Some aspects of catalytic activity of pyrolyzed coals

Thermochimica Acta 569 (2013) 78–84

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Some aspects of catalytic activity of pyrolyzed coals Valentina Zubkova a , Evgenija Grigoreva b , Andrzej Strojwas a,∗ , Marianna Czaplicka c , Victor Prezhdo a , Jolanta Pruszkowska a a b c

Institute of Chemistry, Jan Kochanowski University, Swietokrzyska Str.15G, 25-406 Kielce, Poland Institute of High Temperature, The Russian Academy of Science, 13/19 Izhorskaja Street, Moscow, Russia Institute of Non-Ferrous Metals, J. Sowi´ nskiego Str. 5, 44-100 Gliwice, Poland

a r t i c l e

i n f o

Article history: Received 18 April 2013 Received in revised form 5 July 2013 Accepted 13 July 2013 Available online 21 July 2013 Keywords: Catalytic activity Pyrolysates XRD SEM FT–IR spectroscopy GC–MS.

a b s t r a c t The influence of additives of initial coal and selected pyrolysates of this coal on the reaction rate constant was investigated during the test reaction of breakage of ether bonding. It was stated that pyrolyzed coal at the stage of maximally swollen grains increases the destruction rate constant by 16.7 times. The pyrolysates were investigated using X-ray diffraction, electron scanning microscopy (SEM), and FT–IR spectroscopy. The resistivity values were measured for the coal and its pyrolysates. Dichloromethane extracts of the pyrolyzed coals were analyzed by gas chromatography. It was proved that the composition and structure of substances in the layer of maximally swollen grains differ substantially from those of substances in the nearby layers. The authors suggest that in the maximally swollen grains some substances can be formed which have catalytic influence on the reaction of breakage of ether bonding. © 2013 Elsevier B.V. All rights reserved.

1. Introduction The most characteristic feature of thermochemical conversions of caking coals is their ability to transit into the plastic state. The research carried out by Wachowska and Nandi [1] showed that the cross-linked ether bonds present in the macromolecular structure of coals are responsible for swelling of coal grains in the plastic state. The breakage of ether bonding in coals caused by potassium in tetrahydrofuran solution led to decrease in temperature of the plasticization and huge increase in dilatation. The rise in dilatation and a substantial increase in Gieseler fluidity in coals after treatment with naphthalene anion in tetrahydrofuran were shown in work [2]. Moreover, Khan and Jenkins [3–5] have experimentally proved that K and Ca additives form various compound along with iron oxides and reduce swelling and the plastic properties of coals. Stolarewicz et al. [6] assume that ether bonds can be broken under the influence of different factors and also by various electrontransfer reagents [7,8]. The catalysts for breakage of ether bonds can be rhenium compounds [9], fluoride salt [10], group 5 and group 6 metal chlorides [11], palladium compounds [12,13], nickel compounds [14,15], lithium aluminum hydride [16] etc. Despite numerous studies, the problem of influence of mineral additives on the plastic properties of coals in general and on cleavage of ether

bonds in their macromolecular structure in particular still remains unexplained. In the organic mass of coals during heating, there flow different reactions of destruction and synthesis, polymerization and condensation along with the reactions connected with hydrogen redistribution [17,18]. The ratio and composition of neighboring functional groups change constantly due to these reactions in heated coals [19]. The appearance of neighboring amide and benzamide functional groups can also have a catalytic effect on breakage of ether bonding [20,21]. That is why we cannot exclude that the changes in structure and composition of the organic mass of caking coal during heat treatment can lead to breakage of ether bond. If ether bonds are formed in the organic mass of caking coal during heating [19], it is important to determine the factors or chemical compounds which can facilitate the breakage of these bonds during non-catalytic heating of coal and its transition into the viscous-liquid state. That is why the paper aims at analysis of the influence of changes in composition and properties of organic substance of pyrolyzed coal on the rate of thermolysis model reaction of benzylphenyl ether. 2. Experimental 2.1. Sample preparation

∗ Corresponding author. Tel.: +48 41 349 70 31. E-mail address: [email protected] (A. Strojwas). 0040-6031/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tca.2013.07.013

