- Email: [email protected]
Properties of Kansk-Atchinsk lignite during liquefaction in lower alcohols
Properties liquefaction P. N. Kuznetsov, E. D. Korniyets
of Kansk-Atchinsk in lower alcohols V. I. Sharypov,
N. G. Beregovtsova,
Institute of Chemistry and Chemical Technology Karl Marx St., 660049, Krasnoyarsk. USSR (Received 4 December 7989; revised 26 March
of the USSR,
lignite
during
A. I. Rubaylo Academy
and
of Sciences,
42
7990)
The influence of different factors (nature of alcohols and catalysts, temperature, type of deuterium distribution in alcohol) on hydrogenation and alkylation reactions during liquefaction of Kansk-Atchinsk lignite has been investigated. It has been shown that alkylation and hydrogenation reactions proceed simultaneously. Liquefaction kinetics are described by a first-order equation. A considerable isotope effect takes place after alcohol cc-hydrogen atoms are substituted by deuterium. The composition peculiarities of liquid and solid products have been discussed. It has been shown that the introduction of alkyl groups into aromatic coal structure provides increased lignite liquefaction in alcohols. The formation of alkylated products is characteristic of low-rank humic coal. (Keywords: liquefaction of coal; lignite; alkylation)
The process of coal liquefaction using alcohols is interesting both for obtaining liquid fuel and for studying coal structure and properties. The efficiency of liquefaction is determined by coal properties’-5, alcohol structure5-lo, and catalyst type6’1’v12. Low-rank coals are thought to be the most suitable for liquefaction In the presence of alkali as catalyst, processes2-4. alcohols are able’~‘*’ ‘pi3 to achieve a high degree of coal dissolution (9&95%) at the comparatively low temperature of 30&35O”C. Alcohol action is considered to be determined by its hydrogen donor properties’.7.8.107’ 3, According to Ross’, the liquefaction process involves hydrogenation of coal anthracene-like structures, followed by the thermal destruction of saturated bonds. Bimer experimentally confirmed this consecutive order for the methanol + NaOH + coal system’. Ouchi and Bimer14 showed that besides hydrogenation, the alkylation of aromatic fragments is one of the most important factors determining the increased coal liquefaction in alcohols. Methods of preliminary coal alkylation were used to increase solubility in solvents’ 5--1‘. Various methods of investigating alkylated coals have shown18p21 that the introduction of alkyl groups in coal structure decreases the degree of structural association. This provides easy solvent access and rapid passage of coal to the solution. The quantitative dependence of alkylation degree on type and concentration of alcohol, catalyst and other factors has been studied previouslyg,‘2,22*23. The properties of Kansk-Atchinsk lignite during liquefaction in lower aliphatic alcohols are discussed in this paper.
ethanol) were analytically pure. In comparative experiments toluene was used as a solvent. Catalysts (Na, Fe, Zn, Co, Ni and Sn chlorides and hydroxides) were supported on lignite (amount 1%) using impregnation techniques. Liquefaction was carried out at 380 or 430°C in a batch-flow reactor and in a 250 ml rotating autoclave. A lignite load of 15 g, alcohol charge of 20 ml, and initial hydrogen pressure of 5 MPa were used in the majority of autoclave experiments. In flow reactor experiments a load sample was put into the reactor. After passing argon through, the reactor was heated and alcohol was fed in. Liquefaction was carried out at 380°C over 0.5-6.0 h, at a continuous alcohol solvent feed rate of 0.2 mol h- ‘. After the experiments were finished, liquid products were extracted with hexane (maltenes) and benzene (asphaltenes). The degree of lignite conversion was evaluated on the basis of solid residue quantity. To determine hydrogenation and alkylation sequences, the reactions of methanol with some model aromatic compounds as well as with coal maltene were carried out under the same conditions. Liquid and solid products were investigatd by ultimate analysis (for the C, H, N, S content), i.r. and ‘H n.m.r. spectroscopy, and cryoscopy (for molecular weight determination). Gaseous products were analysed using gas-liquid chromatography. The experimental technique has been described previouslyg*‘2*23. The use of model compounds is also discussed in the literature24. RESULTS
In these experiments the coals used differed in origin and rank, and came from various coal basins (Table I). All the solvents (methanol, ethanol, deuterium labelled at ‘Coal Structure
with methanol in an autodave With no catalyst the degree of liquefaction of Kansk-Atchinsk lignite in methanol at a temperature of 380°C does not exceed 10%. Under the catalytic action of chlorides and hydroxides of transition metals (Ni, Co, Fe, Zn, Sn, MO) the liquefaction increases considerably’*. The use of catalyst in the presence of H, is most efficient. Liquefaction
EXPERIMENTAL
Presented
AND DISCUSSION
X9’, 1618
OO16-2361,‘90!070911&06 8~ 1990 ButterworthbHeinemann
Ltd.
October
1989, Jadwisin,
Poland
FUEL,
1990,
Vol 69, July
911
Liquefaction Table 1
of Kansk-Atchinsk
Analytical
lignite:
et al.
