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 . F r a n k l i n I71St. 222, 563 (1936).
(33) I b i d . , p. 370. (34) I b i d . , p. 429. (35) O’Seill, J., “Applied
I b i d . , 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 I n s t . , 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., I b i d , 3 8 , 4 4 2 (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 (42) Sun Oil Co., unpublished data.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., B r e n n s t o f Chemie 36, 169 (1955). (41)
(45) I b i d . , 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
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
1931
fractions was 196' to 535' F. ( a t 1 micron). The middle cut having a boiling range of 370" to 431' F . and a volume of 1.5 liters was then charged to the still for a second distillation. I n this second run the still was operated as a batch distillation iinit a t a throughput of 40 ml. per hour and a reflux ratio of 20 to 1. A heart cut having a boiling range of 393" to 414' F., a molecular weight range of from C,, to C39, and a volume of 56.5 ml. was selected from this run. The second step in the separation procedure involved the removal of aromatics from the heart cut by elution chromatography on silica gel. As thermal diffusion cannot readily distinguish between aromatic and cycloparaffin rings, it is advantageous to remove aromatics before effecting a separation according to molecular type. SEPARATION OF LUBRICATING OIL
i CHARGE STOCK 196O-535"F:
20- STAGE MOLECULAR DISTILLATION
FRONT
HEART
360-392OF:
393-414OF:
--
BOTTOMS ABOVE 4i4.F:
THERMAL THERMAL THERMAL DIFFUSION DIFFUSION DIFFUSION RUN I RUN 2 RUN 3 IO FRACTIONS 100 FRACT. 43 FRACTIONS
Procedures used for separation of lubricating oil
Table I. Inspections of Lubricating Oil Charge Stock 29.4 Gravity, OAPI, 60' F. Refractive index, 176' F. 1,4610 161 Viscosity, 100' F. (SUS) Viscositv, 210' F. (SUS) 61.8 Viscosity index 99 Pour point, ' F. 0 O
Distillation Data
2 nun.
1.n.P. 10
322 433
20
471
50 70 90
550
528 602
The third and final step in the fractionation procedure consisted of a separation of the narrow boiling saturated hydrocarbons according to molecular type by thermal diffusion. A battery of 10 columns of the type described by Jones and llilberger T m s assembled (6). Fourteen charges of oil of about 30 ml. each were processed in the preliminary separation. A temperature gradient of 200" F. was maintained across the column walls, 300" F. a t the hot wall and 100" F. at the cold wall. At the end of 10 days of operation the fractions were collected by withdraiving from successive ports, starting a t the top. Fractions which were removed from the same portion of each of the columns and having similar compositions were blended-that is, all of the topmost fractions from the 14 runs vere combined, then t,he fractions taken from the second sections were combined, and so on down the columns, As a result of this blending procedure, 10 fractions were obtained of varying composit'ions, xhich ranged from predominantly paraffinic hydrocarbon types to predominantly cycloparaffinic types. The volume of each combined fraction was about 36 ml. A further separation by thermal diffusion was made by chrarging each of the 10 combined fractions to a separate column. Again the columns were operated for 10 days 17-ith a temperature gradient of 200" F. The columns were then emptied by withdrawing 10 fractions from each of the 10 columns, starting at the top. I n this manner 100 fract,ions were obtained. Refract'ive index was measured on each fraction, as seen in Figure 2. Although a significant degree of separation was obtained, i t was evident that a large amount of overlap in composition occurred, due to the lack of a sharp separation in the first thermal diffusion run. For example, fractions 9 (column 1) and 1 (column 4) Tvhich had identical refractive indices lvere run in the mass spectrometer to confirm the similarity in composition. Their mass spectra were almost identical. I n view of the serious overlap in composition which existed, a third continuous run was made in a single 8-foot thermal diffusion column.
+-
Figure 1.
An 8-foot column, 40 mm. in inside diameter was packed with 1950 grams of 28-200-mesh Davison silica gel, No. 12-08, and 555 nil. of the heart cut from the distillation were diluted with an equal volume of cyclohexane and charged to the column. The sample vias then eluted with 4 liters of cyclohexane, which was subsequently removed by evaporation on a steam bath. Final traces of solvent were removed by passing a stream of nitrogen gas through the oil. Cyclohexane was selected as the eluent because it was shoivn by Irish and Karbum ( 5 ) to possess weak elution properties as compared to n-hexane. The 436 ml. of oil eluted with cyclohexane was then used as the charge material for thermal diffusion.
F. .kt m, 658
Ik
i98 547 925 951 1020
95 (E.P.) 620 1046 a Temperatures ronverted to 760-mm. pressure hy Beale and Docksey nomograph (I).