The initial caking coal, the characteristics of which are presented in Table 1, was analyzed along with its pyrolysates. The coal under

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79

Table 1 The main characteristics of the coal. Volatile matter (wt%, daf)

29.09

Total moisture (wt%)

1.40

Ash (wt%, db)

3.20

Swelling index (SI)

8.5

Roga index (RI)

83

Dilatometry (Audibert-Arnu)

Plastometry (Gieseler)

T1 (◦ C)

T2 (◦ C)

T3 (◦ C)

a (%)

b (%)

t1 (◦ C)

tmax (◦ C)

t3 (◦ C)

Fmax (ddpm)

378

417

477

27

+202

386

454

489

2678

the reactor with a reaction mass. The reaction was carried out in the revolving microautoclave under pressure of hydrogen at 5 MP. The catalytic activity of samples was determined by the test reaction of thermolysis of benzyl phenyl ether (BPE) in tetraline in hydrogen medium in the kinetic area according to the techniques in [23]. The temperature was 573 K, the reaction time-up to 60–360 min. The reaction was carried out in 10-times excess of tetraline under identical conditions for all samples. Contrastive experiments were also made without any additives of coal and pyrolysates. The analysis of the reaction mass was performed on a gas chromatograph, model 3700, equipped with a 30 m capillary column with the immobilized liquid phase SE-30 along with flame ionization detector and integrator. The analysis was conducted with increase in temperature of 6 K min−1 in the temperature range of 343–583 K.

2.3. The obtaining of SEM micrographs The SEM micrographs of the samples studied were obtained using the microscope Stereoscan-180 with accelerating voltage of 20 kV according to the techniques described in [24]. A layer of graphite and next a layer of gold were sprayed in vacuum on grains of the initial coal and the samples of coal treated thermally. Then, SEM micrographs were obtained at accelerating voltage of 20 kV. Fig. 1. The change in temperature into heated charge. (a) Relationship between the temperature and the time of coal being heated. (b) X-ray picture of heated charge of coal.

study originates from the Pniowek coal mine and, according to the Polish National Standard, it belongs to orthocoking coal type 35.1. The coal was heated under conditions of one-side vertical heating according to the techniques described in [22]. The coal was ground to grains of <3 mm. 480 g of the ground coal was conveyed into the pyrolytic chamber and heated with the rate of 4 K min−1 on the heaters up to 1023 K. Fig. 1a presents the course of changes in temperature of the coal charge within a distance of 36 mm from the heating wall. It follows from Fig. 1 that in the temperature range of 373–718 K the average accretion rate of temperature in the coal charge was about 3 K min−1 . After the temperature on the heaters reached 1023 K, the pyrolytic chamber was removed from the oven and cooled fast. The temperatures of particular zones of the heated charge were calculated on the basis of the X-ray data of the heated charge, the records of position of the markers in the charge on the X-ray film (Fig. 1b), the records of the data of the thermocouples located in the heated charge along with measurements of thickness of separated layers of the cooled pyrolysate. This technique was described in more detail in [22]. The material for analysis was selected from the three zones of the coal plastic layer such as the zone of swollen grains, the zone of maximally swollen grains, and the gas-saturated zone along with grains of the initial coal (Fig. 2a). 2.2. Thermolysis of benzen-phenol ether The samples of coal and its pyrolysates ground to <63 ␮m were dried at T = 423 K for 2 h and after 5 min cooling placed into

2.4. TGA–DTA analysis of the course of devolatilization of the coal The thermal analysis of the caking coal under study was carried out using the thermoballance TSA/STDA 851 manufactured by Mettler–Toledo. The sample of coal was ground to the size of <0.2 mm and heated from room temperature up to 1023 K with the accretion rate of 3 K min−1 for temperature. The heat treatment was carried out in argon flow with the flow rate of 2 dm3 h−1 .

