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Solvent extraction of nitrogen compounds from coal liquids
Solvent extraction from coal liquids
of nitrogen
Yoichi Kodera, Koji Ukegawa. Yutaka Mite*, Etsuro lshikawaf and Tetsuo Nakayama
compounds
Masashi
Komotot,
National Research Institute for Pollution and Resources. 16-3 Onogawa, Tsukuba, lbaraki 305, Japan * Kobe Steel Ltd. l-3-18 Wakihama-cho, Chuo-ku, Kobe, Hyogo 657, Japan _FNippon Steel Chemical Co. Ltd, 5- 13- 16 Ginza, Chuo-ku, Tokyo 104, Japan
(Received
14 January
7997)
Nitrogen compounds were separated efficiently from coal liquids by solvent extraction with methanol and water. Middle distillates of Wandoan and Battle River coal liquid and a mixture of model compounds were employed as feed oils. This paper reports the experimental conditions for the effective separation nitrogen compounds, such as quinoline and indole. In particular, the effects of extraction solvents extraction yield and selectivities of nitrogen compounds were investigated.
of on
(Keywords: solvent extraction; nitrogen compounds; coal fhpids]
Upgrading of coal liquids is important for producing alternative liquid fuels of good quality; it has been performed by hydrotreating in the presence of However, upgrading requires expensive catalysts’-‘. catalysts and considerable amounts of hydrogen because coal liquids contain large amounts of nitrogen and phenolic compounds, which are converted to ammonia and water. Phenolic and nitrogen compounds are industrially valuable chemicals. Thus, the economical method for both separation and production of these chemicals is thought to be the effective utilization and upgrading of coal liquids. Here, we report on an effective extraction method using methanol and water as solvents for the separation of nitrogen compounds from coal liquids6,7.
Per cent extractions of nitrogen compounds were determined as the ratio of the decreased amount of nitrogen in the residual oil to the nitrogen content of the original feed oil. Nitrogen contents were obtained by a total nitrogen analyzer. The selectivities of nitrogen compounds in a methanol-water layer are defined as the amount of nitrogen compound over the amount of all the components extracted in the layer. Quantitative analysis for the nitrogen compounds and the other components in the methanol-water layer was carried out with a gas chromatograph equipped with a nitrogen detector system (Tracer Instrument Model loo), using a 50 m glass capillary column coated with HR-101 on Chromosorb W. The temperature range was lOO-260°C Using a rate of 1‘C min- ’ with Isothermal periods of 4 min at the start and 30 min at the end of the analysis.
EXPERIMENTAL RESULTS
Materials
AND DISCUSSION
Middle distillates (b.p. 180-45O”C, see Figure I) of Wandoan and Battle River coal liquid were obtained with a 1 t/d coal liquefaction plant of Sumitomo Metal Industries, Ltd. These feed oils contain considerable amounts of nitrogen and phenolic compounds as shown in Table I. The methanol, quinoline and phenol used are commercially available.
The effects of solvents on extraction yields of nitrogen compounds were examined. There is a strong interaction between nitrogen compounds and methanol molecules in the mixture of the feed oil and methanol. The
Procedure for soiuent extraction The procedure fur the separation of nitrogen compounds is shown in Sclzelne 1, Methanol was mixed with a feed oil by shaking in a shaker for 2 min and water was poured into the mixture. The mixture immediately separated into two layers; a methanol-water layer contaning nitrogen compounds and a residual oil layer. After the mixture was left for 10 min at 3O”C, the methanol-water layer was removed and evaporated under reduced pressure to recover the methanol. Removal of methanol caused the nitrogen compounds to separate as an oily material which was insoluble in water.
