Separation of organic matter from asphaltite with supercritical fluid mixtures

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FUEL PROCESSING TECHNOLOGY Fuel Processing Technology 41 (1995) 199 206

Short Communication

Separation of organic matter from asphaltite with supercritical fluid mixtures M u r a t Erol, B e l m a D e m l r e l , T a n e r Tof~rul, A y l a ~ a l l m l l * Department o[' Chemical Engineering, University o[' Ankara, 06100 Ankara, Turkey Received 26 July 1993; accepted in revised form 9 May 1994

Abstract

Supercritical fluid extraction (SFE) of Turkish asphaltite with toluene mixtures was investigated. Experiments were performed in a stirred batch autoclave at 613 K. Organic matter recovered from the SFE were fractionated into oils, asphaltenes and preasphaltenes by solvent extraction. The extract yields are 15.1% with toluene, 16.0% with toluene + 5% methanol and 16.9% with toluene + 5% n-hexane mixtures. Oil yields are 8.8%, 11.1% and 9.7% with toluene and toluene mixtures, respectively. Oils were analysed with a combination of chromatographic and spectroscopic techniques. Results were evaluated to assess the effect of solvent mixtures on product yields.

1. Introduction Intense efforts have been made in the supercritical fluid extraction of fossil fuels for the production of liquid fuels and chemical feedstocks. Although considerable work has been done to study the supercritical fluid extraction of lignites [1-13] and oil shale [14-24] with toluene and toluene mixtures, limited data are available on the SFE of asphaltites [25]. The reserve of Avgamasya seam in ,Slrnak comprises the major part of Turkey's asphaltite resources [26]; the authors therefore report the results on SFE of Avgamasya asphaltite with toluene and toluene mixtures.

2. Experimental Avgamasya asphaltite was used in this study. Analyses of the sample are reported in Table 1. * Corresponding author. 0378-3820/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0 3 7 8 - 3 8 2 0 ( 9 4 ) 0 0 0 5 7 - Z

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M. Erol et al./Fuel Processing Technology 41 (1995) 199-206

Table 1 Analysis of Avgamasya asphaltite Moisture (wt% air dry) Ash (wt% air dry)

1.1 40.4

Ultimate analysis (wt %, daf basis) Carbon Hydrogen Sulphur (total) Nitrogen Oxygen (diff.)

81.4 6.7 4.3 1.4 6.2

Higher heating value Lower heating value

20669 kJ/kg 19246 kJ/kg

2.1. P r o c e d u r e

Supercritical fluid extractions were carried out in a one liter batch autoclave equipped with a stirrer. The weight ratios charged to the autoclave was 1/10 (30g asphaltite/300 g solvent). Solvents used for extractions were toluene, 95 % toluene/5 % methanol (wt/wt) and 95% toluene/5% hexane (wt/wt). The autoclave was heated at 2.5°C/rain to the final temperature 613 K, which was maintained for 30 rain. At the end of the extraction time, the gas phase containing dissolved constituents of the sample was withdrawn through a needle valve into a condenser and then collected in a flask at atmospheric pressure. The residue was washed out of the cooled autoclave with tetrahydrofuran (THF), filtered and washed until the washings were clear, and then extracted with T H F for 20 h in a soxhlet apparatus, dried in a vacuum oven at 212 kPa, 333 K, and weighed. The washings and T H F solubles were added to the

Extract

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Fig. 1. Separation scheme by solvent extraction.

8oiubI (Oils)

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M. Erol et al./Fuel Processing Technology 41 f1995) 199-206

condensed extract. The solvent in the whole liquid mixture was distilled offin a rotary evaporator. The extract obtained was separated into oils (n-pentane/toluene solubles), asphaltenes (AS) (n-pentane insoluble/toluene solubles) and preasphaltenes (PAS) (toluene insolubles) by solvent extraction. The separation is outlined in Fig. 1. The yield of extract was obtained from the following relation: [ wt extract ] %extract yield = LW~ d a f sa-mmpleJ" The alkane fractions (eluated by n-pentane during silicagel c h r o m a t o g r a p h y of the n-pentane soluble fraction) were analysed by gas c h r o m a t o g r a p h y using a Varian 3400 on a 2 m x 2 m m i.d. packed stainless steel column with the stationary phase on the column c o m p o s e d of 3% OV-10I on C h r o m o s o r b W - A W (80/100 mesh) with flame ionization detection. G a s c h r o m a t o g r a p h y / m a s s spectrometry analysis was carried out using a Finnigan M a t model 4165 G C / M S quadrapol type mass analyzer on a 25 m x 0.32 m m i.d., DB-5 glass capillary column. Helium was used as carrier gas and the ionization voltage employed was 65 eV. Infra-red spectra for benzene and methanol eluates of oils fractions were recorded on a Perkin Elmer Model 1710-FTIR spectrophotometer.