2.5. X-ray quantitative phase analysis Content evaluation of the ordered carbon Ccryst in coal and its pyrolysates was carried out using the modified polycrystalline diffractometer equipped with a high voltage generator manufactured by Seifert (Seifert Analytical X-Ray) and a ceramic X-ray tube V4 GE under Cuk␣ radiation (I = 17 mA, U = 33 kV) according to the internal standard addition method described in [24]. The parameter Ccryst was determined according to the formula:

Ccryst =

P · 100 k · x · (100 − P)

where P is the amount of the internal NaF pattern; k is the experimentally determined parameter from the calibration graph, and x is the ratio of the surface area of reflection (002) from the internal pattern to the surface area of reflection (002) of the sample investigated. The pyrolytic graphite GPRTM produced by BDH Laboratory Supplies was used as a model substance to carry out the calibration graph.

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Fig. 2. Transformation of the shape heated grains and the mass loss. (a) SEM micrographs of the zones of heated charge. (b) Thermogravimetric analysis of coal.

2.6. Measurement of specific electrical resistance The resistivity () was measured with the isolation meter BMM2500 at the voltage of 500 V according to the techniques presented in [25]. 2.7. Extraction of coal samples and its pyrolysates The initial coal and its pyrolysates ground up to 0.2 mm of grain size were extracted with dichloromethane in teflon vessels in the microwave extractor Multiwave 3000 manufactured by Anton Paar. The temperature of oven was ≤433 K, the extraction time −15 min. 2.8. FT-IR investigations The initial and pyrolyzed coal was investigated with the FTIR spectrometer Nicolet iS10 manufactured by Thermo Scientific using ATR-module. The IR spectra were obtained in the range of 4000–600 cm−1 , the baseline was automatically corrected by OMNIC8 software.

the temperature of source totaled 423 K, and the ionization energy was 70 eV. The temperature of transfer line amounted to 523 K. Identification was carried out on the basis of comparison of mass spectra of the compounds to the spectra of model samples from the NIST library. The following solvents as n-hexane, benzene, and chloroform were used in turns to separate the material soluble in dichloromethane into aliphatic, aromatic, and polar fractions. A sample was placed at the top of a 20 cm long glass column with an inner diameter of 1 cm and packed with silica gel and aluminum oxide. The upper bed was made of silica gel. Before packing, the columns, both silica gel and aluminum oxide, were activated. The silica gel was treated at 180 ◦ C for 24 h, and the aluminum oxide was activated at 400 ◦ C for 24 h. Before introducing the sample into the column, it was humidified with n-hexane. The elution of compounds was performed first with 20 ml of n-hexane (aliphatic fraction), then with 100 ml of benzene (aromatic fraction). The polar fraction was eluated by metanol + chloroform mixture (1:1). 3. Results and discussion 3.1. The analysis of mass loss during heat treatment of the coal

2.9. GC–MS investigations of extracts The chromatograph Clarus 500 by Perkin Elmer equipped with quadrupole detector and DB-5 MS capillary column having 30 m in length, 0.25 mm in diameter, and 0.25 mm in film thickness was used for GC–MS investigations on the extracts. The column was kept at the initial temperature for 3 min, and next the temperature increased to 583 K at the rate of 10 deg/min with maintenance at 563 K for 5 min and at 583 K for 4 min. The temperature of chromatograph oven varied from 313 K to 583 K. The temperature of feeder was 563 K. The mass detector was working in the range of 30–450 ␮m with speed of 1 s/scan,

During heat treatment there flow complex thermo-chemical transformations in the organic mass of coal due to which the coal grains were swelling, next the maximally swollen grains formed the foamy mass of the coal plastic layer. Fig. 2 shows the temperature intervals of the zones of swollen coal grains and of the foamy mass, which are mapped with temperature curves of mass loss and mass loss rate. It follows from the figure that at the initial stage of swelling of grains the rate of mass loss increases but during transition into the zone of maximally swollen grains and into the gas-saturated zone it decreases substantially. The mass loss before the zone of swollen grains were formed amounted to

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about 9.2% of the mass of the initial coal. About 7.8% of the mass diminished in the zone of swollen grains, and about 2.7% of the mass only diminished in the gas-saturated zone. The total mass loss before the transition of the coal into the viscous-liquid state in the gas-saturated zone amounted to about 17%. It follows from the DTG graph (мɑмɑ, здecь чtо-tо he tɑк. Можet curve? вмectо graph) in Fig. 2 that the decrease in the rate of mass loss takes place in the zone of maximally swollen grains. This gives us a reason to believe that in maximally swollen grains the processes of destruction either slow down (what is rather unlikely under the conditions of heat treatment in this temperature interval) or less volatile products and more high-molecular-weight products are being formed, or gaseous products come into interaction with each other and form more liquid products.