Middle distillate
001~~236~/~1/060763-03 ‘? 1991 Butterworth-Heinemann
Ltd
Table 1
Characteristics
of feed stocks Wandoan
._~~
~~ Nitrogen
content
(%)
0.51
Contents (wt%)b quinoline isoquinoline indole carbazole Acldlc compounds
Battle River
~
0 42
0.29 0.02 0.18 0.22 9 80
40 70
(~1%)
“Determined with a nitrogen analyzer ‘Determined using a gas chromatograph detector ‘Separated with a 20% NaOH solution
FUEL,
1991,
equipped
with a mtrogen
Vol 70, June
765
Solvent extraction
of nitrogen
compounds:
Y. Kodera et al.
a Nitrogen
Compoundsa
h 3
h
mi”
lb
io
;o
;o
;o
min
10
20
30
40
50
. k0
70
S’O
-.-l
1;o
d0
I
J
60
J
100
70
80
90
I
I
70
80
90
100
70
80
90
100
b Nitrogen
0
’
min
min
Compoundsa
lo
20
30
40
lo
20
30
40
50
50
60
60
Figure I Gas chromatographs of a middle distillate of (a) Wandoan coal liquids and (b) Battle River coals. Analytical the text. “Detected with a nitrogen detector. *Detected with a field ionization detector
addition of water formed a new layer of a mixture of water and methanol which was rich in nitrogen compounds. Figure 2 shows the effect of the amount of methanol on per cent extraction of nitrogen. The extraction yields of nitrogen increased significantly as the amount of
766
FUEL, 1991, Vol 70, June
A
conditions
are described
methanol increased. The yields of nitrogen in a methanol-water layer from a middle Battle River coal liquid (0) were larger than middle distillate of Wandoan coal liquid (a). can be explained by the differences in the
in
compounds distillate of those from a This result quantitative
Solvent Feed
Methanol mixing
Water
t standing
Scheme 1
Extraction
of nitrogen
compounds:
Y. Kodera
et al.
indole and carbazole. Selectivities of nitrogen compounds were calculated as the ratio of the peak areas of each compound to the total of all peak areas. The effect of the amount of methanol on the selectivities of the major nitrogen compounds is summarized in Figure 3. The selectivity curves of quinoline and carbazole have the maximum values. The selectivity curve for the sum of the selectivities of the four compounds is shown in Figure 4. The sum of the selectivities of these compounds have the largest values at 1 ml of methanol. The largest sum of the selectivities of all four compounds was 5.9%. This means that these compounds were concentrated 9.7 times in the original feed oil. For all nitrogen compounds, lower values were obtained as more methanol was used. To clarify the reasons for these changes in selectivities, model mixtures (listed in Table 2) were prepared and extracted by the procedure described. The results of the selectivity of quinoline extracted in a methanol-water layer is shown
I--
Methanolwater layer
extraction
Residual oil layer
procedure
50 -
40 l
P
-
Methanol
methanol.
0
2
4
6
Methanol
(ml)
8
(ml)
Selectivities of nitrogen compounds Feed, Wandoan middle, 2.0 ml; water,
versus 2.0 ml
amount
of
10
Figure 2 Per cent extraction of nitrogen versus amount of methanol. Feed, Battle River middle, 2.0 ml and Wandoan middle, 2.0 ml; water, 2.0 ml
ratios of the amount of nitrogen compounds contained in each feed oil to the amount of solvent. A middle distillate of Wandoan coal liquid contains larger amounts of nitrogen compounds than that of Battle River coal liquid. However, a certain amount of solvents can extract the corresponding amounts of nitrogen compounds from each feedstock. Thus, the per cent extractions of nitrogen in the middle distillate of Battle River coal liquid is larger than those of Wandoan coal liquid. The middle distillate of Wandoan coal liquid contains four major nitrogen compounds: quinoline, isoquinoline,
”
0
2
4
6 Methanol,
a
Figure 4 Effect of the amount of methanol selectivities of quinoline, isoquinoline, indole Wandoan middle, 2.0 ml; water, 2.0 ml
FUEL,
10
12
mL
1991,
on the sum and carbazole.
of the Feed,
June
767
Vol
70,
Solvent extraction Table 2
Mixtures
of nitrogen
compounds:
Y. Kodera et al.
of model compounds” ~~. Contents
(wt%)
Mixture
Quinoline
Phenol
A B C D E ~~
1.29 1.29
0.00 0.09 0.47 0.94 1.88 ~~
1.29 1.29
1.29 ~~
“Solution
in I-methylnaphthalene
The effects of shaking time and operating temperature were examined. A feed oil was mixed with methanol and subsequently treated with water without shaking to immediately give a two-phase mixture. The per cent extraction of nitrogen compounds did not increase with the duration of shaking at 3O”C, as shown in Figure 7. Furthermore, the selectivities of the four major compounds were not affected by the shaking period. This means that the separation method does not require a shaking process.
