Fuel Processing Technology, 11 (1985)59--69 59 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

Q U A N T I T A T I V E D E T E R M I N A T I O N OF SHALE OIL COMPOUNDS BY GAS C H R O M A T O G R A P H Y - - M A S S S P E C T R O M E T R Y - - S E L E C T E D ION M O N I T O R I N G

YUDA YURUM and MOSHE LEVY

Department of Materials Research, The Weizmann Institute of Science, Rehovot 76100 (Israel)

(Received September 17th, 1984; accepted March 28th, 1985)

ABSTRACT

The chemical compounds present in a retort oil sample from an Israeli oil shale and their relative amounts were determined using the selected ion monitoring technique. Quantitative determination of the compounds present showed that the data obtained from whole shale and its subfractions produced by solvent extraction could be correlated. It was concluded that detailed structural results may be obtained from whole shale oil samples without the need to separate the shale oil into its subfractions. The shale oil con- tained 18% aliphatic long-chain hydrocarbons; the remaining identified portion consisted of aromatic, hydroaromatic, thiophenic furanic, phenolic and pyridinic compounds.

INTRODUCTION

The oil p roduced f rom the re tor t ing o f oil shales is more complex than crude pe t ro leum. Shale oil has higher con ten t s o f olefins, and nitrogen-, oxygen- and sulphur-containing c o m p o u n d s than does pe t ro leum. Detailed i n fo rma t ion o f the cons t i tuents o f the crude shale oil is an essential pre- requisite for the deve lopment o f convers ion and cleaning processes. Analysis o f shale oil can provide a full charac ter iza t ion o f the types o f chemical com- pounds which can be used in the design of convers ion and refining plants. Shale oil analysis possesses m a n y c o m m o n aspects with pe t ro leum analysis but requires analyt ical modif ica t ions because o f the complex i t y o f the shale oil. Solvent ext rac t ion techniques are basic for the separat ion and character- izat ion of the complex s t ructure o f shale oils. The fract ions ob ta ined in this manner can be analysed fur ther by ch roma tog raph ic and spect roscopic tech- niques. The separat ion, ident i f icat ion and quant i f ica t ion o f shale oil com- pounds require m u c h material and t ime-consuming methods . The purpose o f this s tudy was to develop a rapid, reliable m e t h o d to analyse shale oils and to eliminate the necessi ty of pref rac t ioning shale oil. Gas c h r o m a t o g r a p h y - - mass spec t romet ry - - se lec ted ion mon i to r ing (GC--MS--SIM) represents one o f the few me thods which allow a detai led analysis o f kerogens [1--3] . A

0378-3820/85/$03.30 © 1985 Elsevier Science Publishers B.V.

60

p re l imina ry accoun t o f the presen t w o r k [4] p rov ided qual i ta t ive m e t h o d s to charac te r i ze t he oils (n -pen tane-so lub le mater ia l ) and the asphal tenes (benzene-so lub le mater ia l ) o f a r e t o r t oil f r o m an Israeli oil shale b y GC- - MS--SIM. In the p resen t s t udy we charac te r ized who le shale oil samples w i t h o u t f r ac t i ona t ion and aim to q u a n t i f y the c o m p o u n d s o f d i f f e ren t chem- ical func t iona l i t i es by using the selected ion m o n i t o r i n g t echn ique . A com- par ison o f the con t en t o f the f r ac t iona t ed p r o d u c t s wi th t ha t o f the who le shale is also p resen ted .

EXPERIMENTAL

Fractionation o f crude shale oil

In this w o r k we analysed the r e to r t oil ob t a ined f r o m the Israeli Mishor R o t e m oil shale which was r epo r t ed to con ta in 14% organic m a t t e r [5]. The

Shale oil (70)

100.0

Toluene extraction and filtration

Asphaltenes + Toluene insolubles: n-pentane solubles Asphaltols (73)

Evaporation of toluene and extraction with n-pentane and filtration

n-Pentane solubles: Oils (71)

96.9

L Silica gel chromatography

n-Pentane Toluene Methanol eluate: eluate: eluate: Aliphaties (711) Aromatics (712) Polars (713)

% o f ( 7 0 ) : 16.5 43.3 33.3 %of(71) : 17.2 45.1 34.7

Toluene solubles (n-pentane insolubles): Asphaltenes (72)

3.0

Fig. 1. Scheme for fractionation of shale oil and the yields of fractionation.

