firmed by its brown color with silver nitrate in group I. Both ferrocyanide and phosphate give blue color, have same R, value and remain at the centre. However, phosphate can be confirmed by its yellow color with silver nitrate while ferrocyanide does not give any color. The anions of group IV are detected by spraying the chromatoplate with potassium dichromate. The sampling capillary was successfully employed for taking samples from the surface of the following alloys. The few drops of the solution contained in the sampling capillary were transferred
directly to the TLC plate and the spot ww developed for the suspected group or transferred to a micro test tube for solvent extraction. The elements thus detected are given against each alloy. (1) Nicrome (Ni+*, Cr+a, Fe+a) (2) Chroma1 (&+a, Ni+*) (3) Brass (Cu+2, Zn+2) (4) Misch’s metal (Cefa) LITERATURE CITED
(1) “Chromatography,” p. 132, E. Merck, Darmstadt, 1965. (2) Hashmi, M. H., Shahid, M. A., Ayaa, A. A.,Talanta 12, 713 (1965).
(3) Jakovljevir, M. H., TadiE, I . P., Mikrochim. Acta 1965,937, (4) Meinhard, J. E.,Hall, F. N., ANAL, CHEM.21, 185 (1949). (5) Ibid., 22, 344 (1950). (6) Miller, C. C., Magee, R. J., J . Chem.
soc. 1951, 3183. (7) TadiE, I. P., JakovljeviE, M. H., Mikrochim. Acta 1965, 940. ( 8 ) Seiler, H., Helv. Chim. Acta. 45, 381 (1962). (9) Ibid., 46, 2629 (1963). (10) Seiler, H.,Seiler, M., Zbid., 43, 1939 (1960). ~~-..,.
(11) West, P.W., Mukherji, A. K., ANAL.
CHEM.31, 947 (1959). RECEIVEDfor review March 21, 1966. Accepted June 21, 1966.
Separation of Alkyl Sulfides by Liquid-Liquid Chromatography on Stationary Phases Containing Mercuric Acetate WILSON L. ORR Mobil Oil C o p , Field Research Laboratory, Dallas, Texas
A liquid-liquid chromatographic method is described by which alkyl and cycloalkyl sulfides can be separated from most other classes of organic compounds occuring in petroleum and similar complex materials. The stationary phases consist of mercuric acetate in aqueous acetic acid. n-Hexane is the mobile phase. Hydrocarbons and many other compound types are quickly eluted. Sulfides are delayed according to distribution constants which are proportional to the molecular weight or carbon-number. Sulfides with carbon-numbers up to 18 can be separated. Thiols are irreversibly adsorbed and are not recovered.
A
chromatographic method (LLC) has been developed which gives separations of alkyl sulfides from complex mixtures. Alkyl and cycloalkyl sulfides as a group can be completely separated from most other compound types, including saturated and aromatic hydrocarbons, thiophenes, condensed thiophenes, thiols, and aromatic sulfides. The method is applicable to alkyl sulfides with carbon-numbers up to about 18. Alkyl sulfides can be resolved on a carbonnumber or molecular weight basis. A difference in carbon-number of four is sufficient for complete separation; compounds differing by two carbon atoms can be almost completely resolved under optimum conditions. The method is particularly useful for the isolation of low concentrations of LIQUID-LIQUID
1558
ANALYTICAL CHEMISTRY
sulfides from complex materials such as petroleum, petroleum fractions, extracts of bituminous rocks, etc. It is useful also for the small-scale purification of synthetic or commercial sulfides. The use of heavy metal salts, particularly those of mercury, for the separation, purification, and identification of organic sulfur compounds is well known (1-3, 6, 7). The works of Challenger et al. (S), Birch and McAllan (I), and Emmott (4), pointed out the advantages of mercuric acetate over mercuric chloride for sulfide separations because of the water solubility of the mercuriacetates. Lower molecular weight sulfides can be extracted quantitatively from hydrocarbon solutions by using an excess of mercuric acetate in batchwise extractions. Because precipitates are not formed, there is a clean separation between the hydrocerbon and aqueous mercuric acetate phases. Furthermore, fractional extractions with a limited quantity of mercuric acetate will partially fractionate sulfide mixturese. g., cycloalkyl sulfides extract more readily than alkyl sulfides of comparable molecular weight (4). The composition of the mercuric acetate phase determines the molecular weight range of sulfides which can be extracted effectively. However, all previous work has been preparative and only qualitative observations have been reported. Birch and McAllan (1) used an extractant containing about 21y0 mercuric acetate in water slightly acidified with acetic acid. This reagent was reported to extract 5-thianonane (di-n-butyl sulfide) completely from