100
comoonent
mmtlre
10
qu~nolme
l n
A B
80
30
ohenol 1 -methylnaDhthalene 0 +
0
A
I t
0
I
I
1
I
I
1
2
3
4
5
Methanol
(ml)
Methanol
Figure 6 Relative amounts mixtures ofmodel compounds
(ml)
of the components in extracts from Feed, mixture A, Band E, 2.0 ml; water,
Figure 5 Effect of the amount of methanol on the selectivity of quinoline in the extraction of the mixtures of model compounds. Feed, mixture A-E, 2.0 ml; water, 2.0 ml
in Figure 5. The selectivity decreased with increase in the concentration of phenol in the mixtures. These results indicate that phenolic compounds in coal liquids lower the selectivities of nitrogen compounds in extracts especially at smaller amounts of methanol. The relative amounts of quinoline, phenol and I-methylnaphthalene in the extracts from mixtures A, B, and E are shown in Figure 6. These values are determined by gas chromatography and are based on the extracted amount of quinoline with 1 ml of methanol. These results show that there are two factors which decrease the selectivities of nitrogen compounds in the extraction from coal liquids. The first factor is that a quantitative amount of phenolic compounds is extracted independent of the amount of methanol used. In contrast to the quantitative extraction of the phenolic compounds, a small amount of quinoline was extracted by a small amount of methanol. As a result, a lower selectivity of quinoline was obtained with a decreasing amount of methanol. The second factor is that the amount of I-methylnaphthalene in an extract increases more significantly than that of quinoline as the amount of methanol increases. As a result, the selectivity of quinoline decreased with increasing amount of methanol.
768
FUEL,
1991,
Vol 70, June
X
x-----FX
I
I
I
1
1
,
0
1
2
3
4
5
time
(min)
Shaking
Figure 7 Effect of shaking time on per cent extraction and selectivities ofnitrogencompounds. Feed, Wandoan middle, 2.0 ml; water, 2.0 ml
Solvent extraction
of nitrogen
compounds:
Y. Kodera et al.
because of their low solubilities in water. The isolation procedure will be reported elsewhere. CONCLUSIONS
\
I
I
I
I
I
10
20
30
40
50
Temnerature
Nitrogen compounds can be separated efficiently from middle distillates of coal liquids by solvent extraction using methanol and water. Nitrogen compounds were extracted into a methanol-water layer. The per cent extraction of nitrogen compounds is strongly affected by the amount of methanol used. The selectivities of nitrogen compounds are lowered by simultaneous extraction of phenolic compounds and hydrocarbons. The present method provides a new economical method for the separation of nitrogen compounds from coal liquids. The isolation and purification of nitrogen compounds from a methanol-water layer are now being studied.
%
Figure 8 Effct of the operating temperature on the per cent extraction of nitrogen. Feed, Wandoan middle, 2.0 ml; methanol, 4.0 ml; water, 2.0 ml
A mixture of a feed oil and methanol was treated with water at lo-50°C. The per cent extraction decreased as operating temperature increased as shown in Figure 8. This indicates that the extraction should be operated at low temperatures. Nitrogen compounds were isolated as an oily mixture from methanol-water layers by evaporation of methanol
REFERENCES Song, C., Hanaoka, K., Ono, T. and Nomura, M. Bull C/rem. Sot. Jpn. 1988,61, 3788 Perrot, J. M., Ayadi, A., Bastick, M. and Bastick, J. Fuel Proc. Technol. 1988, 20,223 Sakanishi, K., Zhao, X. Z., Fei, Y. Q., Korai, Y., Fujitusu, H. and Mochida, I. Fuel Proc. Technol. 1988, 20, 233 Song, C., Hanaoka, K. and Nomura, M. Fuel 1989,68,287 Mochida, I. and Sakanishi, K. Fuel 1987, 66, 1584 Kodera, Y., Ukegawa, K. and Takahashi, T. ‘Proceeding of 1989 International Conference on Coal Science’, Tokyo, Japan, 1989, Vol. 2, p. 823 Ukegawa, K., Matsumura, A., Kodera, Y., Kondo, T., Nakayama, T., Tanabe, H., Yoshida, S. and Mito, Y. J. Jpn. Petrol. Insr. 1990, 33, 250
FUEL, 1991, Vol 70, June
769
of nitrogen
Yoichi Kodera, Koji Ukegawa. Yutaka Mite*, Etsuro lshikawaf and Tetsuo Nakayama
compounds
Masashi
Komotot,
National Research Institute for Pollution and Resources. 16-3 Onogawa, Tsukuba, lbaraki 305, Japan * Kobe Steel Ltd. l-3-18 Wakihama-cho, Chuo-ku, Kobe, Hyogo 657, Japan _FNippon Steel Chemical Co. Ltd, 5- 13- 16 Ginza, Chuo-ku, Tokyo 104, Japan
(Received
14 January
7997)
Nitrogen compounds were separated efficiently from coal liquids by solvent extraction with methanol and water. Middle distillates of Wandoan and Battle River coal liquid and a mixture of model compounds were employed as feed oils. This paper reports the experimental conditions for the effective separation nitrogen compounds, such as quinoline and indole. In particular, the effects of extraction solvents extraction yield and selectivities of nitrogen compounds were investigated.
