Designation of highly efficient catalysts for one pot conversion of glycerol to lactic acid

Abstract

Production of lactic acid from glycerol is a cascade catalytic procedure using multifunctional catalysts combined with oxidative and acidic catalytic sites. Therefore, a series of silver-exchanged phosphomolybdic acid catalysts (Ag x H 3 x PMo 12 O 40, x = 1 ∼ 3, abbreviated as Ag x PMo) was designed and applied in glycerol oxidation with O 2 as an oxidant to produce lactic acid (LA) without adding any base. Among all, total silver exchanged phosphomolybdic acid (Ag 3 PMo) was found to be the most active one with LA selectivity of 93% at 99% conversion under mild conditions of 5 h at 60 °C. The exceptionally high efficiency was contributed to the generation of strong Lewis acid sites, enhanced redox potentials and water-tolerance. More importantly, Ag 3 PMo was tolerant in crude glycerol from biodiesel production. And the reaction mechanism was also discussed. Meanwhile, Ag 3 PMo acted as a heterogeneous catalyst for 12 recycles without loss of activity.