The 100 fractions from the second run were first arranged according to increasing refractive index. A sufficient number of fractions having the lowest refractive indices were charged to t,he column. A temperature gradient of 200" F. was maintained for 3 days. The topmost fraction of about 5 ml. n-as then withdrawn from the column, and a sufficient number of fractions in order of increasing refractive index from the previous run were charged into the center port, in order to refill the column to the top. This procedure x a s repeated every other day until 37 fractions were collected and all 100 fractions from the previous run had been charged. During this separation a bottommost fraction of 5 ml. was removed from the column every 10 days and recharged to the center of the column in the proper order according to its refractive index. This prevented a build-up of cycloparaffinic hydrocarbon types in the bottom of the column. The final six fractions were obtained after an additional 3 days bj- emptying the contents of t,he column. A total of 43 fractions of about 5 ml. each was obtained for measurement of physical properties and spectrometric analysis. All the fractions were found to possess a slight odor, which mas attributed to a trace amount of oxidation during the thermal diffusion runs. Consequently, in an additional purification step the oil was percolated over alumina in micro adsorption columns. The oil \vas diluted x i t h 5 ml. of cyclohexane and added to a volumn, 5 mm. in inside diameter and 200 mm. long, filled with alumina. The oil T ~ eluted S Tj-ith 100 ml. of cyclohexane. AAfter evaporation of the solvent, the oil was found to b e odorless and u-ater-white. RIEASUREblENT AND INTERPRETATION OF PHYSICAL PROPERTIES
In order to note the effect of changes in composition on the physical properties of the fractions, a number of physi-
1938
ANALYTICAL CHEMISTRY
cal measurements were made (Table 11). Refractive indices and pycnometer densities shown in Figure 3 were both measured a t 70" C. The refractive indices ranged from 1.44016 to 1.49952, while densities ranged from 0.808 to 0.952 for the first and last fractions, respectively, Microviscosities a t 100' and 210' F. are shown in Figure 4. Because of their extremely high viscosity a t 100' F., the last four fractions could not be determined a t this temperature. Viscosity indices were calculated and are plotted in Figure 5 The viscosity index was highest for fraction 1 at 166.5 and decreased steadily to -40 in fraction 39. Micro pour points of the fractions (Figure 6) showed a maximum in the curve, The "waxy" pour points decreased from a high of 65" F. for fraction 1 to a minimum of -30" F. for fractions 20 to 23. The "viscosity" pour points then increased to a maximum of 115" F. in fraction 43. The physical properties of the original lubricating oil a t different stages in the separation by distillation and chromatography, shown in Table 111, exhibit only slight changes between the original oil and the material charged to the thermal diffusion columns, indicating that the fraction selected for analysis was a representative portion of the lubricating oil charge. I n an effort to obtain additional information which might substantiate the spectrometer analyses to follow, the n-d-M (refractive index, density, and molecular weight) ring analysis method of van Xes and van Westen (19) was employed. From the refractive index and density measurements and average molecular weights found from the mass spectra, it was possible to calculate the average number of rings per molecule for each fraction. As the oil fractions had been subjected to high efficiency distillation to reduce the spread in molecular weight, it was found that only a slight difference existed in molecular weight between the most paraffinic (fraction l ) and cycloparaffinic (fraction 43) fractions. The results given in Figure 7 show that the average number of rings in the molecule varied from 1.7 to 7.2. The number, 7.2 rings per molecule, is an extrapolation of the n-d-Al correlation and therefore is only approximate. For the determination of aromatic rings it was found that negative values resulted for all the fractions. A second attempt was made to determine independently the average number of rings in the molecule from the carbon-hydrogen ratio. This approach was feasible because of the narrow molecular range of the fractions and because the number of hydrocarbon types in each fraction had been reduced. Seven fractions, selected arbitrarily, were subjected to a carbon-hydrogen analysis. These data were then compared with the molecular weight of the fraction and the average number of rings per molecule was calculated. Only saturated hydrocarbon structures were considered in this case. The calculated average number of rings per molecule increased from 0.5 in fraction 2 to about 6 in fraction 43.
1.499
I
I
I
,
I
I
I
!z D C
XW
D
3 W
2
I-
o a
a
LL
W
a
FRACTION NO.
Figure 2.
Refractive indices of fractions from second thermal diffusion run
- 1.496 -1.488
;D
m
n
-1.480 0
I?
-1.472
5
z
- 1.464 X - 1.456 0' 3 ?
-1.448 4
.800L'-
Figure 3.
'
5
0 I
1
10
15
I
I
I
20 25 30 FRACTION NO.
I
35
I
'I 440
40
Densities and refractive indices of fractions from final thermal diffusion run
3000 I
I
I
I
I
I
I
1 ,
I
1
SPECTROMETRIC ANALYSIS
Hydrocarbon-type analyses were determined by means of high temperature mass spectrometry.
Figure 4.
Viscosities of fractions from final thermal diffusion run
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
1939 ~
Frac-
tion No.
1 2
3 4 5 6
7 8 9 10 11 12
13
14 15 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 a
~~~
Table 11. Physical Properties of Fractions from Final Thermal Diffusion Run Av. No. of Rings/Molecule Pour Molecular Wt. Refractive Density Viscosity C/K 5 b a t 70° C . Index, n g Point, F. Ratio n-d-11 (12) MS C-H ratio Index 210' I;.
Viscosity, Cs. -
100° F. 25.0 28 2 30.4 32.2 30.5 35.2 32 4 37.5 39.2 39.8 42 3 41.7 45.1 46.3 47.7 50.4 52.3 54.9 56.5 54.9
5.74 6.05
61.0
64.1 20.7 (4.2 78.6 86.1 89.3 94.6 104 118 123 139 149 199 233 332 439 723 1953
167 158
6.24 6.41 6.11 6.59 6.24 6 76 6.87 6.98 7.10 7 18 7.31 7.43 7.46 7.68 7.77 7.98 8.09 7.96 8 33 ... 8.96
153
9.25 9.73 ... 10.2 10.6 11.2 11 5 12.0 12.3
I'd2
...
...
15 0 17 3 19 6 24.1 35.3 61.5 99 5 1 10 215
I50 150 143 145 140 136
137 132 136 129 128 125 123 121 117 118 119 114
...
109 100
...
96.5 92.5 87.0 86.0 79.0 76.0
...
58 5 41.5 32.5
11.0 -40 0
...
... . . ,..
0.808 0.813 0.813 0.819 0.818 0.822 0,820 0.823 0,822 0.823 0 824 0.824 0.825 0.826 0,827 0.830 0,833 0.834 0.835 0.836 0,840 0.842 0.845 0.847 0.849 0.852 0.854 0.856 0.859 0.862 0.862 0.865
0.867 0.875 0.878 0.884 0.891 0.897 0.912 0.928 0.938 0.941 0.9.72
4402 4422 4437 4447 4442 4456 4448 ,4459 ,4461 ,4462 ,4465 ,4463 ,4469 4474 4478 4486 4497 4504 ,4510
4514 4528 4536 4559 ,4556
,4588 4578 4583 4594 4603 ,4816 ,4619 4632 4642 ,4669 4684 .4712 4735 1767 4824 4890 ,4931 4917 49%:
65
482
55
5.87
45
461
40
35 30
473
25
20 15
478
10 5.82
5 5
1.7 1.9 1.8 2.2 2.1 2.3 2.1 2.3 2.2 2.2 2.2 2.3
0.6
0.5
1.2
0.2
2.2
1.3
2.9
2.8
3.6
3 0
4 8
44
6 5
6 1
2.3 -'1. 3
0
-5
23
- 10
- 15
2.6
480
28 28 3 9 2.9
-20
-25 - 2.5 - 30 - 80 - 70 - 30
6.01 476
- 25
- 25 - 20 - 20
487
6 28
- 15 - 15
- 10 - 10
- 10
6.82
-5
491
0
5
10 G 3'3
20 35 55 89
490
3.0
3.1 3.2 33 3.4 3.4 3.6 3.6 38 38 3.8 3.9
4.0 4.3 44 4.6 49 5,1
5.7 6.3 6.6
YO 93
4T3
6.9
458
11.5
G.94
7.2
.\IS dcrer mination.
