Relationship between Carbon-Type Composition, Viscosity-Gravity
Constant, and Refractivity Intercept of Viscous Fractions of Petroleum
STEWART S. KURTZ, Jr., RICHARD W. KING, WILLIAM J. STOUT', DOROTHY G. PARTIKIAN, and E. A. SKRABEK2
Sun
Oil Co., Marcus Hook and Norwood, Pa.
A triangular graph has been developed which relates
carbon-type composition in terms of per cent aromatic
carbons, per cent naphthenic carbons, and per cent
paraffinic carbons to viscosity-gravity constant and
refractivity intercept for viscous petroleum fractions.
If both viscosity-gravity constant and refractivity intercept are known, carbon-type composition can be determined from this graph with reasonable accuracy.
Viscosity, gravity, and refractive index are the only
experimental data required for the use of this graph.
It is useful in following the effect of solvent extraction,
acid treating, hydrogenation of the viscous fractions
of petroleum, and for comparing the composition of
the viscous fractions from various crude oils.
T
WO other laboratories have been working independently
on the correlation of density, refractive index, and viscosity to
provide a simple method for the analysis of petroleum fractions
(5, 41). The method presented here is believed to be as accurate
as the other methods, and more simple to use.
The information v hich has been accumulated in recent years
concerning the lubricating oil fraction of petroleum indicates
that the structures of the molecules in the lubricating oil fraction
are fairly uniform ( I , 2, 5-11, 14, 16, 17, 20-22, 24-27, 29-33,
36-37, 39, 40, 43-46). It seems probable that only a very small
portion of the theoretically possible structures actually exist in
lubricating oil.
Both viscosity-gravity constant (12) and refractivity intercept (16, 18, 19) were developed with the intent of obtaining
constants which were indicative of the type of hydrocarbon composition and independent of molecular weight. Therefore, it
seemed possible that lines of equal viscosity-gravity constant and
equal refractivity intercept could be established on a three-component graph for carbon-type composition. Carbon type composition is used in the conventional sense (30, 31, 43). Specifically, per cent aromatic ring carbon means the per cent of the
total carbon atoms in aromatic ring structures; per cent naphthenic ring carbon means the per cent of the total carbon atoms
in naphthenic ring structures; and per cent paraffinic chain
carbon means the per cent of the total carbon atoms in chain
structures, free as \\ell as combined with naphthenic and aromatic
rings.
Van Xes and van Westen, in their book "Aspects of the
Constitution of Mineral Oils" (31), have discussed both refractivity intercept (33) and viscosity-gravity constant (32) in
relation to the carbon-type composition, and presented the following approximate equations:
= 0.01065
ri
V.G.C.
=
( % Ca)
+ l l ( 5 6 C A ~ O - +~ )0.0103('%
~
CN) +
0.0105 ("/c C P ) (1)
O.OllO(G C a )
+ 0.00925(% CN)0.00743(%
+
CP)
2
address, University of Delaware, Newark, Del.
Present address, University of Wisconsin, Madison 6, Wis.
V.G.C.
T7.G.C.=
\-.G.C.
=
=
10G - 1.Oi52 log ( V , - 38)
10 - log ( J r i - 38)
G - 0.21 - 0.022 log (1'2 - 3 5 . 5 )
0.755
d - 0.1384 log ( V , - 20)
0.1526[7.14 - log (V3 - 20)]
~~
+
0,579
(3)
(-1)
(5)
where
G
=
=
VI =
V 2=
V 3=
d
specific gravity 60/60° F.
density a t 20" C./4" C.
Saybolt viscosity a t 100' F.
Saybolt viscosity a t 210' F.
kinematic viscosity in centistokes a t 20" C.
These equations all give viscosity-gravity constants equivalent to the Hill and Coats equation for 100' F., which is
Equation 3. Some of the carbon-type composition data
were obtained by the Martin method (16, 26) of calculation and
some by the n-d-M method (30, S1, 43). For aromatic extracts
and other compounds rich in aromatic rings, which are outside
the range recommended for the n-d-Lf method, the Martin analytical technique was used.
VISCOSITY-GRAVITY CONSTANT CORRELATION
(2)
These equations were presented as somewhat tentative, and
were not recommended for general use because of the uncertainty
in regard to the effect of aromatic carbons on the physical properties. These authors quote Leendertse (20) in regard to the
reliability of the refractivity intercept for determining the
1 Present
naphthene carbon content and the paraffin carbon content of
aromatic-free lubricating oil fractions. They were impressed
with its reliability for saturated mineral oil fractions. The
intercept for paraffin carbons chosen by Leendertse (1.0502)
and the value used here (1,0500) both correspond closely with the
value for the limiting point of the paraffin homologous series
(1.0498) (4). A lower value (1.0480) has also been investigated,
because there is no reason to believe that the limiting CH, inO
crement is necessarily the best increment to use in the C ~ to
Cto molecular weight range. However, the higher value is better
for data on lubricating oil fractions. This will be discussed in
more detail below.
The basic problem was to collect enough data for viscous oils
and fractions of viscous oils so that the relation between carbontype composition, viscosity-gravity constant, and refractivity
intercept could be established on an empirical basis. Carbontype composition can be obtained by the n-d-M procedure if
data are available for density, refractive index, and molecular
weight (31, 43). If molecular tveight is not available it can be
estimated from published correlations of molecular weight with
physical properties (28). D a t a were collected from the authors'
own files (42) and from the literature (10, 25, S1) for approximately 258 lubricating oils and fractions of lubricating oils for
which carbon-type composition, viscosity-gravity constant, and
refractivity intercept were available.
Viscosity-gravity constants were calculated with the following
equations or the corresponding nomographs:
I n development of Equation 2 van Nes and van Westen observed ( 3 2 ) that for saturated oils a linear relationship existed
between the viscosity-gravity constant (V.G.C.) and percentage
carbon in paraffinic structures ('% Cp). There also seemed to be
some relation between viscosity-gravity c o n s t p t and % CP for
a number of oil fractions from widely differing crude sources.
Their observations suggested that it might be possible to establish
lines of constant viscosity-gravity constant on a triangular coordinate system by first establishing a relationship between
viscosity-gravity constant and the percentage carbon in aro-
1928
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
1929
Table I.
Data Necessary for C o n s t r u c t i o n of ViscosityGravity Constant Lines" in F i g u r e s 5 and 7
Coordinate Point 1
Coordinate Point 2
V.G.C.
