861
V O L U M E 26, NO. 5, M A Y 1 9 5 4 LITERATURE CITED
(1) Brown, C., J . Phys. Cheni., 4 8 , 2 4 6 (1944). (2) Brown, W.E., paper presented at Electron Xicroscope Society of America Meeting. Pittsburgh. Pa.. Dec. 7 . 194ti. (3) IndiaRubber W o r l d , 118, 245 (1943). (4) Ibid., 1 2 2 , 7 1 (1950). (5) Ibid., 1 2 4 , 2 0 0 ( 1 9 5 l j . (6) Ibid., p. 446. (7) Ibid.. 125, 329 (1951). (8) llaron, S. H., and Ulevitch, I. S . , private comnlunication t o Ofice of Synthetic Rubber. Reconstruction Finance Corp. (9) Ileadors, V. G., and Rlesser. W. E., United States Rubber CO., private communication t o Office of Synthetic Rubber, Recon-
struction Finance Corp.
(10) lleadors. V. G., and Xesser, \T. E., private communication,
Oct. 11, 1946. (11) Norton, F. H., and Speil, S.,J . A m . C‘erum. Soc.. 2 1 , 89 (1938). (12) Schmidt, E., and Kelsey, R. H., I n d . Eng. Chem., 43, 406 (1951). (13) Schramm. E.. and Scripture, E. IT., Jr., *J. -4m.C e r a m Soc., 8 , 243 (192.5,.
Smith, H. 3 . , J\‘erner, H. G., l\-esterhoff, C. B., and H o w l a n d L. H., I d . Eng. Chem., 43, 212 (1951). (15) Svedberg, ’I., and Nichols, ,J. R.,J . A m . Chenz. Sue.. 45, 2910
(14)
(1923). (16) Svedberg. T., and Pedersen. K. O., “The Ultracentrifwe,” p.
67, London, Oxford University Press. 1940. RECEIVED for review May 18, 1953. Accepted February
4, 19.54 Presented before the Division of Rubber Chemistry at the 123rd Meetinr of the - & h l E R i C i S C H E \ r I C . 4 1 . S O c I E T Y , Boston, 1Iass , 192:3.
Analysis of Gas Oil and Cycle Stock from Catalytic Cracking E.
M.CHARLET, K. P. LANNEAU, and F. B. JOHNSON
Esso laboratories, Louisiana Division, Esro Standard Oil Co., Baton Rouge, La. A chromatographic technique is described for a tj-pe separation of the polynuclear aromatic hydrocarhona found in heavy gas oils and cycle oils. Vse of a sectional adsorption column is discussed, as is use of u l t r a \ iolet absorption spectra for identification of the polynuclear aromatic types found in the chromatographic fractions. .A method utilizing infrared ahsorption data, molecular weight, and carbon-hydrogen determinations in conjunction with the chromatographic separations and u l trayinlet absorption spectra is applied in the quantitative analysis of the aromatic fractions f r o m a heavy gas nil and heavy catalj-tic cj-cle nil. The compositions are presented in terms of the w-eight per cent of each molecular type found in the aromatic portions of the oils. The types are classified on the hasis of the configuration of the aromatic rings in the molecitles. Further data are presented to show the ai-erage weight per cent of aromatic rings in each of the nioleciilar types found in the gas oil and cycle oil.
S
ATISFACTORY methods of determining hydrocarbon types in petroleum fractions in the gasoline range have been developed and used for some time ( 5 ) . However, it has become increasingly important in the development of petroleum refining processes to learn more about the composition of higher boiling materials such as gas and cycle oils. This is especially true x i t h reference t o the various types of aromatic hydrocitrbona present. Methods which rely on the measurement of such physical properties as refractive index, depression, and gravit,y are of limitcd value when applied to these heavy fractions. Recently effort has been directed towards the estension of chromatographic techniques to the analysis of heavy petroleum fractions for hydrocarbon types. Clerc, Kincannon, and Wirr (1 ) have applied chromatographic analyses t o the detrrniinntion of monocyclic, dicyclic, and tricyclic aromatics in gas oils. Mair and his coworkers (3,6, 7 ) a t the Sational Bureau of Standards h a w ext,ended their original chromnt,ographic techniques t o the analysis of higher boiling fractions. I n the work described in this paper chromatographic techniques ustd in conjunction n-ith distillation and adsorption spectrophotometric techniques have been extended to obtain quantitativc, determination of various specific aromatic types of gas oil and catalytic cycle oil. Methods have been developed for the determination of the degree of side-chain substitution on the aromatic molecule, so that the actual percentage of aromatic carbons irl each of the various aronxitic types can be obtained.
