Isolation of Olefins from Bradford Crude Oil RICHARD E. PUTSCHER Armour Research Foundation of Illinois Institute of Technology, Chicago, Ill.
A previous paper by Fred and Putscher assigned the 10.3-micron infrared absorption band characteristic of Pennsylvania lubricating oils to trans-olefins. The presence of 10.3-micron absorption in the crude oil was also shown. Therefore, work was undertaken to show the presence or absence of trans-olefins i n the crude oil, and it was decided to investigate the gasoline fraction. Bradford crude oil, typical of Pennsylvania crude oil, was found to contain small quantities of heptenes and octenes of the trans configuration which exhibited the 10.3-micron absorp-
I
tion bands The olefins were separated by a combination of silica gel adsorption and fractional distillation. Although the molecular weights of these olefins are far removed from those in the lubricating fraction, i t is the author's contention t h a t the presence of 10.3-micron absorption in the lubricating oil indicates the same type of olefinic configuration; t h e olefinic double bond is probably in side chains attached to cycloparaffin rings. The author believes it is also the first evidence of the existence of low boiling olefins in Pennsylvania crude oil.
DISTILLATTOIV OF CRUDE OIL
iK A recent paper ( 5 ) on the identification of Pennsylvania
lubricating oils by infrared absorption i t was reported that Pennsylvania oils are characterized by infrared absorption a t the wave length of 10.3 microns. This absorption n-as assigned to trans internal unsubstituted olefins. Several investigators (2-4, 6, 10, 11) have reported the 10.3 micron absorption band as characteristic of the trans configuration. The presence of these olefins was also indicated in the crude oil by the same infrared absorption band. Therefore the present work was undertaken to shoiv the presence or absence of tmns-olefins in the crude
Because Bradford crude oil is considered typical of Pennsylvania crude oil, it was chosen as the crude source for this work.
This crude oil was a sample taken from the supply line to the refinery and had not been touched by any refinery treatment. The specific gravity a t 250' C. of this sample of Bradford crude oil is 0.8061, and the B P I gravity is 42.3 with a sulfur content less than 0.1%. The 10.3-micron absorbance for a 0.101-mm. cell is 0.160. The gasoline fraction boiling below 150' C. was stripped from 7507 grams of the crude oil charged in two batches, to a vacuum still. The pressure in the still head was varied from an initial pressure of 200 mm. to a Table I. Distillation Fractions from Gasoline final pressure of 10 mm. A trap imFraction No. AI A2 A3 A4 A5 A6 mersed in a dry ice-acetone bath was 130-150 90-116 115-130 Boiling range, C. Gas t o 26 26-65 65-90 kept' between the distillate receiver and 14.4 17.1 22.4 9.8 Volume % 17.1 19.2 n '," ... .,, 1.39273 1.40870 1.41860 1.42990 the vacuum pump. The fractionating n s5 ... .,, 1.38114 1.39944 1.40880 1.41950 colunin consisted of a borosilicate glass d 26 ... ,.. 0.6813 0.7130 0.7300 0.7478 vacuum-jacketed column 20 mm. in diSp. dispersion, " c XD 104 ' . , 126.3 129.8 134.2 139.0 ameter, packed with glass helices to a d height of 2 feet. The highest tempera1.0338 1.0466 1,0429 Ref. intercept, nD - 0 . 5 ~ ... ,,, 1.0435 ture reached in the still pot, a: observed 0.185 0.126 0.177 1 0 . 3 p absorbance ... ... 0.09 (0. !Ol-lyrn. cell) on the thermometer was 91 C. The Bromine Bo. ... 1.0 1.5 2.3 3.0 3.8 quantity of material collected and called gasoline in this report consisted of all material boiling below 150" C. (302' F.). Precise cutting of the fraction a t 150" C. was not necessarv. as only olefins boiling lower than 130" C. were oil. It was decided to investigate the gasoline fraction of the investigated. crude oil, because separation techniques are simpler than with hydrocarbons of higher molecular weight and the physical properA total of 20.470, by volume, of gasoline was obtained from ties of the hydrocarbons present are better k n o m . The infradistillation of the crude. The sulfur content of this material is red data, for example, are more complete for compounds in the gasoline range than for hydrocarbons of higher molecular 1%-eight. Table 111. Fractional Distillation ' '
Table 11. B.P. of
Fraction,
c.
,
Fraction
Silica Gel Fractionation of Distillation Fractions Fraction No.
70 of R u n
70 of Gasoline
c2
Brl No.
