Biodiesel from meadowfoam (Limnanthes alba L.) seed oil: oxidative stability and unusual fatty acid composition

Abstract

Meadowfoam (Limnanthes alba L.) seed oil methyl esters (MFME), prepared by a standard transesterification procedure using methanol and sodium methoxide catalyst from refined meadowfoam oil (MFO), were evaluated as a potential biodiesel fuel. MFME contains the unusual 5(Z)-eicosenoate (64.2 wt%) and 5(Z),13(Z)-docosadienoate (18.9 wt%). The cetane number of MFME, 66.9, is among the highest ever reported for a biodiesel fuel. In addition, MFME exhibited exceptionally high oxidative stability of 41.5 h by the Rancimat method. Kinematic viscosity was determined as 6.18 mm² s⁻¹. The cloud, cold filter plugging and pour points of MFME were determined as −6, −9, and −10 °C, respectively. Blending MFME with soybean oil methyl esters (SME) provided kinematic viscosity and oxidative stability values within ranges specified in ASTM D6751 and EN 14214. Other properties such as acid value, free and total glycerol content, as well as sulfur and phosphorus contents were below limits specified in ASTM D6751 and EN 14214. Also reported are lubricity, heat of combustion, and Gardner color. For sake of comparison of some fuel properties, MFME was also prepared from crude meadowfoam oil. The most conspicuous difference in fuel properties was the even greater oxidative stability of 71.6 h by the Rancimat method of MFME from crude MFO. Addition of MFME (from refined MFO) to petrodiesel improved lubricity of ultra-low sulfur petrodiesel while not adversely affecting oxidative stability and low temperature operability. In summary, MFME has unusual fuel properties as a result of its unique fatty acid composition and appears to be a satisfactory blend component for SME and petrodiesel.