Improvement of diesel lubricity by chemically modified tung oil-based fatty acid esters as additives

Authors: Liu, Zengshe - Kevin; LI, JING - Chinese Academy Of Forestry; Knothe, Gerhard; SHARMA, BRAJENDRA - University Of Illinois; JIANG, JIANGCHUNG - Chinese Academy Of Forestry

Submitted to: Energy and Fuels
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2019
Publication Date: 5/3/2019
Citation: Liu, Z., Li, J., Knothe, G., Sharma, B.K., Jiang, J. 2019. Improvement of diesel lubricity by chemically modified tung-oil-based fatty acid esters as additives. Energy and Fuels. 33(6):5110-5115. https://doi.org/10.1021/acs.energyfuels.9b00854.
DOI: https://doi.org/10.1021/acs.energyfuels.9b00854

Interpretive Summary: In this research, we discovered that tung oil based compounds at low additive levels (about 500 ppm) significantly improved the lubricity of diesel fuels. Use of ultra-low-sulfur diesel (ULSD) fuels, as required by regulations in the United States, Europe, and elsewhere, has led to the failure of diesel engine parts such as fuel injectors and pumps. ULSD fuels require additives or blending with another material of sufficient lubricity, thereby increasing the cost. Adding low level additive of 500 ppm to the ULSD decreased the wear scar and friction by 40-47%, respectively. The additive concentrations are 20 and 40 times lower than blending biodiesel at 1-2%, which will benefit the diesel industry.

Technical Abstract: Diesel fuel lubricity has been a concern of diesel fuel injection equipment manufacturers for many years. The problem has drawn attention because of the reduction in lubricity associated with the extreme hydrogenation needed to reach the low sulfur levels required in modern diesel fuels. Ultra-low-sulfur diesel (ULSD) fuels require higher concentrations of additives or blending with other materials of sufficient lubricity, thereby increasing the cost. Here we communicate the synthesis of tung-oil-based fatty acid methyl ester [eleostearic acid methyl ester (EAME)] and the maleation compound (EAME/MA) by reacting with maleic anhydride (MA) via the Diels–Alder reaction. EAME/MA reacts with short-chain alcohols, such as methanol and butanol, by opening cyclic anhydride to form esters, i.e., EAME/MA/ME and EAME/MA/BU. The EAMA/MA/ME and EAME/MA/BU compounds effectively enhanced the lubricity of ULSD. The lubricity of ULSD at low additive levels (500-1000 ppm) of those two compounds resulted in great improvement in the high-frequency reciprocating rig lubricity tests. For instance, by adding low additive levels of 500 ppm and 1000 ppm to the ULSD fuel, sufficient lubricity was induced and the wear scar and friction of ULSD were reduced by 40% and 46-47%, respectively. The additive concentrations were 20 and 40 times lower than blending ULSD with biodiesel at 1-2% (w/w). Further, by adding EAME/MA/BU at a level of 1000 ppm to other kinds of petrodiesel, such as 0150H GP1 base oil and 166 POA, wear scar values were reduced by 25 and 26%, respectively.