3.2. Influence of the additive of initial coal and pyrolysates on the value of the reaction rate constant for decomposition of BPE On the basis of analysis of the reaction mass in the reactor it was stated that the mechanism of destruction of BPE was the same with or without additives. The main process was the breakage of PhO CH2 Ph bonding in the ВРE bridge with formation of equimolar quantities of phenol and toluene, the collateral process to observe was the intramolecular rearrangement with formation of phenyltolyl ethers and benzylphenols (Fig. 3). The relation between the main and side products was the same within the experimental error in all experiments as 80:20. Thus, the additives of initial coals and pyrolysates did not lead to changes in the mechanism of test reaction. However, these additives influenced the destruction rate constant of ВРE (Table 2). As shown in Table 2, the destruction rate constant (k) of ether without additives (0 sample) was 1.8 × 10−5 s−1 . In the presence of initial coal, k increased by 2.3 times (sample 1). After addition of a pyrolysate in the form of swollen grains of coal (sample 2), k increased somehow and returned to the initial value for coal (sample 1) in the presence of a pyrolysate in the form of foamy mass

81

Table 2 Influence additives of coal and coal pyrolysates on the destruction rate constant (k) of benzyl phenyl ether (BPE). Sample

Destruction rate constant k (s−1 10−5 )

0 – Without additive 1 – Initial coal 2 – Swollen grains (613–648 K) 3 – Maximally swollen grains (683–718 K) 4 – Foamy mass (718–783 K)

1.8 4.3 5.3 30.0 4.0

± ± ± ± ±

0.2 0.3 0.3 0.4 0.2

(sample 4). Such increase in the reaction rate is ordinary and can be attributed to the catalytically active components initially present in coal. The reaction rate constant increased by 16.7 times in comparison to sample 0 only in case of one sample – the pyrolysate in the form of maximally swollen grains of coal (sample 3). The effect observed couldn’t be connected with loosening of organic mass of coal due to development of plasticization processes in its grains, which could facilitate the access of reaction mass to the active centers in the form of mineral impurities. It follows from Fig. 2a that the limited swelling of coal grains transits into the unlimited one–the foamy mass of the plastic layer is formed. The total mass loss amounts to about 19.7 due to devolatilization in the temperature range of swelling of grains and in the gas-saturated zone. In the foamy mass, the mineral impurities contained within the organic mass of coals can be accessible to the reactive substances and the increase in the reaction rate of ether bond breakage should be expected. However, despite better accessibility of mineral impurities for reactive substances, the k parameter decreases with addition of sample 4. This shows that catalytically active centers, which facilitate the reaction of breakage of ether bonding in sample 3, were deactivated in some way. Such deactivation of the mineral impurities present in coal at temperatures of the plastic state seems hardly probable [26]. The organic mass of sample 3 may have a specific structure or unique composition. Therefore, we decided to seek for the reason of change in catalytic properties

Fig. 3. The scheme of thermolysis of benzyl phenyl ether (BPE).