% CA % CN % CP
% CA % CN % CP
0.78
4.0
17.0
79.0
0
23.0
77.0
0.79
5.7
18.0
76.3
0
27.0
73.0
0.80
7.5
19.5
73.0
0
31.6
68.4
20
70.2
0
35.8
64.2
0.81
9.8
0.82
12.5
20
67.5
0
40.0
60.0
0.83
15.5
20
64.5
0
45.0
55.0
0.84
18.2
20
61.8
0
60.0
50.0
0.85
21.0
20
59.0
0
54.8
45.2
0.86
23.6
20
56.4
0
60.0
40.0
0.87
26.4
20
53.6
0
66.1
33.9
20
51.0
0
73.0
27.0
0.88
29.0
0.89
31.6
20
48.4
0.7
79.3
20
0.90
34.0
20
46.0
7.5
72.5
20
0.91
36.3
20
43.7
13.7
66.3
20
0.92
38.2
20
41.8
19.9
60.1
20
0.93
40.0
20
40.0
25.0
55.0
20
0.94
41.5
20
38.5
30.0
50.0
20
0.95
43.0
20
37.0
34.5
45.5
20
0.96
44.4
20
35.6
38.4
41.6
20
41.9
38.1
20
0.97
45.7
20
34.3
0.98
46.9
20
33.1
44.5
36.0
19.5
0.99
48.0
20
32.0
47.3
34.7
18.0
1.00
49.2
20
30.8
50.0
33.0
17.0
1.01
50.5
20
29.5
52.0
31.7
16.3
Table 11. Accuracy of Viscosity-Gravity C o n s t a n t Carbon-Type Correlation
Source of D a t a
Lit.
Ref.
No. of
FracAv.
tions V.G.C.
Std.
Dev.
Dev.
of
Averagea
0 830
0 926
0.845
0,813
0.858
0.004
0 004
0.004
0,004
0.006
0.000
+O.OOQ
-0.002
- 0 002
-0,004
+ O 006
-0,006
-0.007
-0,006
+0.010
+0.010
-0.007
Max.
Dev.
Whole oils and cuts
thereof
Water White Oils
Borneo Crude
OklahomaCrude
Pennsylvania Crude
Webster Crude
Distillation fractions
from Naphthenic
Crudes
P a . 180 S e u t r a l
Midcontinent
Neutral I
California Neutral
Gulf Coast Keutral
Rodessa Pieutral
Midcontinent
Seutral 2
($6)
11
(91)
(91)
5
5
(91)
(SI)
4
4
(Sf)
(10)
21
20
0.883
0.819
0.004
0.002
0 000
0.000
17
17
15
0.860
0 892
0.879
0.830
0.003
0.002
0.003
0.002
+O 001
0.000
0.000
- 0 002
005
-0 005
$0.006
-0 004
+ O 006
(10)
(10)
(IO)
(IO)
18
+O
19
0.849
0.004
+ O 001
156
0 858
0.003
0.000
(86)
(48)
12
3
0.800
0.874
0.002
0.007
0,000
+O 006
+ O 004
+ O 011
(42)
21
0.836
0.004
+0.003
+0.009
36
0.837
0.004
t 0 001
+0.011
(42)
3
0.802
0.008
-0
-0
(48)
(48)
3
0.956
4
0.966
0.008
0.014
-0 007
- 0 014
-0,010
- 0 015
(48)
2
0.945
0.014
-0
014
- 0 015
(48)
6
0.9G9
0.005
-0
001
-0
010
1
32
0.948
0 009
- 0 006
-0
015
224
0.005
-0 001
-0
015
Coordinate points given are terminal points of the V.G.C. lines
and define area of composition over which correlation has been tested.
a
t
t
1
40
44
40
52
56
60
64
68
72
76
PER CENT Cp
F i g u r e 1.
Viscosity-gravity constant cs.
saturated oils
7'
C p for
All whole oils
Saturated oils
Water White Oils
Vebster Crude
Distillation fractions
froni Naphthenic
Crudes
All saturated oils
Aromatic extracts
Aromatic conc. froni
solvent refined
lube b
Aromatic cone. from
light lubes b
Aromatic extracts
Aromatic conc. from
Webster Crudeb
Aromatic conc. from
Duosol and furfuralextractionsb
Aromatic conc. of
(10)
-411 aromatic extracts
Complete total
.92
z
z
4
L
0
~
.90
.88
c
>
.86
a
i-
010
010
a Deviation from average of each d a t u m averaged, taking sign into account.
b Concentrated on silica gel; a t least one aromatic ring per molecule.
.94
r
00;
+O
.84
v)
0
:-: . 8 2
>
.80
Viscosity-gravity constant plots for w h o l e o i l s
1930
ANALYTICAL CHEMISTRY
matic, naphthenic, or paraffinic structures on rectangular coordinates.
For saturated oils, the linear relationship betvieen viscositygravity constant and % C p observed by van Xes and van Kesten
(32) was confirmed, as shown in Figure 1. Because theae oils
contained no carbon in aromatic structures, it was possible to
transfer this line to the saturated base line of a triangular coThis gives a series of
ordinate graph for % C P , % C.V, and lo
CP-% CS side of the
viscosity-gravity constant points on
triangle.
I n order to establish a second point for the viscosity-gravity
constant lines, it was necessary to plot tn-o of the composition
variables as a function of viscosity-gravity constant for the series
of whole oils. Per cent C P and % C A gave the best approxiniations to a linear relationship when so plotted (Figures 2 and 3,.
I'ISk
B
.90
t
A plot of 70 C.V showed considerably greater scattering, and is
presented in Figure 4 merely to show that a line constructed from
% C A )fits the
Figures 2 and 3 so that 70C.V = 100 -(70C p
data reasonably well.
It was possible t o fit the data for
C P and % C A n-ith a
straight line up to viscosity-gravity constant values of about
0.885. Above 0.885 the effect of the carbons in aromatic structures became large, and it was necessary to change the slope
abruptly in order to fit the data in this region. These data
mere transferred to triangular coordinates and points of equal
viscosity-gravity constant connected to give a series of lines
covering the viscosity-gravity constant range from 0.790 to 0.910
I n the range from 0.910 to 1.00 the lines were placed by inspection
to give the best fit to the data.
Adjustments to the correlation mere made until the average
deviation was a minimum and the deviation of the average was
close to zero. The viscosity-gravity constant lines on Figure 5
are the final adjusted lines.
Table I gives the data necessary to lay out the lines for viscosity-gravity constant on a three-component graph. For the
present, a t least, the lines are being restricted to that area of the
graph for which supporting experimental data exist. Table I1
shows the degree of agreement obtained for 224 fractions between
the viscosity-gravity constant determined experimentally and
that derived from composition by using a chart corres onding
to Figure 5 . The agreement between experimental and cafculated
values, while not perfect, is satisfactory. It indicates that the
reverse computation-that
is, relating viscosity-gravity constant to composition-should be satisfactory, provided anothei
function, also independent of molecular weight, could be plotted
on the graph in order to obtain intersecting lines.