b Ebulliosctipic determination.
Physical Properties of Lubricating- Oil at Various Stages of Separation Middle Heart Original Saturated Cut Cut Portion Lubrifroin from cating First Final of Oil DistilDistilHeart Physical Properties Charge lation lation Cut" llolecular weight h 540 479 482 474 Refractive index, 7 ~ : 1.4642 1 4644 1 ,4635 1,4588 Density, d 7 c 0.876 0 865 0 864 0.856 Viscosity, Cs.
Table 111.
I000 I..,
99.2
105.2
99 5
2100 I-'. 10 I 10 9 10 6 1-iscositj-index 99 95 98 Pour point, O F. 0 0 0 , n-d-51 ring analysis 48.5 48 0 % C R (total) 55,O 0 0 0 % C R (aromatic) 5.1 3.5 3 8 RT (total rings) 0 0 0 I t 4 (aroniatic, rings) " Charge illaterial to thermal diffusion separation. h F:hiilliosc,oliic molecular weight determination.
88.7
10.0 101 10
190,
I
1
I
110-
n
K
> 70-
t
8 0
30-
v,
' -10-
+
46.9 0 3.6
0
~iipplrmeut:iI.?-informution concerning molecular structure was found kiy menwrement of total methyl groups and methylene grorips present iii aliphatic paraffin chains by infrared spectrometry. The presence of aromatic structures was found by ultraviolet sp~ctrometry. METHOD OF CALCL'LATIOK
I n gene1 31, two different methods of mass spectrometric analysis were employed. In one method parent ions are used to determine compoands according to molecular weight. I n this calculation it is assumed that the intensity of monoisotopic pcaks iq related directly to molar concentration. .4 second pro-
FR.PCTICN NC
Figure 5 .
Yiscosity indices of fractions from filial thermal diffusion run
cedure is based on fragment ions in the spectrum, which are added together to act as it single peak to characterize all or part of a parent compound. Thus, the fragment ion method is considered t o provide information regarding paraffins as parent compounds, and ring systems which generally are only one part of a molecule. The fragment ion analysis used in this work was similar to that previously employed for an eicosane dist'illate (IO). These samples were more complex in composition, however, so that the method had to be extended to include cyclic compounds having as many as nine rings. The final calculation procedure was devised to determine paraffins, mono- and/or noncondensed polycycloparaffins, condensed di- to nonacycloparaffins, free phenyls, free indans and/or Tetralins, and free naphthyls. Polyisohopic peaks and calibration data used in the matrix solution are shown in Tables IV and T:. These include two series
1940
ANALYTICAL CHEMISTRY
of peaks each for paraffins and noncondensed cycloparaffins. I n practice, results from 267 and 2 7 1 are accepted for the analysis, whereas 2 4 1 and 243 serve as a check matrix. This choice is based on the belief that 267 and 2 7 1 might provide greater precision. This is true because these sigmas include only peaks which are scanned at the same magnet field as the other peaks in the matrix. Some of the 2 4 1 and 243 peaks, on the other hand, are necessarily recorded at a lower magnet field. As a rule, paraffins by 243 are 10 relative yo higher than when determined by 271. Cycloparaffins are correspondingly lower when based on 241. These calibration data are subject t o some uncertainty, particularly in the case of compounds having six or more rings for which no direct spectral data were available. Data for paraffine, monocycloparaffins, noncondensed polycycloparaffins, alkyl benzenes, and naphthylenes are probably reliable. This is true because a large number of pure compounds and concentrates of various kinds were examined to select average coefficients. For condensed ring compounds 23 di-, tri-, tetra-, and pentacyclics were studied. Although perhaps only one, cholestane, was representative of structures present in oil, considerable similarity existed b e b e e n its spectrum and that of the other compounds. These spectra shoned that condensed ring molecules may have major ions consisting of (1) the ring system intact, (2) fragments of a ring(s), (3) fragments having the ring system with two 01 four less hydrogen atoms, and (4) any of the major ions mentioned previously with its mass shifted one unit higher, oning to a heavy carbon atom or deuterium. Based on this information pattern, coefficients x-ere estimated for compounds having as many as nine condensed rings. These calibrations s e r e obtained with an ion source temperature of 260" C. Subsequent data a t 2T8" C. showed fragment ions to be more intense than parent ones. -4s a result, ring compounds contributed more to paraffin and noncondensed cycloparaffins. This effect must be taken into consideration befoie these data are applied to another mass spectrometer.
consisted of 505; fraction 2 and 50% fraction 19. The mass spectrometric analysis is compared TTith the "known" composition for each blend in Table VI. Reference to this comparison shows that the major constituents-paraffins, noncondensed cycloparaffins, and condensed di- and tricycloparaffins-generally agree within A10 relative Smaller amounts of compounds differ by 0.2 to 2.3 absolute 52. Examples of this type of error are the 0.8% tricycloparaffins in blend 2 determined to be O . O s , and 4.970 tetracycloparaffins in blend 1 reported as i.2YC, Such errors, although relatively large, are not considered serious, in that they are believed to be constant incremental errors caused by several factors-(1) small errors in pattern coefficients of
s,
\-. Coefficients for Calculation of Saturated Lubricating Oil (Magnet current = 0.9 ampere) Mono- and/or Condensed Noncondensed Cycloparaffins, PolycycloFree Phenyls, Peaks Paraffins, % paraffins, % Indans, 2 4 1 , 55, B9, 8 3 33 100 45 100 51 35 2 4 3 , 57, 71, 85 __ Sensitivity, dir. / & 330 270 Table
CHECKS ON METHOD
The accuracy of this method is difficult to determine. There i; evidence, hon-ever, that gross errors do not exist. One independent check of the method consisted of anal>-zing synthetic blends made from two different pairs of thermal diffusion fractions. Blend 1was a 50-50 mixture of fraction 1 (70% paraffins) and fraction 43 (7593 condensed cycloparaffins), while blend 2
Table IV.