P. N. Kuznetsov
data for coals studied Analysis H
N
S
Ob
45.9
5.6
0.3
0.9
47.3
73.0
9.1
1.0
0.7
16.2
2.57
55.7
6.2
1.6
0.7
35.8
Ash“
C
Coal
Coal basin
Boghead
Yakutsk
4.71
Sapropelite
Irkutsk
18.35
Lignin
(wt% daf)
Lignite
Kansk-Atchinsk
5.60
70.8
4.9
0.8
0.2
23.3
Subbituminous
Kuznetsk
6.44
79.3
5.6
1.9
0.4
12.8
Bituminous
Kuznetsk
4.66
84.8
5.1
2.8
0.6
6.7
’ Dry basis b By difference
Table 2
Without
Comparative
characteristics
methanol
With methanol Conditions:
autoclave,
of liquid products
C
H
N
S
0.54
84.0
8.6
0.6
0.68
82.6
8.9
0.6
380°C; hydrogen
pressure,
obtained
Without Catalyst (wt%)
Elemental
in the autoclave
Maltene fraction in benzene soluble products
‘H n.m.r. data for maltenes
Table 3
obtained
5 MPa;
maltene
catalyst,
by catalytic
analysis
by catalytic
lignite hydrogenation
(X)
with and without
Brown-Ladner
methanol
characteristicsa
0
Molecular weight
H,,,/C,,
f,
(i
n
0.2
6.6
242
0.88
0.61
0.47
2.1
0.2
7.7
277
0.87
0.57
0.58
1.8
1 wt% based on lignite
lignite liquefaction
methanol
with and without
With methanol
methanol
(20 ml)
Calculated
values
H,,
H,
HOI
H “1,
H,,
H,
H,,
H OH
H,
H,,
Degree of alkylation (%)
Ni(OH),,
1%
0.21
0.37
0.39
0.03
0.17
0.44
0.36
0.03
0.43
0.36
14
Zn(OH),,
1%
0.22
0.36
0.38
0.04
0.16
0.45
0.35
0.04
0.46
0.36
20
ZnCl,,
1%
0.23
0.36
0.38
0.03
0.17
0.46
0.35
0.02
0.45
0.35
20
SnCI,,
I%
0.27
0.37
0.34
0.02
0.18
0.47
0.31
0.04
0.48
0.38
24
Fe(OH),,
10%”
0.25
0.36
0.36
0.03
0.19
0.46
0.32
0.03
0.44
0.33
17
Fe(OH),,
10%b
0.28
0.37
0.32
0.03
0.21
0.46
0.27
0.06
0.46
0.29
0.14
0.23
0.62
0.01
0.13
0.35
0.50
0.02
0.26
0.61
16 _
0.22
0.35
0.33
0.10
0.15
0.47
0.35
0.03
0.47
0.32
26
NaOH,
10%
a Data for benzene solubles b Data for benzene solubles at 430°C Conditions: autoclave, 380°C; hydrogen pressure, 5 MPa Formulae for the calculations are given in Appendix A
The use of methanol as a solvent under these conditions does not increase the degree of lignite liquefaction as much as e.g. toluene. However, solvent type influences the product composition. Some characteristics of liquid products obtained by lignite hydrogenation in methanol and toluene are given in Table 2. The comparison shows that benzene-soluble substances obtained in methanol contain more maltenes. These are of higher molecular weight and of greater hydrogen content. A lower aromaticity (/II), higher degree of aromatic ring substitution (CJ) and shorter alkyl substituents (?I) are characteristic of these maltenes. It has recently been shown12,22s23 that the catalytic action of certain compounds leads to acceleration of the lignite hydrogenation reaction by hydrogen:
+
H
Coal
912
FUEL,
1990,
2
catalyst,
Vol 69, July
This process determines the degree of lignite conversion. Simultaneously, the reaction of alkylation by alcohol is proceeding: + CH3OH-+Product
cH3
+ Hz0
(2) Using the literature method22,23, this reaction can be described quantitatively. The method is based on a detailed comparison of the composition of products obtained by hydrogenation both with and without alcohols. The proton distribution data obtained in experiments using ‘H n.m.r. spectroscopy, and those calculated by this method22,23 using Equations (1) and (2), are given in Table 3 for different maltenes. In experiments without catalysts, or with chlorides and hydroxides of transition metals as catalysts, computed and experimentally measured values of H, and H,, fractions are in good agreement. Thus, the composition
Liquefaction
r
90
hgpzcrth~~m, ;
Figure 1 Variation in alkylation degree ofmaltenes obtained by lignite hydrogenation in methanol in the presence of various catalysts, with degree of liquefaction. Conditions: autoclave, 380°C; Pn,, 5 MPa; catalyst content, 1 wt% on coal basis
of lignite soluble substances under these conditions is as described by Equations (1) and (2). This means that apart from alkylation, all other reactions of liquid product formation with methanol participation do not take place to any considerable extent. The methylation degree (AH,, x lOO/H!$), i.e. the proton aromatic fraction substituted by CH, groups, depends on temperature slightly and differs from hexane and benzene soluble substances only weakly. With various catalysts the methylation degree changes in the 1426% range. Taking into account data on elemental analysis and molecular weight, this corresponds to the introduction of 0.771.3 methyl groups into each ‘average molecule’. These values are close to those obtained by Ouchi and Bimerr4. The degrees of alkylation for maltenes obtained in the presence of various catalysts are plotted against the liquefaction degree in Figure 1. With increasing degree of liquefaction, i.e. with increasing catalytic activity in hydrogenation, the degree of liquid product alkylation decreases. Compounds such as ZnCl,, SnCl,, which have Lewis-type acid properties, do not accelerate alkylation under the given conditions. Maltenes obtained without catalysts have the highest degree of alkylation. Computer values of H, and H differ from experimentally measured ones sign1.P’ scantly in the presence of NaOH (Table 3). This suggests that together with methylation, other processes of liquid product formation take place with methanol participation. All alcohols including methanol show H-donor properties in such a system1*7.‘3.
+
CH30H
of Kansk-Atchinsk
lignite:
P. N. Kuznetsov
et al.
obtained from various humic coals. The degree of methylation decreases quickly as coal rank increases (Figure 3). The most intensive alkylation takes place in the case of lignin and lignite: under the conditions studied, 2.1 and 1.3 methyl groups respectively are introduced into every ‘average maltene molecule’. Alkylation is minor in the case of high rank, high aromatic coals. This sequence of coal alkylation ability is the reverse of the one established earlier’9520,25 for the conditions of reductive alkylation. This indicates mechanism pecularities of these reactions. In the case of low aromatic sapropelites, appreciable alkylation is not observed. In no cases were there any 0-alkylated substances in the liquid products. However, they were easily formed in reductive20,26,27 and Friedel-Craftsi alkylation at low temperatures. The absence of 0-alkylated substances seems to be due to their decomposition, as shown by the formation of a large quantity of methane (especially in the case of sapropelites (Table 4)). The model autoclave experiments have shown that in the absence of catalyst the degree of anthracene transformation by methanol is 29%. The yield of alkyl derivatives is only 8%, i.e. in this reaction methanol alkylated only one in every twelve anthracene molecules. Methanol did not interact with naphthalenes, diphenyl,
Figure 2 methanol.
Product yields from various coals during hydrogenation in Conditions: autoclave, 380°C; P,,, 5 MPa; without catalyst
- 30
2.0 -
+
CHZO
(3) To define the influence of coal structure upon liquefaction and alkylation, experiments were carried out with coals of different origin and rank. Bituminous coal, subbituminous coal, lignin and two samples of sapropelite were used. The data on product yields in methanol are given in Figure 2. As expected’,3,4, an increase in coal conversion and in liquid product yields is observed with decrease in coal rank. The reactivity of sapropelites is higher. The methylated aromatic substances, shown by the increasing signal at 2.1 ppm in n.m.r. spectra, are characteristics of liquid products
40
40
50
60
Cn2tranA, Figure 3 Relation between alkylation rank. Conditions as in Figure 2
FUEL,
?o
80
SO
xc degree
1990,
of maltenes
Vol 69, July
and coal
913
Liquefaction of Kansk-Atchinsk Table 4 methanol
Gas product and toluene
yields during
lignite: P. N. Kuznetsov et al.
