Predicting cetane numbers of n‐alcohols and methyl esters from their physical properties

Abstract

Cetane numbers (C#} for the homologous series of straight-chain, saturated n-alcohols, C5-C12 and C14, were determined according to ASTM D 613. Measured C# ranged from 18.2-80.8 and increased linearly with carbon number {CN). Regression analyses developed equations that related various physical properties or molecular characteristics of these alcohols to calculated C#. The degree of relationship between measured and calculated C# was expressed as R 2. The decreasing order of the precision with which these properties correlated with C# was: boiling point (bp) > melting point imp) > CN > heat of combustion {HG) > refractive index (UZ0v} > density (d). This ranking was based upon R 2 (0.99-0.96) and the Average % Error (2.8-7.2%). C# were also determined for straight-chain homologs of saturated methyl esters with CN of 6, 10, 12, 14, 16 and 18. C# ranged from 18.0-75.6 and increased eurvilinearly with CN. Equations were also developed that related physical properties of these esters to C#. The precision with which these properties correlated with C# was: bp > viscosity iV} > heat of vaporization {HV) > HG > CN > surface tension (ST) > mp > n20D> d. R 2 ranged from 0.99 for bp to 0.98 for d. Equations for the alcohols were linear or quadratic, while equations for the esters were linear, quadratic or cubic based upon statistical considerations that included a Student's t-test. With related physical properties and these equations, accurate predictions of C# can be made for saturated n-alcohols and methyl esters.

Precombustion of fatty acids and esters of biodiesel. A possible explanation for differing cetane numbers

“…For example, there is a positive correlation between CN and boiling point of a fatty compound (18). Another work, in which regression analyses were conducted, showed that boiling point was the most reliable property for predicting the CN of fatty compounds (19). It was more reliable than heat of combustion, carbon number, and melting point.…”

Seed Oil from Ten Algerian Peanut Landraces for Edible Use and Biodiesel Production

“…Viola et al 17 calculated the experimental CN for FAMEs whose maximal chain length was 22 carbon atoms. Because the oil from peanut seeds contains C24:0 as the FAME with the maximal chain length, the experimental C24:0 CN was calculated here also on the basis of the equation proposed by Freedman and Bagby 15 and the CN of each peanut oil was predicted as the sum of the mass fraction of all the detected FAME.…”

Detailed chemical kinetic oxidation mechanism for a biodiesel surrogate

“…The present work is intended to provide a reliable kinetic model for a methyl ester fuel that is much larger than the previous methyl butanoate. Instead of the 4 carbon atoms chain of methyl butanoate, the current work provides a kinetic mechanism for methyl decanoate (cetane number of about 47 [ 6,7]), with a chain of 10 carbon atoms with a methyl ester group attached ( Figure 1). …”