Experimental and kinetic modeling studies on the biphasic hydrogenation of levulinic acid to γ-valerolactone using a homogeneous water-soluble Ru–(TPPTS) catalyst

γ-Valerolactone (GVL) is considered a very attractive biomass derived platform chemical. This paper describes the application of biphasic homogeneous catalysis for the hydrogenation of levulinic acid (LA) to GVL using molecular hydrogen. A water soluble Ru-catalyst made in situ from RuCl3·3H2O and sodium-tris(m-sulfonatophenyl)phosphine (Na3TPPTS) in dichloromethane/water biphasic mixtures was used. The hydrogenations were performed at mild conditions in a batch hydrogenation reactor and essentially quantitative GVL yields were obtained at 45 bar, 90 °C and 80 min reaction time (1 mol% catalyst). The effects of process variables like LA concentration, hydrogen pressure, temperature, pH and the catalyst to substrate ratio on the LA conversion and GVL yield were determined. The experimental data were quantified by kinetic modeling and it was shown that the reaction is first order in LA. Catalyst recycle experiments show that the recycled catalyst is still active, though the activity is lower than for the first run (81% LA conversion for first run versus 55% for recycle experiment).

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► Biphasic catalysis was applied to hydrogenate levulinic acid to γ-valerolactone.
► Quantitative GVL yields were obtained with a water soluble Ru–TPPTS catalyst.
► The experimental data were successfully quantified with a kinetic model.
► Recycling of the homogeneous catalyst was successfully demonstrated.