+
REFRACTIVITY INTERCEPT CORREL4TION
I.80
I I I I I I I I I I I I I
0
IO
20
30
40
50
60
70
80
PER CENT C N
Figure 4.
Viscosity-gravity constant
whole oils
TS.
YC C.v
for
It seemed reasonable to use refractivity intercept as the other
plotted function, provided the effect of aromatic carbons could
be evaluated on a reasonable basis. As the aromatic content of
lubricating oil fractions increases, there is evidence that the proportion of condensed aromatic ring structures increases. Because
the composition data for the 224 fractions that Rere available
to the authors formed a fairly narrow band on the triangular
diagram of carbon-type composition, it seemed reasonable to
anticipate that a fairly smooth curve should be obtained if the
equivalent refractivity intercept of the aromatic carbons were
plotted against the observed refractivity intercept of the sample.
Therefore, the equivalent refractivity interiept of the aromatic
carbons was calculated using the follon-ing equation:
r,A =
% AROMATIC RING
CARBONS
% NAPHTHENE
RING CARBONS
Figure 5 ,
r,sample(100) - 1.0300(7,C\) - l . O 5 O O ( % C p )
-
% PARAFFIN
CHAIN CARBONS
Viscosity-gravity constant in relation to carbon-type
composition
n
Figure 6 shows the calculated refractivity intercepts for aromatic ring carbons plotted against
the refractivity intercept of the sample for those
samples which had 5% or more of aromatic ring
carbons. Although some scattering is observed,
the anticipated trend is clear. Because the available data did not include points rich in naphthene
ring carbons and having low intercept values,
some assumption was needed to establish tentative intercept lines in the more naphthenic portion
of the composition chart. -4s there cannot be less
than one aromatic ring per molecule and as it was
not believed necessary to extend the chart below
1.035 refractivity intercept, the intercept value of
benzene (1.0616) was plotted opposite the value
1.035 for refractivity intercept to provide a tentative terminal point for this curve. This was a
rather arbitrary step which xould only be justified if the chart ultimately developed was reliable.
T h e refractivity intercept lines on Figure 7 were
established by interpolating betxeen 1.0300 and
1,0500 on the naphthene and paraffin side of the
triangle and between 1.0300 and r,A on the naphthene and aromatic side of the triangle, and 1.0500
and riA on the paraffin and aromatic side of the
triangle. r,A is determined in each case using
Figure 6 or Table 111. The data necessary for
establishing the intercept lines in Figure i are
given in Table IV.
Study of the oints in Figure 6 suggests the
possibility that &ere should be a sharp downward
curvature of the line for the calculated aromatic carbon intercept betneen the values 1.045
1931
V O L U M E 28, NO. 12, D E C E M B E R 1 9 5 6
;tnd for API 42 compounds (2, 39, 40) would indicate that a
paraffin intercept value of 1.0480 would be better in the range
from 20 to 40 carbon atoms than a value of 1.0500. The corresponding naphthene value is 1.0320. A complete graph was
constructed and evaluated. A statistical study showed little
difference between this graph and Figure 7 . However, when
compared by plotting data for a series of hydrogenated oils, the
graph based on the paraffin intercept value of 1.0480 and a
naphthene intercept value of. 1.0320 showed the completely
hydrogenated naphthene fractions, falling about 2y0 below the
base line representing 0% aromatic carbons. The graph based
on 100% CP = 1.0500 and 1007, CN = 1.0300 showed the completely hydrogenated fractions falling on the base line (Figure 8 )
For this reason it was decided to adhere to values of 1.0500 and
1.0300 for the paraffin and naphthene apexes, respectively,
In constructing this type of graph some thought needs to be
given to what is meant by per cent composition. The data for
per cent carbon type arp in terms of percentage of aromatic,
naphthenic, and paraffinic carbons in the molecule (16, SI j. Refractivity intercept is, ingeneral, additive on a volume per cent
basis for mixtures of liqui s. As shown by Leendertse (2Oj, there
is good agreement between carbon-ty e composition and refractivity intercept for complex saturate8molecules. The graph in
Figure 7 , as derived, represents carbon-type composition and
not volume per cent composition or weight per cent compositiorl.
This should be kept in mind if it is applied to blends.
'Table 111. Data Needed for Drawing Curve of Equivalent
Intercept of Aromatic Carbons os. Intercept of Lube Oil a s
Shown in Figure 6
Intercept
Intercept
of
of Aromatic
Oil
Carbons
1 0616
1.0350
1 ,0695
1.0400
1 0775
1.0450
1 0855
1.0500
1 0926
1,0550
1.0986
1.0600
1.1042
1 ,0650
1.1094
1 ,0700
1.1140
1.0750
1.1186
1.0800
Data for Establishing Refractivity Intercept
Lines"
NaphtheneNaplitheneParaffinItefracParaffin
Aromatic*
Aromatic
Base Line
Side of Triangle Side of Triangle
tivity
% CP % CS 5% CA 7%C.V yo CA 7% C P
Intercept
25
75
15 8
84 2
1 035
74.7
50
25.3
i 040
50
68.4
25
31.6
75
1.045
63.9
36.1
0
1.050
100
60 1
88.3
39 9
11.7
1.055
56 3
79.5
20 5
43
7
1 060
72.3
52 8
27 7
47 2
1 065
po 4 49 6 33 7 66 3
1 070
39 1
46 4
93 6
BO 9
1 n7.5
i &I
56.4
43 4
43.7
56 3
In constructing Figure i values for intermediate lines can he 011tained by plotting columns 2 to 7 us. column 1 and interpolating.
h working graph should have lines for each 2% of carbon-type (TJYIposition, for each unit in the third decimal place of the refractirit?.
intercept, and for each unit in the second decimal of viscoeit!.-gravit!.
constant.
Table IV.
~~
APPLICATIO\
The carbon-type composition of the lubricating oils and frwtions of lubricating oils used in developing Figure 7 , as well as :L
number of other oils on n hich data were available, was determined
by plotting the viscosity-gravity constant and refractivity intercept for all these points on a large graph and reading off the corresponding composition. This study showed that the aromatic.
carbon contents are usually in agreement with the authors'
best analyses to within 1 or 2%, although occasionally deviation3
as large as 4 or 5% may be observed. On the paraffin and naphthene compositions, the agreement is good for fractions containing 30% or less of aromatic carbons. Between 30% and 50%
aromatic carbons, there is an increase of uncertainty in the values
for the paraffin and naphthene carbons, because the angle at
11-hich the correlation lines intersect decreases rapidly. Thp
chart should not be used for samples having viscosity-gravity
constant values between 0.95 and 1.01 which fall below 20%
C,vor 20% CP. This is practical because very few samples having
less than 20% CNor 2O%Cp have been found in this range. Table
V presents data on a number of samples for which rather complete analytical data were obtained in connection with studies
and 1.050 for the intercept of the oliginal oil. This was tried, but
led to an irregular spacing of the intercept lines on the triangular
diagram. The lines so placed did not agree well with the limited
available data for this region. Therefore, as explained above, the
coordinatee 1.0616 and 1.0350 were tried as the terminal point
of the curve. This led to more reasonable spacing of the intercept
lines and better agreement with the data.