-40'
b
'
1
~b
/5
;O
;O
;5
;5
40
FRACTION NO
Figure 6.
Pour points of fractions from final thermal diffusion run
Coefficients for Calculation of Saturated Lubricating Oil (Magnet current = 1.3 amperes)
Mono and/or Noncondensed Paraffins, PolycycloPeaks % paraffins, 100 17-10a Z 71 85 Z 67: 68, 69, 81, 82. 83. 96, 97 64 100 Z (123, 124-333, 334) Z 149, 150-443, 444 Z 189, 190-483, 484 Z 229, 230-509, 510
0 0 0 0
Z 269, 270-607,
0.04
Z 295, 296-505, Z 321, 322-503, Z 347, 348-601,
508 506 504 502
Z (91, 92-175,
176) Z (117, 118-187, 188) Z (141, 142-281, 282) Sensitivity, div./p a
10-17= 0-7Q 0 0
Dicyclic I
57 1 s
go
1.3 0 0
0 0
0.2 0.5 2 3
0 0 0
3 1 1
270
140
112
20
20 1 0.3
0.2 6-16
0.3 0.3 33
Tricyclic 7 57
Indans Free and/or Condensed Cycloparaffins, % Free Tetra- Penta- Hexa- Hepta- Octa- Nona- Phenyls, Tetralins, Naph; cyclic cyclic cyclic cyclic cyclic cyclic 'X % thsls, t o 0.4 7 , 7 7 7 7 3 1 3 67 57 57 57 57 57 5 1.4 10 30
0 0 0 0
40 0
10 30
0 0 0 10
30
10
0
30
10
0 10
0 0
30
20
100
0
20
0 0 1 1
0
20
E O
0
0
30 0 0
'00
0
0
12 3 0.6 137
30 0
100
0
0
1
0
40 3 0.5
6 40
0
0
0
0
30
0 0 10
137
137
137
137
137
Varies between monocycloparaffins and noncondensed polycycloparaffins in order given
0 0
3
0
2
30 0
1
0.2 0 20 1.5 0 0 0 0
0 1 0 0 0 13 0 0.7
137
270
0.3 0.3 3 20 2 0 0 0
4
100 1
215
3 0.3 0 5 0
5 20 2 0
0.5 0.3 100 274
1941
V O L U M E 28, NO. 12, D E C E M B E R 1 9 5 6 Table
YI. Jlass Spectrometer Fragment Ion -inal>sis of
Component Paraffins Mono- andlor noncondensed polycycloparaffins Condensed cycloparaffins DiTriTetraPentaHesaHeptaOctaI'ree phenyl Free indans Free naohthvlsa ~" a
Sjnthetic Blends Blend 1, % -Known Mass spec.
Blend 2, % Known Mass spec
34.8
33.5
43.5
44 0
25 1
23 9
37 5
40 0
10.3 11.4 4.9 4 4 2.1 0.8 0.2 5.6 0.4
12.0 11.7 7.2 3.5 1.5 1 5 0.7 4.2 0.3
16.3
11 6 0 0
100 0
, . . ~ 100 0
-. . .
0.8 0.3 0.1
0.0 0.0 0.0 1.4 0.1
0 0 0 0 0 1 0
3 0 0 0 0 0 1
... ~ 100 0 100 0 No attempt was made t o determine naphthyls, so known com-
position is on a naphthalene-free basis.
U
P
E?
6 -
Table 111. Comparison between Two Different Jlass Spectrometric Jlethods for Calculation of Lubricating Oil Composition (Fragment ion analysis) Fraction 1 from Elution of Fraction 26 Fraction 1 Fraction 26 Fraction 43 on Alumina __This This This This Component paper ( 2 ) paper (2) paper ( 2 ) paper (2) Paraffins 70 67 16 0 0 0 24 16 Cycloparaffins Yoncondensed 25 28 40 66 26 18 45 44 Condensed 4 4 41 29 62 64 23 27 Aromatics 1 1 3 5 1 2 1 8 8 1 3 _
_
their presence in higher fractions was sought. T o do this, fraction 26 (16.2Yc isoparaffins) n-as eluted many times through alumina. Finally, the front and tail ends of this elution were analyzed by the mass spectrometer, as shown in Table STII. Isoparaffins in the front end ( S o . 26, 1) Rere 2 3 3 % as compared with l.Oyoin the last fraction ( S o . 26, 19). This showed isoparaffin enrichment in sample 1 in a manner to be expected for the percolation. This lends considerable credence to the qualitative aspects of the method. S o attempt was made to account for the unexpected enrichment of benzenes in the two fractions.
a iL
0 Lz
w m
54-
Table 1-111. Separation of Fraction 26 by Elution Chromatography on .&lumina (Fragment ion analysis) Eluted % _ _ Fraction, ~ Fraction 26, So. 1 No, 19
I 3
z
3-
FRACTION NO.
