Synthesis of Waste Frying Oil and Trimethylolpropane Based Lubricant Basestocks

Abstract

Research on waste frying oil based lubricant base stocks production and trimethylolpropane (TMP) was investigated. Quality parameters were tested for the waste frying oil. The hydrolysis process was conducted to extract the free fatty acid from waste frying oil. TMP ester was produced via reaction between free fatty acids of waste frying oil and TMP at 130-140°C, for 5 hours with acid-catalyzed condition. Modification of TMP ester by epoxidation reaction followed by ring-opening reaction using a medium branch chain alcohol; 2-ethylhexanol. The TMP ester was reacted with hydrogen peroxide and formic acid at 45-55°C for 2½ hours during epoxidation process. Epoxidized TMP ester was reacted with 2-ethylhexanol in mol ratio of 1:2 to produce ether ester TMP. Concentrated sulphuric acid was used as a catalyst during ring opening and esterification processes. Ether ester TMP functional groups and chemical structure were identified using FTIR and NMR, respectively. Confirmation with FTIR has indicated sharp peak at 1742 cm-¹, proved the existence of ester group which confirmed the TMP ester formation during esterification and broad peak of 3456 cm-1 during ring opening indicated the formation of ether ester TMP. In ¹H NMR analysis, the signal of methylene proton in which the carbon attached to ether esters TMP existed at 4.0-4.1 ppm and for 13C NMR, the carbonyl ester signals existed in the range of 174.1 ppm. Several analyses were conducted on the ether ester TMP base stock such as hydroxyl value, viscosity value, pour point and flash point. It showed good low temperature behaviour with pour point at -40oC and high thermal stability, flash point value exceeding 250oC and viscosity value of 75 cP. The ether ester TMP produced is comparable with a commercial biolubricant in the market respectively.