61

fractionation scheme shown in Fig. I is according to the method described by Yiirfim [6, 7] to separate coal liquids.

Crude shale oil was separated into two fractions by refluxing with 20 times its weight of toluene for 4 h and filtering off precipitated asphaltols (toluene-insoluble materials), fraction 73, from the cooled solution. As- phaltols were washed with toluene until washings were clear. The filtrate and the combined washings were concentrated to 10% of the initial volume and ten times the volume of n-pentane then was added to precipitate the asphaltenes (n-pentane insolubles or toluene solubles, fraction 72). Asphalt- enes were filtered from the cooled solution and washed with n-pentane until washings were clear. The washings were combined with the n-pentane- soluble material (oils) solution. The solution containing n-pentane-soluble material was concentrated in a rotary evaporator under vacuum until it was solvent free.

The oils (n-pentane solubles; fraction 71) were fractionated further by silica gel chromatography in a 50 cm × 2 cm ID column. Silica gel (60-- 200 mesh) was prepared by washing with methanol and then dried at 90°C. Two grammes of oils (71) were eluted with 500-ml portions of n-pentane, toluene and methanol to yield three fractions, labeled aliphatics (fraction 711), aromatics (fraction 712) and polars (fraction 713), respectively. Fractionation was considered complete when the eluate showed the same refractive index value as the pure solvent.

Gas chromatography--mass spectrometry--selected ion monitoring of the fractions separated

All fractions were analysed with a Finnigan Model 4021 quadrupole GC--MS system. The column in the gas chromatograph was a WCOT capil- lary column of SE 54 coating (25 m X 0.25 mm) and nitrogen was used as the carrier gas (flow rate 1.0 cm 3 min-1). The oven temperature was pro- grammed from 50 to 200°C at 10°C min -1. In all the experiments the split- less injection technique was used. The mass spectrometric data were acquir- ed and processed with a Data General Nova 3 Data system. The samples were analysed with the mass spectrometer serving as a selective ion detector. By monitoring the fragment ions with specific m/z values, information has been obtained about the chemical structure of the samples. The selected ion was always the most intense peak in the mass spectrum of the compound searched [8]. The ions used in selected ion monitoring and their mass num- bers are given in Table 1.

Throughout the experiments acridine (9-aza-anthracene, m/z: 179)was used as an internal standard for quantification of the compounds searched. Certain compounds of different chemical functionalities were selected as model compounds to determine a relation between the ion current and the quant i ty of the compound. Tetradecane, naphthalene, dibenzothiophene, p-cresol and quinoline were used as model compounds for alkanes (and

6 2

T A B L E 1

I o n s used in selected ion m o n i t o r i n g

m/z Ion m/z Ion m/z I o n

A liphatic cha ins Th iophe nes 41 P r o p e n y l 84 T h i o p h e n e 43 P r o p y l 97 M e t h y l t h i o p h e n e i

111 D i m e t h y l t h i o p h e n e A r o m a t i c rings 134 B e n z o t h i o p h e n e J

78 B e n z e n e 147 M e t h y l b e n z o t h i o p h e n e k 91 M e t h y l b e n z e n e a 153 D i b u t y l t h i o p h e n e

105 T r i m e t h y l b e n z e n e b 160 P h e n y l t h i o p h e n e 161 D i m e t h y l b e n z o t h i o p h e n e

Naphthalen ics 184 D i b e n z o t h i o p h e n e 1 128 N a p h t h a l e n e c 198 M e t h y l d i b e n z o t h i o p h e n e m 141 E t h y l n a p h t h a l e n e d 142 M e t h y l n a p h t h a l e n e Furans 156 D i m e t h y l n a p h t h a l e n e 82 M e t h y l f u r a n

113 B e n z o f u r a n 131 M e t h y l b e n z o fu r an 168 D ibenzo f u r a n

Hydroaromat ies 116 I n d e n e 130 M e t h y h n d e n e 154 A c e n a p h t h e n e e 166 F l u o r e n e 216 B e n z o f l u o r e n e

