Lactic acid from glycerol transformation using Ni0.2Mg3.8Al-LDO embedded AgO/Oxide catalysts without the addition of a base, O2 or H2

Abstract

Lactic acid is one of the promising products of glycerol valorization as a raw material especially for producing polylactic acid. Alternatively, the catalytic conversion of glycerol can be achieved via three main reactions in series; that are, the dehydration of glycerol to acetol and the oxidation of acetol to pyruvaldehyde, followed by the Cannizzaro reaction to form lactic acid. Due to such complex reactions, the sequential deposition of active components on a catalyst is highly essential, aiming at self driving the reactions without adding a homogeneous base nor external O₂ and H₂. Therefore, a series of Ni_0.2Mg_3.8AlO-embedded AgO/MO catalysts were employed. The embedding Ni_0.2Mg_3.8AlO-LDO was selected to perform the dehydration of glycerol to acetol first, and three inner embedded oxides (namely; MO, where MO was either SnO₂, CeO₂, or Nb₂O₅) were expected to drive the subsequent Cannizzaro reaction due to their excellent Lewis acidity. As a result, it was found that the composite catalysts successfully produced lactic acid. Moreover, the optimum condition was found to be 180˚C and 4 h in order to maximize the lactic acid without the addition of a base nor external O₂ and H₂.