Synthesis and Evaluation of Stearic Acid Derivatives as Cetane Number Improvers

Bull. Korean Chem. Soc. 2011, Vol. 32, No. 6, pp. 1965-1969
Synthesis and Evaluation of Stearic Acid Derivatives as Cetane Number Improvers
Ambadas B. Rode, H. Thajudeen, Keunwoo Chung,† Young-Wun Kim,† and In Seok Hong*
ishong@kongju.ac.kr
Department of Chemistry, Kongju National University, Chungnam 314-701, Korea.*
†Green Chemistry Research Division, Surfactant and Lubricant Research Team, KRICT, Daejeon 305-600, Korea
Abstract
1,2,4,5-tetraoxane, mono and dinitrate glycerol carbonate ester derivatives of stearic acid were synthesized along with the known 9(10)-keto methyl sterate, methoxy mono-nitrate and dinitrate of methyl stearate. Their cetane numbers (CNs) were investigated to evaluate their viability for use as CN improvers. The CN performances of tetraoxane and all of the nitrate derivatives were investigated at 500 and 1000 ppm concentrations and compared to that of a traditional CN improver 2-ethylhexyl nitrate (2-EHN). The experimental results suggest that all derivatives evaluated in this study showed better CN improvement than base diesel fuel. Specifically, the 1,2,4,5-tetraoxane derivative of stearic methyl ester was superior to all derivatives studied, also being superior to 2-EHN. We also discussed the correlations between the observed CN trends and thermo-analytical data resulted from thermo gravimetric analysis curves (TGA) and differential scanning calorimetry (DSC).
Introduction [Excerpt]
The cetane number (CN) measures the readiness of the fuel to auto-ignite when injected into an engine. It is one of the most important properties to specify the ignition quality of any fuel for internal combustion engines. An increase in CN decreases the delay time between fuel injection and ignition. Shorter ignition delay times have been directly correlated with a faster startup in cold weather, reduced NOx and particulate matter emissions from diesel engines, and smoother engine operation.1,2
The CN of a fuel depends on the composition and structure of the hydrocarbons present in the fuel. The CN decreases with an increase in the aromatic hydrocarbon content and increases with an increase in the nparaffin and olefin content.3 The use of cetane-improving additives is necessary to avoid difficulties in cold starting and other performance problems associated with low CNs. Traditionally, alkyl nitrate (e.g. amyl nitrate, hexyl nitrate, and octyl nitrate) have been used as ignition promoters, but the use of azo compounds and alkyl peroxides has also been proposed.4,5
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