liquefaction
of sapropelite
with
Yield (wt% on coal basis) __ Solvent
CO
CO,
CH,
C,H,+C,H,
C,-C‘l hydrocarbons
Methanol Toluene
1.23 1.00
9.28 6.99
8.50 0.83
2.25 0.50
1.16 0.25
Conditions:
flow reactor,
380°C
dx -=k(a-x) dt
2 MPa
or with the lignite maltenes, or in the presence of coal residue addition. These results, as well as literature data8.28,29 for reactions of alcohols with other model compounds, are represented in the following schemes:
Lignite
+ CH30H
-p
tion in methanol, ethanol and isopropanol flows are given in Figure 4. The experiments were carried out without catalysts at 380°C. Lignite liquefaction in methanol is the least effective. The two lignite samples differ considerably in their reactivity, although they have practically the same proximate and ultimate analysis data. The results are described by the first-order equation :
R
D-
maltenes
(cH3)1,3
(4)
where x is the degree of lignite conversion, and a is a constant corresponding to maximum lignite conversion and depending on lignite properties and alcohol type. In the case of ethanol, the kinetics remain in the wide range of conversion for both lignite samples. Liquefaction kinetics in isopropanol are more complex: after 3 h the coal conversion reaches 35%, and an increase in coal reactivity is observed. The change in lignite composition was studied by
methanol
CL)
A%1 Ethanol m - Isopropanol
70
B
60 / A
(6)
OH)Q +
.-b
(C”3’o,04
(8)
@
IO 9
It therefore follows that alkylation of different aromatic hydrocarbons and coal maltenes by alcohols is not typical under liquefaction conditions. The intensive formation of methylated products takes place when only the substrate undergoes destruction (Equations (4) and (9)). Thus in coal liquefaction it is probably not the final products that are subjected to alkylation, but intermediate reactive particles, e.g. radicals. Liquefaction in a flow reactor During autoclave experiments, secondary reactions of products are intensive, making it difficult to investigate coal and solvent interactions. In our experiments a batch-flow reactor was used, in which a stationary lignite bed was liquefied in continuous alcohol solvent flow. The use of such a method inhibits intensive secondary reactions, due to removal of products from the reactor. The kinetic curves of Kansk-Atchinsk lignite liquefac-
914
FUEL,
1990,
Vol 69, July
/I9 1’ A
A
-
OH
CH30H
/
a-x a
070 02 c24
0.6
Figure 4 Kinetic curves of Kansk-Atchinsk lignite liquefaction in various alcohol flows. Conditions: flow reactor, 38O“C, 2 MPa. Analysis of coals (wt%, daf): sample A: ash, 5.20; C, 69.38; H, 5.11; N, 1.05; S, 0.15; 0, 24.31. Sample B: ash, 4.54; C, 69.20; H, 5.16; N, 0.77; S, 0.14; 0, 24.73
Liquefaction
various methods. According to i.r. spectral data the initial lignite samples A and B differed substantially in absorption at 286&2920 cm- 1 (C-H aliphatic bonds vibrations). In the more reactive B sample aliphatic fragments were represented mainly by methylene groups, with a low content of methyl groups. In the A sample the initial CHJCH, ratio was 1.7. During liquefaction the changes in lignite i.r. spectra in the region 286&2920 cm-’ depended on alcohol type. Figure 5 shows the changes in aliphatic group content in solid benzene-insoluble residue with liquefaction time. From Figure 5 one can see that lignite enrichment with aliphatic fragments takes place during lignite liquefaction in alcohols. It is known22,30 that the reverse process occurs during coal liquefaction in typical hydrogen donor solvents. The enrichment observed is due to alcohol alkylation. The solid residue is alkylated most intensively in ethanol. More enrichment with aliphatic groups takes place in the B sample, which has a higher reactivity during liquefaction. In isopropanol, considerable enrichment with aliphatic fragments is observed after 3 h reaction time. Figure 4 shows that this stage is characterized by the sharp increase in degree of liquefaction. For methanol the change in solid residue composition is less meaningful. The formation of benzene-soluble substances changes as follows’. Molecular weight and the degree of aromatic fragments condensation increase with the increase in reaction time, i.e. with the increase in lignite conversion.
of Kansk-Atchinsk
Liquefaction with deuterium labelled ethanol
Data on the influence of type of deuterium substitution in ethanol on the liquid product yield are given in Table 5. It can be seen that the substitution of protium in CH, and OH groups by deuterium does not result in sufficient change of product yield. Introduction of deuterium into the a-position (CH,CD,OH) is accompanied by a considerable isotope effect (K,/K, = 2.8). This indicates that methylene group hydrogen participates in the limiting stage of liquid product formation. A similar isotope effect was also obtained in coal liquefaction in deuterium labelled tetralin31q3*. Hydrogen content in maltenes does not depend on the extent and type of deuterium substitution, and is 8.&8.8%. According to i.r. spectroscopy both liquid and solid products contain deuterium. The spectra change in the region of stretching vibrations of aliphatic C-H and C-D bonds, corresponding qualitatively to deuterium position in the initial alcohol. In all cases solid residues have the highest fraction of C-D aliphatic groups (Table 6) and maltenes the lowest, in agreement with the Variation of lignite liquid substitution in ethanol Liquid
0
I
I
1
4
2
3
I
4
5 hoIL6f
Figure 5 Changes in aliphatic group content for benzene insoluble coal residues during lignite liquefaction in alcohols in the flow reactor
Table 6
Content
of C-H
and C-D
aliphatic
groups
in products
16.1 14.5 14.1 4.8 2.8
_
_
1.1 1.1 1.7 1.7
1.1 1.1 3.3 5.7
of lignite conversion
flow reactor,
in different
Deuteration
38O”C, 2 MPa,
deuterium
Asphaltenes
lignite B
alcohols
in the flow reactor
degree per 1 alcohol
deuterium
atom
Asphaltenes
Maltenes
0.08
0.07
0.06
0.12
0.12
0.08
58
0.18
0.15
0.15
52
0.31
0.25
0.20
Solid residue
25
61
_
CH,CD,OH
20
63
CD,CD,OH
31
54
CD,CH,OH
28
CH,CH,OD
30
vibrations. the sample
effect,
24.3 22.3 22.5 14.2 13.9
Conditions:
was determined
by integral
intensities
of A
of
a&o
CH,CH,OH CH,CH,OD CD,CH,OH CH,CD,OH CD,CD,OH
CH,CH,OH
groups
Isotope
yield,
type
Maltenes
Maltenes
and C-D
with
Asphaltenes
Solid residue
of C-H
yields
Maltenes
Alcohol
content
product U (wt%)
product
Alcohol
Summary content of C-H and C-D groups (relative units)
Summary
et al.
At equal conversion, benzene-soluble substances obtained in methanol, ethanol and isopropanol have the same degree of condensation, i.e. an identical structural nucleus including 2-3 condensed aromatic rings. The main differences in molecular structure are concerned with length and number of alkyl substituents resulting from ‘the alcohol alkylation reaction. The data presented indicate that during lignite liquefaction in alcohols the formation of both liquid and solid alkylated products takes place. This means that alkylated lignite matter is subjected to liquefaction. This may be due to the large number of ethyl groups reducing the stacking of aromatic lignite fragments.