Condensed aromatics 178 3-r ing a~omat ics f 192 M e t h y l a n t h r a c e n e 202 F l u o r a n t h e n e 228 4-r ing a r o m a t i c s g 252 Pe ry lene h

Phenols 94 Pheno l

108 M e t h y l p h e n o l 110 R e s o r c i n o l n 122 D i m e t h y l p h e n o l 170 P h e n y l p h e n o l o

Pyridines 79 Py r id ine 93 M e t h y l p y r i d i n e

107 D i m e t h y l p y r i d i n e 155 P h e n y l p y r i d i n e 156 B i p y r i d y l

Indoles 117 Indo leP 130 Methy l indo le 144 D i m e t h y l i n d o l e 159 T r i m e t h y l i n d o l e 173 T e t r a m e t h y l i n d o l e 187 P e n t a m e t h y l i n d o l e 201 H e x a m e t h y l i n d o l e

Nitrogen c o m p o u n d s 167 A z a f l u r e n e s 169 A m i n o a c e n a p h t h e n e 181 A z a f l u o r e n o n e 191 P h e n a n t h r o p y r r o l e 195 D i m e t h y l c a r b azole 203 A z a f l u o r a n t h e n e t 205 M e t h y l p h e n a n t h r o p y r r o l e 209 T r i m e t h y l c a r b a z o l e 217 A z a b e n z o f l u o r e n e u 223 T e t r a m e t h y l c a r b a z o l e 231 Methy lbe nzocaxbazole v 241 Be nzophe n a n t r o p y r r o l e 243 Methy ld ibe n z o q u i n o l i n e 253 A z a b e n z o p y r e n e w

Quinolines 129 Quino l ineq 143 M e t h y l q u i n o l i n e 157 D i m e t h y l q u i n o l i n e 171 T r i m e t h y l q u i n o l i n e 185 T e t r a m e t h y l q u i n o l i n e 193 M e t h y l b e n z o q u i n o l i n e 199 Pent a m e t hy lqu ino l i ne 207 D i m e t h y l b e n z o q u i n o l i n e r 213 H e x a m e t h y l q u i n o l i n e 227 H e p t a m e t h y l q u i n o l i n e 229 D i b e n z o q u i n o l i n e

a Or d i m e t h y l b e n z e n e ; e t h y l b e n z e n e . b Or m e t h y l e t h y l b e n z e n e ; i s o p r o p y l b e n z e n e . c Or azu lene . d Or b u t y l n a p h t h a l e n e . e Or b i p h e n y l . f Or t e t r a h y d r o f l u o r a n t h e n e . g Or b e n z a n t h r a c e n e ; b e n z o p h e n a n t h r e n e . h Or b e n z o p y r e n e ; b e n z o f l u o r a n t h e n e . i Or e t h y l t h i o p h e n e ; p r o p y l t h i o p h e n e ; b u t y l t h i o p h e n e . J Or a l k y l b e n z e n e . k Or e t h y l b e n z o t h i o p h e n e ; t r i e t h y l b e n z e n e ; h e x a m e t h y l b e n z e n e . 1 Or a l k y l n a p h t h a l e n e s ; d i b e n z o t h i o p h e n e . m O r a l k y l n a p h t h a l e n e s . n Or ca t echo l ; t h i o p h e n o l . o Or d i p h e n y l e t h e r . P Or d i h y d r o i n d e n e . q Or m e t h y l i n d e n e . r Or b e n z a c r i d i n e . s Or d i p h e n y l a m i n e . t Or a zap y rene . u Or m e t h y l a z a f l u o r a n t h e n e ; m e t h y l a z a p y r e n e . v Or m e t h y l a z a b e n z o f l u o r e n e . w o r azabenzo f l u o r a n t h e n e .

