I
BEVERIDGE J. MAIR, PAUL E. EBERLY, KUN LI, and FREDERICK D. ROSSINI Chemical and Petroleum Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Pa.
Polycycloparaffin Hydrocarbons in Petroleum Only 59 of the 1520 possible bicycloparaffins, C4 to Cp, are likely constituents of petroleum
purpose of this article is to summarize the present knowledge of polycycloparaffin hydrocarbon in petroleum. Essentially all hydrocarbons found in significant amounts in naturally occurring petroleums are composed of a relatively small number of component parts -namely, paraffin, cycloparaffin, and aromatic groups (7). With these few parts, however, an almost limitless variety of hydrocarbon compounds can be made. Not all of the above classes of hydrocarbons are equally abundant in petroleum; some are present in relatively large amounts and others in almost insignificant amounts. When the rings of carbon atoms, either cycloparaffin or aromatic or any combination of them, are condensed, some carbon atoms will be counted in more than one ring, and the actual total number of carbon atoms may be appreciably less than the apparent number of carbon atoms obtained from the number of rings and the average number of carbon atoms per ring. This report is concerned with the cycloparaffin hydrocarbons having more than one cycloparaffin ring per molecule. T H E
Bicycloparaffin Hydroccwbons Cq to c9
Information on the total numbcr of possible bicycloparaffins that may exist, has been collected and is presented in Table I. The number of possible bicycloparaffin hydrocarbon compounds having a total of four to nine carbon atoms per molecule are classified according to the bicycloparaffin nucleus, such as bicyclobutane, bicyclopentane, or bicyclohexane (Table I). The designation of the ring system to which the given bicycloparaffin nucleus belongs follows the standard system of nomenclature in giving the number of carbon atoms in each bridge, not counting the two terminal carbon atoms (Table 1). The number of different bicycloparaffin nuclei are: bicyclobutane, one : bicyclopentane, two; bicyclohexane, three; bicycloheptane, four; bicyclo-
octane, six; bicyclononane, seven. For a given bicycloparaffin nucleus, the number of possible compounds increases greatly with the number of carbon atoms attached to the nucleus in the form of alkyl radicals. For example, with the bicycloheptane nucleus, [2.2.1], the number of possible compounds is four when one methyl group is attached to the nucleus, but 25 when one ethyl or two methyl groups are attached to the nucleus. Also, it is clear that the larger the bicycloparaffin nucleus, the greater the number of possible compounds formed with a given number of carbon atoms in attached alkyl groups. For example, adding one carbon atom successively to the number in the attached alkyl groups makes the number of possible compounds increase as follows: bicyclobutanes, 3, IO, 25, 68, 173; bicyclopentanes, 7, 29, 88, 191 ; bicyclohexanes, 22, 119, 437 ; bicycloheptanes, 35, 223 ; bicyclo-octanes, 57. The number of bicycloparaffin compounds having a given total number of carbon atoms in the molecule is as follows: Cd, 1; CS, 5 ; Cg, 22; C, 82; Cs, 219; Cg, 1091. This makes a total of 1520 compounds through Cg. Of these, the literature shows that only 25 have been prepared by man. Gasoline Fraction of Petroleum