light petroleum solutions but would not extract an appreciable amount of 7thiatridecane (di-n-hexyl sulfide). Emmott (4) used a reagent composed of 28y0 mercuric acetate in 67y0 acetic acid. The higher content of acetic acid appears to facilitate the extraction of higher molecular weight sulfides since this reagent was reported to extract 7,9 - dimethyl - 8 - thiapentadecane (dicapryl sulfide) effectively. From the literature observations on batch-wise extractions, it was evident that the adaptation of the same phases to liquid-liquid chromatographic systems would greatly extend the usefulness of mercuric acetate separations if the complexing reactions were rapidly reversible. Distribution Behavior of Sulfides between Mercuric Acetate and nHexane Solutions. The separation of solutes by liquid-liquid chromatography depends on the distribution of solutes between two liquid phases, one stationary (s) and the other mobile (m). Regardless of the complexity of molecular interactions within the system, the distribution constant, K , which is defined as the equilibrium concentration of the substance in the stationary phase divided by the concentration in the mobile phase :
where [C]. and [C], represent the total amount of the solute per unit volume regardless of molecular state in the respective phases.
from 50 to 70% acetic acid. These large and systematic variations in K allow the selection of optimum conditions for specific chromatographic separations. If the useful range of K is considered to be from 0.5 to 15, each of the three phases (Table I) should be suited to the separation of sulfides of different carbon-number ranges as follows : Phase A , carbon-numbers 12 to 18; Phase B, carbon-numbers 9 to 13; and Phase C, carbon-numbers 7 to
'O0I
-
Table II.
o'017
8
0
10 I I
12 13 14 IS 16 17 18 19 20 21 CARBON NUMBER
Figure 1 . Distribution constants for alkyl sulfides
+ zHg(0Ao)z RUS(,)
____f
~t RB(.) t -
R2S :zHg(OAc)zc.) (2) The mercuriacetate complexes have low solubilities in hydrocarbons and the sulfides are eluted, therefore, as the free sulfide in the mobile phase. Separations which can be effected depend on the value of K which is the function of composition of the stationary phase and of structure of the sulfide. Three stationary phase compositions which have been investigated are given in Table I. Solvents are 70, 50, and 5y0 (by volume) acetic acid in water. The first is saturated with mercuric acetate and the others contain 20 wt.% mercuric acetate. Distribution constants for these stationary phases were measured at room temperature as described in the experimental section. K as a function of the carbon-number of the sulfides is shown in Figure 1; numerical data are listed in Table 11. K decreases rapidly with increasing carbon-number of the sulfide in all three phases. K also increases markedly as the acetic acid content of the stationary phase is increased. For a given carbonnumber, K increases about one order of magnitude in going from 5 to 50% or
Composition of Stationary Phases
Stationary phase A B
c
Grams Hg(0Ac)z per 100 grams acetic acid solution 70 satd. (ca. 22.5) 50 20 5 20 Solvent: vel. %
Distribution Constants for Sulfide Distributions between Mercuric Acetate Phases and n-Hexane at Room Temperature
Sulfide 4Thiaheptane 5-Thianonane 2,&Dimethyl-b thianonane 7-Thiatridecane SThiapentadecane 9-Thiaheptadecane
3-Methyl-ethiahexadecane
Alkyl and cyclcalkyl sulfides are essentially insoluble in water and completely miscible with hydrocarbons. A favorable distribution between the salt solution and hydrocarbon solution depends on formation of a coordination complex with mercuric acetate in the stationary phase. Addition of acetic acid to the aqueous phase increases the solubility of sulfides in this phase and may also have an effect on rate of equilibration. The type of equilibrium involved may be indicated as:
Table 1.
