Biodiesel produced from vegetable oils are triglyceride. Their composition is generally of a straight-chain fatty acid length. The existence of long straight-chain fatty acids in triglycerides affects the physical and chemical properties of biodiesel. Problems associated with the use of biodiesel up to now are the high pour point and NOx emissions which are higher than that of diesel fuel. There are two physical properties of biodiesel which is still an issue until now- the high pour point and NOx emissions resulting from the combustion. This resulted from the use of biodiesel which is blended with petroleum diesel. To overcome this problem, additives are required. In order to be compatible with biodiesel and not give a large negative impact on the environment, the expected additive for biodiesel was also made from vegetable oil, likes branched fatty esters. Preparation of branched fatty esters in this study aimed to produce branched fatty ester from sterculia oil through the four stages of the process, namely: extraction, first transesterification, hydrogenation and second transesterification. The results of the analysis show that the branched fatty esters produced in this research contain C22H44O2 with molecular weight of 340 g/mol, whose existence in the form of a mixture with other branched esters with specific gravity at 40°C is 0.870, kinematic viscosity 5.907 St, iodine number 16.25 g I2/100 g sample, cetane number 86.6 and pour point of -18°C.
Key words: Sterculia oil, branched fatty ester, biodiesel, cetane number, pour point.
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