Hydrogenation of Biomass-Derived Levulinic Acid into\nγ‑Valerolactone Catalyzed by Palladium Complexes

Abstract

The selective catalytic hydrogenation\nand cyclization of levulinic\nacid (LA) into valuable γ-valerolactone (GVL) catalyzed by different\npalladium compounds was achieved in water under mild conditions with\nhigh yields. Either formic acid (FA) or molecular hydrogen (H₂) was used as a hydrogen source. The precatalyst [(dtbpe)­PdCl₂] (dtbpe = 1,2-(bis-di-<i>tert</i>-butylphosphino)­ethane)\n(<b>1</b>) was highly active in the processes of LA hydrogenation\n(TON of 2100 and TOF of 2100 h^–1) and in the dehydrogenation\nof formic acid to produce H₂ and carbon dioxide. The catalytically\nactive complexes [(dtbpe)­Pd­(H)­Cl)] (<b>2</b>) and [(dtbpe)₂Pd₂(μ-H)₃]⁺ (<b>3</b>) and the catalytically inactive complex [(dtbpe)₂Pd₂(μ-H) (μ-CO)]⁺ (<b>4</b>) all formed in situ and were identified as species resulting from\nFA decomposition.