Improving biodiesel made from cottonseed and soyabean oil with partial hydrogenation

Abstract

Biodiesel limitations such as poor cold-flow properties and oxidation stability limit its usage in diesel engines. Partial hydrogenation is reported to be one of the ways to improve these limitations. Partial hydrogenation of biodiesel made from cottonseed and soyabean oil was studied. Before and after hydrogenation, the fatty acid methyl ester contents of cottonseed and soyabean biodiesel were detected with gas chromatography–mass spectrometry. It was revealed that methyl linolenic and methyl linoleic decreased while methyl stearic and methyl oleic increased after the partial hydrogenation for both soyabean and cottonseed biodiesel. Methyl oleic increased by 127 and 237% for soyabean and cottonseed biodiesel, respectively. A thermogravimetric test was also conducted on the fuel samples to observe the volatilisation of the fuels. There was an increase in fuel properties such as cetane number and kinematic viscosity, while iodine value decreased after partial hydrogenation. In addition, there was no significant change in oxygen content, low-heat value and density for both soyabean and cottonseed biodiesel. In summary, partial hydrogenation is a good method of upgrading biodiesel fuel properties such as cold-flow properties and oxidation stability.