Boosting γ-valerolactone production from ethyl levulinate hydrogenation over Pd catalyst via alloying with Co and synergistic catalysis with HZSM-5

Catalytic conversion of ethyl levulinate (EL) to gamma-valerolactone (GVL) is a pivotal reaction in biomass conversion. Here, Pd/CoOx was studied and showed much higher EL hydrogenation reactivity than other Pd based catalysts. Further investigation revealed that EL conversion increased linearly with PdCo alloying degree elevating, indicating that PdCo alloy is ascribed to the superior reactivity of Pd/CoOx. Interestingly, Pd/CoOx with low Pd loading also exhibited excellent hydrogenation performance, and surface enrichment of Pd was identified as the main reason. Additionally, employing HZSM-5 as a co-catalyst not only accelerated ethyl 4-hydroxypentanoate lactonization, but also dramatically improved the stability of Pd/CoOx. As a result, a 99.1 % yield of GVL was achieved by the synergistic catalysis of HZSM-5 and Pd/CoOx containing 0.58 wt% Pd, which is comparable with the best catalyst ever reported in alkyl levulinate hydrogenation to GVL. Furthermore, the insights gained from this work have broad potential applications in biomass hydrogenation.