The monocycloparaffins occurring in the gasoline fraction of petroleum are largely alkyl cyclopentanes and alkyl cyclohexanes ( 7 ) . However, a small amount of cycloheptane has also been isolated ( 2 ) . It may be assumed, then, that the bicycloparaffins occurring in the gasoline fraction of petroleum might principally be made up of rings of 5 or 6 carbon atoms, with possibly some rings having 7 carbon atoms. At present, the API Research Project 6 has isolated three different bicycloparaffins and detected a fourth from its representative petroleum. In the gasoline-fraction material boiling near 124.5' C., a very
small amount of a bicycloparaffin (about 1 part in 100,000 of the original crude petroleum) was detected. This material has not yet been identified although it may be a methyl-[2.2.1].bicycloheptane. From the material of the gasoline fraction boiling near 136.5" C., the compound cis-bicyclo[3.3.0]-octane has actually been isolated in reasonable purity (7). This compound, which has a freezing point of -49' C., occurs in this petroleum at about 1 part in 2000. From the material of the gasoline fraction boiling near 138' C.,the compound bicyclo- [3.2.1]-octane has been isolated with good purity (7). This compound, occurring in the petroleum at about 1 part in 12,000, is unusual in that it freezes a t f141' C. From the material of the gasoline fraction boiling near 146.7' C., a bicycloparaffin, CgHle, has been isolated with high purity (7). This compound freezes a t +5.7' C. The amount of it in the petroleum has not yet been determined, but is known to be small. Many additional bicycloparaffins boiling above 138' C. may be found in the higher gasoline fraction of the representative petroleum of the API Research Project 6. No other laboratories have reported the isolation of any bicycloparaffin hydrocarbons from the gasoline fraction of petroleum, Kerosine Fraction of Petroleum
T o date, only two individual bicycloparaffin hydrocarbons ( 7 ) have been 'isolated from the kerosine fraction of this representative petroleum-at 187.25' C., trans-decahydronaphthalene, or irans-bicyclo-[4.4.0]-decane, constituting about 1 part in 600 of the crude petroleum; a t 202.5' C., a bicycloparaffin compound which has not yet been identified. In the work on the kerosine fraction of its representative petroleum (7), substantially all the cycloparaffin material has been separated into a concentrate of monocycloparaffins and a concentrate of VOL. 50, NO. 1
JANUARY 1958
115
Table 1. Bicycloparaffin Nucleus Bicyclobutane Bicyclopentane
Number of Possible Bicycloparaffin Hydrocarbon Compounds (Four t o nine carbon atoms per molecule) Total Number of Carbon Atoms in hlolecule Ring c4 c5 C6 Cr CS CS System Number of Compounds [1.1.0]
1
[2.1.0] [1.1.1]
Bicyclohexane
[3.1.0] [2.2.0] [2.1.1J
Bicycloheptane
[4.1.0] [ 3 . 2 .O] [3.1.1] [ 2 . 2 . 1J
Bicyclo-octane
[5.1.0] [4.2 .O] [3.3.0] [4.1.1] [3.2.1] [2.2.2]
Bicyclononane
[6.1.0] [5.2.0] [4.3.0] [5.1.1] [4.2.1] [ 3 . 3 . 1j [3 2.21
a
10
25
68
173
1 1
5
21
2
8
67 21
130 61
I* 14, i b
7a, 5 b 3 ~ 3* , 4
34a, 2gb 18", 1 @ 20
133", 115* Sa,61b 70
la,
1
l a , 16
6b
l", l b 1
7a, 6* 5
I
4 l", l b 15, I* l a , I* 1 1 1
43a, 42b 43a, 40b 30 25 95, 9b 7 a , 76 55, 46 5 9 2 la, l b l a , I* la, l b 1 1
1
I
Total
3
1
5
22
82
319
1
1091
Number of isomers with the ring system in cis configuration. Number of isomers with the ring system in trans configuration.