63

alkenes), aromatics, thiophenics, oxygen-containing compounds and nitro- gen-containing compounds, respectively. Dilute solutions of different ratios of model compound/acridine in toluene were injected under the same ex- perimental conditions into the gas chromatograph--mass spectrometer sys- tem. For every model compound the relation y = m x was obtained, where

y = ion current (model compound)/ ion current (acridine)

x = weight (model compound)/weight (acridine)

The slopes of the standard graphs were determined by the method of least squares for at least 5 experimental points. The slopes for tetradecane, naphthalene, dibenzothiophene, p-cresol and quinoline graphs were found to be 0.55, 1.87, 1.75, 0.19 and 0.68, respectively. These empirical relation- ships obtained were used to determine the quantities of different types of compounds in the shale oil fractions. To each shale oil fraction to be analys- ed a known amount of acridine was added. After measuring the ion current of acridine and the ion currents of the compounds searched in the fraction and using the appropriate empirical relationship, the quantities of the com- pounds were determined. The m / z values and the percentages of the com- pounds searched obtained from at least two identical experiments are given in Table 2.

RESULTS AND DISCUSSION

F r a c t i o n a t i o n o f shale o i l

The most interesting feature of the shale oil sample analysed is that it contains 96.9% n-pentane-soluble (oils) material and lacks asphaltols entire- ly. Solvent extraction of the sample yielded less than 3.0% toluene-soluble material (asphaltenes) in addition to the oils. Since the oils (fraction 71) are the major fraction of the whole shale oil sample, detailed investigation of this fraction should closely approximate the original sample. Silica gel c h r o matography of the oils (fraction 71) yielded 17.2% aliphatics, 45.1% aromat- ics and 34.7% polar aromatic material. The immediate conclusion of the chromatographic separation is that the oils contain 79.8%' material of aromat- ic nature. Since this material is soluble in n-pentane, it is expected that these should be compounds of lower polarity and have solubility parameters more or less similar to that of n-pentane (~ = 14.3 MPa 1/2) [9]. This is most interesting because, although the shale oil sample is of aromatic nature with probably some polar character, it is also soluble in the standard solvent which contains the least functionalities for polar interactions.

The elemental analyses of the shale oil and its fractions are presented in Table 3. The elemental analysis of oils (fraction 71, n-pentane-soluble material) which may be considered as representative of the whole shale oil, has a 100 X (H/C) value of 150 which is slightly lower than the generally

64

T A B L E 2

P e r c e n t a g e s o f c o m p o u n d s in sha le oil f r a c t i o n s

F r a c t i o n n u m b e r C a l c u l a t e d P e r c e n t a g e t o t a l o f 71 d i f f e r e n c e

m/z 70 71 72 711 7 1 2 7 1 3

A liphatic chains 41 9 . 6 0 9 . 5 0 1 5 . 2 8 12 .45 1 5 . 9 5 1 7 . 8 2 1 5 . 5 2 43 8 . 4 0 8 . 1 5 1 2 . 4 2 2 1 . 6 6 5 . 6 9 6 . 3 8 8 .51

Aromatic rings 78 1 .54 0 . 4 6 1 .20 0 . 6 5 0 . 6 5 1 .00 0 .75 91 5 . 4 4 5 . 3 3 0 . 0 3 6 . 8 2 9 . 4 5 10 .86 9 . 2 0

105 0 . 9 2 0 . 8 1 0 . 0 2 0 .81 0 . 7 4 1 .09 0 . 8 4

Naphthalenics 1 2 8 0 . 2 1 0 .21 0 . 0 2 0 . 2 0 0 . 3 6 0 .37 0 . 3 3 141 0 .15 0 .17 0 . 0 2 0 . 0 4 0 . 1 8 0 . 0 5 0 . 1 1 142 0 . 2 0 0 . 2 0 0 . 0 2 0 . 0 9 0 . 2 4 0 . 1 4 0 . 1 8 156 0 . 1 3 0 . 1 1 0 . 0 2 0 .17 0 . 0 8 - - 0 .07

Hydroaromatics 116 0 . 1 8 0 .15 0 .01 0 . 1 2 0 . 2 0 0 . 2 5 0 . 2 0 130 0 . 1 5 0 . 1 6 0 . 0 2 0 .01 0 . 0 2 0 . 0 2 0 . 0 2 154 0 .17 0 . 2 0 0 .01 0 . 0 2 0 . 0 5 0 . 0 3 0 . 0 4 166 0 . 0 5 0 . 0 6 - - 0 . 01 0 . 0 2 0 . 0 3 0 . 0 2 2 1 6 - - 0 . 2 6 - - 0 . 3 2 0 .21 0 . 3 4 0 . 2 6

Condensed aromatics 178 0 . 2 3 0 . 2 6 0 . 0 2 - - 0 . 0 8 - - 0 . 0 4 192 0 .01 0 . 0 2 0 . 0 2 . . . .