of on
(Keywords: solvent extraction; nitrogen compounds; coal fhpids]
Upgrading of coal liquids is important for producing alternative liquid fuels of good quality; it has been performed by hydrotreating in the presence of However, upgrading requires expensive catalysts’-‘. catalysts and considerable amounts of hydrogen because coal liquids contain large amounts of nitrogen and phenolic compounds, which are converted to ammonia and water. Phenolic and nitrogen compounds are industrially valuable chemicals. Thus, the economical method for both separation and production of these chemicals is thought to be the effective utilization and upgrading of coal liquids. Here, we report on an effective extraction method using methanol and water as solvents for the separation of nitrogen compounds from coal liquids6,7.
Per cent extractions of nitrogen compounds were determined as the ratio of the decreased amount of nitrogen in the residual oil to the nitrogen content of the original feed oil. Nitrogen contents were obtained by a total nitrogen analyzer. The selectivities of nitrogen compounds in a methanol-water layer are defined as the amount of nitrogen compound over the amount of all the components extracted in the layer. Quantitative analysis for the nitrogen compounds and the other components in the methanol-water layer was carried out with a gas chromatograph equipped with a nitrogen detector system (Tracer Instrument Model loo), using a 50 m glass capillary column coated with HR-101 on Chromosorb W. The temperature range was lOO-260°C Using a rate of 1‘C min- ’ with Isothermal periods of 4 min at the start and 30 min at the end of the analysis.
EXPERIMENTAL RESULTS
Materials
AND DISCUSSION
Middle distillates (b.p. 180-45O”C, see Figure I) of Wandoan and Battle River coal liquid were obtained with a 1 t/d coal liquefaction plant of Sumitomo Metal Industries, Ltd. These feed oils contain considerable amounts of nitrogen and phenolic compounds as shown in Table I. The methanol, quinoline and phenol used are commercially available.
The effects of solvents on extraction yields of nitrogen compounds were examined. There is a strong interaction between nitrogen compounds and methanol molecules in the mixture of the feed oil and methanol. The
Procedure for soiuent extraction The procedure fur the separation of nitrogen compounds is shown in Sclzelne 1, Methanol was mixed with a feed oil by shaking in a shaker for 2 min and water was poured into the mixture. The mixture immediately separated into two layers; a methanol-water layer contaning nitrogen compounds and a residual oil layer. After the mixture was left for 10 min at 3O”C, the methanol-water layer was removed and evaporated under reduced pressure to recover the methanol. Removal of methanol caused the nitrogen compounds to separate as an oily material which was insoluble in water.
Middle distillate
001~~236~/~1/060763-03 ‘? 1991 Butterworth-Heinemann
Ltd
Table 1
Characteristics
of feed stocks Wandoan
._~~
~~ Nitrogen
content
(%)
0.51
Contents (wt%)b quinoline isoquinoline indole carbazole Acldlc compounds
Battle River
~
0 42
0.29 0.02 0.18 0.22 9 80
40 70
(~1%)
“Determined with a nitrogen analyzer ‘Determined using a gas chromatograph detector ‘Separated with a 20% NaOH solution
FUEL,
1991,
equipped
with a mtrogen
Vol 70, June
765
Solvent extraction
of nitrogen
compounds:
Y. Kodera et al.
a Nitrogen
Compoundsa
h 3
h
mi”
lb
io
;o
;o
;o
min
10
20
30
40
50
. k0
70
S’O
-.-l
1;o
d0
I
J
60
J
100
70
80
90
I
I
70
80
90
100
70
80
90
100
b Nitrogen
0
’
min
min
Compoundsa
lo
20
30
40
lo
20
30
40
50
50
60
60
Figure I Gas chromatographs of a middle distillate of (a) Wandoan coal liquids and (b) Battle River coals. Analytical the text. “Detected with a nitrogen detector. *Detected with a field ionization detector
addition of water formed a new layer of a mixture of water and methanol which was rich in nitrogen compounds. Figure 2 shows the effect of the amount of methanol on per cent extraction of nitrogen. The extraction yields of nitrogen increased significantly as the amount of
766
FUEL, 1991, Vol 70, June
A
conditions
are described
methanol increased. The yields of nitrogen in a methanol-water layer from a middle Battle River coal liquid (0) were larger than middle distillate of Wandoan coal liquid (a). can be explained by the differences in the
in
compounds distillate of those from a This result quantitative
Solvent Feed
Methanol mixing
Water
t standing
Scheme 1
Extraction
of nitrogen
compounds:
Y. Kodera
et al.
indole and carbazole. Selectivities of nitrogen compounds were calculated as the ratio of the peak areas of each compound to the total of all peak areas. The effect of the amount of methanol on the selectivities of the major nitrogen compounds is summarized in Figure 3. The selectivity curves of quinoline and carbazole have the maximum values. The selectivity curve for the sum of the selectivities of the four compounds is shown in Figure 4. The sum of the selectivities of these compounds have the largest values at 1 ml of methanol. The largest sum of the selectivities of all four compounds was 5.9%. This means that these compounds were concentrated 9.7 times in the original feed oil. For all nitrogen compounds, lower values were obtained as more methanol was used. To clarify the reasons for these changes in selectivities, model mixtures (listed in Table 2) were prepared and extracted by the procedure described. The results of the selectivity of quinoline extracted in a methanol-water layer is shown
I--
Methanolwater layer
extraction
Residual oil layer
procedure
50 -
40 l
P
-
Methanol
methanol.
0
2
4
6
Methanol
(ml)
8
(ml)
Selectivities of nitrogen compounds Feed, Wandoan middle, 2.0 ml; water,
versus 2.0 ml
amount
of
10
Figure 2 Per cent extraction of nitrogen versus amount of methanol. Feed, Battle River middle, 2.0 ml and Wandoan middle, 2.0 ml; water, 2.0 ml
ratios of the amount of nitrogen compounds contained in each feed oil to the amount of solvent. A middle distillate of Wandoan coal liquid contains larger amounts of nitrogen compounds than that of Battle River coal liquid. However, a certain amount of solvents can extract the corresponding amounts of nitrogen compounds from each feedstock. Thus, the per cent extractions of nitrogen in the middle distillate of Battle River coal liquid is larger than those of Wandoan coal liquid. The middle distillate of Wandoan coal liquid contains four major nitrogen compounds: quinoline, isoquinoline,
”
0
2
4
6 Methanol,
a
Figure 4 Effect of the amount of methanol selectivities of quinoline, isoquinoline, indole Wandoan middle, 2.0 ml; water, 2.0 ml
FUEL,
10
12
mL
1991,
on the sum and carbazole.
of the Feed,
June
767
Vol
70,
Solvent extraction Table 2
Mixtures
of nitrogen
compounds:
Y. Kodera et al.
of model compounds” ~~. Contents
(wt%)
Mixture
Quinoline
Phenol
A B C D E ~~
1.29 1.29
0.00 0.09 0.47 0.94 1.88 ~~
1.29 1.29
1.29 ~~
“Solution
in I-methylnaphthalene
The effects of shaking time and operating temperature were examined. A feed oil was mixed with methanol and subsequently treated with water without shaking to immediately give a two-phase mixture. The per cent extraction of nitrogen compounds did not increase with the duration of shaking at 3O”C, as shown in Figure 7. Furthermore, the selectivities of the four major compounds were not affected by the shaking period. This means that the separation method does not require a shaking process.
