Determination of Aromatic and Naphthene Rings in Aromatics from Petroleum Fractions C. C. MARTIN AND ALBERT SANKIN Sun Oil Co., Norwood, Pa. and 210” F., or from density and mid-boiling point. Average deviations of about 0.1 of an aromatic ring and about 0.2 of a naphthene ring are shown for aromatics from a number of petroleum fractions and for individual aromatics with benzene, naphthalene, or phenanthrene nuclei. Compounds which interfere with the analysis are generally absent or are present in minor amounts in arc% matic concentrates from petroleum. The new method is more rapid than any previous method of comparable accuracy that has been used for determining the average composition of high-boiling aromatics from petroleum.
Know-ledge of the aromatic hydrocarbons in petroleum is useful in comparing various fractions or different processing methods. Previously published methods for analyzing the aromatics from high boiling petroleum fractions are either inaccurate or too time-consuming for routine use. A graph is presented in this paper for the calculation of average number of aromatic rings and number of naphthene (cycloparaffin) rings per molecule in aromatics concentrated from straight-run or cracked petroleum fractions. The required properties are density, specific dispersion, and molecular weight. 3folecular weight may be derived from viscosities at 100’
S
TUDY of the aromatic hydrocarbons in petroleum fractions is usually facilitated by their separation from other hydrocarbons, for which solvent extraction and adsorption methods have been used. Silica gel adsorption has been found to be particularly effective in the quantitative separation of aromatics from saturates and nonaromatic olefins. Methods have been published for silica gel separation of gasolines and light gas oils (3, 8, 19) and of heavy gas oils and lubricating oils ( 1 4 , 19, 31 ). Low boiling aromatics in petroleum can be analyzed by physical separation of individual compounds (20) or by spectroscopic ”determination of individual isomers ( 5 , 24, 28, 3 2 ) . A highquality distillation can yield fractions containing sufficiently few components for spectroscopic analysis as long as molecular weight is low. .4s molecular weight increases, however, a limit is reached beyond which the large number of possible isomers makes individual compond analysis impractical. There are 51 possible isomeric Cll alkylbenzenes (10) and 32 CI3alkl-lnaphthalenes; natural fractions which might contain these compounds are usually considered too complex for detailed study. Lubricating oil, with millions of possible isomers, poses problems many times more difficult. High boiling petroleum fractions can be analyzed in terms of groups of hydrocarbons which are similar in some respect. h o matic hydrocarbons can be conveniently grouped according to “aromatic type,” a term used in this paper to describe compounds having the same number and grouping of aromatic rings. Naphthene rings and alkyl chains are not considered in discussion of aromatic type. Each of the following is said to contain a ben-
ing are “conjugated dibenzenes”:
.
I I 1 1.
(o&\
cenes” include those three-aromatic ring compounds containing phenanthrene
and anthracene
\
u/ I
nuclei. IVhen tlio or more nuclei are in the same molecule and are neither fused nor coniumted with one another. they are ” termed
“isolated.”
A/ q-’-? /‘I lq ’ V WdQ
Thus.
1
/
and
are “isolated dibenzenes.” Aromatic olefins are not included in these classifications. They are discussed elsewhere (18). Qualitative identifications of aromatic types in petroleum have been made by the use of physical properties such as ultraviolet spectra (1, 4, SI) and refractive dispersion (18). The various aromatic types in high boiling aromatic concentrates have been quantitatively determined by carrying out exhaustive fractionations and studying the fractions ( 4 , 20). Exhaustive fractionation is too time-consuming and expensive to be used in routine analysis. For many purposes, it is sufficient to get a quantitative description of an aromatic concentrate in terms of its average composition. Elemental analyses, before and after complete hydrogenation, have been used to get such information (21, 29). This is still not a satisfactory routine method, even though a more rapid hydrogenation procedure has been developed (17). Physical property correlations using molecular weight and either density or refractive index (11, 15) have been used to d e termine the average number of aromatic rings per molecule in mixtures of alkyl aromatics. For both methods, i t was shown that erroneous results would be obtained for aromatic naphthenes. Practically all of the aromatic molecules in the lubricating oil
zene nucleus and is classed as a “benzene”:
and
The aromatic types “phenanthrenes” and “anthra-
