Highly selective conversion of glyceric acid to 3-iodopropionic acid by hydriodic acid mediated hydrogenation

Abstract

Glycerol, generated in abundance as the by-product in the process of biodiesel production and saponification, has seen attempts to convert it into value-added chemicals. However, due to the low selectivity of hydrogenolysis of the secondary hydroxyl group, valuable 1,3-substituted chemicals are difficult to obtain from glycerol by chemocatalysis. In this work, glyceric acid (GA), a renewable biomass from glycerol, was quantitatively converted to 3-iodopropionic acid (3-IPA) at 373 K in 3 h by hydroiodic acid mediated hydrogenation. As the reductant in this process, HI is oxidized to I₂ and then regenerated in situ by metal catalysts and H₂. The reaction pathway was proposed by intermediate identification and verified by a kinetics study and computational method. The catalytic system was shown to be stable and can be reused several times without loss in activity. As a 1,3-substituted chemical, 3-IPA is not only a potential monomer to form poly-3-hydroxypropionic acid, but also a good platform molecule to produce useful chemicals, e.g. 3-hydroxypropionic acid (3-HPA) and acrylic acid (AA), due to its highly reactive nature.