Vapor-phase hydrogenation of levulinic acid and methyl levulinate to γ-valerolactone over non-noble metal-based catalysts

Abstract

Vapor-phase hydrogenation of levulinic acid (LA) and methyl levulinate (ML) to γ-valerolactone (GVL) was performed over non-noble metal-based catalysts such as Cu/Al2O3, Ni/SiO2 and Co/SiO2. The catalytic activity and stability of the Cu-, Ni- and Co-based catalysts for the formation of GVL from ML and LA were investigated and compared at a low contact time of 0.3h. In the hydrogenation of ML to GVL, the order of the catalytic activity for the conversion of ML was Cu/Al2O3>Co/SiO2>Ni/SiO2. Cu/Al2O3 was the most selective for the formation of GVL, whereas it was unstable in contrast to the other catalysts. In the hydrogenation of LA to GVL, the order of the catalytic activity for the conversion of LA was Ni/SiO2>Cu/Al2O3>Co/SiO2, which is the same as the order of the catalyst stability, while Cu/Al2O3 was the most selective for the formation of GVL from LA. The reactions were also performed in N2 atmosphere in order to study the reaction pathways. Methyl 4-hydroxypentanoate was supposed to be the intermediate in the hydrogenation of ML to GVL, whereas the reaction pathways in the hydrogenation of LA to GVL were dependent on the catalyst species. Based on the TG analysis of the used catalysts, it was found that LA led to more severe catalyst deactivation than ML did.