If two aromatic rings are fused together to
”
the compound is called a “naphthalene.” If two benzene rings are joined by a carbon-carbon bond with no intervening atoms, they constitute a “conjugated dibenzene” nucleus. The follow-
206
V O L U M E 25, NO. 2, F E B R U A R Y 1 9 5 3
207
portion of Ponca, Okla., crude. have been found to contain naphthene rings ( 2 0 ) . I t is the authors' experience that this is true for all high boiling straight-run fractions, so the methods derived for alkyl aromatics are probably not applicable to heavy gas oil or lubricating oil. The purpose of this paper is to present a rapid method for the determination of both number of aromatic rings and number of naphthene rings per molecule in an aromatic concentrate from petroleum. These values are determined from density, specific dispersion, and molecular aeight of the aromatic concentrate. As molecular weight can be estimated from density and mid-boiling point ( 2 3 ) ,or from viscosities a t 100' and 210" F. (IZ),the entire analysis requires only the determination of physical properties of the aromatic concentrate. This method is based upon a combination of tn-o previously published physical property correlations developed in this laboratory: the method for determining average number of aromatic rings per molecule in a mixture of alkyl aromatics, using density and molecular weight ( 1 5 ) ; and double bond index ( 1 8 ) ,which relates specific dispersion t o aromatic type and molecular n eight. These tMo correlations !$ere combined in the light of the conclusions discussed below as to the predominant aromatic types in petroleum. The dnierican Petroleum Institute Research Project 6 concluded from its comprehensive study of data for Ponca, Okla., crude that, in this oil, the compounds containing two aromatic rings per molecule are predominantly naphthalenes, and that when three aromatic rings are present they are also fused together ( 9 0 ) . Double bond index confirmed the predominance of naphthalenes and phowed that the compounds with three aromatic rings are phenanthrenes rather than anthracenes (18). Studies of manv high boiling fractions using ultraviolet spectroscopy (1, 4 , 25) and double bond index have consistently demonstrated the predominance of naphthalenes and phenanthrenes over other compounds containing two and three aromatic rings per molecule. Isolated polybenzene~are difficult to distinguish in the ultra-
violet spectra of complex mixtures, but conjugated dibenzenes and anthracenes can be recognized. Double bond index, on the other hand, is somewhat insensitive to the presence of conjugated dibenzenes in a fraction containing naphthalenes, but can detect anthracenes and isolated polybenzenes. The authors believe that the two approaches considered together constitute fairly definite proof of the predominance of benzenes, naphthalenes, and phenanthrenes over all other aromatics in petroleum having less than four aromatic rings per molecule. Small quantities of conjugated dibenaenes have been indicated in some petroleum fractions ( I ) , and small quantities of anthracenes in some cracked products (6, 31). These quantities are too small, in general, to affect a method based upon density and specific dispersion. They were indicated by methods which are sensitive to traces. In the four-aromatic-ring range, very little is known a t present. Pyrenes have been identified in petroleum by ultraviolet spectra, and chrysenes, benzphenanthrenes, and benzanthracene have been indicated as possibilities (4,6, 25, 31). Kaphthacenes have distinctive spectral characteristics which have not been found in petroleum spectra. DERIVATIOY OF NEW METHOD
The new analytical method has been developed on the basis of data for individual hydrocarbons and for petroleum fractions. Two functions were derived to represent the significant portions of two previous correlations. (The detailed derivation of thepe functions is presented a t the end of the paper.) Values of these functions were correlated with the structures of the pertinent individual hydrocarbons for which sufficient literature data were available. The available data on petroleum fractions u ere then included to obtain the final analytical method. From double bond index (18) a function \\-as derived:
F ( ~ , J I )= (6
I
O L l G H T CRACKED GAS OIL
0 WEBSTER aLlGHT
A
0
CRUDE
EXTRACT
9.
FRACTIONS
/' 0'
/
/
I
I
1
2.0
1.0
AROMATIC
RINGS
I
I
I
3.0
FROM E L E M E N T A L ANALYSES
Figure 1. Determination of Average Number of Substituents in Petroleum Fractions
(1)
(7)lo4, and JI
is molecular weight.
The value of the
function depends primarily upon aromatic type but is also influenced to a minor extent by the number of substituents on the aromatic nucleus. A substituent is defined as a nonaromatic carbon which is substituted for the hydrogen in an aromatic
>-H.
