Detection of methyl fluorenones in Athabasca oil sand bitumens

Org. Geochem. Vol. 9, No. 1, pp. 31-37, 1986 Printed in Great Britain, All rights reserved

0146-6380/86 $3.00+ 0.00 Copyright © 1986 Pergamon Press Ltd

Detection of methyl fluorenones in Athabasca oil sand bitumens T. W. MOJELSKY and O. P. STRAUSZ* Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Received 30 January 1985; accepted 10 September)

A~traet--A series of mono- to tetramethylfluoren-9-ones has been detected in Alberta oil sand bitumens and isolated chromatographically after conversion to the fl-hydroxy ester derivatives via a modified Reformatsky reaction employing zinc powder and ethyl bromoacetate. Individual members of the series were identified by capillary gc retention time and mass spectral comparison with synthetically prepared standards. 1,4-Dimethylfiuoren-9-one has been identified as one of the major dimethyl derivatives present. The methylfluoren-9-ones may have been formed by the geochemical oxidation of their parent hydrocarbons, the corresponding methylfluorenes, and as such could be regarded as indicators of the redox potential in the reservoir. This oxidation process may also be partially responsible for the aging of mined oil sands upon air exposed storage. Key words: fiuorenones, organic geochemistry, formation of r-hydroxyl esters, identification of some dimethyl isomers, Athabasca oil sand

INTRODUCTION

be present in few geological samples. Alkylfluoren-9ones have been identified in a Wilmington, California crude oil (Latham et al., 1962). Bulgarian workers (Vuchev et al., 1976) have found fluoren-9-one in cores of Triassic formations at depths less than 4000 m. Others have identified fluorenones in weathered, surface-retorted oil shale (Pereira et al., 1981) and pyrolyzed kerogen (van Grass et al., 1981). The origin or geochemical significance of fluoren-9-ones, however, has not been discussed. We wish to report here the detection, isolation and identification of a series of alkylated fluorenones in Athabasca oil sands.

Ketones have been detected in geological samples of diverse origin. Seldom were they the prime target of geochemical investigation but were identified during systematic analysis. Structurally the ketones were almost as varied as the other constituents of the samples. Isoprenoid ketones have been found in recent marine sediments (Ikan et al., 1973; Dastillung et aL, 1980), in Green River Oil Shale (Anders et al., 1975) and in Aleksinac Oil Shale (Vitorovic and Saban, 1983). It has been postulated (Ikan et al., 1973) that the probable source of these ketones is phytol obtained from chlorophyll. Hopanoid ketones have been found in oil shale (Vitorovic and Saban, 1983) and in sediments (Dastillung et al., 1980). Sediments have also been the source of steroidal ketones (Dastillung et al., 1980; Gagosian and Smith, 1979). Long chain alkyl ketones have been seen in geological samples as well. There are reports (de Leeuw et al., 1979; Volkman et al., 1979) documenting the identification of long chain unsaturated methyl and ethyl ketones in marine sediments. Methyl n-alkyl ketones have been isolated from soil and peat (Morrison, 1969), oil shale (Vitorovic and Saban, 1983) and from sediments (Cranwell, 1977). These aliphatic methyl ketones were suggested to be products of microbial attack on n-alkanes or r-oxidation of carboxylic acids followed by decarboxylation. Costa Neto et al. (1979, 1983) have found aromatic ketones in Irati Oil Shale. Other simple aromatic ketones such as fluoren-9-one have been reported to

EXPERIMENTAL

All solvents were distilled prior to use. Reagents were used without further purification. In addition, the benzene solvent used in the Reformatsky transformation was also dried over 3A molecular sieves for several hours immediately before use. The samples used were located 18 m below surface in the Syncrude mine site 1-2-93-1 l-W4, Alberta, Canada. The mean assay gave 11.7 wt% bitumen and 2.96 wt% H20. The extraction and deasphalting procedure was the same as previously described (Selucky et al., 1977). Gas chromatographic (GC) analyses were performed on a Hewlett-Packard HP 5730A gas chromatograph with a 18850A GC terminal in the flame ionization mode. A 30m x 0.252mm J&W fused silica glass capillary column coated with DB-I was used. After a 2.5 min delay at 50°C, the oven was programmed to increase the temperature at a rate of 30°C/min for 1.5 min and then at 2°C/min to 290°C.