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Table 3 The characteristics samples of coal and pyrolysates. Sample

Ccryst (%)

 10−9 ( cм)

1 – Initial coal 2 – Swollen grains (613–648 K) 3 – Maximally swollen grains (683–718 K) 4 – Gas-saturated zone (718–783 K)

10 11 11. 7 21.8

4 0.8 2.7 1.6

where Ccryst , the amount of the ordered phase; , the resistivity.

of pyrolysates in the processes of structural transformations taking place in the organic mass of coal. 3.3. Determination of degree of structural ordering and resistivity of pyrolyzed coals In order to understand a possible reason for this phenomenon for the samples studied, the amount of the ordered phase Ccryst was determined and their resistivity () was measured, the values of which are shown in Table 3. It follows from the data in Table 3 that in the temperature range of about 613–718 K the swelling of grains occurs under the conditions when the ratio between the ordered and non-ordered phases (parameter Ccryst ) does not practically change. The value of the  parameter during the process of swelling decreases from 4 × 109  cm to 0.8 × 109  cm at the temperature of about 648 К. This implies that a sharp decrease in resistivity is observed in the temperature interval, in which the increase in mass loss rate was observed. The  parameter increases up to 2.7 × 109  cm in the zone of maximally swollen grains. Next, in the temperature range of 718–783 K it decreases to 1.6 × 109  cm. Podder and Majumder [27] have also observed such character of change in resistivity of the heated coals. However, they have registered the appearance of the maximum of resistivity in the temperature range of about 450–473 K, which was explained by the increase in mobility of current carrying impurity ion and moisture removal. The decrease in resistivity from the point of higher temperatures the authors attributed to the appearance of charge transfer complexes between the aromatic and heteroaromatic molecules. We strongly believe that the peak of resistivity observed by the authors was caused by moisture removal. We cannot agree with the statement about formation of complexes of aromatic and hydroaromatic lamellas at the temperature of about 573 K because the XRD data point at the lack of increase in amount of the ordered phase up to the temperature of 718 K. However, in the temperature range of 718–783 K the parameter Ccryst rises spasmodically. All mentioned above gives a good reason to imply in maximally swollen grains the formation of compounds which initiate the processes of ordering and growth of the crystalline phase. We cannot also exclude the catalytic influence of such compounds on breakage of ether bonds. Speaking about unique properties of pyrolysates in the narrow temperature range under study, we should also mention a very interesting experimental fact. Podder and Hossain [28], when studying the processes of carbonization of benzene extracts from Bangladeshi coking coal, registered the mesophase transformations in the same narrow temperature range of 703–723 K. We have earlier [25] also suggested the possibility of influence of mesophase transformations on anomalous increase in resistivity. The data in our previous work [29] showed that a greater amount of substances soluble in pyridine and chloroform are formed during the process of heat treatment at the stage of maximally swollen grains of caking coals. The anomalous increase in resistivity was exactly bound with their occurrence. This gave a reason to believe that a great amount of compounds soluble in organic solvents could have been formed in the maximally swollen grains of the coal under study, and their composition could also

Fig. 4. The fragments of FT–IR spectra of the coal and its pyrolysates.

have changed. Some compounds may have formed which influence the breakage of ether bonding and the transition of coals into the viscous-liquid state. 3.4. FT–IR investigations of coals and their pyrolysates The fragments of FT-IR spectra of the coal and its pyrolysates were presented in Fig. 4. To make the analysis of the spectra easier, the peak heights of the appropriate lines at 1600 cm−1 were taken equal. It follows from Fig. 4 that the spectrum of maximally swollen grains differs from the spectra of the zone of swollen grains and the gas-saturated zone. In addition it should be noticed that the peak of the band at 1650 cm−1 , which corresponds to increase in concentration of the conjugated C O-groups [30], rises in the spectrum of the extract of maximally swollen grains. Table 4 The chromatographic separation results of dichloromethane extracts of pyrolysates. Fraction of extract (%)

Swollen grains

Maximally swollen grains

Gas-saturated zone

Aliphatic fraction Aromatic fraction Polar fraction

42 30 28

47 23 30

36 28 36

Table 5 Polycyclic aromatic hydrocarbons identified in dichloromethane extracts of coal under study. Compound

Content of PAHs in zone of maximally swollen grains

Change in content of PAHs in gas-saturated zone

Naphthalene Acenaphthylene Acenaphthene Biphenylene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzo[a]anthracene Chrysene Benzo[b]fluoranthene Benzo[e]pyrene Benzo[a]pyrene Perylene Sum mg/100 g

0.0514 nd nd nd nd 0.6811 0.0978 0.7957 1.2438 6.2599 15.2577 1.3463 1.0989 0.7112 nd 27.5438

−0.0286 0 0 0 0 +0.4471 +0.0655 −0.3336 −0.282 +0.0237 −2.2761 −0.5092 −0.4221 −0.3053 0 −3.6206

where nd, not detected; +, increase compared to the amount of the extract at the stage of swollen grains; −, decrease compared to the amount of the extract at the stage of swollen grains.