Considerable thought has been given to the significance of
pure compound data in relation to locating the intercept lines on
Figure 7 . Consideration of data from the A4PI44 tables ( 3 , 35)
I
I
In
I
I
I
I
I
I
1.12
m
a
4:
g
gI
1.11
1.10
a
LL
..-
0
1.09
n
w
tj
1.08
i8
1.07
1.030
1.040
1.050
1.060
1.070
1.080
r i OF SAMPLE
Figure 6.
Refractivity intercept of aromatic carbons us. refractivity
intercept of sample
ANALYTICAL CHEMISTRY
1932
of rubber processing oils (16, 48). I n general, the agreement
between composition obtained with Figure i and the composition obtained by more complete analysis is satisfactory-that is,
within 1 or 2%. -4few deviations larger than 4% are shonn.
Table V also contains data obtained by the n-d-bI procedure
of Tadema, van Xes, and associates (31, 43). I n the range for
which the n-d-11 method is recommended-that is, for samples in
which the ratio of % C A to yo Cy is 1.5 or less-the agreement is
quite good. I n the higher aromatic range the data obtained by
Figure 7 are in better agreement with detailed analyses b j the
Martin (16, 26) method than are the data by the n-d-11
method .
Table VI compares carbon-type analyses obtained x ith Figuie
i and with the n-d-?\I procedure on the cuts of five tlpical oils
studied by Hill and Ferris (13). The data on these oils xere
used by Hill and Coats (12) in deriving the viscosity-gravity constant, The t a o methods agree xell for these typical oils. The
range of carbon-type composition is about 20% for % C.4 and
% C Vand about 40% for % C p . To prepare Table VI data weie
read from photostatic enlargements of the curves published by
Hill and Ferris. Data were corrected to 20' C. when necessary.
A statistical study of all the data (Table YII) shows that, for
oils having a viscosity-gravity constant of 0.900 or less, Figure
i nil1 give the value of yo C A n ith a standard deviation of ahout
1.0%. For % C.V and % C p the standard deviation is roughly
1.5% for samples m-ith a viscosity-gravity constant below 0.900.
Most naturally occurring crude oils have viscosity-gravity constant values below 0.900.
For samples with viscosity-gravity constants between 0.900
and 1.000, the standard deviation for % C A is approximately 2.0%
and for % C,y and % C p , approximately 4.5%. The samples
having viscosity-gravity constant above 0.900 are, for the most
part, aromatic concentrates obtained either by solvent extraction
or gel separation. These samples are outside the range of materials for x hich the viscosity-gravity constant was originally
developed.
Table 1-111presents corresponding data arranged b j groups
based on per cent carbon in aromatic rings. For samples having
less than 30% carbon in aromatic rings the standard deviation is
as follons: per cent aromatic carbons, 1.2%; per cent naphthenic
carbons, 2 . 0 % ; per cent paraffinic carbons, 1.7%.
The data used in developing this chart represent a Fide variety
of samples. Consideration of the data indicates that Figure 7
is sufficiently reliable for obtaining many of the carbon-type composition data ahich are needed in practical petroleum refining.
The relation betn-een refractivity intercept and composition,
and beta een viscosity-gravity constant and composition is more
accurately presented by Figure 7 than hy Equations 1 and 2
% AROMATIC RING
CARBONS
.os00
LRBONS
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
1933
Table V. Comparison of Carbon-Type Analysis by
Viscosity-Gravity Constant-Refractivity Intercept and
Other Methods
011
No.
1
Mol. wt.
V.G.C
.
T%
n
d
2
Mol. nt.
V.G.C.
1L
n
d
3
A I O l , n.t.
T.G.C.
ri
n
d
4
1101. a t .
T.G.C.
ri
ri
d
5
698
0.798
1.0448
1.4865
0,8835
T.G.C.
rt
d
7
>roi.art.
V.G.C.
T l
n
d
8
3101. wi.
1.. G.C.
rt
12
d
9
JIol. rvt.
T.G.C.
ri
n
d
10
IIOl. wt.
V.G.C.
rt
n
d
11
Mol. ai.
V.G.C.
1%
d
12
\r01.nt.
V.G.C.
rt
71
d
13
Mol. wt.
1'. G .C.
rl
n
d
14
Ll01.nt.
T.G.C.
IL
n
d
1.5
16
x-z
352
0.818
1.0440
1.4748
0.8613
Fig. 7
x
n-d-XI u
Martin z
464
0,842
1.0419
1.4971
0.9105
Fig. 7
z
n-d-XI
y
Martin z
x-2
2-y
2-2
FIE. 7
2-2/
z-z
442
0 892
1 ,0332
1.5352
0.9600
Fig. 7
x
n-d-XI y
Martin z
2-Y
365
0,915
1.0501
1.5291
0,9580
Fig. 7
s
n-d-11 y
Martin z
427
0 927
1.0631
1 5550
0 9837
Fig. 7
x
n-d-ll y
Martin z
369
0.93fj1 ,066.2
Fig, 7
n-d-115
hIartin
x-z
x-2
x-y
2-2
z-y
2-2
x
y
z
x-y
0.9783
2'-2
373
0.936
1 0039
1.5537
0.9797
Fig. 7
x
n-d-Ma y
Martin z
373
0,943
1.0654
1.5649
0,9990
Fig. 7
x
n-d-MQ y
LIortin z
361
0.970
1.0735
Fig. 7
x
n-d-Ma y
Martin z
x-y
x-z
s-y
x-z
1,5804
z-y
1.0138
5-2
Fig. 7
x
n-d-Ma u
Nartin z
2-y
2-2
Fig. 7
z
n-d-lIe y
Martin z
x-y
l f o l . wt.
V.G.C.
Fig. 7
x
n-d-3Ia y
n
d
310
0 997
1.0734
1.5872
1.0236
x-z
Martin
z
x-y
s-2
0
70
69
70
+ I
0
3
3
3
33
33
35
64
64
0
0
0
0
3
3
3
34
34
34
0
0
0
0
4
45
43
45
0
0
50
0
+ I
4
64
0
0
63
63
63
0
0
51
-
2
3
3
1
1
49
47
47
+ 7
49
50
50
- 1
+ 2
- 1
20
19
16
1
4
38
39
42
- 1
42
42
42
0
0
25
24
25
1
0
34
35
30
i - 4
41
41
45
0
- 4
45
43
45
+ ?