9-T hianonadecane 11-Thiaheneicosane
C No. 6
Phase A
10 12 14 16 16 18 20
... 12.2 4.4 1.7
8
9. Obviously, intermediate concentrations of acetic acid could be selected to optimize specific separations near the extremes of these ranges. For ideal chromatographic behavior, K should be independent of the total solute concentration (linear isotherm) and the equilibrium between the two phases should be rapidly established (6, 8). The distribution constant for 7thiatridecane (di-n-hexyl sulfide) was measured at three concentrations with the results shown in Table 111. The highest concentration is in the range used in our chromatographic experiments. K is constant within the accuracy of the measurements for concentrations ranging over an order of magnitude. The rate at which equilibrium is established in the chromatographic system is not directly measurable. Rates measured by shaking bulk phases are not applicable to the finely divided phases in the chromatographic system. However, it was noted in shaking bulk phases that the systems approach equilibrium after 1 hour of shaking. Analyses were not made a t shorter times. It appeared likely that equilibration would be reasonably rapid in the highly dispersed phases existing in a chromatographic column. Chromatographic Behavior of Alkyl Sulfides on Stationary Phases Containing Mercuric Acetate. The experimental conditions used for chromatographic experiments were selected primarily to develop a system for practical separations rather than to study the theory of the chromatographic process. However, conditions were idealized to some extent by
...
...
1.7
0.40 0.17
K Phase B 300
33 8.8 1.5
...
Phase C 23 2.2 0.33 0.02
.~~ ...
... ...
... ... ... ... ...
Table 111. Distribution Constant for 7-Thiatridecane between Stationary Phase A and n-Hexane at Room Temperature
Initial sulfide concn. in No. of hexane meas(moles/liter) urements K 0.0277 6 12.2 0.0138 12 12.1 0.00277 9 12.3
Std. dev. I-tO.3 f1.3
f0.9
keeping the flow rate and initial solute concentrations as low as was considered practical. Chromatographic separations were all carried out a t room temperature in a simple glass column 48 cm. in length and 0.81 em. i.d. The stationary phase was supported on 100to 200-mesh silica gel (deactivated) and the mobil phase was n-hexane saturated with 50% aqueous acetic acid. The sample was introduced in 0.5 to 1.0 ml. as a dilute solution in n-hexane. Solute concentrations were kept in the range of 5 to 20 pl./ml. in the sample solutions. Other details are given in the experimental section. Data for a typical LLC separation on stationary Phase A are shown in Figure 2. The sample contained five dialkyl sulfides, ranging in carbon-number from 8 to 20, and one n-paraffin (n-hexadecane). I n general, the analyses are based on one or two GLC runs on each cut and the accuracy is estimated to be 3 to 5%. The indicated total recovery of solutes ranged from 90 to 109yo. For the plot of percentage recovery us. VOL 38, NO. 1 1 , OCTOBER 1966
1559
IOOC
IO_
KI 1.01
Figure 2.
Typical separation on phase A
n-Cl6Haa
x
C8SClO C
0 ClOSClO
A
CCC-S-Ci,
0
0.1 .OB
C6SCa
.04
I
e
-
.os-
CdCt
-
.02
volume eluted (Figure 2), the data were normalized to the indicated recovery as 100%. Solute retention volumes were interpolated from plots of this type. Examination of Figure 2 indicates the specificity of this stationary phase for sulfide separations. The Cle sulfide (3-methyl-4-thiahexadecane) is almost completely separated from the 11.paraffin, the CI2sulfide (7-thiatridecane), and the C20sulfide (11-thiaheneicosane). There is a reasonable fractionation between the C16 and C,S sulfides (9thianonadecane). The separation between the Cia and C20 sulfides is poor and the sulfide is not adequately separated from the hydrocarbon. The Cs sulfide (5-thianonane) is so strongly retarded on this stationary phase that displacement with dimethyl sulfide was required for recovery in a reasonable volume of solvent (cf. experimental section). Separation characteristics are best summarized by means of retention volumes. The retention volume R' is defined as the eluant volume required
Table IV.
