Fatty acid esters: a potential cetane number improver for diesel from direct coal liquefaction

Diesel from direct coal liquefaction (DDCL) is a product obtained from direct coal liquefaction (DCL). Compared with petrodiesel, DDCL contains almost no sulfur element. Other than this feature, several other properties of DDCL are similar to those of petrodiesel. Therefore, DDCL is applicable to automobile diesel fuel. However, the cetane number (CN) of DDCL is only 44. In this article, fatty acid esters are investigated as potential CN improvers for DDCL. According to the recent standard GB 19147-2013, 1 vol% fatty acid esters can be added to diesel fuel. The performance of different fatty acid esters and the other properties of ester blending are also investigated. Several fatty acid esters can be considered potential CN improvers to enhance DDCL for automobile diesel fuel. The structures of fatty acid esters, such as chain length, double bonds, and different alkyl head group on the fatty acid alkyl esters, can affect the performance of CN improvers. Moreover, the obtained wear results showed that 1% of fatty acid esters can improve fuel lubricity from 630 μm to 514 μm. The other properties of DDCL are changed a little after fatty acid esters are added.