Figure 7 . Average total number of rings per molecule in fractions from final thermal diffusion run
major constituents in a mixture, ( 2 ) the difficult?- of selecting ions which are due solely to one type of ring system (Parent ions, for instance, are not included in sigma values because they are considered usually to consist of more than one ring system. Ions formed by the loss of a substituent on a ring also would be in this category.), and (3) the method of reading peak heights from a mass spectrometer record (simple tape measure used to rrad total peak intensities). The methods n-ere internally consistent in that analyses of the original charge to the thermal diffusion columns agreed well with the composite of analyses for the 43 individual fractions. This agreement is 8hon.n in Tables I S and S. ;Inother over-all check on the method vias obtained by comparing results on fractions 1, 26, and 43 with those obtained busing an alternative scheme of calculation (2). This latter method employs an entirely different combination of peaks and groups condensed cycloparaffins together. Comparison of results is shown in Table VII. This agreement is good, particularly in view of the fact that the calibrations presented by the authors of the alternative method were used directly. Further confirmatory data have been obtained based on independent checks for individual compound types. Isoparaffins, for instance, are reported in fractions 1 t o 39. This was expected, in that a preliminary study of the mixture spectra showed no isoparaffinic peaks in the parent mass region of fractions 19 and higher. For this reason a qualitative confirmation of
Paraffins Noncondensed cvcloparaffins Condensed cl-cldparaffins .~ DiTriTetraPentaHexaPhenyl Indan
1 0
16 2 40 2
23 5 45 5
36.1
29.1 9 0 1 0 1.1 0.2 3 1 0 1
18 9 3 2 0 1 0 6 0 3 6 4 15 -~ 100 0
19.4 15.3 8.1 3.0 1.4 12.1 3.6 100 0
1000
~
Infrared and ultraviolet analyses have also helped to affirm and supplement the mass spectrometric analyses. Molar absorptivities at 215 and 228 mM were used to determine benzenes and naphthalenes by solving tn-o simultaneous equations based on calibration data similar to those of Kinder (?). Typical comparisons b e t w e n the two methods for total phenyl groups are shon-n below:
Fraction N o .
A16
Total Aromatics
_ . ~
U1tra riole t
The ultraviolet data are summarized as total aromatic carbon atoms in Figure 8. Infrared measurements of some selected fractions served to determine total methyl arid aliphatic methylene groups as sholvn in Figure 9. T h e method of Hastings and others ( 4 )and Francis (5)Tvas used to do this, based on calibrations for a Beckman IR-2 instrument. A semiqnantitative compariqon can be d r a a n be-
1942
ANALYTICAL CHEMISTRY
tween such infrared results and the mass spectrometric analyses. Thus, 1470 methyl groups and 72y0 aliphatic methylene groups were found in fraction 1 by infrared. For the same sample the mass spectrometer reported 70.1% isoparaffins and 29.97, cycloparaffins. Fragment ions in the mass spectrum indicated isoparaffins to be primarily mono- or dimethyl paraffins. Based o n the parent ion analysis, the cycloparaffin molecules were found to contain, on the average, about ten carbon atoms in ring htructures. For molecules having an average of 35 carbon atoms then, 25 carbons would be present as side chains. If, then, it is assumed that the average side chain contains four carbon xtoms, methyl and methylene groups calculated from mass spectrometric data become 12.1 and 76.5%, respectively, which compare favorably with infrared results. Results on other fractions can be compared with less certainty. It is apparent, however, that trends of infrared and mass spectrometric 1esults agree qualitatively with one another.
$1 t
i I
F i g u r e 8.
COMPOSITION OF LUBRICATING OIL
Results of parent and fragment ion analyses are tabulated in Tables IX and X. Data from parent ions shoa- that fractions 1 through 43 increase in cyclization and decrease in paraffinicity. Fraction 1 contains TOY0 isoparaffins and 207, monoc) cloparaffins, whereas fraction 37 has none of these hydrocarbons. Dicylics also occur in fraction 1 and are absent from fraction 38. Heptacyclics appear from the first time in fraction 25, octacyclics in fraction 34, nonacyclics in fraction 39, and finally decacyclics in fraction 43. Fragment ion calculations summarized in Table X are thought to furnish information of a different nature. However, these
Table IX. Fraction No. 1 >
3
4
5 6 7 8 9
10
11 12
13 14 15 1li
17 18 19 20 21 22 23 21 25 26 27
:; -I
30 31
32 33 31 3.5 3 (i 37
Isoparafina
10 J, .5 4 50 49
48 46 44
4I6 44 47
45 14 42 41 36 32 31 30 2fi "3
"2
?n 18 17 In I6 13 13 12
~
Mono20 2 .?I 19
19
is1.?I 15
I4 14 I3 12
13 12 12 11 11
in 1:
; 7
0 1
3 2
40 41 42 43 Coni posite Direct MS a na 1y sis
17 21 22 23 23 24 23 23
_'J .7
21 21 21 22 22 24 28 23 20 24 22 21 20 20
19 17
1t i 1: 13
13
4
11 !?
? J
...
...
..
4
... ...
. ..
...
4
Tri2
5 6 6 7 9
.~
Tetra-
3 2 3
3 4 4
10 11
11 11 11 12 13 17 17 19 20 21 22 24 25 2z 20
27 27 27
26 29 28 27 26 20 20 10
11 in
Total aromatic carbon atoms as determined by ultraviolet absorption
Cycloparaffin I'cntaHcxa1
1 1 1 2 7
-.
-~
~~
Hepta-
Octa-
Sona-
Deca-
1
2 4
1
6 6
>
I
1
7
4
2
4
1
in
2
10
1 1 5
10
J
b
12 12 14 15
17 IS 19 20 21 22 24 24 26 27 30 28 29 32 30 22 16
10
10 11 12 13 13 15 16 21 21 21
15
13
26
8b
1n c
15
16
14
11
'?
2 2 2 4
6 8 8 8 9
15
, .
1
4
8
..
1 1
4
2 (3
1 1
1
-f
..
3
1 1 1
2
..
..
40
35
Parent Ion Analysis
In
3
...
20 25 30 F R A C T I O Y NO
1
1
... ... ...
