Continuous gas phase catalytic transformation of levulinic acid to γ‐valerolactone over supported Au catalysts

Abstract

Abstract BACKGROUND γ‐Valerolactone ( GVL ) is a high value chemical obtained from hydrogenation of bio‐derived levulinic acid ( LA ). Work to date has focused on batch pressurised catalytic systems where high GVL yield is challenging. In this work, the role of support redox and acidity properties is examined in the continuous gas phase hydrogenation of aqueous LA at ambient pressure over gold on Al 2 O 3 , CeO 2 and TiO 2 ; Pd/ Al 2 O 3 served as a benchmark in catalyst tests. RESULTS 100% GVL yield was achieved under stoichiometric conditions (inlet H 2 / LA = 1) over supported Au (mean size = 3.0–4.3 nm). Greater catalytic activity was recorded for Au on reducible TiO 2 and CeO 2 . Under the same reaction conditions, Pd/ Al 2 O 3 delivered higher LA consumption rates but promoted formation of pentanoic acid. CONCLUSIONS GVL formation proceeds via 4‐hydroxypentanoic as reactive intermediate. Surface oxygen vacancies (confirmed by O 2 titration) formed during temperature programmed reduction of reducible oxides activate LA for reaction. Greater GVL productivity (with full hydrogen utilisation) is demonstrated in this work relative to state‐of‐the art supported Pd and Ru catalysts. © 2017 Society of Chemical Industry