Synergistic Effects of Skeletal Isomerization on Oleic and Palmitic Acid Mixtures for the Reduction in Cloud Point of Their Methyl Esters

Biodiesel is composed of saturated and unsaturated fatty acid esters, both of which have significant effects on the cloud point of biodiesel. These two classes of fatty acids also react differently to isomerization reactions for cloud point improvement. This study examines the effects of isomerization and hydroisomerization on the two most common saturated and unsaturated fatty acids that make up vegetable oils, i.e., palmitic and oleic acids, respectively. The two fatty acids are placed under two different reactions and analyzed both separately and mixed for the cloud point improvement of their esters. The two reactions, isomerization and hydroisomerization, are run at 250 °C and 1 MPa H 2 and at 300 °C and 4 MPa H 2, respectively. Negative and positive results were shown, i.e., cis to trans isomerization, causing an increase in cloud point, and branching, causing a reduction in cloud point. A 7.5 °C reduction in cloud point is achieved on the esters of a 55:45 (%) oleic acid/palmitic acid ratio, showing that isomerization and hydroisomerization reactions can successfully lower the cloud point of a mixture of fatty acid methyl esters.