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

This is the first report of HCl/ZrO(OH)(2) catalysts prepared in situ by the autonomous decomposition of ZrOCl2 center dot 8H(2)O in levulinic acid (LA)/2-butanol solution, which catalyzed the esterification of LA in tandem with hydrocyclization to gamma-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 mu mol g(-1) min(-1) were achieved in 2-butanol at 240 degrees 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.