LUBE OILS
10-3
where 6 is specific dispersion for the F and C lines of hjdrogen, X
I
- 98)(~1+ 12) x
Two compounds of the same aromatic type and number of substituents have the same value of F ( s , M ) , even if they differ in molecular weight. h study of the 69 benzenes and 14 naphthalenes for which specific dispersion data are available in the literature ( 8 , 7 , 9 ) shows that each substituent causes a regular increase in F ( 6 , M ) and that the increase per substituent is larger for naphthalenes than for benzenes. A substituent has the same effect upon F ( 8 , M ) whether i t is part of an alkyl chain or a naphthene ring-for example, tetralin has the same F ( 6 , M ) as does a dialkyl benzene because in each case there are two substituents on the aromatic ring. Alkyl chains and naphthene rings count as substituents only if thcxy are directly attached to the aromatic nucleus. Data for aromatic fractions from petroleum were plotted on Figure 1 in an attempt to ascertain the average number of substituents in petroleum aromatics. The solid lines connect the points representing mono-, tri-, and penta-substituted benzenes and naphthalenes as determined from data for individual compounds. The symbols on this graph represent aromatic concentrates for which numbers of aromatic rings have been calculated from elemental analyses before and after complete hydrogenation. The Ponca, Okla., crude data have been published (21); the other fractions have been studied in this laboratory (see below). The points between one and two aromatic rings scatter fairly evenly about the line representing three substituents, and
a
the authors believe that an average of three substituents per molecule is reasonable for the benzenes and naphthalenes in petroleum. There is no assurance that the extrapolation of the line for trisubstituted benzenes and naphthalenes represents trisubstituted phenanthrenes. The
- 0.854)(M + 12)
g d
m
6o
3 /L/- -/+-/
-
nS0 nS" d:o
x
/
/
/'
-
- -/L - -/ /
-
/
/
a' m
-
0 40-
Li
-W
-
-
3 20;
-
-
:o
I
-
n8O) with
104
If F-C specific dispersion cannot be determined directly, F-C refractive dispersion may be calculated from refractive
I
RINGS
LO
I
I
60
+O
-
5
4 N!4P)THENE:
0
1. Concentrate the aromatics using silica gel (3,8, 14) or anv other means capable of retaining- no more than 5 % of nonar6matics. 2. Calculate molecular weight from two viscosities ( l a ) , boiling point and density ( W ) , or any other method capable of an accuracy of *5%. 3. Determine density at 20" C. with an accuracy of *1 X
=
I
/
/
,/
AROMATIC
PRESENTATION OF METHOD
bFC
I
/
"
-
This method, which is intended for the study of aromatic concentrates from straight-run or cracked petroleum fractions, is as follows:
(n$O
I
I
I
-
thene rings. I t can be used in conjunction Figure 2. with F ( 6 , M ) to estimate number of naphtheiie rings, However, in addition to number of rings and number of substituents, F(d,M) varies with the bize of naphthene rings (cyclopentane or cyclohexane) and length, position, and degree of branching of alkyl chains. The determination of naphthene rings will be less reliable than the determination of aromatic rings, but in petroleum fractions where an averaging of isomer effects can be expected, it should be sufficiently accurate for most purposes. Values of F(d,M) were calculated for 51 alkyl benzenes, 15 benzenes mith one naphthene ring, 2 benzenes with two naphthene rings, 1 benzene with three naphthene rings, 12 alkylnaphthaIenes, 2 naphthalenes with one naphthene ring, and 1 alkylphenanthrene (2, 7 , 9 ) , and the 29 petroleum fractions used in Figure 1. Number of naphthene rings v a s calculated from elemental analyses before and after hydrogenation for the petroleurn fractions, From these data were calculated average values of F(d,ilI) for the alkyl aromatics and the average increment in F(d,hI) per naphthene ring. The& values were used in establishing the positions of the lines for constant numbers of naphthene rings in Figure 2. I n view of the lack of data in the three-aromatic-ring range, analysis of a fraction having more than 2 . 5 aromatic rings per molecule is less certain than in the range of 1.0 to 2.5 aromatic rings, If a fraction shows much more than 3.0 aromatic rings per molecule by this correlation, the calculated analysis should be used only for purposes of comparison and should not be interpreted literally.
4. Determine F-C refractive dispersion an accuracy of =k2 X lo-'. 5. Calculate specific dispersion:
I
I
(2)
__
1
I
+
in which d is density a t 20" C. and AI is molec-
1n -3. .
I
E ! -
extrapolated line, however, appears to represent the few fractions which contain appreciable quantities of phenanthrenes. This relationship between F ( 6,114) and number of aromatic rings was used in establishing the positions of the horizontal lines in Figure 2. From the method for determining average number of aromatic rings per molecule in alkyl aromatics (15), the following function was derived: F(d,M) = (d
I
8(x
X
I
1 100
1
80
Graph for Analysis of Petroleum Aromatic Fractions
indices for any two wave lengths of light (26) or F-C specific dispersion can be calculated from refractive index for the sodium D line, density, and molecular weight (16).
6.
Calculate:
F(~,M= ) (6
- ~ S ) ( J I + 12) x
10-3
(1)
and
+
F(d,M) = (d - 0.864)(M 12) (2) 7 . Read number of aromatic rings, RA, and number of naphthene rings, R Y , from Figure 2. The data for construction of this graph are presented in Table I. As an alternative method, the following equations give results identical with those obtained from the graph:
+ 0.55
(3)
+ 0.64 - 0.0?3F(6,M)
(4)
RA = 0.042F(6,-11)
If 1.00
RA G 2.00: RV = 0.073F(d,Jf)
If 2.00 G R a
< 3.00:
R.v = 0.073F(dIM)
+
-
0.95 0.082F(6,M) (5) of RA and R.v calculated from Equations 3 and 5 may be used for comparing samples, but they should not be interpreted literally.
