Lithium zirconate as solid catalyst for simultaneous esterification and transesterification of low quality triglycerides

Abstract

Alkali metal (Li, Na and K) doped zirconium oxide was prepared (Li/ZrO2, Na/ZrO2 and K/ZrO2) by wet chemical route and used as active heterogeneous catalyst for the transesterification of waste cottonseed oil with ethanol and methanol to produce fatty acid ethyl and methyl esters, respectively. The catalyst characterization supports the formation of lithium zirconate single phase in the case of Li/ZrO2 and it was able to catalyze simultaneous esterification and transesterification of high free fatty acid containing vegetable oils (VOs). The reaction conditions, such as catalyst concentration, reaction temperature, the molar ratio of alcohol/oil and stirring speed, were optimized in the presence of Li/ZrO2 catalyst. The catalyst activity was found to be a function of its basic sites which in turn depends on calcination temperature and lithium content of the catalyst. A pseudo first order kinetic equation was applied to evaluate the kinetic parameters for the transesterification of waste cottonseed oil with methanol and ethanol. The activation energy (Ea) for the Li/ZrO2 catalyzed methanolysis and ethanolysis was found to be 40.8 and 43.1kJmol−1, respectively. The catalyst could be reused up to nine cycles without significant loss of performance as >90% fatty acid alkyl ester yield was maintained.