Compounds Sulfides BThianonane 2,8-Dimethyl-5thianonane
7-Thiatridecane 8-Thiapentadecane 9-Thiaheptadecane
3-Methyl-4-thiahexadecane
9-Thianonadecane 1 1-Thiaheneicosane Other compound types Naphthalene Phenanthrene Benzothiophene Dibenzothiophene Diphenylsulfide
to elute 50% of the solute. Values of
R' are interpolated from plots of solute recovery us. eluant volume such as Figure 2. The zero volume cannot be accurately determined from the sample introduction in these experiments because the sample volume is large compared to the total volume of mobile phase in the column. This is a major reason for including a paraffin hydrocarbon in each sample; its retention volume can be used as a reference point and as an approximate measure of the mobile phase volume. Normal paraffins are assumed to have no appreciable interaction with the stationary phase and their movement follows that of the mobile phase through the column. The corrected retention volume, R, for each solute is obtained by subtracting the retention volume of the n-paraffin, R,' from R' for the solute :
R
R'
- R,'
Finally the equivalent retention volume, l?, is defined as the corrected retention
Equivalent Retention Volumes
(E)
c No.
PhaseA
R PhaseB
8 10 12 14 16 16 18 20
... ...
... ...
10
14 8 12 12
(3)
6.6 3.7 1.2 1.1 0.35 0.19 0.06 0.05 0.05 0.05 0.03
1.2
...
...
0.08
0.03
...
... ... ... ... ...
PhaseC 22 3.4 0.17 I
.
.
... ...
... ... ... ... ... ...
4
7
I
4 Ib
1'1
L I; /4 I; lk
;1
I8 ;9
do
CARBON NUMBER
Figure 3. Equivalent retention volumes (R) for alkyl sulfides 0 aecondary
0 primary
volume per milliliter of stationary phase in the column : =
R/V,
(4)
where V , is the volume of stationary phase expressed in milliliters. Table IV summarizes the equivalent retention volumes for all alkyl sulfides measured to date. The lower part of the table gives approximate values for other compound types and illustrates the low values characteristic of aromatic hydrocarbons, condensed thiophenes, and aromatic sulfides. 22 as a function of carbon-number of alkyl sulfides is shown in Figure 3. DISCUSSION
For the conditions used in the present experiments, an 22 value of 0.5 or greater is required to give a good separation from paraffin and aromatic hydrocarbons. Essentially complete separation from hydrocarbons is easily obtained when R exceeds 0.8. Reference to Figure 3 shows that the highest carbon-number alkyl sulfides which can be separated effectively from hydrocarbons is in the range of 17 to 18 for Phase A , 13 to 14 for Phase B , and 10 to 11 for Phase C. Longer columns and slower flow rates could extend these ranges somewhat. The effect of the structure of the alkyl sulfide (branching and position of branching) on 3 is not as important as the number of carbon atoms per molecule for the limited structural variations studied.
Optimum separations are obtained when B is between 0.5 and perhaps 5. Dilution of the solute by mobile phase increases the larger the value of R_ because elution band width increases Useful separations with increasing may be made when R is as large as 10, perhaps larger, but analysis of the eluant by GLC becomes difficult when R exceeds 5 unless the cuts are concentrated. Components with excessively large & values are recovered most conveniently by displacement with dimethyl sulfide. 5Thianonane was recovered in this way in the typical example shown (Figure 2). According to chromatographic theory (6, 8) the distribution constant of a substance between the stationary and the mobile phase is related to the retention volume of the substance by the equation :
c.
