Page 157 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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3. CHARACTERIZATION OF PETROLEUM FRACTIONS 137

FIG. 3.30—Apparatus to measure aniline point of petroleum fuels by
ASTM D 611 test method (courtesy of KISR).

value of −65 C. The result is quite satisfactory considering in which M P is the molecular weight of n-paraffin whose boil-
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minimum data on T b and SG are used as the only available ing point is the same as mid boiling point of the fraction which
parameters. can be determined from Eq. (3.41).
3.6.5.3 Linden Method
3.6.5 Aniline Point
This relation is a mathematical representation of an earlier
Aniline point of a petroleum fraction is defined as the mini- graphical method and is given as [73]
mum temperature at which equal volumes of aniline and the 1/3
oil are completely miscible. Method of determining aniline (3.125) AP =−183.3 + 0.27(API)T b + 0.317T b
point of petroleum products is described under ASTM D 611 where AP is in C, T b is the mid boiling point in kelvin and
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test method and the apparatus is shown in Fig. 3.30. Aniline API is API gravity. The blending index for aniline point may be
point indicates the degree of aromaticity of the fraction. The calculated from the following relation developed by Chevron
higher the aniline point the lower aromatic content. For this Research [61]:
reason aromatic content of kerosene and jet fuel samples may
be calculated from aniline point [59]: (3.126) BI AP = 1.124[exp (0.00657AP)]
where AP is in C and BI AP is the blending index for the aniline
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(3.122) %A = 692.4 + 12.15(SG)(AP) − 794(SG) − 10.4(AP)
point. Once the blending indexes of components of a blend are
where %A is the percent aromatic content, SG is the specific determined, Eq. (3.117) should be used to calculate blending
gravity, and AP is the aniline point in C. There are a number index for aniline point of the blend.
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of methods to estimate aniline point of petroleum fractions.
We discuss four methods in this section. 3.6.5.4 Albahri et al. Method
Most recently Albahri et al. [68] developed predictive meth-
3.6.5.1 Winn Method ods for determination of quality of petroleum fuels. Based on
Aniline point can be estimated from Winn nomograph the idea that aniline point is mainly related to the aromatic
(Fig. 2.14) using T b and SG or M and SG as the input pa- content of a fuel, the following relation was proposed:
rameters. (3.127) AP =−9805.269(R i ) + 711.85761(SG) + 9778.7069
3.6.5.2 Walsh–Mortimer where AP is in C and R i is defined by Eq. (2.14). Equations
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The aniline point can be calculated from the following rela- (3.123), (3.125), and (3.127) were evaluated against data on
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tion [61, 71]: aniline points of 300 fuels with aniline point range: 45–107 C
boiling range: 115–545 C and API gravity range of 14–56. The
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100.5C 1/3 average absolute deviation (AAD) for Eq. (3.127) was 2.5 C
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(3.123) AP =−204.9 − 1.498C 50 + 50
SG while for Eqs. (3.123) and (3.125) the errors were 4.6 and
6.5 C, respectively [68]. Error distribution for Eq. (3.127) is
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where AP is the aniline point in C and C 50 is the carbon
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number of n-paraffin whose boiling point is the same as the shown in Fig. 3.31.
mid boiling point of the fraction. C 50 may be calculated from
the following relation: 3.6.6 Cetane Number and Diesel Index
M P − 14 For diesel engines, the fuel must have a characteristic that fa-
(3.124) C 50 =
2 vors auto-ignition. The ignition delay period can be evaluated

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