Storage Studies on Plant Oils and Their Methyl Esters

Esters of plant oils are preferred to parent oils if used as fuels in diesel engines because esterification reduces the viscosity of plant oils and makes it comparable to that of diesel. The present work mainly deals with the effect of storage time on the quality of plant oils and their esters with respect to mainly FFA content, viscosity and change in weight. The study was carried out for a period of one and a half-year. Maximum change in FFA content (%) was observed in case of linseed oil ester followed by sunflower oil ester and rice bran oil ester. Minimum change was observed in the case of Jatropha curcas oil ester. In all the four esters, the increase in FFA content (%) after one year was found to be below the BIS requirements. Initially all the four plant oil esters had comparable viscosity values. In case of linseed oil ester and sunflower oil ester, the increase in viscosity was 1.6 times after a storage period of six months whereas in case of rice bran oil ester and Jatropha curcas oil ester, the increase was 1.4 and 1.3 times respectively. During storage, linseed oil ester, sunflower oil ester and rice bran oil ester showed increase in weight indicating absorption of moisture or reaction with oxygen in air. However, in case of Jatropha curcas oil ester, the increase in weight was negligible. The effect of selected plant oil ester on various engine parts (metallic and non-metallic) was also studied. No significant change in weight of metal components was observed during contact period of two months (i.e. components kept dipped in ester for two months) in any of the four esters. In case of non-metallic components, signficant changes were observed in the rubber parts during the contact period of two months in all the four plant oil esters.