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Crystallization Behavior of Fatty Acid Methyl Esters
Author(s) -
Dunn Robert O.
Publication year - 2008
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-008-1279-x
Subject(s) - differential scanning calorimetry , freezing point depression , crystallization , thermodynamics , pour point , freezing point , chemistry , biodiesel , fatty acid methyl ester , melting point , soybean oil , miscibility , organic chemistry , materials science , physics , food science , catalysis , polymer
Biodiesel from most agricultural feedstocks has flow properties that are prone to startup and operability problems during cold weather. Biodiesel from soybean oil is generally a mixture of long‐chain fatty acid alkyl esters composed of 0.15–0.20 mass fraction saturated esters (melting point [MP] ≫ 0 °C) mixed with unsaturated esters (MP < 0 °C). This work investigates the crystallization properties of two saturated fatty acid methyl esters (FAME) commonly found in biodiesel from soybean oil. Differential scanning calorimetry (DSC) heating and cooling scans of methyl palmitate (MeC16), methyl stearate (MeC18) and methyl oleate (MeC18:1) in pure form were analyzed. Crystallization behavior in ternary FAME mixtures was inferred by the application of thermodynamic models based on ideal solution and freezing‐point depression theories. Activity coefficients for MeC16 and MeC18 in MeC18:1 solvent were determined by analyzing DSC cooling curves for binary FAME mixtures. Eutectic points were predicted by both models. Crystallization onset temperatures inferred from freezing point depression theory were more accurate than those for ideal solutions with respect to a direct DSC cooling curve analysis of corresponding ternary mixtures. This work shows that the crystallization onset temperature (cloud point) of biodiesel may be predicted by freezing‐point depression theory if the activity coefficients of the component FAME are known.