*Author to whom correspondence should be addressed. 31

32

T.W. MOJELSKYand O. P. STRAUSZ (about 50 ml of each) prior to drying for 1 hr at 95°C. The zinc powder was subsequently interspersed with 50 g glass helices in a 125 ml dropping funnel which served as the column. This dropping funnel was wrapped with heating tape and inserted into a 250 ml three-necked flask equipped with a serum cap and magnetic stirrer. To the top of this Zn powder charged funnel were attached by means of a Y-tube adapter a second dropping funnel on one arm and a condenser protected by a CaC12 drying tube on the other. A flow of argon was introduced via a needle through the serum cap. The voltage passing through the heating tape around the lower dropping funnel was adjusted to maintain a gentle reflux when an initial 10 ml anhydrous benzene was introduced from the upper dropping funnel. In 50 ml anhydrous benzene were dissolved 0.016 g of the orange oil containing the mixture of ketones and 470mg (2.8mmol) ethyl bromoacetate. This solution was permitted to flow dropwise from the upper dropping funnel at a rate of about 1 ml/min through the Zn impregnated column into the threenecked flask. The collected solution in the flask soon became turbid. A further 20 ml benzene was used to flush the system. The solution was stirred for an additional 1 hr at ambient temperature. The reaction mixture was then added to 100 ml ice-cold 15% H:SO4 solution. The benzene extract was subsequently washed with 50ml aliquots of saturated NaHCO 3 and NaCI solutions. The resulting organic residue was subjected to chromatographic separation on 20g silica gel packed as a CH2CI 2 slurry. The column was eluted with 100 ml CH2CI 2 to yield 0.01 g of a yellow oil. Upon subsequent elution with I00 ml of a 10% EtOAc in CH2C12 solution, a band of yellowish material, 0.01 g, was isolated.

A second 30 m x 0.252 mm J&W fused silica glass capillary column coated with DB-5 was used for co-elution studies. The Fourier transform infrared spectra were recorded on a Nicolet 7199 instrument in the transmittance mode. The spectra were obtained on a CH2C12 cast. The gas chromatographic-mass spectrometric (GC/MS) experiments were performed on a Vacuum Generators 70-70E spectrometer equipped with a VG-II-250 data system and a Varian 6000 gas chromatograph. Samples were chromatographed on a 30 m x 0.252 mm DB-1 wall-coated glass capillary column programmed as for the GC determinations. The instrument was run in the splitless mode using He as carrier gas. The mass spectrometer was operated at 70eV in the electron impact mode and scanned from 50-500 dalton every 0.8 sec. In a typical experiment the maltene (9 g) obtained after deasphalting the bitumen was dissolved in about 10ml CH2CI 2 and preadsorbed onto 10g silica gel. The solvent was removed in an argon atmosphere and this preadsorbed silica gel was then placed on the top of a column (45 x 500 mm) to which had been added previously a slurry of 175 g silica gel in n-pentane. The column was eluted with 350 ml npentane to remove saturates. Next it was eluted with 400 ml 15% toluene in n-pentane to remove aromatic hydrocarbons. Then upon elution with 600 ml CH2Ci2, 1.54 g of a reddish-black oil was obtained. This crude fraction was found to have a weak carbonyl absorption at 1700 cm -~ and was subjected to re-chromatography. The oily residue was added to a previously prepared column of 41 g silica gel in CH2C12. Following elution with 250ml CH2C12, 1.36 g of a reddish coloured residue was isolated. A portion of this (1.18 g) was vacuum distilled (230°C, 10 -3 torr) to yield a distillate (0.016 g, 1.35%).

Synthesis of methylated fluorenones The dimethylfluoren-9-ones were prepared according to the method of Sellers and Suschitzky (1969) from o-carboxybenzenediazonium tetrafiuoroborate and the appropriate xylene. The isomers were separated by column chromatography. 1,2,3,4Tetramethylfluoren-9-one was prepared analogously from 1,2,3,4-tetramethylbenzene. The following compounds were synthesized:

Reformatsky reaction on chromatographed mixture For the conversion of the fluorenones to the corresponding fl-hydroxy esters, a variation of the modified Reformatsky reaction (Ruppert and White, 1974) was used. In this method a benzene solution of the ketone mixture and ethyl bromoacetate was

m.p.