3. Results and discussion Table 2 shows the solvents and pressures at which supercriticai fluid extraction of asphaltite were carried out at 613 K. As can be seen from Table 2, the highest extract yield was obtained with the toluene + 5% hexane mixture. Table 2 SFE of Avgamasya asphaltites at 613 K Solvents

Extraction pressure (MPa)

Extract yield (wt% daf asphaltite)

Toluene Toluene + 5% methanol Toluene + 5% hexane

6.0 5.5 5.5

15.1 16.0 16.9

Table 3 Results of SFE of Avgamasya asphaltite at 613 K with toluene and toluene mixtures Solvents

Toluene Toluene + 5% methanol Toluene + 5% hexane

wt% extract

wt% daf asphaltite

Oils

AS

PAS

Oils

AS

PAS

58.8 69.2 57.2

40.4 30.1 42.1

0.8 0.7 0.7

8.8 11.1 9.7

6.1 4.8 7.1

0.2 0.1 0.1

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M. Erol et al./Fuel Processing Technology 41 (1995) 199-206

The results of the separation into oils, asphaltenes (AS) and preasphaltenes (PAS) fractions are given in Table 3. Comparing the results with lignite and oil shale 1-24], PAS fractions are very low, but AS and oils fractions are higher. Table 4 Results of oils fractions obtained from SFE of Avgamasya asphaltite Solvents

n-Pentane eluate

Benzene eluate

Methanol eluate

Toluene Toluene + 5% methanol Toluene + 5% hexane

42.3 40.4 41.8

51.9 53.5 45.3

5.8 6,1 12.9

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i ! i.... Fig. 2. G C / M S analysis of n-alkanes fractions from Avgamasya asphaltite with (a) toluene, (b) toluene + 5% methanol, (c) toluene + 5% hexane. Column 25 m x 0.32 mm i.d. glass capillary coated with DB-5. Temperature programme 50°C to 285°C at 5°C/min.

M. Erol et al./Fuel Processing Technology 41 (1995) 199 206

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Table 5 n-Pentane eluate of oils fraction Components

n-C11 n-C12

n-Cl3 n-C14 n-C~5

n-Cl6 n-C17 n-C18

n-C19 n-C20 n-Cz i

n-C2z r/-C23 n-C24

n-C25

F/-C26 F/-C27 n-C2s n-C29 n-C3o

Solvents Toluene (%)a

Toluene + 5% methanol (%).

Toluene + 5% hexane t%)"

-1.4 3.3 8.2 7.6 7.4 5.6 2.3 1.8 1,3 0.9 0.6 0.4 0.4 0.3 0.2 0.2 0.2 0.] 0.1

1.1 2.8 3.9 5.6 5.1 4.7 3.8 3.2 2.4 1.9 1.3 1.5 0.8 0.7 0.5 0.4 0.2 0.2 0.2 0.|

1.1 2.8 4.1 5.8 5.3 4.9 3.9 3.3 2.6 2.1 1.4 1.5 0.8 0.6 0.5 0.4 0,3 0.2 0.1 0.|

" % on n-pentane eluate.

M. Erol et al.lFuel Processing Technology 41 (1995) 199-206

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M. Erol et al./Fuel Processing Technology 41 (1995) 199-206

205

T a b l e 4 shows the eluates s e p a r a t e d by silicagel c o l u m n c h r o m a t o g r a p h y of oils fraction which c o m p r i s e d m o r e t h a n 50% o f the extract. G C / M S c h r o m a t o g r a m s of n - p e n t a n e eluates are s h o w n in Fig. 2. The d i s t r i b u t i o n of n-alkanes in these eluates is listed in T a b l e 5. As o b s e r v e d from these data, n-C14, n-C15 a n d n-C16 a p p e a r as higher p e r c e n t a g e in the eluates. A l t h o u g h it is difficult to d e t e r m i n e the exact c o m p o s i t i o n of each fraction which c o n t a i n s h u n d r e d s of c o m p o u n d s using IR spectroscopy, an o p i n i o n can be f o r m e d a b o u t the structures of each fraction. The IR s p e c t r a of benzene a n d m e t h a n o l eluates are given in Figs. 3 a n d 4, respectively. As shown in Fig. 3, m o s t of the benzene eluates c o n t a i n a r o m a t i c fractions a n d benzene eluates have little phenolic oxygen. It can be seen in Fig. 4 that a r o m a t i c structures in m e t h a n o l eluates b e c o m e less a n d C - O , C = O a n d O - H g r o u p s with a l i p h a t i c structures increase. T h e r e is a little phenolic oxygen as well.

4. Conclusions The yield of extract o b t a i n e d from S F E of a s p h a l t i t e is 15.1% with toluene, but it reaches a b o u t 17% with toluene mixtures [27]. This i n c r e m e n t is not very high, so different solvents can be tried in o r d e r to increase the yield. O n the o t h e r hand, it is clear t h a t the type of solvent has no effect on the n-paraffin distribution. F u r t h e r m o r e , it can be r e p o r t e d t h a t solvent effects are a b o u t the s a m e for benzene eluates a l t h o u g h eluates o b t a i n e d with t o l u e n e / m e t h a n o l mixtures c o n t a i n slightly m o r e C - O , C = O a n d O - H structures t h a n the others.

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