0
3<5
33
- 5 5
- 5 5
++
+
25.5
22
20
3.5
5.5
++
36
36
33
0
3
- 4
- 1
28.5
22
26
6.5
2 5
+
++
39
42
35
- 3
4
26
16
26
+10
0
+
37
39
33
- 2
4
35.5
42
41
- 6.5
5.5
-
29
22
33
+ 7
- 4
32
- 3
0
46
- 9
1
23.5
12
19
+ll 5
4.5
+
31.5
34
35
- 2.5
- 3.5
40
55
46
- 9
0
30.5
15
30
+l.5 5
0.5
+
23.5
30
24
- 6.5
0.5
37
21
31
+16
+ 6
25
-10
- 8
-
46
52
+-
44
6
2
49
59
46
-10
+
3
31
11
31
+20
0
NO.
of
Data
64
118
(3.4
Group
0- 9 9
10-19 9
Standard Deviation
% CA
5% C Y
70 cp
1 1
1 1
2 2
1 4
1 4
1 6
- 6
- 3
3"
3.5
-
17
27
20
30
23
-10
- 3
Mol. wt. 314
Fig. 7
x
50
15
35
1 010
V.G.C.
6
31
n-d-lIa 1~
1 0825
hlariin z
23
25
rl
n
1.5997
z-y
-13
+ 9
A 4
1.0343
d
2-2
- 2
- 8
+lo
a Beyond range f o r which n-d-11 method is recommended: also beyond
range for which T.G.C. w a s derived.
:;
5%
6
39
43
35
- 4
54
Table YIII. Standard Deviation of Carbon-Type ,inalj sis
by Figure 7 for Per Cent 4romatic Groups
;3;
+ 8
43
Q
36
42
39
- 7
- 4
+
+4
Table VIIS Standard Deviation of Carbon-Type Analysis
by Figure 7 for V.G.C. Groups
NO.
V.G.C.
of
Standard Deviation
Group
Data
% Ca
%Cv
%CP
Less than 0 819
36
0 7
1 2
1 0
0 820-0 849
75
0 8
1 9
1 4
0 850-0 899
103
1 3
2 3
2 0
0 900-0 949Q
25
2 8
4 2
3 5
0 950-0 999a
16
1 8
3 5
3 4
Above 1 OOa
3
1 2
6 1
7 3
258
Maximum V.G.C. shown in Hill and Coats (12) is 0.935; above
0.935 V.G.C. is extrapolated function.
29 5
;
;
31
- 1
Comparison of Figure 7 and n-d-3%Analysis
[Data of Hill and Ferris (13) ]
Characteriaation
%
%
%
V.G.C.
Factor Method CA C N C P
Pennsylvania
0.808
12.4
Fig. 7
6 . 5 24.5 69
n-d-11 6 . 5 24.5 69
1Iidcontinent
0.839
12.0
Fig. 7 1 2 . 5 29
58.5
n-d-;\I 12.5 2 8 . 5 59.0
Gulf Coast No, 1 0.863
11.7
Fig. 7 1 6 . 5 34
49.5
n-d-M 15
3 4 . 5 50.5
Gulf Coast No. 2 0,883
11.5
Fig. 7 17.5 42.5 40.0
n-d-M 16
42.5 41.5
Gulf Coast No. 3 0.910
11.2
Fig. 7 2 4 . 5 44.5 31
n-d-M 22
44
34
Range (maximum - minimum)
1 8 . 0 20.0 38
51
0
1
z
n-d-RI y
Martin z
% CP
28
28
28
0
0
1
x-y
Fig.7
z
n-d-11 y
Martin z
s-Y
272
0 982
1.0724
1.5737
1.0026
-
5-2
39s
0 883
1.0491
1.5210
0.9439
1, 5 5 3 6
2
3
2
2-y
Mol. nt. 278
0.983
V.G.C.
1.0700
rt
n
1.5725
d
1 ,0050
Ti
17
2-y
Fig. 7
x
n-d-;\.I y
Martin z
3101. nt. 347
1 .G.C.
0.846
1.0407
I1
1,4847
d
0.8879
1101.xi.
Fig. 7
x
n-d-11 y
lIartin z
419
0.815
1.0441
1,4793
0.8704
rt
G
Composition of Oil
% CA % CY
Propel.iy of Oil
Table VI.
Table I S s h o w data for aromatic concentrates obtained by
silica gel from five rubber processing oils. These data indicate
that Figure 7 gives good values on the per cent aromatic carbons
in such aromatic concentrates, but poor values for the yo (23, and
% C P . By subtracting 0.015 from the viscosity-gravity constant
value in each case, much better agreement is obtained, as shown
in the table. I n general, any method of this sort must be used
with caution for fractions which are too homogenous as to type
and, therefore, may not fit correlations based on averages.
The effect of sulfur on a correlation of this sort is important if
i t is to be used with high-sulfur oils. When d a h were used for
approximately 60 oils on which sulfur data were available, the
following correction factors were derived for % Cy and % Cp:
Sulfur correction for 5 2 C.,-
=
41 C p
=
Sulfur correction for
~
~
-Kt.?<
0.288
s
+Wt.C7,
0.216
s
(7)
( 8)
The corrected values for % C.4 can be obtained from the equation
70 C a
=
100 -
i%
C,.
+ % CP)
(9)
Table S s h o w the effectiveness of the sulfur correction in
ANALYTICAL CHEMISTRY
1934
reducing the deviations between values read from Figure 7 and
those obtained using more detailed methods of analysis. The
tabulation only includes those samples containing more than
0.5% sulfur. I n the region above 0.8% sulfur, the agreement
between the viscosity-gravity constant-refractivity intercept
method and other methods may be substantially improved by
applying the sulfur correction.
I n addition to viscosity-gravity constant another relation
between viscosity and gravity, the characterization factor, hap
been widely used (46, 4 7 ) . A graph similar to Figure 7, based
on characterization factor, could undoubtedly be developed. The
authors have preferred to provide tables so that data recorded in
terms of characterization factor can be converted to viscositygravity constant and studied with the aid of Figure i .
% AROMATIC RING
CARBONS
A
1.0300
/e
'
-1.0600
1.0400
NAPHTHENE RING
CARBONS
% PARAFFIN CHAIN
CARBONS
Figure 8. Hydrogenation and solvent extraction data in relation to carbontype composition
Lines 1, 2, and 3 explained i n text
Table IX. Aromatic Fractions Concentrated by Silica Gel
[From rubber processing oil (48) I
Aromatic
Fraction
of
Si, relatively
naphthenic
Property of Oil
Mol. \vt. 366
V.G.C.