Thiophenes 84 0 . 2 2 0 . 2 1 0 . 0 3 0 . 3 4 0 .11 0 . 2 0 0 . 1 8 97 0 .21 0 . 1 9 0 .05 0 . 2 8 0 . 1 0 0 . 0 8 0 . 1 2

111 1 .46 0 . 4 0 0 .08 0 . 2 6 0 .17 0 . 0 2 0 . 1 3 134 0 . 3 0 0 .31 0 . 0 3 0 .01 0 . 0 3 0 .01 0 . 0 2 147 0 .27 0 . 2 8 0 . 0 3 - - 0 . 1 0 0 .01 0 . 0 5 153 0 . 2 4 0 . 2 3 0 . 1 5 0 . 1 8 0 . 2 3 0 . 2 3 0 .21 160 0 . 0 5 0 . 0 6 0 .01 - - 0 . 0 2 - - 0 .01 161 0 . 1 7 0 . 2 0 0 . 0 2 - - 0 . 0 8 - - 0 . 0 4 1 8 4 0 . 0 3 0 . 0 4 0 .01 0 .08 0 . 0 2 - - 0 . 0 2 198 0 . 0 2 0 . 0 3 - - 0 . 07 - - - - 0 .01

Furans 82 3 . 6 4 1 .98 0 .51 4 .22 1 .58 0 . 8 3 1 .73

118 2 .49 2 .41 0 . 0 9 0 . 0 4 0 . 0 3 0 . 0 2 0 . 0 3 131 2 .11 2 . 0 2 0 . 1 7 0 . 2 4 0 . 3 3 0 . 0 2 0 . 2 0 168 0 . 7 7 0 . 8 7 0 .07 0 .17 0 . 1 4 0 . 0 3 0 . 1 1

63 .4 4 .4

63 .1 7 2 . 6

3.7

57 .1 35 .3 10 .0 36 .4

33 .3 8 7 . 5 8 0 . 0 66 .7

0

1 0 0 . 0

14 .3 36 .8 67 .5 93 .6 82 .1

8 .7 8 3 . 3 8 0 . 0 5 0 . 0 66 .7

12 .6 9 8 . 8 90 .1 8 7 . 4

Phenols 94 2 .49 2 . 5 ] 1 .18 1 .34 2 .01 2 .52 2 .01 19 .9

65

T A B L E 2 (continued)

F r a c t i o n n u m b e r

m/z 70 71 72 711 712 713

Calcu la ted to ta l of 71

Pe rcen tage d i f f e rence

Phenols (continued) 108 2 .49 2.60 0 .82 0 .04 0 .02 110 1.24 1.25 0 .31 0 .20 0 .05 122 1.63 1.54 0 .42 0 .04 0 .02 170 0 .48 0 .58 0 .05 1.71 0 .35

0.27 0 .22 0 .35 0 .01

0.11 0 .13 0 .14 0 .46

Pyridines 79 0 .73 0 .92 0 .28 0 .98 0 .87 1.34 1.03 93 8 .35 8 .10 0 .03 9 .33 14.71 14.78 13.37

107 0 .70 0 .60 0 .28 0 .35 0 .36 0 .64 0 .45 155 0 .14 0 .13 0 .02 0 .08 0 .09 0 .23 0 .13 156 0.35 0 .44 0 .06 0 .50 0.21 0.01 0 .19

0.II

0.06

0.01

0.01

Indoles 117 1.11 1 .03 0 .07 0 .05 0 .09 130 0.41 0 .44 0 .04 0 .02 0 .04 144 0 .22 0.27 0 .04 - - 0.07 159 0 .19 0 .22 0 .02 - - 0 .06 173 0 .16 0 .22 0 .02 - - 0 .08 187 0 .05 0 .08 0 .01 - - 0 .03 201 0.03 0.03 -- -- 0.01

