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A Mathematical Model for Estimating Molecular Compressibility of Fatty‐Acid Methyl Ester and Biodiesel
Author(s) -
Krisanangkura Piyawan,
Lilitchan Supathra,
Aryusuk Kornkanok,
Krisnangkura Kanit
Publication year - 2019
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 - 10.1002/aocs.12162
Subject(s) - biodiesel , fatty acid methyl ester , gibbs free energy , fatty acid , chemistry , compressibility , methanol , thermodynamics , organic chemistry , materials science , physics , catalysis
In this study, the molecular compressibility ( k m ) of a fatty‐acid methyl ester (FAME) or a biodiesel is correlated with Δ G , lnk m MW = − Δ G k mRT , via the Gibbs energy additivity method, where MW is the molecular weight of the FAME or the average MW of the biodiesel. The Gibbs energy associated with molecular compressibility ( Δ G k m ) is further correlated with the structure of FAME. Thus, the relationship between the structure (of a FAME or a biodiesel) and the physical property ( k m ) is established. Thus, k m of a FAME at different temperatures can be easily estimated from the carbon numbers of fatty acid ( z ) and the number of double bonds ( n d ) with good accuracy. For biodiesel, k m is calculated from the same equation with the average z ( z (ave) ) and average n d ( n d (ave) ). k m is not temperature independent and a slight change in k m depends on the structure of the FAME and biodiesel. For FAME having 14 carbon atoms or less in the fatty acid, k m decreases as temperature is increased. On the other hand, for FAME with a longer chain length (16 or higher), k m increases as temperature is increased. Similarly, a double bond in the long‐chain FAME is more sensitive to temperature than the saturated FAME.