If Rx
> 3.00, values
TESTING OF METHOD ON INDIVIDUAL HYDROCARBOh S
Table I1 shows the accuracy of the method described in the previous section when it is applied to the individual hydrocarbons for which sufficient literature data are available. In using this method, the number of aromatic rings is determined most ac-
Table I. RA
2
3
Data Needed for Construction of Figure 2 R.Y F(6,W F (d,M )
0 1 2 3 4
34.6
0 1 2 3
58.4
25.8
39.5 53.2 66.9 80.6 52.6 66.3 80.0 93.7
V O L U M E 25, NO. 2, F E B R U A R Y 1 9 5 3 Table 11.
Type of Aromatic Benzenes
Substituents on Aromatic Nucleus 0
KO.of
Naph- KO. of thene ComRings pounds
Carbons per Molecule 6
209
.4ccuracy of Method for Individual Aromatics
Av. dev.a
Aroinrttic Rings Equation Taking No. of Substituents into .4ccount Av. Dev. of Max. dev. av. dev.
Naphthene Rings b y .4v. Method Dev. of ,Max. dev. av. dev.
Av. Method ,Max. Dev. of av. dev.
4v.
0.10 0.07 0.06
-0.10 -0.07 - 0 06
-0.10 -0.08 -0.06
0.02 0.02 0.00
-0.02 -0.02 0.00
-0.02 -0.03 0.00
0.19 0.04 0.03
so.19
11
4-0.04 +0.03
+O. 13
18 4 1
8-12 9-13 18
0.03 0.06 0.08
-0.08 +0.01 +0.08
-0.04 + O . 15 +0.08
0.00 0.06 0.12
0.00 +0.04 +o. 12
fO.01 +o. 19 +o. 12
0.07 0. 13 1.59
+0.04
+ O . 19
-1.59
f0.28 -1.59
0 1
9 6
9-10 11-28
0.01 0.02
-0.01 +0.01
-0.02 -0.03
0.01 0.02
-0.01 f0.01
-0.02 +0.03
0.13 0 17
+o.
12 fO.05
+o. 28 +0.32
4 4 4
0 1 2
3
10 12-17 14
0.02 0.04
+0.02 +0.04 +0.03
f0.02 fO.05 + O . 08
0.02 0.00 0.03
-0.02 0.00 f0.02
-0.02
+O.Ol +0.05
0.26 0 06 0.18
+0.26
0.05
4-0.04 + O . 18
4-0.37 +o. 10 +0.30
J
1
1
6
1
1 -
19 21
0 . os 0.14
+0.08 + O . 14
+ o , 08 + O . 14
0.04
0.02
f0.02 f0.04
+0.02 +0.04
0.00 0 10
0.00 i-0.10
+O. 10
0 1 2 2
0 0 0
3
0
0 0
1 20
1
1
2
0 1 3
3 3
1 1
2 2
2 2
All henzenes S a p h-
thalenes
19
1-0.03
0.00
6-28
0.04
-0
to.15
0.02
0.00
fO.19
0 12
+0.05
-1.59
1
0.28 0.16 0.10 0.12
-0.28 -0.16 -0.10 -0.12
-0.28 -0.20 -0.11 -0.15
0.00 0.04 0.01 0.03
0.00 +0.02 0.00 -0.03
0.00 +0.06 -0.02 -0.06
0.35 0.20 0 22 0.30
+0.35
+0.20 +0.22
f0.35 +0.33
2
10 11-12 12-14 12-14
+0.26
1
15
0.01
-0.01
-0.01
0.01
-0.01
-0.01
0.10
+o.
+o.
10-15
0.13
-0
13
-0
*o.ofi
0.23
+0.23
+0.41
-0
11
-0.11
0 30
f0.30
+0.30
-
A l l nalhthalenes
f0.07
+o.
69 4 6
1
7-22
14
l’henantlirene 1 0 1 16 0.11 ‘ I Averane of all deviations without regard to sign. Average of all deriations taking sign into account.