Table 5 deuterium
90
lignite: P. IV. Kuznetsov
=& jD(v)dv i.r. absorption
of C-H
Integration intervals were 275G3050 and 2OG%2300 cm-’ for the C-H and C-D regions respectively. quantities and thicknesses of absorbing layer were constant, so the results are given in relative units
FUEL,
and C-D
stretching
In the series of experiments,
1990,
Vol 69, July
915
Liquefaction of Kansk-Atchinsk
lignite: P. N. Kuznetsov et al.
data of Yamamoto33 and Cronauerj4 for liquefaction in labelled tetralin. The total content of C-H and C-D aliphatic groups in products obtained in various deuterium-analogues of ethanol differs only slightly, i.e. the type of deuterium substitution does not influence alkylation. This means that the alkylation process does not include the breakdown of C-H and O-H bonds in alcohol, or that breakdown is not a limiting stage in alkylation. The deuterating activity of the different deuterium ethanols changes as follows: CH,CH,OD > CD,CH,OH > CD,CD,OH > CH,CD,OH. Thus, the methylene group is a very weak deuterating agent. The higher degree of deuteration takes place with CH,CH,OD, probably due to intensive heteromolecular exchange. The analysis of proton distribution in alcohols has shown that under the reaction conditions a considerable exchange of deuterium (80%) takes place from CD, groups to hydroxyl groups. This type of exchange in the presence of catalyst was noted recently35. Thus the high deuterium content in the products of coal conversion using CD,CH,OH is probably related to such an exchange. CONCLUSIONS Alkylation of aromatic fragments of Kansk-Atchinsk lignite takes place simultaneously with liquefaction in lower aliphatic alcohols. Destruction of alkylated lignite leads to the formation of low-molecular soluble alkylated substances. In ethanol this process proceeds most actively. Low-rank lignite is subjected to alkylation and liquefaction most easily. The catalysts studied do not influence alkylation but accelerate the lignite hydrogenation by molecular hydrogen. REFERENCES
10 11 12 13 14 15 16 17 18
19 20 21 22
23 24
916
Makabe, M., Hirano, Y. and Ouchi, K. Fuel 1978, 57, 289 Kershaw, J. K. and Bagnell, L. J. Fuei 1987, 66, 1739 Bimer, J. and Salbut, D. Koks, Smola, Gas 1986, 31, 23 Ozaki, V., Mondragon, F., Makabe, M. etal. Fuel 1985,64,767 Luyk, H. E. and Klesment, I. R. Oil Shale 1986, 3, 319 Mondragon, F., Itoh, H. and Ouchi, K. Fuel 1982, 61, 1131 Bimer, J. and Salbut, P. D. Koks, Smola, Gas 1987, 32, 63 Ross, D. S. and Blessing, J. E. Fuel 1979, 58, 433 Kuznetsov, P. N., Sharypov, V. I., Rubaylo, A. I. and Korniyets, E. D. Fuel 1988, 67, 1685 Tegai, F., Aliulin, V. V., Plopsky, E. Ya. and Kirilets, V. M. Chim. tverd. topl. 1983, 5, 92 Salbut, P. D. and Bimer, J. Koks, Smola, Gas 1988,3, 62 Tarabanko, V. E., Beregovtsova, N. G., Ivanchenko. N. M. et al. Chim. tverd. topl. 1985, 4, 76 Ross, D. S. and Blessing, J. E. Fuel 1979, 58, 438 Bimer, J. and Salbut, P. D. Erdiilund Kohle-Erdgas-Petrochemiej Hydrocarbon Technology 1988, 4 Sharma. D. K.. Sarkar. M. R. and Mirza. 2. B. Fuel 1985,64,449 Flares, R. A., Geigel, M. A. and Mayo, F. Fuel 1978, 57, 697 Neoman, D. S., Winans, R. E. and McBeth, R. L. J. Electrochem. Sot. 1984, 131, 1079 Wachowska, H., Ignasiak, T., Strausz, 0. ef al. Fuel 1986. 65, 1081 Lazarov, L., Stefanova, M. and Petrov, R. Fuel 1986, 65, 58 Erbatur, G. and Erbatur, 0. Fuel 1986, 65, 1273 Duber, S., Wachoswka, H. M. and Wieckowski, A. B. Fuel 1987. 66, 1069 Kuznetsov, P. N., Tarabanko, V. E. and Sharypov, V. I. ‘IV All-Union Conference on the mechanism of catalytic reactions’. Inst. of Organic Chem., Moscow, USSR, 1986, p. 328 Tarabanko, V. E., Beregovtsova, N. G., Ivanchenko, N. M. and Kuznetsov, P. N. React. Kinel. Catal. Letter. 1986, 32, 245 Kuznetsov, P. N., Bimer, J. and Salbut, P. D. Khim. rowd. top/. submitted for publication
FUEL, 1990, Vol 69,
July
25 26 27 28 29 30
Kato, T. and Koukuchi, F. Fuel Sot. Jap. 1985,64, 321 Sternberg, H. W. and Delle Donne, C. L. Fuel 1974,54, 172 Stock, L. M. and Willis, R. S. J. Org. Chem. 1985, 50, 3566 Makabe, M. and Ouchi, K. Fuel Proc. Technol. 1982, 64, 307 Makabe, M., Fuse, S. and Ouchi, K. Fuel 1978,57,801 Vassalo, A. M., Fredericks, P. M. and Wilson, M. A. Org. Geochem. 1983, 5, 75 Brower, K. R. J. Org. Chem. 1982,47, 1889 Skowronski, R. P., Ratto, J. J., Goldberg, I. B. and Heredy, L. A. Fuel 1984,63, 440 Yamamoto, K., Kimura, K., Ueda, K. ef al. ‘Proc. 1987 Int. Conf. on Coal Science’, Amsterdam, The Netherlands, 2630 October 1987, p. 211 Cronauer. D. C., McNeil, R. I., Young, D. C. and Ruberto, R. G. Fuel 1982,61, 610 Nueent. W. A. and Zubvk. R. M. Inorrr. Chem. 1986,25,4604 Baryle, K. D. and Jones, D. W. in ‘Analytical Methods for Coal and Coal Products’, Academic Press, London, UK, 1978, Vol. 2, pp. 103-160
31 32 33
34 35 36
APPENDIX
A
Evidence for the correctness of Equation (2) can be secured from quantitative comparison of ‘H n.m.r. spectra of soluble products obtained by hydrogenation both with and without methanol, assuming that the hydrogenation is the same in both cases22’23. The substitution of some aromatic protons (AH,,) by CH,-groups should result in a corresponding decrease in the aromatic proton fraction in alkylated products: HCHSOH
ar
_
Hr; - AH,, 1 + 2AH,,
(AlI
where the CH,OH and H, symbols are related to the products obtained by hydrogenation with and without methanol, respectively. The denominator of Equation (Al) takes into account the increase in the total number of protons in the products as a result of substitution of one aromatic proton by three methyl protons. By analogy the following expressions can be written for H:H20H and HCH~OH. PY
.
