A comparative study of the production of ethyl esters from vegetable oils as a biodiesel fuel optimization by factorial design

Abstract

Abstract In recent years, the development of alternative fuels from renewable resources, like biomass, has received considerable attention. Fatty acid methyl or ethyl esters, known as biodiesel, show large potential applications as diesel substitutes. Ethyl esters are the product of transesterification of fats and vegetable oils with ethanol (obtained from fermentation in our case) in the presence of an acid or an alkaline catalyst. In addition, the process yields glycerol, which has large applications in the pharmaceutical, food and plastics industries. In the present work, the process of synthesis of ethyl esters from high oleic sunflower oil (HOSO), high and low erucic Brassica carinata oils (HEBO and LEBO), as alternative vegetable oils, using KOH as catalyst, has been developed and optimized by application of the factorial design and response surface methodology. The effect of temperature, ethanol/oil molar ratio and catalyst concentration were studied. Catalyst concentration was found to have the most significant influence on conversion. A second-order model was obtained to predict conversions as a function of temperature and catalyst concentration for LEBO process. The model has been found to describe the experimental range studied adequately. The best results for laboratory scale reactions were obtained at 32 °C with 5:1 ethanol/oil molar ratio and 1.5% of KOH for HEBO and HOSO, while for LEBO was at 20 °C with 6:1 ethanol/oil molar ratio and 1.5% of KOH.