+
R' = V , K V , (5) where V , and V 8 are the volumes of mobile and stationary phases, respectively, in the column. Because R' = R V , and B = R/Vdby definition (Equations 3 and 4), Equation 5 can he simplified to :
+
R = K
-
(6)
The validity of Equations 5 and 6 depends on several assumptions and a p proximations made in the derivation. A constant K (linear isotherm), rapid equilibration, and a large number of theoretical plates (effective transfer units) are the major assumptions. Deviation from the simple relationship = K in excess of experimental errors indicates failure of the system to comply with the ideal behavior assumed. Figure 4 shows a plot of R us. K for data in Tables I1 and IV. Points for Phases A and B (phases with a high acetic acid content) are close to the theoretical 1: 1 relationship. The three points for Phase C, however, fall on a line indicating the relationship R = 10K. The reason for this rather large deviation for Phase C is not certain from available data but a slow rate of transfer of sulfide from the mercuriacetate complex to the mobile phase appears most likely. This deviation makes Phase C less useful for separations than was predicted from the distribution constants. For sulfides with carbon-numbers less than 10, the & values for Phases B and C are of comparable magnitude (Figure 3). Variations in _R and K caused by structural variations in isomeric sulfides have not been studied sufficiently to warrant detailed discussion. Most of the sulfides studied have been di-nalkyl sulfides and all compounds have a t least one primary carbon attached to sulfur. Larger structural effects are expected for cycloalkyl sulfides (sulfur in five or
six membered saturated rings) but suitable compounds of this type have not been available for testing. Distribution constants are expected to increase for cycloalkyl sulfides and the effect may be equivalent to a carbon-number decrease of two to four compared to alkyl sulfides ( 4 ) . Tertiary sulfides are reported to be cleaved by mercuric salts (7). Preliminary experiments with one tertiary (2,2-dimethyl-3-thiapentadecsulfide ane) indicate that cleavage does occur. However, the decomposition is not complete under the conditions of the LLC separation and partial recovery can be made. The behavior of tertiary sulfides will be reported separately. The behavior of other compound types which react with mercuric acetate requires a few comments. Thiols appear to be retained on the columns as mercaptides. They are not eluted even with large volumes of solvents when present in amounts equivalent to the sulfides. Simple thiophenes with 2,bsubstituents and condensed thiophenes such as benzothiophene and dibenaothiophene are eluted early with hydrocarbons. Simple thiophenes with the 2 and/or 5 position unsubstituted have not been tested but they may be retained on the column as insoluble mercuration products. The behavior of olefins and disulfides may be complex and experimental studies should be made to define their behavior during LLC separations. EXPERIMENTAL
Column. All experiments were carried out in a borosilicate-glass chromatographic column consisting of a reservoir top-section of 50-ml. capacity and a column section 48 X 0.81 cm. i.d. The tube was constricted to a drip-tip a t the bottom and plugged with a small piece of glass wool before packing. The top terminated with a 35/20 ball joint for attachment to a nitrogen supply which was used for flow control. Solid Support for Stationary Phase. Davison silica gel (Code No. 923-08226, 100-200 mesh) deactivated by adding distilled water and drying for 16 hours a t 110' C. was a satisfactory support. Stationary Phases. The stationary phases which have been investigated were prepared from reagent grade chemicals as indicated in Table I. Mobile Phase. Redistilled nhexane (Phillips Pure Grade) equilibrated with aqueous acetic acid (1 : 1 by volume) was used for the mobile phase. Chromatographic Procedure. The chromatographic column was packed with 25 ml. of the dry solid support and 15.0 ml. of the stationary phase was added. Xitrogen pressure was applied to slowly force the liquid phase through the column. When the level just reached the top of the solid support, 40 ml. of the mobile phase