EXFERIIIENT4 L PROCE1)UREb
Chromatographic Technique. -1 grrat deal has 1)een published oil the general application of chromatography to hydrocarbon separations. Fink and coworkers (9) have extensively invwtig:itetl the factors affecting efficiency of separation. Therefori,, thc gencral principles involvcd :ind the accepted procedures ire not discuswd hcri:. In each case the techniques t o 1~ uwd have to h a d n ~ ~ t ct od thc problem untlcr consideration. The v.ork tiiscuswd in thr pxpc’r w w done on a heavy c y l e oil froni c:it:ilytic cracking and on a hc1:ir.y g:w oil (Tat)le I). In both c:tsc’s the experimental trchniqucBs u s t d were similnr. Det:iileti :in:ilyticd data are prewiitcd only for t lie cycle oil.
Table I.
Inspection Data for Heavy Catalytic Cycle Oil and Heavy Gas Oil Cycle Oil
Gravity, A P I -4niline pt , F. Pour p t . , O F. Viscosity. Saybolt a t 210’ F Conradson carbon, nt. pc Carbon Hydrogen Sulfur .iromatics Distillation (coni.ertrd f r o i l l Ilit ijS distilled lopc distilled 20% distilled 3 0 q distilled 40V distilled 30‘7 distilled “0‘% distilled ( 0 % distilled 80% distilled 9 0 7 distilled 9.5% distilled Final R e c o v e r y . vel. c;
Gas Oil 21: 4 20.3
22.2 183 80 37.5 0 . 2li.5
10: 6’478
86.98 I S 00 0 2!li
88.14 11.ti2
0.138
31
44
4An
58.5
640 720 778 828 867 904 937 973 1020
..
708 71 . ..7
721’1 738 735 782 832 870
...
898 98.0
1045 44.0 ~~
.I diagram of the separation procedure employed is e h o w i i r i Figure 1. The oil was first separated into an aromatic arid a nonaromatic portion by adsorption on silica gel. The apparatus consisted of a conical glass percolator of 2-liter volume, 13 inches long, wit,h a 5-inch top diameter which tapers to 2.5-inch bottom diameter. The percolator was packed with a 28- to 200-mesh Davison silica gel. The sample charge, 175 ml. in the case of the heavy cycle oil, was diluted n-ith 350 ml. of n-heptane and M - ~ P allowed to drip rapidly from a separatory funnel onto a piece of filter paper placed on top of the silica gel in the adsorption vewA When all of the sample was in the gel, the nonaromativs werc~ washed from the column wit11 approsiniately 2500 mi. of n-ht,:)-
ANALYTICAL CHEMISTRY
862 tane. The removal of nonaromatics was indicated when the refractive index of the liquid dripping from the bottom of the vessel was the same as that for n-heptane. The aromatics remaining in the column were then recovered by desorption with approximately 2500 ml. of acetone. Finally the two separated fractions were stripped of heptane and acetone, respectively. The time for this separation procedure was 2.5 hours, exclusive, of stripping, one man being able to handle as many as four percolators simultaneously. It was found that the tapered shape of the vessel minimizes “channeling.” The method was found to be reproducible within 1%. The adsorptive capacity of the gelpacked vessel was a t least 75 ml. of the heavy aromatics in the materials being studied. Accordingly, the size of the sample charged was adjusted on the basis of its aromatic content.
‘A7k’ ( I ) SILICA
CHROMATOGRAPHY
SATURATES
AROMATICS
V
W
A H
M DISTILLATION
( I l l ) ALUMINA
CHROM.
Figure 1. Diagram of Analytical Procedure
The aromatic fraction was then separated into nine fractions by simple batch distillation a t absolute pressures of 0.08 to 0.15 mm. of mercury. Each of these fractions, or in some cases a composite, was then percolated through a sectional column packed with alumina. This special percolator consisted of a glass column of 25-mm. diameter, in ten 6-inch sections, connected by ground spherical joints and surmounted by a glass reservoir, Figure 2. Each section had a glass frit a t its bottom and was filled with activated alumina, Grade F-20, from the Aluminum Ore Co., East St. Louis, Ill. In each case the sample charge was 25 ml. of the aromatic distillation fraction. The sample was diluted n