26-65
B1 B2
94.9 5.1
18.22 0.98
0 4
65-90
B3 B4
81.1 18.9
7.95 1.85
0 5
115-130
B9 B10 B11
70.0 22.8 7.2
10.08 3.28 1.04
0 6.6
130-150
B12 B13 B14
70.0 15.0
12.02 2.54 2.54
0.2 10 9
15.0
c1
c3 c4 c5 C6 c7 C8 c9 c10
c11 c12 C13 C14 Cl5
5.7
1551
Boili5g Point, C. 62-60
% of Distillate
% of Gasoline
Silica Gel Fraction B2 50.0 0.49
Brz KO.
10.3-p Absorbance (0.101-Xlm. Cell)
1
60-66 7.5 ... 7 66-69 29.5 0.49 10 69-74 13.0 .. 9 Blend of Silica Gel Fractions B4, B7, B11, and B14 70-78 4.1 0.26 18 8.2 0.52 2.5 7 8-8 1 81-98 4.1 0.26 44 98-108 8.8 0.56 23 10&120 19.5 1.25 120-125 4.1 0.26 30 lo ' 125-134 4.1 0.26 23 134+ 47.1 3.00 10 Blend of Silica Gel Fractions B6. B10. a n d B13 58-80 12.2 1.05 2 3.21 5 80-112 37.3 112-124 21.2 1.82 8 124-132 5.4 0.46 9 23.9 2.06 12 132 T
... 0.210 0.264 0.129
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... ... ...
... ...
1552
ANALYTICAL CHEMISTRY
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0.05%. I n the following report this gasoline fraction is considered as the 100% starting material. If approximate percentages based on the crude are desired, the figures given may be divided by 5. ISOLATION O F OLEFINS FROM GASOLINE FRACTION
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MICRONS
Figure 6. Infrared Spectrograms Upper. Center.
Lower.
Adsorption fraction F3, 0.101-mm. cell l e n g t h Adsorption fraction F4, 0.101-mm. cell l e n g t h Adsorption fraction F5, 0.101-mm. cell l e n g t h
I n order to simplify reference to any particular fraction in this work, the different operational steps have been designated by capital letters in the block-type flon diagram shown in Figure 1. Fractions obtained in any step are designated by consecutive numbers in each section. The letter S after a given block indicates that that fraction was set aside a t that point because it v a s substantially olefinfree. The gasoline fraction, obtained above, was next charged to the same distillation column previously used and distilled into closer boiling fractions. These fractions are shonn schematically in Section A of Figure 1. Table I summarizes the distillation data and other properties of interest. Removal of the gases through pentane nas done a t atmospheric pressure, after R hich the pressure was successively reduced during the distillation to prevent high temperatures in the still pot. The highest still temperature observed u a s 142" C , !%rich occurred during the depentanization a t 760 mm. Fraction A l , amounting to 17.1%, n a s discarded, as very little olefin content was expected. The 10.3-micron absorbances and bromine numbers (1) of the other fractions amounting to 82.9% of the gasoline are shown in Table I. Since methylcyclohe-tane (boiling point 98.6" C.) \Fill also show 10.3 absorbance, the values shov,n are not due solely to trans-olefins. Silica gel adsorption \\as used, in the next step, to concentrate any olefins contained in fractions A2 to A6. These operations are shown in Section B of Figure 1. The adsorption columns used have been described ( 6 ) . The adsorption technique is es-entially the same as developed by bIair (8) a t the Xational Bureau of Standards. Table I1 shoas the fractions collected from each filtration and their bromine numbers. Work was continued with those fractions containing olefins, as shown by the bromine numbers. These fractions (B2, B4, B6, B i , B10, B11, B13, and B14) amount to lE1.957~of the gasoline. Section C of Figure 1 shows the nevt step in the olefin isolation-the distillation of the olefin-containing fractions from adsorption step B. The distillation column used here and throughout the rest of this nork was a 100-plate Podbielniak column. The fractionating
1556
ANALYTICAL CHEMISTRY