15
IO
data are consistent with parent ion analyses, in that they show a steady increase in cyclic compounds from fraction 1 through 43. The most condensed material found mas a small percentage of octacyclic compounds first appearing in fraction 41. From the parent ion analysis data the average rings per niolecule were calculated for a number of fractions. These results are shown and compared with the ring analyses of van X e s and van Westen (12) and carbon-hydrogen ratio in Figure 7 . It is seen that the ring analyses calculated from mass spectrometric
27 29 33 34 32 32 28 11
Based on fragment ion analysis b Includes octacycloparaffins. c Includes nonacycloparaffins. a
4 18
I?
38 34
Ili-
5
O'
3 3 4 1 5 5 5 6 7
1 1
2
7
7
8 9 11
12 11 15 17 22 24 25
'2
3
25 21
i
3
1
5 9 1
5
1
..
..
4
V O L U M E 28. N O . 1 2 , D E C E M B E R 1 9 5 6
1943
~~~
Table X .
Fraction T o .
-i ti
7 8
9
10 11 12 13 I4 16 1b 17 18 19 20 21 '2 23 24 2A 26 27 28 29 30 31 31 33 34
llonocycloparafiin. Noncond cycloparaffin
Isoparaffin 70.1 87 4 54 49.t 49.2 48 4 45.7 43.8 45 0 44 2 47.1 44.i 43 0 42.1 -10.8 36.0 32.4 31.0 29.6
24 4 36 1 38 2 40 4 40 8 36 7 35 3 34.8 33 8 34.I 32.8 32.1
25 24.,
41.7 42 2 40 2
33.1
33. 34 I 3 7 . tj 38 4
38 8 39 2
z
21.7 20 3 18.2 17 0 I6 2 16.3 15.2 12 i 11 7 11 D 9.4 9.1 4.6 5 1 3.8 3 9
85 3 ti 37 38 39 40
42 :3 43.7 46 5
40.2 42.G 4l.l 43.2 41.2
39.8 37 38.0 37.8
,
3 8 3 s ..
... ...
41
42 43
, . .
5
Figure 9.
IO
15
:;x
6 8 " 8 , 13.3 17.2 19.ii 18 8 18.9 18 2 20 8 21 3 21.4 22 0 23 1 25 8 26 4 17 5
2:
n
20 1 29 3 27.0 26 I 24.1 29.1 29 9 28 r, 27 0
29 1; 30 2 31.4 25,9 27.2
3i.0 34 I 33 :i 34.1 32.7 24 $4 25 1 23.2
2fi. f)
25.9 36 3 i
10 1
25 81 Coniposite Direct .lis 31; 0 analysis 26.3 a Determined by ultral-iolet.
., I
Di-
2.5.9 2 3 . .5 20.9 19.4 19.9 18 7 18.0
Tri-
-
0 2
0 2 0 4 0 2 0 4 0.4 O R 0.4
0 8 0 4 0.9 0.9 0.9 0 2 0.9 0.9 1 2 1 5 .7 2 2 ij 3 1 5 0 7.1 6 3 9.0 6.5 8.3 11.7 10.9 11.0 14 4 19 5 16.5 llj 2 17 tj 20 1 18 7 17 2 2l.tj 21 4 22 8 21.9
Fragment Ion Analysis
Condensed Cycloparaffins TetraPentaHeux0.1 0.2
0 3 0 1 0 A
0 2 0.1
0.4 0.6 0 9 0 9 1 1 0 8 0 6 1.2 0.4 0 9 0 9 1 1 1.2 1 0 2.4 I .8 0.8 1.8 3.2 2.1 1.8 6.1 8.1 9.1 7.9 10 1 11.9 11.9 10 8 11 1 0 7
0 1 0 1 0 1 1 0.1 0.1 0 1 0.1
n.
Phenyl
Indan
S-aphthalene"
0.3 0.1 0.4 0.6 0 8 0.8
O H 1.0 1.1 0 5 1 1 1 1 1 1 0 8 1 2
I.!
2 , .> 2 3 3 7
41' 4 3 .5 i 0,ti 10 8 9 i
19 8
i.O
1 4
I
data fall midway betxveen the ring value; by the other two methods.
1.L
n: 1
2.89
Functional groups determined by infrared absorption
0 1
0 6
i 50
40
0 1
... ..
21 79
35
Octs-
.. 0 1 0 1 0.2
8 3 1 77
20 25 30 FRACTION NO.
Hepta-
ti
.. 0 3 0 1 0 2 0 2 0 2 0-7 0 2 0 2 0 4 n 2 0 3
0 3 0 0 0 1 1 1 1 2 3 3 3 4
4 4 9 2 5 4 4 1 2 7 3 8
...
.. 0 4
0 5
1 0 0 6
... ... 0 3 0 5 0 7
1.3 1 3 1.3 1.4 1.4 1,4 1 5 1. 5 1 3 3 :7
..
... , . .
3 5 3-1 2 9 3 . fj
n i 0.I 0 1 0.1
.4'
0.1 0.1 0.1 0.1 n. 1 0.1 0.1 0.1
!
2 , "8 3 0 8 2 2 8 3 2 3 3 3.7 3.0 3.5 .5 . I 5 8
A .j 7 7 7.E 8.t 10.2
0 2 n i
0 2 0 1
0 1
0 5
0 6 0 5 5 2 3 3 3 n
0.3 0.3 0.4 0.4 0.5 0.5 0 6 0 7 0.8
0 2 0 0 0 0 0 i
0.2
0 63
0 06
0 03
2.96
0 12
0.14
0 5
0 1
0 9
4.9
0 5
0 1
I n higher numbered fractions fragment ions shift to lower masses, indicating long side chains or increased degrees of branching. Monocycloparaffins. A study of the spectrum of frartion 1 indirated that these hydrocarbons were multisuhstituted. It appeared that side chairis generally consisted of two or more carbon atoms, because the spectra shon-ed peaks \rhich resulted from the loss of only ethj.1 and henyier groups from p a r m t molecules. PolycycloparafEns. The structure of these rompounds unquestionably varies from rather simple molecules having only two rings &h many side chains to highly cyclic ones having mostly methyl group side chains. This is borne out by a study of combined infrared and mass spectrometric data. The most cyclic separated material was fraction 43, as indicated by fragment and parent ion analgsps. This sample was alsv of interest because of its high viscosity and other extremc physical properties. A thnrough study was made of its spectroscopic data, therefore, to establish proh:i!de molecular st,ructure. STRUCTURE STUDY O F FRACTION 43
STRUCTURE STLDY OF LUBRICATING OIL RIOLECULES
Isoparafbs. Paraffins present in this sample are all bran-hedchain molecules, as indicated by the absence of parent ions which would result from normal paraffins. The amount of branching seems to increase in proceeding from fraction 1 to 39. Those present in fract,ion 1, for instance, have some ions near the parent mass region which are apparently due to the presence of a methyl group on the fourth or fifth carbon atom from the end of the chain. It is also possible that some molecules contain an ethyl or propyl side chain or two methj-1 groups along the chain.