02
28
0.02
0.00
f0.30
10
+0.41
10
‘
~
curatel? on the trisubstituted benzenes and trisubstituted naphthalenes. In compounds with fewer substituents the deviations are negative, and in those with more substituents the deviations are positive. The effect of a substituent is about 0.03 of an aromatic ring for benzenes and 0.09 for naphthalenes. Deviations are no greater than 0.1 ring for any benzene nor for naphthalenes having from two to four substituents. On the one phenanthrene, the deviation is about 0.1 aromatic ring. The following equation takes number of substituent. into account for tienzenes and naphthalene\: RA
O.O528(6,M) = 1 0.08s
+
+ 0.55
where S is the number of substituents. When the number of aromatic rings is recalculated on these compounds, making use of Equation 6, most of the deviations (also shown in Table 11) are so small that they may reflect only the experimental uncertainty in specific dispersion measurements. The average deviation for both benzenes and naphthalenes is only 0.02 ring. This means that, as far as can be ascertained from data available a t present, the only important source of error in the determination of aromatic rings in benzene-naphthalene mixtures is the uncertainty of the average number of substituents in an unknown sample. I n a specific case where the average nuniber of substituents is known, Equation 6 should give very accurate results. The last group of columns in Table 11 s h o w the accuracj- of the calculation of the number of naphthene rings. The deviations are somewhat larger than for the aroniatic rings, but there is no apparcnt trend with number of substituents or number of naphthene rings. The average deviation for the benzenes is about 0.1 ring and for the naphthalenes about 0.2 ring. For the one phenanthrene the deviation is 0.3 ring. There are not enough aromatic naphthenes, on which specific dispersion data are availrtble, to give a really adequate test of the R.V determination. Rings per molecule and F ( 6 J f ) are both additive on a molar hasis. Therefore, the data for a mixture will fit the correlation between aromatic rings per molecule and F ( 6 , M ) if the data for each of the components fit. F ( d , U ) is not additive on any siniple basis, hut for most samples the net effect upon the accuracy
of naphthene ring determination would probably not be noticed in view of the other uncertainties in the determination of naphthene rings. TESTING OF METHOD ON PETROLEUM FRACTIONS
The only petroleum aromatic concentrates on which sufficient published data are available to provide a test of the method are the solvent extracts prepared by American Petroleum Institute Research Project 6 in its thorough study of Ponca, Okla., crude ( 2 1 ) . Additional data are included in the present paper on a variety of petroleum aromatic concentrates separated by silica gel adsorption (14). Table I11 summarizes comparisons of the new correlation 11-ith other methods of calculating average analyses for all these aromatic concentrates. Table IV shows the detailed c\perimental data on the fractions studied in this laboratory. Equations used for the comparison calculations are listed i n Table V. Xumber of aromatic rings and nuniber of naphthene rings per niolecule can be calculated on aroniatic concentrates from petroleum, using elemental analyses before and after complete hydrogenation, if some assumptions are made (Equations lr-1and V-2, Table V). As discussed below, this calculation is probably independent of the F(&M)-F(d,Jf) correlation, so that agreement betneen the analyses by the two methods is significant. The average differences are 0.1 aromatic ring and 0.2 naphthene ring for the 29 fractions for which such data are available. From elemental analyses on the unhydrogenated samples alone, the quantity ( ~ R A R N ) can be calculated (Equation V-3) The average difference in values of (3R.4 R x ) , calculated from elemental analysis and from the new aromatic anal? sie graph, is 0.2 for 76 fractions. These fractions include the 29 for which RA and R,v have been calculated separately. Since hydrogenation converts aromatic rings into naphthene rings, the Vlugter, Waterman, and Van Westen ( 3 0 ) naphthcne ring method (Equation V-4) can be used to calculate total number of rings from specific refraction after complete hydrogenation. The average difference in ( R A R v ) is 0.15 for 31 fraction-. The determined differences in (3RA R v ) and ( R A RN) are smaller than those predicted from thc differences in RA and R y by the theory of errors ( 2 2 ) . This demonstrates that the
+
+
+
+
+
210
ANALYTICAL CHEMISTRY Table 111. Testing of Method for Aromatic Concentrates from Petroleum Comp. with Compn. Calcd. Comparison with Composition Calcd. from Elemental Analyses from Spec. Refraction Before and after Complete Hydrogenation Unhydrog. Samples, of Hydrog. Samples, Differences in Rda Differences in RN" Differences (3RA RN)" Differences (RA RN)= Eo. of No. of s o . of s o . of frac- A v . Diff. Max. frac- A v . Diff. Max. frac- A v . Diff. Max. frac- .4v. Diff. Max tions diff. of ax-. diff. tions diff. of av. diff. tions diff. of av. diff. tions cliff. of av. diff.'
+
+
Source of Aromatic Concentrate Ponca, Okls., crude Dist. key fractions Series -4 extracts Series B extracts Series C extracts Beries D extracts Series E extract,s Light cracked gas oil Fractions from Webster crude Light lube oils hliscellaneous distillate fractions Extract fractions Raffinate fractions Acid treated oils All
References (81)
(srj
01)
(21) (31)
(22)
(21)
o
0 3 8 0
1
. . . . . .
a
0 3
-'o.'27 +0.08
0 07
-0.07
-0.07
...
8 0 1
. . . . . .
Table I T
4
0.11
-0
6
0.11 0.16
-0.06 -0.16
Table I V TableIV
0 3
Table I T Table IF'
0 29
.
-0'14 +0.02
TableIV Table I T
4
,
0.'1'4 0.03
.,. 0.18
,
10
..