HCH30H
a
_
-
HH2 + 3AHar 1 + 2AH,,
642)
UH2
HCHJOH
PY
“Pi - 1 + 2AH,, _
643)
So we have three equations and four unknown values: H;;HJOH, HC/~OH and AH,,. To solve this problem o;e can make use of the experimental value of HzF30H. Now it becomes possible to calculate the AH,, value using: HCH~OH,
(44) which is simply a rearrangement of Equation (Al). Using the AH,, value one can easily compute the values of H~HsOH and H‘$‘o” for methanol products. By comparing the experimental and computed values, evidence showing the correctness of Equation (2) can be obtained. The ratio AH,, x lOO%/H$ is the alkylation degree, i.e. the fraction of aromatic protons substituted by CH,-groups. Knowing the alkylation degree, elemental composition and molecular weight, we can calculate the number of methyl groups introduced into the ‘average molecule’.
of Kansk-Atchinsk in lower alcohols V. I. Sharypov,
N. G. Beregovtsova,
Institute of Chemistry and Chemical Technology Karl Marx St., 660049, Krasnoyarsk. USSR (Received 4 December 7989; revised 26 March
of the USSR,
lignite
during
A. I. Rubaylo Academy
and
of Sciences,
42
7990)
The influence of different factors (nature of alcohols and catalysts, temperature, type of deuterium distribution in alcohol) on hydrogenation and alkylation reactions during liquefaction of Kansk-Atchinsk lignite has been investigated. It has been shown that alkylation and hydrogenation reactions proceed simultaneously. Liquefaction kinetics are described by a first-order equation. A considerable isotope effect takes place after alcohol cc-hydrogen atoms are substituted by deuterium. The composition peculiarities of liquid and solid products have been discussed. It has been shown that the introduction of alkyl groups into aromatic coal structure provides increased lignite liquefaction in alcohols. The formation of alkylated products is characteristic of low-rank humic coal. (Keywords: liquefaction of coal; lignite; alkylation)
The process of coal liquefaction using alcohols is interesting both for obtaining liquid fuel and for studying coal structure and properties. The efficiency of liquefaction is determined by coal properties’-5, alcohol structure5-lo, and catalyst type6’1’v12. Low-rank coals are thought to be the most suitable for liquefaction In the presence of alkali as catalyst, processes2-4. alcohols are able’~‘*’ ‘pi3 to achieve a high degree of coal dissolution (9&95%) at the comparatively low temperature of 30&35O”C. Alcohol action is considered to be determined by its hydrogen donor properties’.7.8.107’ 3, According to Ross’, the liquefaction process involves hydrogenation of coal anthracene-like structures, followed by the thermal destruction of saturated bonds. Bimer experimentally confirmed this consecutive order for the methanol + NaOH + coal system’. Ouchi and Bimer14 showed that besides hydrogenation, the alkylation of aromatic fragments is one of the most important factors determining the increased coal liquefaction in alcohols. Methods of preliminary coal alkylation were used to increase solubility in solvents’ 5--1‘. Various methods of investigating alkylated coals have shown18p21 that the introduction of alkyl groups in coal structure decreases the degree of structural association. This provides easy solvent access and rapid passage of coal to the solution. The quantitative dependence of alkylation degree on type and concentration of alcohol, catalyst and other factors has been studied previouslyg,‘2,22*23. The properties of Kansk-Atchinsk lignite during liquefaction in lower aliphatic alcohols are discussed in this paper.
ethanol) were analytically pure. In comparative experiments toluene was used as a solvent. Catalysts (Na, Fe, Zn, Co, Ni and Sn chlorides and hydroxides) were supported on lignite (amount 1%) using impregnation techniques. Liquefaction was carried out at 380 or 430°C in a batch-flow reactor and in a 250 ml rotating autoclave. A lignite load of 15 g, alcohol charge of 20 ml, and initial hydrogen pressure of 5 MPa were used in the majority of autoclave experiments. In flow reactor experiments a load sample was put into the reactor. After passing argon through, the reactor was heated and alcohol was fed in. Liquefaction was carried out at 380°C over 0.5-6.0 h, at a continuous alcohol solvent feed rate of 0.2 mol h- ‘. After the experiments were finished, liquid products were extracted with hexane (maltenes) and benzene (asphaltenes). The degree of lignite conversion was evaluated on the basis of solid residue quantity. To determine hydrogenation and alkylation sequences, the reactions of methanol with some model aromatic compounds as well as with coal maltene were carried out under the same conditions. Liquid and solid products were investigatd by ultimate analysis (for the C, H, N, S content), i.r. and ‘H n.m.r. spectroscopy, and cryoscopy (for molecular weight determination). Gaseous products were analysed using gas-liquid chromatography. The experimental technique has been described previouslyg*‘2*23. The use of model compounds is also discussed in the literature24. RESULTS
In these experiments the coals used differed in origin and rank, and came from various coal basins (Table I). All the solvents (methanol, ethanol, deuterium labelled at ‘Coal Structure
with methanol in an autodave With no catalyst the degree of liquefaction of Kansk-Atchinsk lignite in methanol at a temperature of 380°C does not exceed 10%. Under the catalytic action of chlorides and hydroxides of transition metals (Ni, Co, Fe, Zn, Sn, MO) the liquefaction increases considerably’*. The use of catalyst in the presence of H, is most efficient. Liquefaction
EXPERIMENTAL
Presented
AND DISCUSSION
X9’, 1618
OO16-2361,‘90!070911&06 8~ 1990 ButterworthbHeinemann
Ltd.
October
1989, Jadwisin,
Poland
FUEL,
1990,
Vol 69, July
911
Liquefaction Table 1
of Kansk-Atchinsk
Analytical
lignite:
et al.
P. N. Kuznetsov
data for coals studied Analysis H
N
S
Ob
45.9
5.6
0.3
0.9
47.3
73.0
9.1
1.0
0.7
16.2
2.57
55.7
6.2
1.6
0.7
35.8
Ash“
C
Coal
Coal basin
Boghead
Yakutsk
4.71
Sapropelite
Irkutsk
18.35
Lignin
(wt% daf)
Lignite
Kansk-Atchinsk
5.60
70.8
4.9
0.8
0.2
23.3
Subbituminous
Kuznetsk
6.44
79.3
5.6
1.9
0.4
12.8
Bituminous
Kuznetsk
4.66
84.8
5.1
2.8
0.6
6.7
’ Dry basis b By difference
Table 2
Without
Comparative
characteristics
methanol
With methanol Conditions:
autoclave,
of liquid products
C
H
N
S
0.54
84.0
8.6
0.6
0.68
82.6
8.9
0.6
380°C; hydrogen
pressure,
obtained
Without Catalyst (wt%)
Elemental
in the autoclave
Maltene fraction in benzene soluble products
‘H n.m.r. data for maltenes
Table 3
obtained
5 MPa;
maltene
catalyst,
by catalytic
analysis
by catalytic
lignite hydrogenation
(X)
with and without
Brown-Ladner
methanol
characteristicsa
0
Molecular weight
H,,,/C,,
f,
(i
n
0.2
6.6
242
0.88
