Journal of Catalysis, Vol.320, 198-207, 2014
Investigation of the reaction kinetics of isolated Lewis acid sites in Beta zeolites for the Meerwein-Ponndorf-Verley reduction of methyl levulinate to gamma-valerolactone
We investigate the reaction kinetics of the Meerwein-Ponndorf-Verley (MPV) reduction of methyl levulinate (ML) to 4-hydroxypentanoates and subsequent lactonization to gamma-valerolactone (GVL) catalyzed by Lewis acid zeolites. Reaction kinetics studies show a first-order dependence on ML and 2-butanol, confirm that the hydride shift is the rate-limiting step, and support a dual-binding mechanism on a single Lewis acid site. All catalysts generate GVL with selectivities >97%, with Hf-Beta exhibiting the highest activity in the temperature range of 393-453 K. Sn-, Zr-, and Hf-Beta show apparent activation energies of ca. 52 kJ mol(-1), which is significantly lower than that of Ti-Beta (69 kJ mol(-1)). Secondary alcohols consistently exhibit higher reaction rates than primary alcohols with lower apparent activation energies. Increasing polarity of the hydrogen donor leads to a decrease in reaction rates. The experimental data are used to build a kinetic model for the MPV reaction in a tubular packed-bed reactor. (C) 2014 Elsevier Inc. All rights reserved.
Keywords:Liquid-phase transfer hydrogenation;gamma-Valerolactone;Lewis acids;Zeolites;Reaction kinetics