100
comoonent
mmtlre
10
qu~nolme
l n
A B
80
30
ohenol 1 -methylnaDhthalene 0 +
0
A
I t
0
I
I
1
I
I
1
2
3
4
5
Methanol
(ml)
Methanol
Figure 6 Relative amounts mixtures ofmodel compounds
(ml)
of the components in extracts from Feed, mixture A, Band E, 2.0 ml; water,
Figure 5 Effect of the amount of methanol on the selectivity of quinoline in the extraction of the mixtures of model compounds. Feed, mixture A-E, 2.0 ml; water, 2.0 ml
in Figure 5. The selectivity decreased with increase in the concentration of phenol in the mixtures. These results indicate that phenolic compounds in coal liquids lower the selectivities of nitrogen compounds in extracts especially at smaller amounts of methanol. The relative amounts of quinoline, phenol and I-methylnaphthalene in the extracts from mixtures A, B, and E are shown in Figure 6. These values are determined by gas chromatography and are based on the extracted amount of quinoline with 1 ml of methanol. These results show that there are two factors which decrease the selectivities of nitrogen compounds in the extraction from coal liquids. The first factor is that a quantitative amount of phenolic compounds is extracted independent of the amount of methanol used. In contrast to the quantitative extraction of the phenolic compounds, a small amount of quinoline was extracted by a small amount of methanol. As a result, a lower selectivity of quinoline was obtained with a decreasing amount of methanol. The second factor is that the amount of I-methylnaphthalene in an extract increases more significantly than that of quinoline as the amount of methanol increases. As a result, the selectivity of quinoline decreased with increasing amount of methanol.
768
FUEL,
1991,
Vol 70, June
X
x-----FX
I
I
I
1
1
,
0
1
2
3
4
5
time
(min)
Shaking
Figure 7 Effect of shaking time on per cent extraction and selectivities ofnitrogencompounds. Feed, Wandoan middle, 2.0 ml; water, 2.0 ml
Solvent extraction
of nitrogen
compounds:
Y. Kodera et al.
because of their low solubilities in water. The isolation procedure will be reported elsewhere. CONCLUSIONS
\
I
I
I
I
I
10
20
30
40
50
Temnerature
Nitrogen compounds can be separated efficiently from middle distillates of coal liquids by solvent extraction using methanol and water. Nitrogen compounds were extracted into a methanol-water layer. The per cent extraction of nitrogen compounds is strongly affected by the amount of methanol used. The selectivities of nitrogen compounds are lowered by simultaneous extraction of phenolic compounds and hydrocarbons. The present method provides a new economical method for the separation of nitrogen compounds from coal liquids. The isolation and purification of nitrogen compounds from a methanol-water layer are now being studied.
%
Figure 8 Effct of the operating temperature on the per cent extraction of nitrogen. Feed, Wandoan middle, 2.0 ml; methanol, 4.0 ml; water, 2.0 ml
A mixture of a feed oil and methanol was treated with water at lo-50°C. The per cent extraction decreased as operating temperature increased as shown in Figure 8. This indicates that the extraction should be operated at low temperatures. Nitrogen compounds were isolated as an oily mixture from methanol-water layers by evaporation of methanol
REFERENCES Song, C., Hanaoka, K., Ono, T. and Nomura, M. Bull C/rem. Sot. Jpn. 1988,61, 3788 Perrot, J. M., Ayadi, A., Bastick, M. and Bastick, J. Fuel Proc. Technol. 1988, 20,223 Sakanishi, K., Zhao, X. Z., Fei, Y. Q., Korai, Y., Fujitusu, H. and Mochida, I. Fuel Proc. Technol. 1988, 20, 233 Song, C., Hanaoka, K. and Nomura, M. Fuel 1989,68,287 Mochida, I. and Sakanishi, K. Fuel 1987, 66, 1584 Kodera, Y., Ukegawa, K. and Takahashi, T. ‘Proceeding of 1989 International Conference on Coal Science’, Tokyo, Japan, 1989, Vol. 2, p. 823 Ukegawa, K., Matsumura, A., Kodera, Y., Kondo, T., Nakayama, T., Tanabe, H., Yoshida, S. and Mito, Y. J. Jpn. Petrol. Insr. 1990, 33, 250
FUEL, 1991, Vol 70, June
769