Quantitative formation of gamma-valerolactone from furfural aldehyde with a recyclable acidic system and Ru-MACHO catalyst under a H2 atmosphere

Abstract

This study presents an efficient catalytic system for the direct conversion of carbohydrate-derived furfural aldehyde (FA) into γ-valerolactone (GVL) in high yields. Using a homogeneous Ru-MACHO-BH catalyst in combination with a recyclable solid acid as co-catalyst, GVL is obtained in up to 99% NMR yield under the optimized conditions of 0.5 mol% Ru-MACHO-BH, 5 mol% Amberlyst-36, ethanol, 30 bar H₂, 120 °C, and 24 h. Full conversion and complete selectivity toward GVL are achieved with 0.5 mol% Ru-MACHO-BH and 5 mol% Amberlyst-36. The solid acid co-catalyst can be reused for at least ten cycles provided that Amberlyst-36 is regenerated with H₂SO₄(aq) between runs, as the resin otherwise shows significant deactivation after three cycles. The robustness of the method was evaluated through scale-up experiments up to 20 mmol (1.9 g) of FA. At this scale, conversions decrease to 65–72% when using 0.5 mol% Ru-MACHO-BH, maintaining 100% selectivity to GVL, whereas increasing the catalyst loading to 1 mol% restored full conversion and quantitative GVL formation. Overall, this work demonstrates a selective and scalable approach to FA valorization under well-defined reaction conditions.