1,4-dimethylfluoren-9-one (la) 2,4-dimethylfluoren-9-one (lb) 2,3-dimethylfluoren-9-one (lc) 3,4-dimethylfluoren-9-one (ld) 1,2,3,4-tetramethylfluoren-9-one (le)

88°C 135°C 109°C 113-114°C 148-149°C

slowly dropped through a heated column containing activated zinc into a receiving flask maintained at room temperature. Zinc powder (5 g, 0.077 g-atom) was activated by washing successively with 2% HC1, water, 95% EtOH, acetone and anhydrous ether

Reported m.p. 89°C (Cologne and Davnis, 1961) 136°C (Sellers and Suschitzky, 1969) 110°C (Marvel and Hinman, 1954) 117°C (Sellers and Suschitzky, 1969)

The fluorenones were subjected to the reaction with activated Zn powder-ethyl bromoacetate as described. The resultant fl-hydroxy esters were used as standards in the identification of some of the peaks in the gas chromatogram of the unknown fl-hydroxy esters of the bitumen sample.

Methyl fluorenones in oil sand bitumens RESULTS AND DISCUSSION

33

Based upon chromatographic separation, the alkylated fluorenones occur to the extent of about 0.2% in the Athabasca oil sand maitene. Field ionization mass spectral studies (Payzant et al., 1985) of the polar fractions of Athabasca oil sand maltene have shown that there is a series of compounds of molecular formula C, H2,_ t~O. Carbonyl containing structures that share this molecular formula include fluorene-9-one, 3, anthrone, 4, and phenalen-l-one, 5. Prior to reaction with Zn and ethyl bromoacetate, the maltene fraction showed a weak carbonyl absorption at about 1700cm-~. Fluoren-9-one has C------Oabsorption at 1695cm-]; anthrone at 1680cm -~ and phenalen-l-one at 1640cm -~ (Pouchert, 1975). Alkyl groups on the

Ketones of geological interest have been identified generally by mass spectrometry following some chromatographic concentration procedure. With the Athabasca oil sand bitumen such a method was not feasible due to the numerous non-carbonyl components which contribute to complex and poorly resolved gas chromatograms. Costa Neto (1979, 1983) developed a solid phase extraction method for the isolation of carbonyl compounds from the bitumens. This, however, requires special reagents. We have developed a procedure for selectively converting the fluorenones to the corresponding /~-hydroxy esters using a simple procedure based on a minor variation of the improved Reformatsky reaction method of Ruppert and White (1974). o

6 F ' ~ ~ ~

, R2

II

la lb lc ld le

2

R2

R1

II o 3

R2

EtOCCH2

E

o

1

R1

3 BrCH2COEI

4

CH 3 H H CH 3 H CH 3 H CH 3 H CH 3 CH 3 H H H CH 3 CH 3 CH 3 CH 3 CH 3 CH 3

(5-8)

H H H H H

The introduction of the hydroxyl group into the product molecules facilitates separation by silica gel column chromatography from the as yet unidentified compounds of isopolarity to the ketones in the bitumen sample. The Girard reagent (Wheeler, 1962) has also been used to isolate ketones from complex mixtures. Typically this procedure requires the use of ethanol to dissolve the sample. Maltene fractions, however, are insoluble in alcoholic solvents. Our method permits the isolation of ketones from maltene in a shorter period of time than by using the solid support procedure of Costa Neto (1979), albeit in a derivatized form. The use of the modified Reformatsky reaction procedure resulted in a much higher yield of product (essentially quantitative for fluoren-9-one). Competing side reactions such as self-condensation of the ct-bromo ester and ketone as well as elimination or retrograde aldol condensation of the intermediate/~alkoxyzinc ester are minimized (Ruppert and White, 1974). Preliminary experiments have suggested that similar, near-quantitative results can be achieved with ketones of such diverse structure as 2-nonanone, fl-ionone, anthrone and 5-cholesten-3-one. In the polar fraction investigated, only the fluorenones appear to be responsible for the carbonyl absorption.