I L. . '
IW
Figure 4. and R
't '
'
yo""
'
-R
'
""
1.0
'
'
k'
0 10
Relationship between K
0 phase C; solid line R/K = 1.0; dashed line, _R/K = 10
0 phases A and B ;
was added and slowly passed through the column. Generally about 5 ml. of stationary phase was displaced and the amount remaining on the support was determined by difference. Column preparation required about 3 hours. When the 40 ml. of mobile phase reached the top of the solid support, the sample solution (0.5 to 1.0 ml.) was added by pipet and brought into the column with a minimum volume of mobile phase. The reservoir was then filled with mobile phase and the flow rate was increased to about 0.5 ml./ minute. Eluant was collected in small cuts (1 to 5 ml.) starting just after the sample was introduced. All operations were carried out without temperature control a t ambient temperature (22' to 26' C.). Solutes which were so strongly complexed as not to be eluted in a convenient volume were found to be quickly displaced by the addition of 1.0 ml. of dimethylsulfide to the mobile phase a t the appropriate time. When displacement was used, calculation of the equivalent retention volume was prohibited but recovery of strongly complexed sulfides was allowed. Other possible displacing agents have not been investigated. Sample Solutions. Sample solutions were prepared in hexane t o contain from 5 to 20 pl./ml, of each sulfide and/or other solute. A normal paraffin, usually n-hexadecane, was included in each sample mixture. Sulfur Compounds. Commercial sulfur compounds were from either J. T. Baker, Aldrich Chemical Co., or Eastman Chemical Co. The following compounds were synthesized by standard methods ( 4 , 7 ): 9-thianonadecane: 9-thiaheptadecane : 3-methyl4-thiahexadecane. Analysis of Fractions. The sample solutions and chromatographic fractions were analyzed by gas chromatography using an Aerograph Model 1520 with a hydrogen flame detector.
VOL. 38, NO. 1 1 , OCTOBER 1966
1561
Measurements were made by peak area using a Disc Integrator on a Minneapolis Honeywell Class 15 recorder. The sample solutions were used as standards and the fractions analyzed in terms of percentage recovery of each solute in each fraction. Because of the large number of cuts, replicate runs were not always made and analyses are considered to be accurate to only 3 to 5OJo0. Solute recoveries, from the sum of the contents of each cut, ranged from about 80 to 110%. Lower recoveries were generally associated with more strongly adsorbed solutes which eluted over a larger number of cuts. More accurate determinations would be required to determine whether actual losses are involved or whether the lower indicated recoveries are accumulated errors for the more dilute solutions. Distribution Constants. Equal volumes of the stationary phase and a
hexane solution of the sulfide were shaken in vials sealed by serum caps. Samples of the hexane layer were withdrawn by a syringe at various intervals from 1 to 24 hours and analyzed by GLC. The distribution constant, K , was calculated assuming that the decrease in sulfide concentration in the hexane layer represented the sulfide concentration in the stationary phase layer. In all cases, the value of K did not change appreciably after 1hour of shaking but the tabulated values are based on analyses made after 24 hours. Most measurements were made with an initial sulfide concentration of 6.66 pl./ml. in the hexane. ACKNOWLEDGMENT
The author expresses his gratitude to C. H. Calvert for assistance in the laboratory.
LITERATURE CITED
(1) Birch, S. A,, McAllan, D. T., J . Inst. Petroleum Tech. 37, 443 (1951). (2) Challenger, F., “Aspects of the Organic Chemistry of Sulfur,” pp. 1-20, 73-90, Butterworth, London, 1959. (3) Challenger, F., Haslam, J., Bram-
hall, R. L., Walkden, J., J . Inst. Petroleum Tech. 12, 106 (1926). (4) Emmott, R., Zbid., 39, 695 (1953). (5) Hopkins, R. L., Coleman, H. J., Thompson, C. J., Rall, H. T., U . 8. Bur. Mines, Rept. Invest. 6458 (1964). (6) Keulemans, A. I. M., “Gas Chromatography,” pp. 96-129, Reinhold, New York, 1957. (7) McAllan, D. T., Cullum, T. V., Dean, R. A., Fidler, F. A., J . Am. Chem. SOC.73, 3627 (1951). (8) Purnell, H., “Gas Chromatography,” p. 93, Wiley, New York, 1962.