section \\as 13 mni. in diameter and contained 3 feet of Heli-grid packing. The paraffin-naphthene fractions containing the olefins were blended together (see Section B of Figure 1) for fractional distillation, vhile the aromatic fractions \\ere separately blended and distilled, as better separation can be obtained in this manner. Table I11 s h o m the rewits of the three distillations. I n this etep 7.12% of the gasoline (fractions I , 4, 10, 11, and 15) was set aside and work n as continued on the remaining 8.83%. T n o fractions, C5 and C8, were obtained in the distillation of the aromatic fractions that showed bromine numbers of 44 and 30, respectively. The boiling range indicates that sample C5 contains heptenes and C8 octenes. Infrared 2 3 4 5 6 7 e s IO I I I2 13 I5 spectrograms obtdined on these fractions are shown in Figure 2. The presMICRONS ence of trans-olefins is clearly shown in Figure 7. Iiifrarecl Spectrograms of Phillips (95 Mole 'j&)2-Octene these curves by absorption a t 10.3 mi0.025-mm. cell length crons and substantiated by the bromine numbers shown in Table 111. Section C of Figure 1 shows that three blends were prepared Table 1.. Distillation of Fraction D10 from Silica Gel from the distillation fractions for further concentration of the ,idsorption olefins by silica gel adsorption. Adsorption runs were made on 10.3-r Abnarrox boiling cuts rather than the total gasoline, in order to :.P., Fraction "c of Di3ccof sorbance (0.101 C. so. tillate (:asoline Br2 No. M m . Cell) qecure shaiper separation zones of the olefins on silica gel than 6!)-7Ij El 0 "2 17.0 3 \ \ o d d be obtained if a grpater range of molecular weight olefins E2 i2.2 76-93 0 16 28 0 : 630 were present. E3 12.8 93-103 0.17 52 1.370 E4 1 4 . 9 103-112 0 20 52 0.630 Section D of Figure 1 shons the next step in which the three 115-120 E5 19.2 0 25 48 0,820 120-125 52 E6 i.j.4 0 20 0.990 blends from Section C \%erefiltered through silica gel. The re125-132 E7 8.5 0 12 39 0.640 fractive index as closely follon ed in these separations to determinr cut points. Table I V summarizes the data obtained in this separation. Fractions D6 and D9 nere set aside because 'Tahle iI. Silica Gel Fractionation most of the hydrocarhons piecent nere aromatics and the frac10.3-p r2bsorhtions were a very small percentage of the whole. Olefin frac:.P., Fraction 7 of Gasoance (0.101C. So. cc of Run line Br? No. Aim. Cell) tions obtained were blended together again and another adsorpBlends of E2, E8, and E4 tion run v a s made to secure a more concentrated olefin fraction iR-I12 F1 63 0 33 6 0 430 (D10) for distillation. Figure 1 shoT\s that 1.32%of the original F2 37 0 20 98 1.300 gasoline remained for further work after this adsorption step. Blends of E5, E6, and E7 Fractional distillation (see Section E of Figure 1) of the remaining 1.32% of the gasoline was next performed using the Podbielniak distillation column. Table V shons the fractions collected, the bromine numbers, and infrared absorbance a t 10.3 microns. Infiared qpectrograms were also obtained on fractions E2 to Table VII. Physical Properties E7 and ai e shown in Figures 3 and 4. Fraction so.
F2
Table IV. B . P . ofbraction, C.
Silica Gel Fractionation
Fraction 50. % of Run
70 of Gasoline
Br? To.
n'D" d:5 1.44021 1.42684 0 . 7 4 3 6 ln2f
F4 1.4289% 1.41780 0.733.5 Phillips 1.42371 1.41277 0 , 7 2 1 0 4 2-octene
Refractiv10.3-p Absorbity InterSp. ance (0.101cept Disp. Mm. Cell) 1.0580 179.8 1.300 1.0611 1 0323
151.6 i51.7
2.700 2,360
Blend of Fractions C2 and C3 65-i8
D1 D2 D3
63.0 27.5 9.5
0.47 0.21 0.07
..
.. ..
Blend of Fractions C5, C6, and C12 81-112
112-134
65-134
D4 80.3 3.24 D5 15.7 0.63 D6 4.0 0.16 Blend of Fractions C8, C13, and C14 D7 58.0 2.33 D8 39.2 1.59 D9 2.8 0.11 Blend of Fractions D2, D 3 , D 5 , and D 8 D10 D11
53.0 47.0
1.32 1.18
.. 9
..
10
40
Because greater purity of an olefin fraction was desired, another separation x a s made using silica gel adsorption. Two blends nere prepared (see Section E of Figure 1): (1) fractions E2, E3, and E4 (0.53% of the gasoline), containing trans-heptenes, and (2) fractions E5, E6, and E7 (0.57% of the gasoline), containing trans-oc tenes. The small quantity of material available from these two blends necessitated the construction of two small adsorption columns of &mm. glass tubing packed with Davidson silica gel (through 200 mesh) t o a height of 118 em. I n these separations the refractive index was clo~el\folloned and uqed as a guide in chang-
1557
V O L U M E 2 4 , NO. 10, O C T O B E R 1 9 5 2
7~5~ trans-2-Octene cis-2-Octene trans-3-Octene cis-3-Octene
Table IX.
