Optimization of Transesterification of Sunflower Oil with Ethanol using Eggshell as Heterogeneous Catalyst

Abstract

Biodiesel is currently mostly produced by homogeneous catalysis. Recently, however, heterogeneous catalysis is being considered as a cheaper alternative to the homogeneous process. Heterogeneous transesterification is considered a green process. The process requires neither catalyst recovery nor aqueous treatment steps and very high yields of ethyl esters can be obtained, close to the theoretical value. However, heterogeneously catalyzed transesterification generally requires more severe operating conditions, and the performance of heterogeneous catalysts is generally lower than that of the commonly used homogeneous catalysts. This study seeks to address this problem by studying the production of biodiesel using eggshells as heterogeneous catalysts. Heterogeneous catalysts can make biodiesel production more energy efficient, and therefore less expensive, by eliminating the need for expensive purification processes that separates the catalyst from reaction products typical in the use of homogeneous catalysts. Matlab was employed for the experimental design, statistical analysis and process modeling. Fatty acid ethyl ester was produced by transesterification of sunflower oil and ethanol using calcined eggshells as a heterogeneous catalyst. To optimize the process, some important variables such as reaction temperature, molar ratio of ethanol to oil and mass weight of catalyst were selected and studied. At the following conditions: 343K of reaction temperature, ethanol to sunflower oil ratio of 9:1 and 1 mass wt% of catalyst, an optimum fatty acid ethyl  ester yield of 92% was obtained, indicating that eggshells have the potential of being used as a heterogeneous catalyst for the production of fatty acid ethyl ester from sunflower oil. Physico-chemical characterization of the fatty acid ethyl ester was performed and compared with the US Standard biodiesel properties, and it was observed that the biodiesel compared well with the standards.

Keywords: Transesterification, eggshell catalyst, process optimization, sunflower oil, ethanol