II o

OH

2

aromatic nuclei would not be expected to shift significantly the frequency of ketone stretch.

o

o

3

,4

5

The capillary GC/MS total ion current for the isolated fl-hydroxyesters of the fluorenones is shown in Fig. l(a). The dominant fragmentation (Fig. 3) is the loss of---CH2COOEt, mass 87. A cross-scan of R1

HO

R2

CH2.C.OEt

the base peaks of m / e 195, 209, 223 and 237 corresponding to mono-, di-, tri- and tetramethylfluorenones, respectively, is shown in Figs l(b) to l(e). As can be seen, the major components in the mixture correspond to di- to tetramethylfluorenones, scans l(b)-(e) each showing peaks corresponding to about one half of the number of theoretically possible isomers. Unsubstituted fluoren-9-one is absent. There may be some pentamethylfluorenones and higher homologues in very small individual concentrations.

34

T . W . MOJELSKYand O. P. STRAUSZ

SO

•

60 40 20 0 2O0O

60 40 20 Oi 2OOO

'°f

>=

3OOO

b

J ~

n,

4OOO

-. . . . . .

n-

@

60

'°I 40

2O

rr

Oi 2O0O

.

6O 2 ,= 2OOO

3o00

60

i

40

~o

,

2

a~o

2OOO

4o~o

Scan Number

Fig. 1. Capillary GC/MS scans of fl-hydroxy esters of fluorenones. (a) Total ion current. (b)-(e) Cross scans for fragments of m/e 195, 209, 223 and 237, respectively.

a

1 145

I 185 ABc D

E

I

I 145

b

L

I 185

Temperature °C Fig. 2.(a) Capillary gas chromatogram of fl-hydroxy esters of fluorenones. (b) Same but spiked with fl-hydroxy esters of: (A) 1,4-dimethylfluoren-9-one; (B) 3,4-dimethylfluoren-9-one; (C) 2,4-dimethylfluoren-9-one; (D) 2,3-dimethylfluoren-9-one; (E) 1,2,3,4-tetramethylfluoren-9-one.

Methyl fluorenones in oil sand bitumens In Fig. 2(a) is shown the capillary gas chromatogram of the fl-hydroxy esters of the fluorenones obtained after chromatographic separation. Fig. 2(b) is the same sample after being spiked with prepared fl-hydroxy esters of 1,4-dimethylfluoren-9-one (A), 3,4-dimethylfluoren-9-one (B), 2,4-dimethylfluoren9-one (C), 2,3-dimethylfluoren-9-one (D) and 1,2,3,4-tetramethylfluoren-9-one (E), respectively. In Figs 3(a) to 3(d) are shown the mass spectra of the GC/MS scans of the sample that correspond in retention time to the co-injected standards (A to D) of Fig. 2(b). Similar co-elution results were obtained when a second capillary column of different polarity was used. It can be seen that Fig. 3(a) is clearly due to a dimethylfluorenone fl-hydroxy ester which co-elutes with the major dimethylated fluorenone compound of Fig. 2(a). Compound B of Fig. 2(b), 3,4-dimethyifluorenone fl-hydroxy ester, may be present as a minor component [Fig. l(c)]. The mass spectrum of the corresponding peak [Fig. 3(b)], has masses at 296 and 310 which suggest the presence of a di- and a trimethylated compound that co-elute. Likewise, the fl-hydroxy ester of 2,4-dimethylfluoren-9-one (C) of Fig. 2(b) may be present as a minor component in Fig. l(c). Its mass spectrum is shown in Fig. 3(c). The correct m/e, 296, is present as required for a dimethyl compound but other unexpected fragments also appear. The corresponding peak for the fl-hydroxy ester of 2,3-dimethylfluoren-9-one (D) of Fig. 2(b) gave the

35

mass spectrum shown in Fig. 3(d). It has mle 310 which is that of a trimethylated compound and, hence, not the 2,3-dimethyl isomer. The fl-hydroxyester of 1,2,3,4-tetramethylfluoren-9-one, compound E of Fig. 2(b), did not co-elute with any major peak in Fig. 2(a). From the data obtained it can be concluded that 1,4-dimethylfluoren-9-one is one of the major dimcthylated fluorenones in the Athabasca oil sand bitumen. 2,4-Dimethylfluoren-9-one and 3,4-dimethylfluoren9-one may be present but only as minor components and 2,3-dimethylfluoren-9-one is absent. Such compounds have not been previously reported to be found in oil sand bitumens. The methyl groups need not be confined to one ring of the fluorenone nucleus but more probably are randomly distributed as suggested by the large number of isomers present, [Figs l(c) to l(e)]. Of the four possible monomethyl derivatives only two appear to be present [Fig. 1(b)]. The geochemical significance of this substitution is not known. In contrast to the few reports identifying fluorenones in geological samples, there are numerous papers citing the presence of fluoren-9-one and alkylfluoren-9-ones occurring in conjunction with numerous other polycyclic aromatic hydrocarbons. They have been found in emissions of burning biomass (Randahl and Becher, 1982), in particulate matter of diesel exhaust (Choudhury, 1982; Jensen and Hites, 1983; Erickson et al., 1979), in cigarette