0.61
0.47
2.1
0.2
7.7
277
0.87
0.57
0.58
1.8
1 wt% based on lignite
lignite liquefaction
methanol
with and without
With methanol
methanol
(20 ml)
Calculated
values
H,,
H,
HOI
H “1,
H,,
H,
H,,
H OH
H,
H,,
Degree of alkylation (%)
Ni(OH),,
1%
0.21
0.37
0.39
0.03
0.17
0.44
0.36
0.03
0.43
0.36
14
Zn(OH),,
1%
0.22
0.36
0.38
0.04
0.16
0.45
0.35
0.04
0.46
0.36
20
ZnCl,,
1%
0.23
0.36
0.38
0.03
0.17
0.46
0.35
0.02
0.45
0.35
20
SnCI,,
I%
0.27
0.37
0.34
0.02
0.18
0.47
0.31
0.04
0.48
0.38
24
Fe(OH),,
10%”
0.25
0.36
0.36
0.03
0.19
0.46
0.32
0.03
0.44
0.33
17
Fe(OH),,
10%b
0.28
0.37
0.32
0.03
0.21
0.46
0.27
0.06
0.46
0.29
0.14
0.23
0.62
0.01
0.13
0.35
0.50
0.02
0.26
0.61
16 _
0.22
0.35
0.33
0.10
0.15
0.47
0.35
0.03
0.47
0.32
26
NaOH,
10%
a Data for benzene solubles b Data for benzene solubles at 430°C Conditions: autoclave, 380°C; hydrogen pressure, 5 MPa Formulae for the calculations are given in Appendix A
The use of methanol as a solvent under these conditions does not increase the degree of lignite liquefaction as much as e.g. toluene. However, solvent type influences the product composition. Some characteristics of liquid products obtained by lignite hydrogenation in methanol and toluene are given in Table 2. The comparison shows that benzene-soluble substances obtained in methanol contain more maltenes. These are of higher molecular weight and of greater hydrogen content. A lower aromaticity (/II), higher degree of aromatic ring substitution (CJ) and shorter alkyl substituents (?I) are characteristic of these maltenes. It has recently been shown12,22s23 that the catalytic action of certain compounds leads to acceleration of the lignite hydrogenation reaction by hydrogen:
+
H
Coal
912
FUEL,
1990,
2
catalyst,
Vol 69, July
This process determines the degree of lignite conversion. Simultaneously, the reaction of alkylation by alcohol is proceeding: + CH3OH-+Product
cH3
+ Hz0
(2) Using the literature method22,23, this reaction can be described quantitatively. The method is based on a detailed comparison of the composition of products obtained by hydrogenation both with and without alcohols. The proton distribution data obtained in experiments using ‘H n.m.r. spectroscopy, and those calculated by this method22,23 using Equations (1) and (2), are given in Table 3 for different maltenes. In experiments without catalysts, or with chlorides and hydroxides of transition metals as catalysts, computed and experimentally measured values of H, and H,, fractions are in good agreement. Thus, the composition
Liquefaction
r
90
hgpzcrth~~m, ;
Figure 1 Variation in alkylation degree ofmaltenes obtained by lignite hydrogenation in methanol in the presence of various catalysts, with degree of liquefaction. Conditions: autoclave, 380°C; Pn,, 5 MPa; catalyst content, 1 wt% on coal basis
of lignite soluble substances under these conditions is as described by Equations (1) and (2). This means that apart from alkylation, all other reactions of liquid product formation with methanol participation do not take place to any considerable extent. The methylation degree (AH,, x lOO/H!$), i.e. the proton aromatic fraction substituted by CH, groups, depends on temperature slightly and differs from hexane and benzene soluble substances only weakly. With various catalysts the methylation degree changes in the 1426% range. Taking into account data on elemental analysis and molecular weight, this corresponds to the introduction of 0.771.3 methyl groups into each ‘average molecule’. These values are close to those obtained by Ouchi and Bimerr4. The degrees of alkylation for maltenes obtained in the presence of various catalysts are plotted against the liquefaction degree in Figure 1. With increasing degree of liquefaction, i.e. with increasing catalytic activity in hydrogenation, the degree of liquid product alkylation decreases. Compounds such as ZnCl,, SnCl,, which have Lewis-type acid properties, do not accelerate alkylation under the given conditions. Maltenes obtained without catalysts have the highest degree of alkylation. Computer values of H, and H differ from experimentally measured ones sign1.P’ scantly in the presence of NaOH (Table 3). This suggests that together with methylation, other processes of liquid product formation take place with methanol participation. All alcohols including methanol show H-donor properties in such a system1*7.‘3.
+
CH30H
of Kansk-Atchinsk
lignite:
P. N. Kuznetsov
et al.
obtained from various humic coals. The degree of methylation decreases quickly as coal rank increases (Figure 3). The most intensive alkylation takes place in the case of lignin and lignite: under the conditions studied, 2.1 and 1.3 methyl groups respectively are introduced into every ‘average maltene molecule’. Alkylation is minor in the case of high rank, high aromatic coals. This sequence of coal alkylation ability is the reverse of the one established earlier’9520,25 for the conditions of reductive alkylation. This indicates mechanism pecularities of these reactions. In the case of low aromatic sapropelites, appreciable alkylation is not observed. In no cases were there any 0-alkylated substances in the liquid products. However, they were easily formed in reductive20,26,27 and Friedel-Craftsi alkylation at low temperatures. The absence of 0-alkylated substances seems to be due to their decomposition, as shown by the formation of a large quantity of methane (especially in the case of sapropelites (Table 4)). The model autoclave experiments have shown that in the absence of catalyst the degree of anthracene transformation by methanol is 29%. The yield of alkyl derivatives is only 8%, i.e. in this reaction methanol alkylated only one in every twelve anthracene molecules. Methanol did not interact with naphthalenes, diphenyl,
Figure 2 methanol.
Product yields from various coals during hydrogenation in Conditions: autoclave, 380°C; P,,, 5 MPa; without catalyst
- 30
2.0 -
+
CHZO
(3) To define the influence of coal structure upon liquefaction and alkylation, experiments were carried out with coals of different origin and rank. Bituminous coal, subbituminous coal, lignin and two samples of sapropelite were used. The data on product yields in methanol are given in Figure 2. As expected’,3,4, an increase in coal conversion and in liquid product yields is observed with decrease in coal rank. The reactivity of sapropelites is higher. The methylated aromatic substances, shown by the increasing signal at 2.1 ppm in n.m.r. spectra, are characteristics of liquid products
40
40
50
60
Cn2tranA, Figure 3 Relation between alkylation rank. Conditions as in Figure 2
FUEL,
?o
80
SO
xc degree
1990,
of maltenes
Vol 69, July
and coal
913
Liquefaction of Kansk-Atchinsk Table 4 methanol
Gas product and toluene
yields during
lignite: P. N. Kuznetsov et al.