RECEIVEDfor review June 13, 1966. Accepted July 25, 1966.
Identification of Thiaindans in Crude Oil by Gas-Liquid Chromatog rap hy, DesuIfurization, and Spectral Techniques C. J. THOMPSON,
H. J.
COLEMAN, R. 1. HOPKINS, and H. T. RALL
Barflesville Petroleum Research Center, Bureau of Mines,
b Knowledge of the sulfur components in petroleum is of both theoretical interest and practical value to the petroleum industry. The apparent absence of thiaindons in petroleum has been of interest to sulfur and petroleum chemists for many years. Recently the authors have identified 1 -thiaindan and 17 alkylthiaindans, in Wasson, Texas, crude oil by a combination of gas-liquid chromatography, desulfurization, and spectral techniques. This represents the first known identification of this class of sulfur compound in petroleum. These identifications and the techniques employed are described.
C
of the sulfur compounds in petroleum has special significance for petroleum scientists. Information, both qualitative and quantitative, concerning these compounds is valuable, not only as an addition to fundamental knowledge but also as an aid in processing applications. The presence in petroleum of thiols ( I , S), chain sulfides (9), cyclic sulfides (1, 6, IO), thiophenes ( I , II), and benzothiophenes ( 2 ) is well documented. While the presence or absence of thiaindans in petroleum has been of int,erest for some time, their identification has HARACTERIZATION
1562
ANALYTICAL CHEMISTRY
U. S.
Department of the Interior, Bartlesville, Okla.
not been reported gespite their expected presence because of a close similarity in structure to the relatively abundant benzothiophenes. This paper describes the procedures used for the isolation and identification of thiaindans in a Wasson, Texas, crude oil distillate boiling at 200’ to 250’ C. It discusses the p r e p arat,ion of the thiaindan concentrate, the positive identification of l-thiaindan,
a ,
%methyl-1-thiaindan,
DC ,
2,2-dimethyl-1-
thiaindan,
and the tenta-
and
m z
tive identification of alkylthiaindans.
15 additional
EXPERIMENTAL
Preparation of Thiaindan Concentrate. The 200” to 250” C. distillate in which the thiaindans were identified was obtained by a series of isothermal, molecular, and fractional distillations as outlined in Figure 1. The all-glass, steam-heated, isothermal stripping unit previously described (8) was used to strip the lower boiling distillate from the crude oil. The higher boiling distillate was removed using a Consolidated Vacuum Corp. centrifugal molecular still. The residence time in the heated zone of both the isothermal
still and the centrifugal molecular still was but a few seconds. This short contact time and the low temperatures employed tended to protkct the sulfur compounds from thermal breakdown or rearrangement. The distillate prepared from the crude oil then was fractionated into selected boiling ranges a t 15 mm. Hg through a concentric tube column having an annulus of 0.04 inch and a lengtKof 48 inches. The 200’ to 250” C. boiling ranee distillate produced in the above tre& ment was percolated through silica gel to provide two fractions-one a hydrocarb )n discard essentially free of sulfur and the other a sulfur compound concentrate. This concentrate was treated successively with sodium hydroxide and sodium aminoethoxide (6) to extract thiols and phenols. The thiol-free concentrate was filtered through a 15foot by 2-inch diameter bed of H-41 alumina using gradient elution chromatography. This treatment produced 27 fractions as indicated at the bottom of Figure 1. The sulfur-containing fractions-Le., 19 through 26-were treated, as shown in Figure 2, with anhydrous H I in butane solution at -78” C. to extract the sulfides (4)after those substances which crystallize upon chilling were first removed. The residues from the HI treatment and the precipitates from the butane treatment were combined and treated twice with trinitrobenzene to remove benzothiophenes and
