Thesis (M.Sc.)--Chulalongkorn University, 2012

The purpose of this research is to synthesize pour point depressants (PPDs) from dicarboxylic acids for improving cold flow properties of soybean methyl ester (SME) and palm methyl ester (PME). The 16 types of PPDs (dimethyl succinate (DMS), dimethyl adipate (DMAD), dimethyl azelate (DMAZ), dimethyl phthalate (DMP), diisopropyl succinate (DIS), diisopropyl adipate (DIAD), diisopropyl azelate (DIAZ), diisopropyl phthalate (DIP), di 2-butyl succinate (DBS), di 2-butyl adipate (DBAD), di 2-butyl azelate (DBAZ), di 2-butyl phthalate (DBP), di 2-ethyl hexyl succinate (DES), di 2-ethyl hexyl adipate (DEAD), di 2-ethyl hexyl azelate (DEAZ) and di 2-ethyl hexyl phthalate (DEP)) were synthesized by esterification reaction. Their structures were characterized by FT-IR and 1H-NMR techniques. The cloud point (CP) and pour point (PP) of SME and PME were improved by addition of PPDs at 10,000, 100,000, and 300,000 ppm. At 300,000 ppm, could point and pour point of both biodiesels were reduced in the range of 2.70±1.0 °C to 6.00±1.0 °C and 2.00±1.0 °C to 6.00±1.0 °C. 2-Butyl esters gave good results on improving flow property of both SME and PME. Moreover, the results indicated that DBAZ was the most effective when compared with other PPDs, due to branch substituent (2-butyl) in its structure. At 300,000 ppm of DBAZ, the CP and PP of SME were reduced by 5.15±1.0 °C and 5.40±1.0 °C while the CP and PP of PME were reduced 6.00 ±1.0 °C in both CP and PP.