bicycloparaffins. For the boiling range, 180' to 230' C., the cycloparaffins constitute about 44% of the material, with the ratio of bicycloparaffins to monocycloparaffins being about 1 to 3. Further processing may result in the isolation of additional individual bicycloparaffin hydrocarbons from this material. Only one other polycycloparaffin hydrocarbon has been isolated from the kerosine fraction of petroleum. Landa and Machacek (3) described the isolation of a tricycloparaffin from the material boiling near 192' C. of a Hodonin crude petroleum. The compound, which they named adamantane, was most unusual for it has a high density, 1.07 grams per ml., and a freezing point of 268' C., which is 76' C. above the boiling temperature of the material from which the compound was isolated. Later, Prelog and Seiwerth (6) established the structure of this compound to be tricyclo- [3.3.1.13J]-decane, a highly symmetrical compound with four bridges. Gas Oil and lubricant Fractions of Petroleum
To date, no individual polycycloparaffins have been isolated from the gas oil or lubricant fractions of petroleum. The API Research Project 6 has separated from its representative petroleum a concentrate of the branched paraffins plus cycloparaffins from the other hydrocarbons in the light gas oil range, C13 to CI,, and also, in an aliquot part, from
1 16
the heavy gas oil and light lubricating range, CIS to C25. From the data obtained, it is estimated that the light gas oil fraction, C13 to C17, of the representative petroleum contains about 46% of cycloparaffins with the ratio of mono- to bi- to tricycloparaffins being approximately 7 to 3.5 to 1. Similarly. the heavy gas oil and light lubricating distillate fraction, CIS to C25, of the representative petroleum contains about 47% of cycloparaffins, with the ratio of mono- to bi- to tri- and higher cycloparaffins being approximately 2 to 1.25 to 1. The lubricant fraction, C26 to C35, of the representative petroleum has been separated, principally by distillation at very low pressures and by extraction with reflux in tall columns, to give several series of fractions. Key fractions resulting from this operation were examined spectroscopically by 15 laboratories in the petroleum industry. The final results (4) indicate that this lubricant fraction contains about 45% of cycloparaffins, with the ratio of mono- to bi- to tri- and higher cycloparaffins being about 2 to 1 to 2. The mass spectral data also indicated that both condensed and single ring structures are present in nearly equal amounts in the polycycloparaffins, and that the ratio of cyclopentyl groups to cyclohexyl groups (present as free structures) in the cycloparaffins is nearly 2 to 1. Melpolder and coworkers, (5) reported that the greater part of the poly-
INDUSTRIAL AND ENGINEERING CHEMISTRY
cycloparaffins in a dewaxed lubricating oil fraction contain from one to six rings per molecule, and that higher cycloparaffins also appear to be present in small amounts. Conclusion
This article indicates the limited amount of knowledge of the polycycloparaffin hydrocarbons in petroleum, which constitutes appreciable amounts of the kerosine and higher-boiling fractions of every petroleum. A representative petroleum (I)-for example, polycycloparaffins-constitutes 11% of the kerosine fraction, 18% of the light gas-oil fraction, C13 to (217, 25% of the heavy gas-oil and light lubricating distillate fraction, C18 to ( 2 2 5 , and 36% of the lubricant fraction, Cne to ( 2 3 5 . From this information the bulk of the polycycloparaffin hydrocarbons apparently occur in condensed rings, the juncture may be made both through adjacent and nonadjacent carbon atoms, and in any given ring the number of carbon atoms is likely to be 5 or 6, or possibly 7, rather than some smaller or larger number. Assuming the number of carbon atoms in the rings to be 5, 6, or 7, the bicycloparaffins up to Cg in petroleum would have these nuclear structures : bicyclohexanes, none ; bicycloheptanes, [2.2.1]; bicyclo-octanes, [3.3.0], [3.2.1], and [2.2.2]; bicyclononanes, [4.3.0], [4.2.1], [3.3.1]: and [3.2.2]. The total number of compounds of this kind would be 59. literature Cited
(1 ) American Petroleum Institute Research Project 6, Chemical and Petroleum Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Pa., unpublished data. (2) Glasgow, A. R., Jr., Gordon, R. J., Willingham, C. B., Mair, B. J . , Rossini, F. D., Anal. Chem. 29, 357 (1957). (3) Landa, S., Machacek, V., Collection Czechoslov. Chem. Communs.
(4) (5)
(6) (7)
5,
1
(1933). Mair, B. J., Rossini, F. D., IND.ENG. CHEW47, 1062 (1955). Melpolder, F. W., Brown, R. A., Washall. T. A,. Dohertv. W.. Headington, C. E:, Anal. C&n. 28; 1936 (1956'1. Prelog, 'V,, 'Seiwerth, R., Ber. 74, 1644 (1941). Rossini, F. D., Mair, B. J., Streiff, A. J., "Hvdrocarbons from Petroleum," American Chemical Society Monograph 21, Reinhold, New York, 1953. RECEIVED for review March 14, 1957 ACCEPTED June 8, 1957
Division of Petroleum Chemistry, 130th Meeting, ACS, Atlantic City, N. J., September 1956. This work was performed under the American Petroleum Institute Research Projects 6 and 44, jointly. Part of the work is from a thesis submitted by Paul E. Eberly to Carnegie Institute of Technology in partial fulfillment of the requirements for the degree of Ph.D.
