Optimizing esterification of safflower, cottonseed, castor and used cottonseed oils

Depletion of fossil fuels warrants the use of biofuels as an alternate source to minimize the usage of petroleum reserves. Biodiesel fuels are renewable source of energy derived from plant oils or animal fats. They are mono alkyl esters of long chain fatty acids formed by transesterification of oils/fats. Efficiency of transesterification of oils from four sources (safflower, cottonseed, castor, used cottonseed oil) was determined in this study with both methanol and ethanol as alcohols and sodium hydroxide and potassium hydroxide as catalysts. Methanol was found to be a better solvent and sodium hydroxide a better catalyst. The highly viscous nature of raw vegetable oils has been shown to decrease through transesterification process. In our experiments, the highest viscosity reduction was observed for castor oil even though it was the most viscous among four oils, both methyl and ethyl esters of safflower was shown to have a similar viscosity as No. 2 diesel.

► Optimized transesterification reaction was studied in safflower, castor, cottonseed and used cottonseed oils.
► Methanol was a better solvent than ethanol and sodium hydroxide a better catalyst than potassium hydroxide.
► Castor oil gave the highest yield in spite of its high viscosity and high water (moisture) content.
► Castor oil showed the greatest viscosity reduction after transesterification reaction among four oils.
► Methyl and ethyl esters of safflower oil had similar viscosity as No. 2 diesel.