0.900
ti
1,0530
1,5269
n
d
0,9465
Ss, relatively
Mol. u t . 435
naphthenic V.G.C.
0.886
112
1 0536
n
1 5330
d
0 9588
Sr. relatively
Mol. a t . 350
paraffinic
Y.G.C.
0.898
T,
1 0547
n
1 5223
d
0 9355
91. relatively
Mol. wt. 418
paraffinic
V.G.C.
0 879
ti
1,0530
n
1.5180
d
0.9300
As, relatively Mol. wt. 409
aromatic
V.G.C.
0.957
Ti
1.0706
n
1.5767
d
1.0124
a 0.015 subtracted from V.G.C.
.
~
Composition of Oil
c'r C.V
% CP
30
38
32
44
28
45
4-8
- 7
- 1
7-4
B Tr
42
% CA
Figure 7
Correcteda
Martin
Figure 7
Correcteda
Martin
X
d
z
2-2
- 1
u-2
- 3
22
22
24
- 2
2:
u
z
+-z
21-2
Figure 7
Correcteda
Martin
5
Y
z
X-Z
ll-2
Figure 7
Corrected"
Martin
Figure 7
Corrected"
Martin
26
24
27
X
u
z
- 1
27
25
27
0
- 2
23
21
24
2-2
- 1
21-2
- 3
x-2
42
42
42
0
u-2
0
2
21
2
50
44
28
82
+.I
- 4
- 2
C 6
33.5
29
27
6 .5
A 2.0
+
30.3
27
12
+ 8 5
+ 5
25
22
21
+ 4
+ I
-
39 5
46
46
6 5
0
16 5
'0
54
- 7 5
- 2
33
36
37
- 4
- 1
Table XI gives enough data so that viscositygravity constant can be obtained from characterization factor and viscosity by interpolation.
An example of the application of Figure 7 is
given in Figure 8. Line 1 on this graph represents data from the paper by M. R. Lipkin,
C. C. Martin, and R. C. Worthing (33)shon-ing
steps in the hydrogenation of a viscous oil
fraction. The gradual decrease in aromatic carbon content and increase in naphthenic carbon
content is clearly shown. There is also an indication that the final hydrogenation ti eatments,
which were continued in an effort to eliminate the last trace of ultraviolet absorption,
may have resulted in some ring opening, because
there is a decrease of between 2 and 4% in the
naphthene ring carbons and a corresponding increase in the paraffin chain carbons during these
last hydrogenations Other data for hydrogenated samples confirm the constancy of % C p as
aromatic rings are converted to naphthenic
rings. Line 2 on this graph shows the change
in an oil on repeated solvent extraction (34).
I n this case there is a progressive decrease in
V O L U M E 28, NO. 12, D E C E M B E R 1 9 5 6
1935
Table X.
Correction of Carbon-Type Composition Data for Effect of Sulfur
Deviation from Best Analvses
V.G.C. V S . rt
V.G.C. us. r ,
(corr. for % SI“
Lit.
Sample
%
S
%
C
a
%
C
\
%
CP
%
C
a %C.v % C P
Ref.
NO.
V.G.C.
rl
16
0.997
1.0754
0.57 + 3 . 0
0
- 3 . 0 $2.4 - 2 . 0
-0.4
(42)
18
0,943
1,0607
0.73 + 3 . 6 - 1 . 3 - 2 . 3 + 2 . 7 - 3 . 8 + l , l
(42)
20
1,0699
0.72 - 2 . 1 + 3 . 8 - 1 . 7 - 2 . 9 + 1 . 4 + 1 . 5
(42)
0,970
21
0.965
1.0693
0.67 - 2 . 3 + 0 . 9 t 1 . 4 - 3 . 1 - 1 . 4 1-4.5
(42)
1.0739
0.75
0
- 0 9 + 0 . 9 - 0 . 9 - 3 . 5 +4 4
23
0.982
(42)
24
0.973
1.0746
0.73 $ 2 . 5 - 3 . 6 $ 1 . 1 $ 1 . 6 - 6 . 1 + 4 . 5
(42)
25
0.980
1.0700
0 . 5 6 + 1 . 2 S i 6 - 8 . 8 +0.5 $ 5 . 7 - 6 . 2
(48)
26
1.011
1.0788
0 . 5 7 + 1 . 8 $ 5 . 3 - 7 . 1 $1.2 + 3 . 3 - 4 . 5
(42)
27
0.956
1.0642
0 . 7 7 - 3 . 2 $ 3 . 7 - 0 . 5 - 4 . 1 $1.0 + 3 . 1
(42)
11
0.936
1.0639
0.56 1 4 . 3 - 1 . 0 - 3 . 3 + 3 . 6 - 2 . 9 - 0 . 7
(42)
9
1.0631
0.62 + 3 . 0 + 2 . 5 - 5 . 5 $ 2 . 4 $ 0 . 3 - 2 . 7
0.927
(42)
14
1.0724
0.55
0
-0 5 - 0 . 5 - 0 . 7 - 1 . 3 + 2 0
0.982
(42)
1.0665
0.73 $ 3 . 8
0
-3.8 $2.9 -2.5 -0.:
10
0,936
(48)
0 70
33
0.831
1.0434
-1.5 +3 0 -1 5 -2.3 $0.6 + l . t
(34)
34
1.0670
0.79 i 3 . 0 - 3 0
0
+ I 5 -5.2
0.909
+3.7
(42)
35
0
- 1 . 0 +O.l -2.7
1,0560
0.77 7 1 . 0
0.929
S2.6
(49)
Std. dev. ( 0 . 5 to 0 . 8 % E)
2 0
3 1
3 R
2 4
3.2
3 2
Dev. of av.