0.09 0 .04 0 .04 0 .03 0 .04 0 .02 0.01

Quinolines 129 0 .43 0.57 0.05 0.21 0.37 0 .42 0 .35 143 0.27 0.35 0 .03 0 .02 0 .10 0 .04 0 .06 157 0 .14 0 .16 0 .02 0 .02 0 .05 0 .02 0 .03 171 0 .08 0.11 0 .02 0 .19 0 .04 0.01 0.05 185 0 .03 0 .06 0 .01 0.01 0.01 - - 0 .01 193 0 .08 0 .12 0 .10 0 .03 0 .04 0 .04 0 .04 199 0 .02 0 .03 - - 0 .02 - - - - 0.01 207 0 .02 0 .02 - - 0.01 0.01 - - 0.01 213 0 .01 0 .02 - - 0.02 - - - - 0.01 2 2 7 0 . 0 1 0 . 0 1 - - 0 . 0 1 - - - - 0 . 0 1

229 0.01 0.01 . . . . .

Nitrogen compounds 167 0 .14 0 .16 0 .02 0 .02 0 .06 0 .04 0 .04 169 0 .05 0 .08 0 .01 0 .06 0 .04 0.01 0 .03 181 0 .11 0 .10 0 .03 0 .02 0 .03 0 .02 0 .02 191 0 .24 0 .04 0 .02 0 .02 0 .09 0 .03 0 .05 195 0 .02 0 .03 0 .01 - - 0 .01 - - 0 .01 2 0 3 0 . 0 2 0 . 0 3 0 . 0 1 . . . .

2 0 5 0 . 0 1 0 . 0 2 . . . . .

2 0 9 0 . 0 1 0 . 0 2 . . . . .

217 0.01 0.01 . . . . .

223 0 .02 0 .01 . . . . . 231 0 .01 0 .01 . . . . . 241 0 .01 0 .01 - - 0.01 - - - - 0.01

95.8 89.6 90.9 20.7

12.0 65.1 25.0

0 56.8

91.3 90.9 85.2 86.4 81.8 75 .0 66.7

38.6 82 .9 81.3 54.6 83.3 66.7 66.7 50.0 50.0

0 100.0

75.0 62.5 80 .0 25.0 66.7

100.0 100.0 100.0 100.0 100.0

0

Total 61 .93

66

TABLE 3

Elemental analyses of shale oil and fractions

Fraction C H N S O 100 X 100 x 100 X 100 x (diff.) H/C N/C S/C O/C

No. Name

70 Shale oil 77.48 9.58 1.29 6.66 4.99 148.0 1.4 3.2 4.8 71 Oils 78.48 9.83 1.54 6.69 3.46 150.0 1.7 3.2 3.3

711 Aliphatics 85.10 1 4 . 0 4 - -- 0.86 198.0 -- -- 0.8 712 Aromatics 80.82 8.27 0.50 7.77 2.64 123.0 0.5 3.6 2.5 713 Polars 72.14 8.58 2.44 4.80 12.04 143.0 2.9 2.5 12.5

72 Asphaltenes 59.15 5.89 2.65 4.26 28.05 120.0 3.8 2.7 35.6

ob ta ined values of 155- -165 . This po in t s to some d e h y d r o g e n a t i o n having occur red during the re to r t ing process o f the shale. On the o the r hand, the oils con ta in very few h e t e r o a t o m s . F o r every 100 ca rbon a t o m s , the re are 1.7, 3.2 and 3.3 n i t rogen, su lphur and oxygen a t o m s , respect ively . A l though there m a y be some funct ional i t ies in the average s t ruc tu re o f this f rac t ion , the b a c k b o n e o f the sample consists o f h y d r o g e n and ca rbon a t o m s p rob- ably arranged in highly subs t i tu ted a roma t i c rings, o r l ight ly subs t i tu t ed a romat ic s toge the r wi th long-chain al iphatics.