-0.18
. . . . . . . . . . . . 0.11
-0.08
......
...
5
o.'i9 0 22
+'O.'IQ -0.19
+'d.'40 -0.36
io
0.29
+'0.'29
f'0.29
D
15 4
4
0.21 0 21 0.21 0 1: 0.22 0.23
-0.20 -0 21 - 0 20 -0 13 -0 21 -0.19
-0.35 -0 38 -0.41 -0.36 -0.41 -0.40
+
+-
3 8 0 1
. . . . . .
,..
0.'30 +'o.'30 0 . 1 0 +0.05
+'o.'38 +0.40
+'0.'64
+'0'64
0 64
-0 24
4
0.14
i-0 02
+0.27
4
0.28
-0.28
-0.45
4
0.14
+0.14
+0.16
-0.24 -0.24
6 4
0.13 0.22
SO.11 +0.22
+0.36 10.39
6 4
0.20 0.26
-0
06 26
+O
36 -0.45
6
fO.11 fO.14
f0.28
4
0 12 0.14
...
0 3
...
2 10
0.30 0.18
+O
30 +0.05
+O
-16 +0.37
2
0.08
+O
+O.lO
3
0.09
08 +O 09
2
0.48
-0.48 -0.23
-0.49 -0.61 -0 61
0 0
-0.24
...
...
-0.27
0 0
-29
...... 0.42
+0.42
. . . . . . . . . . . . 0.21
+0.53 ,
..
...
f0.08 + O 53
4
76
0.29 0.22
-0
-0.13
Calculated from differences in RA and RN b y theory of errors (22) 0 3Yb -0.16' Values calculated from F(8,Mj and F(d,.M)by Equations 3, 4 , and 5 minus values calculated by equations in Table V. 0 . 3 9 = d ( 3 X 0.11j2 (0.21j27 e -0.16 = 3 X (-0.08) 0.08 d 0 . 2 4 = .\/(0.11)2 (0.21)2. 0.00 =z - 0 . 0 8 0.08.
'
0 0
31
... 0.15 0 24d
f0.27
+D
13
.. ..
, .
+0.13
f0.64
0 O0e
++
differences for samples which have either been hydrogenated or subjected to elemental analysis agree, in general, with the differences for samples on which the complete data have been obtained. The first three equations listed in Table V, all of which require carbon-hydrogen data, are exact for mixtures of benzenes, naphthalenes, phenanthrenes, and anthracenes. However, when other types of hydrocarbons are present, the calculations from physical properties and elemental analyses are affected in opposite directions. For example, anisolateddibenzene has 2 aromatic rings, but would be calculated to have 2'/2 aromatic rings from elemental analyses and about 11/2 aromatic rings from F( 6,M). Therefore, the presence of significant quantities of such compounds would result in poor agreement between the aromatic analysis graph and the elemental analysis calculation. The presence of nonhydrocarbon compounds undoubtedly affects the calculation of average compositions from elemental analyses before and after hydrogenation, as well as from the new graph. Until more is known about the structure and behavior during hydrogenation of the nonhydrocarbon molecules in high boiling petroleum, neither the direction nor magnitude of nonhydrocarbon effects can be predicted. With the possible exception of nonhydrocarbon effects, elemental analysis and physical 6o property methods are independent of one another. The fact that nearly the same agreement a, was obtained on petroleum fractions as with individual hydrocarbon data is very encouraging. Figure 3 shows the extent of variation in average compositions of the fractions now available for testing the new method. All the petroleum fraction data summarized in Table I11 have been plotted on the aromatic analysis graph. There are insufficient data for aromatic fractions with no naphthene rings, one naphthene ring, and three or more aromatic rings. The individual compound data fill in the gaps for alkyl 0 aromatics and aromatics n ith one naphthene ring, but more data are needed for aromatic Figure 3. concentrates with three or more aromatic rings.
These petroleum fraction data illustrate the predominance of aromatic naphthenes in petroleum. There are only six fractions which average less than one naphthene ring per molecule. Four of these aromatic concentrates are from catalytic cracked fractions and, therefore, contain little, if any, naphthene ring. The other two are light gas oil fractions in which alkylbenzenes still predominate. The previous methods derived for alkyl aromatics are inaccurate for high boiling aromatic concentrates, because of the naphthene rings in such fractions. The average difference between number of aromatic rings calculated from elemental analyses before and after hydrogenation and calculated by thenew method was 0.1 ring for 29 aromatic concentrates (Table 111). The average difference for the same data is 0.4 ring when the refractive index-molecular weight method ( 1 2 ) is used; it is 0.7 ring when the density-molecular weight method is used. I n both cases the amount of difference increases with increasing
5
20
40
F(d,M)=(DENSlTY-
60
0854)(MOL WT
80
+ 12)
I00
Compositions of Aromatic Concentrates Used in Testing of Method
V O L U M E 2 5 , NO. 2, F E B R U A R Y 1 9 5 3 Table IV.