+1.2 +1.1 - 2 3 f 0 . 3 -1.2 + 0 . 9
i o 9 1 4 G - 5 5 - 0 . 1 +1 8 - 1 7
19
1 0629
0.82
0 946
22
1 0709
1.08 -0 6 $ 1 5 - 2 . 1 - 0 . 6 -2 3 + 2 9
0 971
1 0816
0 . 9 2 - 1 . 0 - 3 0 t 4 0 -2 1 - 6 1 + 8 2
1011
36
1.01
0 892
1 0532
0
+ 4 3 - 4 3 - 1 . 2 +O 8 + o 4
1 . 0 3 -1 0 +4 5 - 3 . 5 -2 2 +o 9 + I 3
1
0735
13
0 970
1 0543
28
0 892
2.05
+ 1 . 0 +8 0 - 9 . 0 - 1 . 4 +O 9 $ 0 5
1 0498
29
0 870
1 . 6 7 $0 5 + 4 5 - 5 . 0 - 1 . 2 -1 5 +2 7
1 0468
30
0 854
1.35 + 0 . 5 +:3 0 - 3 5 - 1 . 1 -1 7 +2
31
1.12 - 1 0 + 3 5 - 2 5 - 2 3 - 0 4 +2 i
1
0452
0 844
32
1 0441
0.89 -1 0 + 3 0 - 2 0 - 2 0 -0 1 +2 1
0 837
37
1 0501
+1 5 +4 0 - 5 5 + 0 5 $1 0 -1 5
0 838
0.86
1 0505
38
0 866
1.50 + l . 5 + 5 n - 6 5
- 0 2 - 0 2 +o 4
39
0 871
1.62 + 4 0 +2 5
1 0544
+2.1 -3 1 + I 0
- n .i $0 1 $0 4
1.70 + l . 5 +8 0 - !
40
0 892
1 0515
1.50 + 0 . 5 +9 5 - 1 0 0 - i i + 4 3 - 3 1
41
0 8.59
1 0522
42
1.51 + 1 . 0 + 8 0 - 9 0 - 0 7 +2 8 - 2 1
1 0.534
0 863
1.73 + l . 5 +9 0 - 1 0 5 - 0 5 + 3 0 - 2 5
43
1 0550
0 871
Std. dev. ( 0 . 8 to 2.0% S )
1.4
5 -5
6.3
1.4
2 4
2 8
D e i . of av.
+O.B
+ 4 . G -5 2 - 0 . 9
0 0 +0.9
a Correction applied to % C.Yand % CP; % CA adjusted accordingly
-!.e
Table XI. Viscosity-Gravity Constant Corresponding to
Indicated Viscosity and Characterization Factor
VlSCO’.ltJ,
1000 E
Characterization Factor
12 5
12
11 5
11
10 5
10
KineSa.\niatir
bolt
Visrosity-Gravit> Constant
6
45 6 0 795 0 828 0 865 0 908 0 954 1 006
52 1 0 796 0 830 0 869 0 910 0 958 1 013
8
58 9 0 797 0 832 0 872 0 914 0 962 1 019
10
97 8 0 799 0 836 0 879 0 924 0 973 1 0 3 5
20
232
0 801 0 842 0 886 0 937 0 991 1 0 5 3
50
100
463
0 802 0 845 0 890 0 942 1 001 1 067
200
927
0 803 0 846 0 894 0 948 1 011
500
3317
0 804 0 848 0 898 0 953 1 023
1000
4635
0 805 0 849 0 901 0 957 1 0 3 0
2100 r
_____
5
10
20
50
100
12 7
59 3
98 5
234
467
0 796
0 803
0 806
n 809
0 811
0 837 0 884 0 938 0 995
0 844 0 892 0 947 1 005
0 849 0 898 0 954 1 015
o 854 o 904 o 960 1 021
0 856 0 906 0 963 1 0 2 3
1
082
1 073
1 080
1 086
1 087
aromatic carbon conteiit and increase in paraffinic and naphthenic carbon content up to the last stage of extraction. In the
last stage of extraction, aromatic carbon content changes
little and naphthenic carbon decreases as paraffinic carbon
increases.
The oil for which data are presented in Line 2 contained 2.05%
sulfur before eutraction. The composition of this oil as read
from the graph is 26% ‘2.4, 32% CY,and 42% Cp. After applying
the sulfur corrections, the composition is 24% C A , 25% C.V,
and 51% C P . Van S e s and van Westen give 25% C A ,24% C r ,
and 51% C p . Line 3 shows the composition data corrected
for the effect of sulfur These data confirm both the usefulness
of the plot of the raw data to show trends, and the validity of
the sulfur correction.
ACKNOWLEDGMENT
The authors JS ish to acknoa ledge the assistance and helpful
discussion of C. C. Martin, J. C. S. Wood, and J. W. Loveland.
LTTER.4TURE CITED
(1) American Petroleum Institute, Research Project 6, Carnegie
Institute of Technology, Pittsburgh, Pa.
(2) Ibid., Research Project 42, Pennsylvania State University,
University Park, Pa.
(3) Ihid.,Research Project 44, Carnegie Institute of Technology,
Pittsburgh, Pa.
(4) Beverly, J. B., Marschner, R. T., Preprints, Petroleum Division
ACS, iipril 1955.
( 5 ) Boelhouwer, C., Watermarl, H. I., J . In& Petroleum 40, 116
(1954).
(6) Bondi. A . , “Physical Chemistry of Lubricating Oils,” Reinhold,
Sew York, 1951.
(7) Charlet, E. bI.,Laniieau, K. P.. Johnson, F. B., ANAL CHEM.
26, 861 (1954).
( 8 ) Clark, R. J.. Hood, .\.. O’Keal, LI. J., Jr., Ibid., 27, 868 (1955).
(9) Dudenbostel, B. F., Jr.. Priestley, William, Jr., “Chemistry of
Petroleum Hydrocarbons,” Vol. 1, Chap. 12, Brooks, B. T.,
others, eds.. Reinhold. Nem- York, 1954.
(10) Fenske, 11. R.,Carnahan, F. L., Breston, J. N., Caser. A . H.,
Rescorla. A . R., Ind. E ~ L Q
Chem.
.
34, 63846 (1942).
(11) Hazelwood. I?. S’.,ANAL.CHEM.26, 1072 (1954).
(12) Hill, J. B., Coats. H. B., I n d . Eng. Chem. 20, 6 4 1 4 (1928).
(13) Hill, J. B., Ferris, S.W., Ibid., 17, 1250 (1925).
(14) Kurtr. S. S., Jr., “Chemistry of Petroleum Hydrocarbons,” 5-01.
1, Chap. 11, Brooks, B. T., others, eds., Reinhold, New York,
1954.
(15) Kurtr, S. S., Jr., Headington, C. E., IND.ENG. CHEM.,-4x.4~.
ED. 9, 21 (1937).
(16) Kurtr, S. S.,Jr., Martin, C. C., India Rubber World 126, 495
(1952).
ANALYTICAL CHEMJSTRY
1936
Kurta, S. S., Jr., Sankin, d.,“Physical Chemistry of Hydrocarbons,” 1-01. 11, Chap. 1 , Farkas, d.,ed., Academic Press,
Sew York, 1953.
Kurtz, S. S., Jr., Xard, d.L., J . Franklin I71St. 222, 563 (1936).
(33) Ibid., p. 370.
(34) Ibid., p. 429.
(35) O’Seill, J., “Applied
Ibid., 224, 583, 697 (1937).