The al iphatics ( f rac t ion 711) conta in prac t ica l ly no h e t e r o a t o m s . There is on ly a b o u t one oxygen a tom per 100 ca rbon a toms , thus this f rac t ion can be cons idered a s pure ly a l iphat ic h y d r o c a r b o n . The m a j o r f rac t ion separa ted f r o m the shale oil is tha t o f the a roma t i c s ( f rac t ion 712) , and as the n a m e implies, this f rac t ion is a ro ma t i c accord ing to the e l ementa l analysis. I t conta ins 123 hyd rogen a t o m s for every 100 ca rbon a toms , indicat ing the presence of a r o m a t i c s t ruc tures wi th min ima l subs t i tu t ion . H e t e r o a t o m con t en t o f the f rac t ion is a lmos t the same as t ha t o f the oils sample ( f rac t ion 71), wi th the excep t ion o f an even lower c o n t e n t o f n i t rogen a toms . The polars ( f rac t ion 713) conta in 143 hyd rogen a t o m s per 100 ca rbon a t o m s , thus this f rac t ion is even m o r e highly h y d r o g e n a t e d t h a n the a roma t i c s f rac t ion . Ano t he r i m p o r t a n t f ea tu re o f this f rac t ion is the o x y g e n a t o m con ten t , it conta ins 12.5 o x y g e n a t o m s per 100 ca rbon a toms . These o x y g e n a t o m s are p r o b a b l y in po la r funct ional i t ies which a l lowed separa t ion b y silica gel c h r o m a t o g r a p h y and e lu t ion wi th a po la r solvent like m e t h a n o l .

The on ly o the r cons t i tuen t s isolated wi th solvent e x t r a c t i o n besides oils were asphal tenes ( f rac t ion 72); these cons t i tu t e less t h a n 3% of the whole shale oil sample . The aspha l tenes seem to be highly a r o m a t i c and con ta in the highest o x y g e n c o n t e n t o f any o f the f rac t ions . The re are 36 o x y g e n a t o m s for every 100 ca rbon a t o m s in asphal tenes . This indicates the p resence of high o x y g e n funct ional i t ies o f d i f f e ren t k inds , the t y p e and quan t i t i e s o f which are invest igated and discussed in the fol lowing sect ion.

67

Quantitative determination of shale oil compounds by GC--MS--SIM

The percentages of the compounds searched in all of the fractions separat- ed are presented in Table 2. The sum of all the percentages of the com- pounds searched in the whole shale oil sample totalled 62.31. Thermo- gravimetric measurements of the same sample with the same temperature programming as in the gas chromatography experiments done in this work, showed that 63.9% of the sample was evaporated within the temperature range of 50 to 200°C. Of the material injected into the gas chromatographic column, 36% was not eluted off the column under the chromatographic c o n ditions specified. This, of course explains the total percentage found in the SIM experiments for the whole shale oil and this finding gives a reasonable basis for the evaluation of our method. The aim of this work was to develop a rapid, reliable method for the quantitative determinat ion of the shale oil compounds by selected ion monitor ing wi thout separating the shale oil into its sub-fractions. Therefore, in assessing the results obtained this should be the base line. The results of the analysis of the whole shale oil can be com- pared with its major fraction; oils (n-pentane solubles, 96.9% of the whole shale oil sample). The comparison of the results of oils to its subfraction by the use of "calculated to ta l" values should give an indirect evaluation of the method in terms of the whole shale oil sample.

In Table 2 the percentages of the compounds in shale oil and its fractions are presented. The "calculated to ta l " values for the whole shale oil from the results of fractions 71 and 72 were not computed, because the fraction 71 made up 96.9% of the whole shale oil (fraction 70). The "calculated to ta l" values for the whole shale oil would be affected by the values of fraction 71. Therefore, direct comparison of fraction 70 with fraction 71 would give the same conclusion. A very satisfactory correlation between the percentages of compounds in the whole shale oil (fraction 70) and the oils (fraction 71) was observed. The only compounds which showed differences are those with m/z = 111, 82 and 191. The rest of the compounds were found to have al- most identical percentages within the limits of experimental error. This is the most interesting conclusion about the closeness with which the results of different fractions agree (i.e., the precision of the method that we are suggesting).