The parent ion analysis shon-ed that mono-, di-, and tricyclic compounds were absent, and tetra- through decacyclics present. Fragment ion analysis on the other hand showed a preponderance of mono-, di-, tri-j tetra-, and pentacyclic systems. This indicated that more than one ring system was in an average molecule. At this point an attempt was made to show how fragments might be arranged in parent molecules. To do this a statistical calculation was carried out to piece fragments together mathematically into combinations comprising these molecules. The calculation is based on the assumption that different rings in a
1944 given molecule form ions with equal probability independent of the number of rings of a given kind. This means that the number of ions formed by dissociation is a function only of ring structure. According to this, a molecule having only one single ring aould have single ring ions as intense as a molecule having two or more single rings. This assumption is obviously not absolutely valid, as indicated by the nonuniform distribution of rings For instance, the progression of 21.97, tri-, 16 1% di-, and 2 5 . 0 7 monocyclics shou s a higher amount of rnonocyclics than \Todd be expected. This inconsistency does not appear to affect seriously the over-all conclusions as to structure However, it does influence the distribution of the parent molecules n hich are calculated to have four, five, six, etc., rings. For this reason it was further assumed that single rings originating from different molecules had a concentration of 11% instead of 25.0%. The first step in this calculation involved estimates of molecules which had only one system of rings in them It seemed that molecules having seven (0.65;) or eight (0.77,) condensed rings as measured by fragment ions were in this category. I n addition, a fraction of the molecules having five and six condensed rings were also assigned to this class. This is illustrated by the data in Table XI, third column. Molecules having aromatic groups 15-ere considered next. Such compounds form ions consisting primarily of aromatic nuclei. For these molecules there would be essentially no ions t o indicate saturated rings. For this reason phenyl, indan, and naphthalene nuclei u-ere assumed to be evenly distributed in molecules having a total of three to five rings. The mathematical value of this assumption appears in column four of Table X I and the final probabilities used in the calculation are in the fifth column. The procedure of piecing together fragments may be illustrated by considering how a few of the individual combinations were calculated - 1 q parent ion analysis ruled out the presence of mono-, di-, and tricyclic compounds, the simplest one is a tetracyclic. Combinations of individual ring systems which a-odd constitute a tetracyclic and their probabilities of occurrence would be: Combination Probability of Occurrence 1. Four single rings (0 1 1 1 4 = o 0002 2. Two single rings and one two3 X (0 11)2 X 0 161 = 0 0058 ring 3. One single ring and one threering 2 X 0 11 X 0 219 = 0 0482 4. Two-two-ring (0 161)* = 0 0259 5. One tetracyclic = 0 0000 0 0801 The sum of the individual probabilities, 0.0801, represents the total mole fraction of tetracyclic compounds. More complex molecules result from an increasing number of combinations. Pentacyclics can arise from seven different ones and decacyclics from as many as 33. This latter number would have been even greater, except that it was assumed that no more than seven individual ring systems n ere present in a molecule. The complete calculation consisted of calculating probabilities for individual combinations and summing them to obtain the concentration of compounds having from four through ten rings. The sum of all probabilities was less than loo%;,,so that the final calculated composition M as obtained by normalization. This result is given in Table XI1 and is compared with the corresponding values based on the parent ion analysis. This comparison is favorable enough to indicate that the piecing together process was fairly reasonable. By combining the statistical picture ilith infrared structural data, some of the principal molecules can be visualized within certain limits. Pentacyclic compounds, for instance, show by statistical calculation a predominant molecule consisting of condensed di- and tricyclic systems. Infrared data show that of 35 carbon atoms in an average molecule 24y0 (or 8.4 atoms) are methyl groups and 67, or 2.1 carbon atoms are aliphatic meth-
ANALYTICAL CHEMISTRY ylene groups. Using these data and assuming hydrindan and perhydroacenaphthene ring structures, the number and kind of carbons in this molecule may be as follom: No. of Carbon Atonis
Structure Condensed two-ring (hrdrindan) Condensed three-ring (Gerhydroacenaphthene) AMethylgroups Aliphatic methylene groups Unaccounted for
9 12
8
2
-4 35
Based on the mixture spectrum, it also appeared a t least one propyl group is present in some molecules. The composite molecules could then be: CH?
CHa CH2CH2CHa
ihCH3
CH3-q~
CH2-CH2-
0
7
I
3
1
CH, CHzCH3
CHa
An alternative possibility is that the rings are bonded directly to one another: CHa CHL'H?CHa
I-CH~CH~CH~
I n these molecular formulas side chains, such as methyl, ethyl, and propyl groups, are positioned a t random with no experimental data t o indicate specific locations. On this basis other abundant molecules would be of the nature shown belov.
NO.