211
Experimental Data for Individual Fractions Summarized in Table I11 Refore Hydrogenation
n go
After Hydrogenation
H"
6FC
Coc
F ( 6 , M ) F(d,.W)
ngo
dO :
.MH~
HH*
C H ~
1.6163
1.0217
289
196*
0.0796
Light Cracked Gas Oil 0.9119 39.7 34.9
1.4829
0.8930
200*
0.1310
0.8679
1,5862 1.6249 1.6404
0.9848 1.0314 1.0518
255 300 3 17
196* 196* 208*
0.0888 0.0775 0,0733
0.9078 0.9142 0.9182
1.4793 1.4855 1.4885
0.8830 0.8998 0.9071
193* 203* 212*
0.1326 0.1300 0.1305
0.8696 0.8676 0.8716
1.6474 1.5283 1.5413 1.6458 1.5511 1.553Y
0.9689 0.9230 0,9506 0.9666 0,9808 0.9889
169 179 183 172 153 182
289 167* 193* 244 331 408
0.1030 0.0996 0.1006 0.1030 0.1053 0.1074
Fractions 0.8756 0.8820 0,8852 0.8813 0.8732 0.8728
from Webster Crude 21.4 34.6 1.4887 14.5 12.4 1.4677 17.4 19.9 1.4759 18.9 28.0 1.4860 18.9 43.6 1.4985 56.7 1.5041 35.3
0.9034 0,8397 0.8793 0,8988 0.9227 0.9335
285* 165* 201* 263* 332 405
0.1322 0.1379 0.1340 0.1322 0.1290 0.1303
0.8668** 0 . 8 6 11 0.8650** 0.8668** 0.8700** 0.8671
East Texas Michigan Webster Mirando
1.5642 1.5449 1.5478 1.5568
0.9857 0.9575 0.9742 0.9876
198 181 167 174
247 304 299 2 84
0.0966* 0.1047* 0.1030 0.1007
Light Lube Oils (650-750' F.) 30.9 40.8 1.4897 0.8729* 0.8679* 26.2 32.9 1.4814 0,8730 21.5 37.3 1.4900 0.8775* 22.5 39.7 1.4959
0,9052 0.8846 0.9056 0,9205
311 307 311 301
0,1305 0.1338 0.1316 0.1293
0.8690 0.8598 0.8670 0.8710
.4
1.5599 1.5619 1.5597 1.5623
0.9989 0.9976 0.9966 0.9994
178 185 181 183
345 325 356 359
0,1048
0 .'92'83
330
...
...
0 .'Q3'06
366
... ... ... ...
... ...
1.5643 1.5651 1.5676 1.5734 F.) 1.5851 1.5876 1.5957 1.5784 1.5767 1 5900
0.9888 0.9916 0.9973 1.0051 1.0224 1.0185 1.0338 1.0168 1.0124 1.0305
201 199 200 208 222 229 235 217 220 229
266 292 317 325 332 268 3 10 358 409 361
0.0974 0.1008* 0.0998 0.0993 0.0973 0.0923 0.0922 0.1001 0.1012 0.0963
Extract Fractions 28.6 37.5 0.8837 0.8894* 30.7 42.0 33.6 47.0 0.8846 37.1 50.9 0.8859 42.7 57.8 0.8822 36.7 45.9 0,8946 44.1 58.0 0.8921 44.0 60.3 0.8836 51.4 66.5 0.8799 48.9 65.6 0,8844
1.4879
0.9039
270
0.1325
0.8665
1.'4950 1.4089
0 .'920l 0.9264
323 329
0 .'8680 0.8683
...
...
o.'iiiz 0.1303 ... ... ... ... ... ...
350 418
0.1138 0.1174
Raffinate Fractions 29.7 0.8767 15.2 18.1 32.7 0,8749 0.8836 0,8961 0,8850
30.1 35.6 42.3
53.1 45.0 57.3
0,8885
29.5
54.2
Whole aromatic Ad_sorption fraction 1
I1 I11 400-922' 400-500" 500-600° 600-700° 700-800' 800-922'
F.
F. F. F. F. F.
B C D
G H I
J K
0.9335 0.9300
1,3225 1.5180
140 140
o .'io70
...
32.7 42.0 48.2
27.2 36.8 43.6
Miscellaneous Distillate Fractions 28.6 51.8 0.8827 29.3 48.5 l.'jb'OO 52.6 @.'8828 30.5 ... 31.5 53.8 l.'sOO9
... , . . ... ... ...
...
... ... ...
...
...
...
... ...
... ... .
I
.
**
...
...
... ... ... ... ,..
...