liquefaction
of sapropelite
with
Yield (wt% on coal basis) __ Solvent
CO
CO,
CH,
C,H,+C,H,
C,-C‘l hydrocarbons
Methanol Toluene
1.23 1.00
9.28 6.99
8.50 0.83
2.25 0.50
1.16 0.25
Conditions:
flow reactor,
380°C
dx -=k(a-x) dt
2 MPa
or with the lignite maltenes, or in the presence of coal residue addition. These results, as well as literature data8.28,29 for reactions of alcohols with other model compounds, are represented in the following schemes:
Lignite
+ CH30H
-p
tion in methanol, ethanol and isopropanol flows are given in Figure 4. The experiments were carried out without catalysts at 380°C. Lignite liquefaction in methanol is the least effective. The two lignite samples differ considerably in their reactivity, although they have practically the same proximate and ultimate analysis data. The results are described by the first-order equation :
R
D-
maltenes
(cH3)1,3
(4)
where x is the degree of lignite conversion, and a is a constant corresponding to maximum lignite conversion and depending on lignite properties and alcohol type. In the case of ethanol, the kinetics remain in the wide range of conversion for both lignite samples. Liquefaction kinetics in isopropanol are more complex: after 3 h the coal conversion reaches 35%, and an increase in coal reactivity is observed. The change in lignite composition was studied by
methanol
CL)
A%1 Ethanol m - Isopropanol
70
B
60 / A
(6)
OH)Q +
.-b
(C”3’o,04
(8)
@
IO 9
It therefore follows that alkylation of different aromatic hydrocarbons and coal maltenes by alcohols is not typical under liquefaction conditions. The intensive formation of methylated products takes place when only the substrate undergoes destruction (Equations (4) and (9)). Thus in coal liquefaction it is probably not the final products that are subjected to alkylation, but intermediate reactive particles, e.g. radicals. Liquefaction in a flow reactor During autoclave experiments, secondary reactions of products are intensive, making it difficult to investigate coal and solvent interactions. In our experiments a batch-flow reactor was used, in which a stationary lignite bed was liquefied in continuous alcohol solvent flow. The use of such a method inhibits intensive secondary reactions, due to removal of products from the reactor. The kinetic curves of Kansk-Atchinsk lignite liquefac-
914
FUEL,
1990,
Vol 69, July
/I9 1’ A
A
-
OH
CH30H
/
a-x a
070 02 c24
0.6
Figure 4 Kinetic curves of Kansk-Atchinsk lignite liquefaction in various alcohol flows. Conditions: flow reactor, 38O“C, 2 MPa. Analysis of coals (wt%, daf): sample A: ash, 5.20; C, 69.38; H, 5.11; N, 1.05; S, 0.15; 0, 24.31. Sample B: ash, 4.54; C, 69.20; H, 5.16; N, 0.77; S, 0.14; 0, 24.73
Liquefaction
various methods. According to i.r. spectral data the initial lignite samples A and B differed substantially in absorption at 286&2920 cm- 1 (C-H aliphatic bonds vibrations). In the more reactive B sample aliphatic fragments were represented mainly by methylene groups, with a low content of methyl groups. In the A sample the initial CHJCH, ratio was 1.7. During liquefaction the changes in lignite i.r. spectra in the region 286&2920 cm-’ depended on alcohol type. Figure 5 shows the changes in aliphatic group content in solid benzene-insoluble residue with liquefaction time. From Figure 5 one can see that lignite enrichment with aliphatic fragments takes place during lignite liquefaction in alcohols. It is known22,30 that the reverse process occurs during coal liquefaction in typical hydrogen donor solvents. The enrichment observed is due to alcohol alkylation. The solid residue is alkylated most intensively in ethanol. More enrichment with aliphatic groups takes place in the B sample, which has a higher reactivity during liquefaction. In isopropanol, considerable enrichment with aliphatic fragments is observed after 3 h reaction time. Figure 4 shows that this stage is characterized by the sharp increase in degree of liquefaction. For methanol the change in solid residue composition is less meaningful. The formation of benzene-soluble substances changes as follows’. Molecular weight and the degree of aromatic fragments condensation increase with the increase in reaction time, i.e. with the increase in lignite conversion.
of Kansk-Atchinsk
Liquefaction with deuterium labelled ethanol
Data on the influence of type of deuterium substitution in ethanol on the liquid product yield are given in Table 5. It can be seen that the substitution of protium in CH, and OH groups by deuterium does not result in sufficient change of product yield. Introduction of deuterium into the a-position (CH,CD,OH) is accompanied by a considerable isotope effect (K,/K, = 2.8). This indicates that methylene group hydrogen participates in the limiting stage of liquid product formation. A similar isotope effect was also obtained in coal liquefaction in deuterium labelled tetralin31q3*. Hydrogen content in maltenes does not depend on the extent and type of deuterium substitution, and is 8.&8.8%. According to i.r. spectroscopy both liquid and solid products contain deuterium. The spectra change in the region of stretching vibrations of aliphatic C-H and C-D bonds, corresponding qualitatively to deuterium position in the initial alcohol. In all cases solid residues have the highest fraction of C-D aliphatic groups (Table 6) and maltenes the lowest, in agreement with the Variation of lignite liquid substitution in ethanol Liquid
0
I
I
1
4
2
3
I
4
5 hoIL6f
Figure 5 Changes in aliphatic group content for benzene insoluble coal residues during lignite liquefaction in alcohols in the flow reactor
Table 6
Content
of C-H
and C-D
aliphatic
groups
in products
16.1 14.5 14.1 4.8 2.8
_
_
1.1 1.1 1.7 1.7
1.1 1.1 3.3 5.7
of lignite conversion
flow reactor,
in different
Deuteration
38O”C, 2 MPa,
deuterium
Asphaltenes
lignite B
alcohols
in the flow reactor
degree per 1 alcohol
deuterium
atom
Asphaltenes
Maltenes
0.08
0.07
0.06
0.12
0.12
0.08
58
0.18
0.15
0.15
52
0.31
0.25
0.20
Solid residue
25
61
_
CH,CD,OH
20
63
CD,CD,OH
31
54
CD,CH,OH
28
CH,CH,OD
30
vibrations. the sample
effect,
24.3 22.3 22.5 14.2 13.9
Conditions:
was determined
by integral
intensities
of A
of
a&o
CH,CH,OH CH,CH,OD CD,CH,OH CH,CD,OH CD,CD,OH
CH,CH,OH
groups
Isotope
yield,
type
Maltenes
Maltenes
and C-D
with
Asphaltenes
Solid residue
of C-H
yields
Maltenes
Alcohol
content
product U (wt%)
product
Alcohol
Summary content of C-H and C-D groups (relative units)
Summary
et al.
At equal conversion, benzene-soluble substances obtained in methanol, ethanol and isopropanol have the same degree of condensation, i.e. an identical structural nucleus including 2-3 condensed aromatic rings. The main differences in molecular structure are concerned with length and number of alkyl substituents resulting from ‘the alcohol alkylation reaction. The data presented indicate that during lignite liquefaction in alcohols the formation of both liquid and solid alkylated products takes place. This means that alkylated lignite matter is subjected to liquefaction. This may be due to the large number of ethyl groups reducing the stacking of aromatic lignite fragments.
