Catalytic performances of potassium and sodium hydroxides/carbonates and calcium and magnesium oxides on hydrolysis of α-chloropropionic acid to lactic acid

Abstract

Catalytic hydrolysis of α-chloropropionic acid to lactic acid in liquid phase over different alkaline catalysts, such as alkali metal hydroxides, alkali metal carbonates, and alkaline-earth metal oxides, was investigated. Lactic acid was mainly produced by the hydrolysis of α-chloropropionic acid over the alkaline catalysts. The catalytic activities of the alkaline catalysts were in an order of KOH > NaOH > K2CO3 > Na2CO3 > CaO > MgO. The catalytic activities of the alkali metal hydroxides and carbonates were related to both concentrations of their hydroxide anions and hydrated ionic radiuses of K+ and Na+. For the alkaline-earth metal oxide catalysts, their catalytic activities in the hydrolysis of α-chloropropionic acid were mainly related to the solubilities of the resultant hydroxides. A power-function type kinetic equation was used for the evaluation of the effect of catalyst loading and reaction temperature on the hydrolysis of α-chloropropionic acid to lactic acid. The activation energies over the alkaline catalysts were in an order of E a,KOH < E a,NaOH < $$ E_{{\rm a},{\rm K}_{2}{\rm CO}_{3}} $$ < $$ E_{{\rm a},{\rm Na}_{2}{\rm CO}_{3}} $$ < E a,CaO < E a,MgO. The alkaline catalyst with low activation energy had high catalytic activity for the hydrolysis of α-chloropropionic acid to lactic acid.