Leendertse, J. J., in “Aspects of the Constitution of 11ineral
Oils.” a. 368. Elsevier. Kew York. 1951.
Lillard, i.G., Jones, W,C.,
Jr., Anderson, J. A , , Jr., I n d . Eng.
Chern. 44, 2623 (1952).
Lipkin, RI. R., Hoffecker, 11‘. A., Martin, C. C.,Ledley, R. E.,
. h A L . CHEM. 20, 130 (1948).
Lipkin, AI. R., Martin, C. C., Worthing, R. C., Third World
Petroleum Congress, Section VI, 1951; E. J. Brill, Leiden,
Rossini, F. D., Mair, B. J., Streiff, A . J., “Hydrocarbons from
Petroleum.“ Reinhold, New York, 1954.
(37) Ibid., Chap. 22.
(38) Rossini, others, “Tables of Physical and Thermodynamic Properties,” API 4 4 , Carnegie Press, Pittsburgh, Pa.
(39) Schiessler, R. W., Rytina, C.H., Weisel, Fischl, F., JIcLaughlin.
R. L., Keuhner, H. H., Proc. Am. Petroleum Inst., 26, 111,
Holland, 1951.
Lipkin, l f . R., Sankin, A, Martin, C.C., ANAL. CHEM.20, 598
(40) Schiessler, R . W.,
Whitmore, F. C., I n d . Eng. Chem. 47, 1660
(1948).
AIair, B. J., Schicktane, 8. T., I n d . Eng. Chem. 28, 1446-51
(1936).
Martin, C. C., Sankin, A , , A~NAL.
CHEV.25, 206 (1953).
llikeska. L. -4.,
I n d . Eng. Chem. 128, 978-84 (1936).
Mills, I. IT.,Hirschler, A. E., Kurte, S.S., Ibid , 3 8 , 442 (1946).
hliron, S., ANAL.CHEW27, 1947 (1955).
Xes, K. van, “Chemistry of Petroleum Hydrocarbons,” Vol. 1 ,
Chap. 16, Brooks, B. T., others, eds., Reinhold, New York,
1954.
Kea, K. van, Westen, H. A . van, “..lspects of the Constitution of
Mineral Oils,“ Elsevier. K e n . York. 1951.
(32) Ibid., p. 200.
Mass Spectrometry,” pp. 27-46, Report
Conference. published by Institute of Petroleum, London,
1954.
(36)
254 (1946).
(1955).
Smith, Edwin E., Engineering Experiment Station, Bull. 152.
Ohio State University, Columbus, Ohio, May, 1953.
(42) Sun Oil Co., unpublished data.
J., in “Aspects of the Constitution of Mineral Oils.”
pp. 250, 317, 318, Elsevier, Ken. York, 1951.
(44) Waterman, H. J., Brennstof Chemie 36, 169 (1955).
(41)
(45) Ibid., p . 199.
(46) Katson, K. AI.,
“Science of Petroleum,” Vol. 2, p. 1377, Dunstan, et al., Oxford University Press, London, 1938.
(47) Watson, K. lI.,Selson, E. F., I n d . Eng. Chem. 29, 880-7 (1933).
(48) Weinstock, K. V., Storey, E. B., Sweely, J. S., Ibid., 45, 1036
(1953).
R E C E I T - Efor
D review N a y 8 , 1956. Accepted September 14, 1S5B.
Composition of Lubricating Oil
Use of Newer Separation and Spectroscopic Methods
F. W. MELPOLDER, R. A. BROWN, T. A. WASHALL, WILLIAM DOHERTY, and C . E. HEADINGTON
The Atlantic Refining Co., Philadelphia, Pa.
A study was made of the composition and physical
properties of fractions separated from a solvent-refined
oil heart cut. The oil charge was fractionated by means
of 20-stage molecular distillation, silica gel chromatography, and liquid thermal diffusion to yield saturated
fractions ranging from predominantly isoparaffins to
multiring cycloparaffins. Hydrocarbon-type analyses
were determined by mass and ultraviolet spectrometr?
and several molecular structures were postulated from
mass and infrared data. One fraction which exhibited
extreme ph) sical properties w-as found to contain from
four to ten rings per molecule.
THE
present-day trend in the refining of petroleum products
and the development of new and more ponerful analytical
techniques have promoted a growing interest in the composition
of heavy petroleum product-. Detailed information concerning
the molecular structure of hydracarbon types is needed because
of the many factors related to performance and stabilitj- characteristics of lubricants.
A long-range approach to the problem has been extensivelj
investigated during the past t v o decades by API Project 6
(14). This work has been directed toward a separation of oil
according to hydrocarbon types, and measurements of numerous
physical properties of the fractions. Additional data for a group
of “homogeneous” fractions were recently reported for a cooperative spectroscopic study ( 9 ) . Further progress in this field has
been dependent on the development of more efficient separation
techniques, extension of spectroscopic methods of analysis, and
the synthesis of representative hydrocarbons as standards to
guide the interpretation of spectra. Despite the lack of such
standards, O’Keal (IS)and Lumpkin and Johnson (8) were able
t o postulate the structure of many aromatic h j drocarbons and
sulfur compounds in gas oil. 3Ielpolder and coworkers were also
able to make a mass spectrometric analysis of thermal diffusion
fractions separated from a light lubricating oil ( I O ) .
I n viex of the significant new developments which have been
made in the past fen- years in both separations and spectroscopic
methods, the authors have undertaken a thorough study of the
composition of a heart cut lubricating oil fraction. Working on
the saturated portion only, many fractions were separated from
the oil, in which specific hydrocarbon types of a narrow molecular
Jveight range were concentrated. Physical properties and spectrometric anal>-sesof the fractions were determined, and an effort
was made to determine molecular structures from the interpretation of niass ppectrometric data.
LUBRICATIYG OIL STOCK
The oil charge used in this work \vas a solvent-refined lubricating oil in the SAE-20-30 grade viscosity range. The oil was obtained from a mixed crude source as a pipe still distillate, solventextracted n-ith nitrobenzene, dewaxed n-ith methyl ethyl ketone,
and filtered through clay. Inspections of the oil are shown in
Table I
SEPARATION PROCEDURES
T h e lubricating oil charge stock n-as separated by means of
distillation, adsorption, and liquid thermal diffusion to yield 43
fractions containing concentrates of paraffin and cycloparaffin
hydrocarbons. The procedures are summarized in the block
diagram shown in Figure 1.
Starting with 5.5 liters of oil, having a molecular weight range
of from CIB to Cso, a series of distillations was made in a 20-stage
molecular still (11) a t 1-micron pressure. A total of 14 separate
equilibrium-type distillation runs and one batch distillation run
was required t o process the oil. The boiling range of the resulting