Table 5 deuterium
90
lignite: P. IV. Kuznetsov
=& jD(v)dv i.r. absorption
of C-H
Integration intervals were 275G3050 and 2OG%2300 cm-’ for the C-H and C-D regions respectively. quantities and thicknesses of absorbing layer were constant, so the results are given in relative units
FUEL,
and C-D
stretching
In the series of experiments,
1990,
Vol 69, July
915
Liquefaction of Kansk-Atchinsk
lignite: P. N. Kuznetsov et al.
data of Yamamoto33 and Cronauerj4 for liquefaction in labelled tetralin. The total content of C-H and C-D aliphatic groups in products obtained in various deuterium-analogues of ethanol differs only slightly, i.e. the type of deuterium substitution does not influence alkylation. This means that the alkylation process does not include the breakdown of C-H and O-H bonds in alcohol, or that breakdown is not a limiting stage in alkylation. The deuterating activity of the different deuterium ethanols changes as follows: CH,CH,OD > CD,CH,OH > CD,CD,OH > CH,CD,OH. Thus, the methylene group is a very weak deuterating agent. The higher degree of deuteration takes place with CH,CH,OD, probably due to intensive heteromolecular exchange. The analysis of proton distribution in alcohols has shown that under the reaction conditions a considerable exchange of deuterium (80%) takes place from CD, groups to hydroxyl groups. This type of exchange in the presence of catalyst was noted recently35. Thus the high deuterium content in the products of coal conversion using CD,CH,OH is probably related to such an exchange. CONCLUSIONS Alkylation of aromatic fragments of Kansk-Atchinsk lignite takes place simultaneously with liquefaction in lower aliphatic alcohols. Destruction of alkylated lignite leads to the formation of low-molecular soluble alkylated substances. In ethanol this process proceeds most actively. Low-rank lignite is subjected to alkylation and liquefaction most easily. The catalysts studied do not influence alkylation but accelerate the lignite hydrogenation by molecular hydrogen. REFERENCES
10 11 12 13 14 15 16 17 18
19 20 21 22
23 24
916
Makabe, M., Hirano, Y. and Ouchi, K. Fuel 1978, 57, 289 Kershaw, J. K. and Bagnell, L. J. Fuei 1987, 66, 1739 Bimer, J. and Salbut, D. Koks, Smola, Gas 1986, 31, 23 Ozaki, V., Mondragon, F., Makabe, M. etal. Fuel 1985,64,767 Luyk, H. E. and Klesment, I. R. Oil Shale 1986, 3, 319 Mondragon, F., Itoh, H. and Ouchi, K. Fuel 1982, 61, 1131 Bimer, J. and Salbut, P. D. Koks, Smola, Gas 1987, 32, 63 Ross, D. S. and Blessing, J. E. Fuel 1979, 58, 433 Kuznetsov, P. N., Sharypov, V. I., Rubaylo, A. I. and Korniyets, E. D. Fuel 1988, 67, 1685 Tegai, F., Aliulin, V. V., Plopsky, E. Ya. and Kirilets, V. M. Chim. tverd. topl. 1983, 5, 92 Salbut, P. D. and Bimer, J. Koks, Smola, Gas 1988,3, 62 Tarabanko, V. E., Beregovtsova, N. G., Ivanchenko. N. M. et al. Chim. tverd. topl. 1985, 4, 76 Ross, D. S. and Blessing, J. E. Fuel 1979, 58, 438 Bimer, J. and Salbut, P. D. Erdiilund Kohle-Erdgas-Petrochemiej Hydrocarbon Technology 1988, 4 Sharma. D. K.. Sarkar. M. R. and Mirza. 2. B. Fuel 1985,64,449 Flares, R. A., Geigel, M. A. and Mayo, F. Fuel 1978, 57, 697 Neoman, D. S., Winans, R. E. and McBeth, R. L. J. Electrochem. Sot. 1984, 131, 1079 Wachowska, H., Ignasiak, T., Strausz, 0. ef al. Fuel 1986. 65, 1081 Lazarov, L., Stefanova, M. and Petrov, R. Fuel 1986, 65, 58 Erbatur, G. and Erbatur, 0. Fuel 1986, 65, 1273 Duber, S., Wachoswka, H. M. and Wieckowski, A. B. Fuel 1987. 66, 1069 Kuznetsov, P. N., Tarabanko, V. E. and Sharypov, V. I. ‘IV All-Union Conference on the mechanism of catalytic reactions’. Inst. of Organic Chem., Moscow, USSR, 1986, p. 328 Tarabanko, V. E., Beregovtsova, N. G., Ivanchenko, N. M. and Kuznetsov, P. N. React. Kinel. Catal. Letter. 1986, 32, 245 Kuznetsov, P. N., Bimer, J. and Salbut, P. D. Khim. rowd. top/. submitted for publication
FUEL, 1990, Vol 69,
July
25 26 27 28 29 30
Kato, T. and Koukuchi, F. Fuel Sot. Jap. 1985,64, 321 Sternberg, H. W. and Delle Donne, C. L. Fuel 1974,54, 172 Stock, L. M. and Willis, R. S. J. Org. Chem. 1985, 50, 3566 Makabe, M. and Ouchi, K. Fuel Proc. Technol. 1982, 64, 307 Makabe, M., Fuse, S. and Ouchi, K. Fuel 1978,57,801 Vassalo, A. M., Fredericks, P. M. and Wilson, M. A. Org. Geochem. 1983, 5, 75 Brower, K. R. J. Org. Chem. 1982,47, 1889 Skowronski, R. P., Ratto, J. J., Goldberg, I. B. and Heredy, L. A. Fuel 1984,63, 440 Yamamoto, K., Kimura, K., Ueda, K. ef al. ‘Proc. 1987 Int. Conf. on Coal Science’, Amsterdam, The Netherlands, 2630 October 1987, p. 211 Cronauer. D. C., McNeil, R. I., Young, D. C. and Ruberto, R. G. Fuel 1982,61, 610 Nueent. W. A. and Zubvk. R. M. Inorrr. Chem. 1986,25,4604 Baryle, K. D. and Jones, D. W. in ‘Analytical Methods for Coal and Coal Products’, Academic Press, London, UK, 1978, Vol. 2, pp. 103-160
31 32 33
34 35 36
APPENDIX
A
Evidence for the correctness of Equation (2) can be secured from quantitative comparison of ‘H n.m.r. spectra of soluble products obtained by hydrogenation both with and without methanol, assuming that the hydrogenation is the same in both cases22’23. The substitution of some aromatic protons (AH,,) by CH,-groups should result in a corresponding decrease in the aromatic proton fraction in alkylated products: HCHSOH
ar
_
Hr; - AH,, 1 + 2AH,,
(AlI
where the CH,OH and H, symbols are related to the products obtained by hydrogenation with and without methanol, respectively. The denominator of Equation (Al) takes into account the increase in the total number of protons in the products as a result of substitution of one aromatic proton by three methyl protons. By analogy the following expressions can be written for H:H20H and HCH~OH. PY
.
HCH30H
a
_
-
HH2 + 3AHar 1 + 2AH,,
642)
UH2
HCHJOH
PY
“Pi - 1 + 2AH,, _
643)
So we have three equations and four unknown values: H;;HJOH, HC/~OH and AH,,. To solve this problem o;e can make use of the experimental value of HzF30H. Now it becomes possible to calculate the AH,, value using: HCH~OH,
(44) which is simply a rearrangement of Equation (Al). Using the AH,, value one can easily compute the values of H~HsOH and H‘$‘o” for methanol products. By comparing the experimental and computed values, evidence showing the correctness of Equation (2) can be obtained. The ratio AH,, x lOO%/H$ is the alkylation degree, i.e. the fraction of aromatic protons substituted by CH,-groups. Knowing the alkylation degree, elemental composition and molecular weight, we can calculate the number of methyl groups introduced into the ‘average molecule’.