In Situ Generated Catalyst System to Convert Biomass-Derived Levulinic Acid to γ-Valerolactone

Graphical In situ generated catalyst system: HCl/ZrO(OH) 2 catalysts are prepared in situ by the autonomous decomposition of ZrOCl 2 ⋅ 8 H 2 O in levulinic acid (LA)/2-butanol solution. The esterification of LA was catalyzed in tandem with hydrocyclization to γ-valerolactone (GVL) by Meerwein–Ponndorf–Verley reduction. This is the first report of HCl/ZrO(OH) 2 catalysts prepared in situ by the autonomous decomposition of ZrOCl 2 ⋅ 8 H 2 O in levulinic acid (LA)/2-butanol solution, which catalyzed the esterification of LA in tandem with hydrocyclization to γ-valerolactone (GVL) by Meerwein–Ponndorf–Verley (MPV) reduction without the use of external H 2 . A maximum GVL yield of 92.4 % from neat LA and a GVL formation rate of 1092.2 μmol g −1 min −1 were achieved in 2-butanol at 240 °C in 2 h. The in situ generated ZrO(OH) 2 was characterized comprehensively and its unexpected catalytic efficiency was attributed mainly to its extremely high surface area. A crude LA stream from the acid hydrolysis of cellulose was extracted into 2-butanol and subjected to this catalyst system to give a GVL yield of 82.0 % even in the presence of humins.