Chemoselective Lactonization of Renewable Succinic Acid with Heterogeneous Nanoparticle Catalysts

The production of chemicals from renewable resources, resulting in the establishment of biorefineries, represents a challenge of increasing importance. Here we show that succinic acid, a C4 compound increasingly being produced on a kiloton scale by the microbial fermentation of sugar, can be selectively converted into a variety of important chemicals. Optimal performance in terms of activity, selectivity and reusability is observed with Al₂O₃-supported Pd nanoparticles, which mediate the selective, hydrogenative lactonization of succinic acid to γ-butyrolactone at >90% selectivity, even at high levels of conversion (<70%). Through a variety of kinetic, spectroscopic and microscopic studies, preliminary structure-activity relationships are presented, and the roles of the reaction conditions, the choice of metal and the nature of the support in terms of guiding the overall process selectivity, are also investigated. On a broader level, these studies demonstrate the suitability of succinic acid to act as a platform for renewable chemical production in future biorefineries.