In Table 2 the 'calculated total ' values of fraction 71 were also presented. These values were computed using the following equation:

Calculated total of fraction = 0.172 × (% of compound in fraction 711)

+ 0.451 X (% of compound in fraction 712) + 0.347 X (% of compound

in fraction 713)

The direct comparison of these values in the corresponding column in Table 2 with the percentages found for fraction 71 indicates the accuracy of the method. Therefore, in Table 2 the percentage difference of the values of

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column 71 and the "calculated to ta l" values were also presented. The aver- age difference for the compounds making up more than 5% of fraction 71 and the calculated total values is 51%. The average difference for the com- pounds making up 1--5% was calculated to be 74% from the values of the same compounds in the calculated total column. For the trace compounds ranging between 0.1 and 1%, the average difference is 55 and for the com- pounds of percentages less than 0.1 the average difference was calculated as 55.

It seems that the more the whole shale oil sample was fractionated, the more errors were introduced into the results of the SIM analysis. There is good accord between the results of the whole shale oil sample and the oils sample (fraction 71), which represented 96.9% of the original sample. There- fore, it seems feasible to directly determine the major compounds in the whole shale oil quantitatively without serious errors. The method itself con- tains several sources of experimental errors; therefore all of these should be standardized. The quantification was based on model compounds represent- ing a specific group of compounds analysed. The model compounds chosen may not be ideal representatives of the complex compounds present in the group and therefore the response of such compounds may be different from that expected and this may result in some error. Nevertheless, the method based on the assumptions stated above produced satisfactory results. Better selection of the model compounds should improve the experimental results.

Based on our results obtained above, the experimental findings for the original shale oil itself can be considered as representative for all of its frac- tions. Therefore, detailed investigation of the SIM results for the original shale oil characterizes the sample. Table 2 presents the quantitative identifi- cation of the compounds present in the shale oil. The shale oil sample in- vestigated contains 9.6% unsaturated and 8.4% saturated aliphatic hydrocar- bon structures. This constitutes 18% of the whole shale oil sample and is in very good agreement with the solvent extraction and chromatography fractionation results in which the aliphatics were found to be 16.5% of the whole shale oil. According to SIM results the remainder of the shale oil is aromatic; this was confirmed by the separation experiments. Eight percent of the shale oil consists of alkyl-substituted one-ring aromatic compounds; mono- and dimethyl-substituted structures were the largest fraction among these. One percent of the original sample consisted of naphthalenics includ ing mono- and dimethyl-substituted structures. Hydroaromatics make less than 0.5% of the whole shale oil and of the condensed aromatics, 3-ring compounds were the highest present, at 0.25% of the sample.

The shale oil contained about 3% thiophenic compounds, approximately half of these were dimethyl-substituted thiophenes. In fact, the total sulfur content is expected to be higher according to the elemental analysis of the sample. The lower experimental findings are due to the small number of sul- phur compounds searched by the SIM method. Our results represent about 62% of the whole shale oil. It is probable that additional, varied sulphur

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c o m p o u n d s are p resen t in the remain ing 40% o f the shale oil. Our nex t task will be to iden t i fy m o r e c o m p l e t e l y the su lphur c o m p o u n d s p resen t in the shale oil.

I t is qui te interest ing t ha t 9% o f the cons t i t uen t s o f the shale oil are fu ran ic c o m p o u n d s . D i b e n z o f u r a n s were the least pa r t and the rest equal ly spread a m o n g m e t h y l f u r a n , b e n z o f u r a n and m e t h y l - s u b s t i t u t e d benzofu rans . Phenols also made up a p p r o x i m a t e l y 9% of t he who le shale oil and the p resence o f m o n o - and d i m e t h y l - s u b s t i t u t e d pheno ls was c o n f i r m e d b y the SIM results .

F o u r t e e n pe rcen t o f t he ident i f ied 62% of the shale oil cons is ted o f ni tro- gen-conta in ing a r o m a t i c c o m p o u n d s . The m a j o r f r ac t ion of these are the pyr id ine c o m p o u n d s wi th 10% concen t r a t i on . The m e t h y l p y r i d i n e s were the m o s t a b u n d a n t o f all w i th 8% concen t r a t i on . Also p resen t are 2% indoles , and 1% quinol ines . The remain ing 1% of the n i t rogen c o m p o u n d s consis ted o f py r ro l e and o t h e r aza - type c o m p o u n d s .

REFERENCES

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