...
...
...
... ...
... ...
, . .
,..
...
...
...
.. .. ..
...
...
...
...
Acid-Treated Oils
C 85% H&04 treated E ' 85% HgSOa treated G' 85% HzSOa treated G : 97% HzSO4 treated
1.51311 1.5870 1.5782
0.9974 1.0169 1.0110
179 214 177
359 264 353
0.1055 0.0916 0.0982
1.5ti77
0,9994
227
362
0.1023
. _-__
...
...
...
...
...
...
...
hlolecular weights from two viscosities (18) if unstarred, from boiling point and density (83) if starred. Per cent hydrogen divided by 100. Starred values are from Huffman Microanalytical Laboratories, Denve;. Colo. Per cent carbon divided by 100. Starred values are from Huffman Microanalytical Laboratories, Denver, Colo. Doubly starred values of CH have been assumed equal to 0.9990 - H H . a
Equations Lsed for Testing New llethod molecular weight before hydrogenation molecular weight after complete hydrogenation per cent hydrogen 100 before hydrogenation per cent hydrogen after complete hydrogenation 100 per cent carbon - 100 before hydrogenation per rent carbon after complete hydrogenation n 2-1 -~ 71' 2
+
1 d
d are refractive index and densitv at 20' C. determined after hydrogenation. (V-1)" RA = 0.248.110 - H Q ) - 0.50
("c",'" .iro(o.os33ca~
=
( (R.4
0.496Ho) - 3~~
+ ~R . ~~ =) .~ro(o.0633co- o 496Ho) + R.s) = 1 + 0.2145.Tf~ - 0 6611-11~r H
3
(V-210 (V-3)bc (V-4)
a These two equations are exact for mixtures of benzenes, naphthalenes, phenanthrenes, and anthracenes. providing complete hydrogenation is obtained and no structural change occurs except saturation of aromatic rings. This equation is exact for all mixtures of benzenes, naphthalenes, phenanthrenes, and anthracenes. This equation is the Vlugter, Waterman, and Van Westen (SO) relation for calculating total rings in a saturated hydrocarbon mixture. It represents a check of the method for any aromatic type, providing no structural change occurs during hydrogenation except saturation of aromatic rings.
number of naphthene rings, Rhile the new method exhibits no discernible variation in accuracy with change in number of naphthene rings. The following table shows the molecular weight range over which the new method has been tested with petroleum fractions. The fractions are the same as shown in Figure 3. Mol. Wt. Range
I R., . Sankin. A , , and Martin, C. C., ANAL.CHEM.. 20, 598 (1948).
Mair, B. J., I n d . E7kg. Chem., 42, 1355 (1950). Mair, B. J., and Rossini, F. D., “The Science of Petroleum,” Vol. V, Part I, ed. by B. T. Brooks and A. E. Dunstan, London, Oxford University Press, 1950. Mair, B. J., Willingham, C. B., and Streiff, A. J., J . Research A-atl. B u r . Standards, 21, 535, 565, 581 (1938).
Margenau, H., and Murphy, G. hl., “The Mathematics of Physics and Chemistry,” p. 498, New York, D. Van Nostrand Co., 1943. Mills, I. W., Hirschler, A . E., and Kurtr, S. S.,Jr., I n d . Eng. Chem., 38, 442 (1946).
Rosenbaum, E. J., Martin, C. C., and Lauer, J. L., IND.ENG. CHEM.,ANAL.ED, 18, 731 (1946). Rosenbaum, E. J.. and Rinehart, M..4.,unpublished spectroscopic data obtained within Sun Oil Co. Sankin, A , , Martin, C. C., and Lipkin, 11.R., - ~ N A L CHEM., . 22, 643 (1950).
Thorpe, R. E., and Larsen, R. G., I n d . Eng. Chem., 34, 853 (1942).
Tunnicliff, D. D., Brattain, R. R., and Zumwalt, L. R., ANAL. CHEM.,21, 890 (1949). Van Nes, K.. and Van Westen, H. A . , “Aspects of the Constitution of Mineral Oils,” pp. 242-335, New York, Elsevier Publishing Co., 1951. Vlugter, J . C., Waterman, H. I., and Van Westen, H. A., J . Inst. Petroleum Technol., 21, 661 (1935). Wanless, G. G., Eby, L. T., and Rehner, J., Jr., ANAL.CHEM., 23, 563 (1951).
Williams, R. B., Hastings, S. H., and Anderson, J. A., Jr., paper presented before Division of Petroleum Chemistry, 121st meeting AM.CHEM.Soc., Milwaukee, 1952. RECEIVED for review June 20, 1952. Accepted October 4 , 1952. Presented before the Division of Petroleum Chemistry at the 122nd Meeting of the A M E R I C CHEMICAL A~ SOCIETY, ritlantic City, H.J.