No. of Rings in Parent Molecule
Structure C H3 I
CHI I 1
6
2
6
3
7
1945
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6 Because fairly specific formulas have been proposed for compounds in a mixture as complex as lubricating oil, it is of interest to consider the likelihood of their existence. This problem narrows don n to the reliability of structural information. I n this respect it is felt that methyl and aliphatic methylenes are reliably determined. Similarly, the parent ion analysis appears reasonable, as indicated in Figure 7 by the degree of its agreement n ith the ring analyqis calculated by the n-d-Rl and carbonh j drogen ratios. The least reliitble structural data are the degree of ring condensation that exists. This latter information, which is based on fragment ion or functional group anal>-&, is subject to some uncertainty. Spectra of mono- through pentacyclic compounds verify the method. However, only one of these compounds \vas considered to be representative in structure. Because of this and the lack of spectra for pure compounds of greater condensation, it is impossible to be snre that these more highly cyclic compounds do not dissociate to yield major ions which appear to originate from compounds of lesser cyclization. If, for instance, the principal dissociation of a condensed octacyclic resulted in ions corresponding with one, tlvo, and three rings, the conclusions regarding condensation would be erroneous. For this case the hexacyclic compound, S o . 2 above, could then be of the nature:
CH,
CH,
D I S C U S S I O N OF R E S U L T S
T h e data on composition and physical properties for the series of 43 fractions indicate that two general groups of hydrocarbon types may be responsible for the characteristics of the oil. T h e first group, which includes fractions 1 t o 34, is comprised largely of isoparaffins and cycloparaffins containing one t o six rings or an average of about two rings per molecule. These fractions usually exhibited the favorable properties of the oil, such as good viscosity, viscosity index, and pour point. The second group, which includes fractions 35 to 43, contains cycloparaffins having
Fragment of Molecule Monoc.ycloparaffin ring Condensed cycloDaraffin rineD iTriTetraPentaHexaHeptaOctaFree phenylb Free hydrindanb Free naphthalene*
0 0
0 5
25 9.
16 1 21 9 9.7 8 3 4.8 0.6 0.7
0 0 0 0 0 0
3.3 2.4
4 1 4 0 3 4
16 1 21 9 9 7
0 . 8
..
10.2 1. o
100.0 b
Fragments Free t o Be Combined with Others (Probabilities), yo
25 9
0.0 0.0 0.0
0.6
0.0 0.0
0 1
.. ..
~
0.0 0.0 12.0
Value of 11% assumed for calculation. Only fragment of parent molecule determined.
XII. Comparison of Calculated with Parent Ion Analysis of Fraction 43
Cycloparaffin Component TetraPentaHexaHeptaOctaYonaDeea-
Calculated, % 9 17 21 19 16 10
8 100
Parent Ion Analysis, % 5
28 24 17 13 9 4 100
ACKNOWLEDGRlENT
The authors wish to acknowledge the material assistance of John K a t t , who supervised the viscosity measurements. They also appreciate the efforts of Frances Galbraith and George Rlartin, who carried out most of the calculations, and V, A. Cirillo, who Tyas responsible for the infrared and ultraviolet data. Thanks are due also to API Research Project 42 for the loan of pure hydrocarbons used in this study. LITERATURE CITED
XI. Fragment Data for Fraction 43 Molecules Fragments Containing Assumed Only t o Be Fragment One Associated Ion System with Analysis, of Rings, Aromatic 70 % Nuclei, %
Table
-1lthough a small portion of the rings were aromatic, it is believed that the preponderance of cycloparaffin rings controls the physical behavior of these molecules. I n regard t o the composition of fraction 43, the properties of this material are by far the most unusual for any predominantly saturated oil ever examined in this laboratory or reported in the literature to date. The oil has the appearance of a colorless, thick, tack>-liquid which does not flow visibly below a temperature of 115” F. Mass spectrometric analysis has shown that this oil is comprised mainly of multiring cycloparaffins containing a t least four and as high as 10 rings per molecule. Of particular interest to those concerned with the composition of petroleum is the appreciable concentrations of 8-, 9-, and 10-ring hydrocarboni in the sample.
S o . of carbon atoms = 33
Table
three to 10 rings, or an average of about five rings per molecule. I n this case the properties of the oil changed very rapidly as the number of rings per molecule increased. A sharp rise Tvas noted in viscosities and in pour point, while the decrease in viscosity index was equally rapid. It is seen in Figure 9 that as the number of rings increased in the molecule, the length of aliphatic chains decreased.
5 0
2.4 0 0 0.0
.. ..
..
(1) Beal, E. S. J., Docksey, P., J . I n s t . Petroleum 21, 860 (1935). (2j Clerc, R. J., Hood, A., O’Seal, XI. J., Jr., ASAL. CHEM.27, 868 (1955). ( 3 ) Francis. S. d..I b i d . . 25. 1466 (19531. (4) Hastings, S. H., Watson, A. T., Williams, R. B., Anderson, J. A., Jr., Ibid., 24, 612 (1952). (5) Irish, G. E., Karbum, .4.C., I b i d . , 26, 1445 (1954). (6) Jones, A. L., Nilberger, E. C., I n d . Eng. Chem. 45, 2689 (1953). . 23, 1379 (1951). (7) Kinder, J. F., A N ~ LCHEW. (8) Lumpkin, H. E., Johnson, B. H., Ibid.; 26, ‘1719 (1954). (9) hlair, B. J., Rossini, F. D., I n d . Eng. Chem. 47, 1062 (1955). (10) hlelpolder, F. W., Brown, R. A., Washall, T. A., Doherty, W,, Young, W.S., ANAL.CHEM.26, 1904 (1954). (11) llelpolder, F. W., Washall, T. 4., Alexander, J. A, Ibid., 27, 974 (1955). (12) Xes, K. van. Westen, H. A . van, “.ispects of the Constitution of Mineral Oils,” Elsevier, lietherlands, 1951. (13) O’Iieal, 11.J.. Jr., “Applied Mass Spectrometry,” p. 27, Institute of Petroleum, London, 1954. (14) Rossini, F. D., Proc. Am. Pet~oleumI n s t . 19, 111. 99 (1938). RECEIVEDf o r review M a y 26, 1955. Accepted July 18, 1956. Group Seusion on Analytical Research, 20th Mid-Year Meeting, Division of Refining, American Petroleum I n s t i t u t e , St. Louis, RIo., M a y 9, 1955.