Refractivity Intercept 1,0529 1 0525 1.0647 1 033
d:' 0.7157 0.7201 0.7110 0.717
1.4107 1.4125 1.4102 1.4111
Physical Properties of Two Olefin Fractions Olefin Fraction from Lube Oil
Fraction F2 Octenes 0 . 1 9 (of gasoline) 2.7
f e r cent 1 0 . 3 - r abqorbance 1 0 .101-mm. cell) Bn S o . ,/ I!
Fraction F4 (octenes) appears to he pure olefin according to the bromine number and specific dispersion, but the density, refractive index, and refractivity intercept show the presence of some other compound or compounds-probably cycloparaffins. -4s the density is higher than that of the olefins expected to be present, paraffins are excluded, and as She intercept is lower than that of the olefins espected, aromatics are also excluded. cisOlefins will also reduce the intercept and increase the deivity and, therefore, may be present. The physical properties of F4 are close (allowing for the presence of cycloparaffins and cisolefins) to the literature values shown in Table I'III. X comparison of the infrared spectrum n-ith the infrared curve of 2-octerie (Figure 7 ) shows that the most similar portions of the spectra are in the 10.3-micron region. The spectrogram of Figure 7 is essentially the same in this region as the API infrared spectrogram serial S o . 635 of 2-octene and n-as obtained on a middle cut from the fractional distillation of Phillips 2-octene (95 mole yo).
Phj sical Properties of Olefins
'Table VIII.
148 1,42892 1,41780 0.7335 1.0511 151.6
'2
:;
(!25
REI. intercept Sp. dispersion,-
1 0 . 2 (of neutral) 0.930
d
40 1,48744 1,47595 0,86204 1.04493 133.3
CO1IP.ARISON O F OLEFINS FROM GASOLINE 4 S D LUBRICATING OIL
The similarity of the olefin fraction F4 and olefins concwitrated by silica gel adsorption froin Bradford neutral lubricating oil may he seen b y coniparing Figure 6 (center), the infrared curve of sample F4, and Figure 8, the infrared curve of the olefin from lubricating oil. The olefin fraction from lubricating oil was obtained by repeated adsorption runs of olefin containing frartions closely following the elution technique developed t>y Lipkin et aZ. (7'). The physical properties of these olefin t'ractions are coinpared in Table I S . This similaritj- furnishes very good substantiating evidence that the olefins in lubricating oil contain the same trans-olefin linkage present in the gasoline fraction, although they may be present not in straight chains but in Bide chains attached to cycloparaffin and aromatic rings. I n a recent study of the revised -4PI infrared curves of olefins, i t appears that the 6.1-micron band shown in the infrared spectrum of the above olefins [see Figures6 (center)and ilischaracteristic of cis-olefins. Further \\-ark ip being done to obtain more informa tion in answer to these interesting questions.
ing receivers. X poor septration of blend 1 containing the heptenes \\-as obtained. but a much better separation of blend 2 \vas ohtained, as shonn in Table VI. Section F of Figure 1 : i l ~ oIlriefiy summarizes this. Infrared spectrograms of fractions F1 to F 5 were also obtained and are s h o m in Figures 5 and 6. Figure 5 (F2) and 6 (center), of most interest here, shoiv respectively the presence of Irnnr-heptenes and trans-octenes. PHYSICAL PROPERTIES O F FINAL OLEFIN FRACTIOYS
Physical characteristics of fractions F 2 and F4 were also obtained and are shown in Table VI1 along with data for a sample of Phillips 2-octene (95 mole yo) which was available in the Iahoratory. Table VI11 shovs the physical properties of olefins that are of interest here (9). The values for heptenes were not transcribed, aq fraction F 2 contains considerable toluene as s h o w by the iritrared curve, the specific dispersion, and refractivity intercept. There should he about 60% olefins in fraction F2, by calculation !rani the hiornine number.
SUM.1IAKY
Bradford crude oil, 13-hich is tvuical of Pennsvlvania crude oil, .. contains trans-olefins. There is iome evidence that czs-olefins are also present, but this has not been definitely established. The olefins shown hy this report to be present are heptenes and octenes. During the Fork some evidence of hexenes was obtained but not in sufficient quantity to isolate. The gasoline fraction contains a t least 0 6'70 (11v volume) of olefins.
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iCKNOWLEDGMENT
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Thanks are due to W. C. NcCrone for his helpful suggestions and comments during the course of this work and to Mrs. L. J. Patterson for 01)taining the infrared spectra shown in this report.
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