrizio Cavani^{2

3}, Gadi Rothenberg¹, N Raveendran Shiju¹

Affiliations

¹ Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, P.O. Box 94157, 1090GD Amsterdam, The Netherlands.
² Dipartimento di Chimica Industriale, ALMA MATER STUDIORUM Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy.
³ Consorzio INSTM, UdR di Bologna, Firenze, Italy.
⁴ Department of Chemical and Environmental Engineering, University of Oviedo, C/Julián Clavería, s/n., E-33071, Oviedo, Spain.
⁵ Unit of Environmental Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel.
⁶ Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, People's Republic of China.

Abstract

The direct oxidative dehydrogenation of lactates with molecular oxygen is a "greener" alternative for producing pyruvates. Here we report a one-pot synthesis of mesoporous vanadia-titania (VTN), acting as highly efficient and recyclable catalysts for the conversion of ethyl lactate to ethyl pyruvate. These VTN materials feature high surface areas, large pore volumes, and high densities of isolated vanadium species, which can expose the active sites and facilitate the mass transport. In comparison to homogeneous vanadium complexes and VO _x /TiO₂ prepared by impregnation, the meso-VTN catalysts showed superior activity, selectivity, and stability in the aerobic oxidation of ethyl lactate to ethyl pyruvate. We also studied the effect of various vanadium precursors, which revealed that the vanadium-induced phase transition of meso-VTN from anatase to rutile depends strongly on the vanadium precursor. NH₄VO₃ was found to be the optimal vanadium precursor, forming more monomeric vanadium species. V⁴⁺ as the major valence state was incorporated into the lattice of the NH₄VO₃-derived VTN material, yielding more V⁴⁺-O-Ti bonds in the anatase-dominant structure. In situ DRIFT spectroscopy and density functional theory calculations show that V⁴⁺-O-Ti bonds are responsible for the dissociation of ethyl lactate over VTN catalysts and for further activation of the deprotonation of β-hydrogen. Molecular oxygen can replenish the surface oxygen to regenerate the V⁴⁺-O-Ti bonds.