2O9

=f 40

2

J

1651~L8

78 89

5o

162L 1;o

l&

i

!P. 2~o

96 3~o

2~o 223

2 f

•~'~

0

9

8

0

80

40 t-

->

50 57

1~2l 100

150

I

I

296 310 .L L

247 J...,.. = ,

2~

2~

155

2o~ 5O

/19a ,I /

3~

127

=~ 80 0

I

165179

20t--81 7689

215

243

..lllll,lll i.Jil I'll i.,JLill,I "i,

il,'iil.lLi

1~o

l~o

1;o

I,,iUl,,I

I ,

ill

l~o

3~o

223

80 60 40 201. . . . . . .7669j..., ..... 111 50

100

'i9 X7 •

~

11o

J..

_

iN

I

llo

'

~o

Mass Number (Daltons)

Fig. 3.(a)-(d). Mass spectra of scans corresponding, respectively, to retention times of compounds A-D of Fig. 2(b).

36

T.W. MOJELSKYand O. P. STRAUSZ

smoke condensate (Bell et al., 1969) and on carbon black (Fitch et al., 1978). Chemically, fluoren-9-one has been generated by non-catalytic hydrocracking (Sakai and Hattori, 1974; de Champlain and de Mayo, 1972) of structurally related anthraquinone and phenanthraquinone. It appears, therefore, that fluorenones can arise from pyrolytic processes and are relatively stable toward subsequent degradation or transformation. Fluoren-9-one has also been shown (Korfmacher et al., 1980) to form in a nonphotochemical oxidation of fluorene. Hence, the fluorenones of the Athabasca oil sand bitumen may be a thermodynamic end product of the geochemical oxidation of fluorenes. The oxidation could have taken place biogenically or abiogenically, catalyzed possibly by the inorganic matrix. In either case the distribution of fluorenes, fluorenones and flourenols may serve as an indicator of the redox potential in the reservoir during geological times. It is known that mined oil sands undergo changes upon air-exposed storage which may adversely affect the separability of the bitumen from the sand in the hot water extraction process. Neither the nature nor the immediate course of this phenomenon is known. We propose that the aerial oxidation of alkylttuorenes to the much more polar and surface active alkylfluoren-9-ones in partly responsible for the alteration. In the accompanying paper (Mojelsky and Strausz, 1985), evidence is presented to suggest that fluorenones present in the Alberta oil sand bitumens are oxidation products of indigenous fluorenes.

Acknowledgements--We gratefully acknowledge support from the Natural Sciencesand Engineering Research Council of Canada and the Alberta Oil Sands Technology and Research Authority. We thank Syncrude Canada Ltd, for providing samples. We also wish to thank Drs J. D. Payzant, T. D. Cyr and D. S. Montgomery for their helpful comments and discussion.

REFERENCES

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37

Volkman J. K., Eglinton G., Corner E. D. S. and Sargent J. R. (1979) Novel unsaturated straight chain C37-C39 methyl and ethyl ketones in marine sediments and a coccolithophore Emiliania huxleyi. In Advances in Organic Geochemistry (Edited by Douglas A. G. and Maxwell J. R.), pp. 219-227. Pergamon Press. Vuchev V., Kovachev G., Petrova R., Stoyanova G. and Tsakov K. (1976) Organic matter in the Triassic formations of Bulgaria. II. Disseminated organic matter in the Middle Triassic carbonates from the holes near the city of Knezha (northern Bulgaria). Neft. VuglishtnaGeol. 4, 3-22, Chem. Abs. (1977) 87, 553201". Wheeler O. H. (1962) The Girard reagents. Chem. Rev. 62, 205-221.