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Table 6 The results of the identification of selected compounds in a dichloromethane extracts of pyrolysates. No.

Compound

Maximally swollen grains

Gas-saturated zone

1 2 3

methyl indole bis(1,1-dimethylethyl)phenol diethyl phthalate trimethylnapthtalene dibenzo[a,e] 7,8-diazobicyclo[2,2,2] octa-2,5-diene 2-hydroxystilbene + biphenyl derivative benzene-1,2-dicarboxylic acid, bis(2-methylpropyl) ester 3-amino-9-ethylcarbazole biphenyl derivative methylphenanthrene methylcarbazole dibutyl phthalate 5-methyl-2-phenylindolizine dimethylphenathrene trimethylphenantrene benzo[b]fluorene 1,2,3,4,7,12-hexahydro-benzo[a]anthracene methylfluoranthene + dimethylpyrene 6,6-diphenylbicyclo[3,1,0]hex-3-en-2-one bis(2-ethylhexyl)phthalate dihydrochrysene 6-methylbenzo[b]naphtho[2,3,-d]tiophene, methylchrysene 5,8-dimethyl benzo[c]phenanthrene + 7,12-dimethyl benzo[a]anthracene dibenzo[5,6:7,8]cyclodeca[1,2-c]furan napthalene, 1-(2-naphtalenyloxy) 8H-indeno[2,1-b]phenathrene 9-ethyl-3,6-dimethoxy-10-methylphenathrene 1-(3-methoxybenzyl)-6-methoxy- 3,2-dihydroisoquinoline, 2-butyloxycarbonyloxy-1,1,10-trimethyl-6,9-epidioxydecalin dimethyl-naphthalene

– – – + + + + – + + – – + + + + – + + – + + + + + – + – – + +

+ + + + + – – – + + – – – + +

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 26 27 28 29 30 31

Moreover, absorption of the band in the range of 1225–1150 cm−1 falls substantially what corresponds to decrease in concentration of alkyl- and aryl ethers. Thus, the form of the curves in the FT–IR spectra proves that the composition of compounds in organic substance of maximally swollen grains differs from the composition of

– + – – + – + – – – – + + – –

compounds in the nearby layers. Namely, the material of maximally swollen grains in comparison to the neighboring layers is characterized by a high content of C O groups and low concentration of ether bonds. We can assume that this distinction implies the unique properties of maximally swollen grains of the coal under study.

Fig. 5. Structural formulas of the compounds found in maximally swollen grains but not in the gas saturated zone.

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3.5. GC-MS investigations of the material soluble in dichloromethane The dichloromethane extract was separated into fractions to prove the aforementioned statement. The results of this separation are presented in Table 4. It follows from Table 4 that with increase in temperature the maximally swollen grains contain much more aliphatic compounds and less aromatic compounds than the nearby layers. The amount of polar fraction increases gradually with rise in temperature of pyrolysis. The quantitative content of some polynuclear aromatic hydrocarbons (PAHs) was determined in the material soluble in dichloromethane. The data of quantitative determination of PAHs were shown in Table 5. It follows from the data in this table that the content of the PAHs changed in the material soluble in dichloromethane. The amount of PAHs extracted by dichloromethane from maximally swollen grains totals 27.54 mg/100 g of the material soluble in dichloromethane; meanwhile 23.92 mg/100 g of the material soluble in dichloromethane was extracted from the gas-saturated zone. A large number of compounds such as fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, benzo[e]pyrene and benzo[a]pyrene was identified in the extract of maximally swollen grains. These changes can be observed in a narrow temperature range when the zone of maximally swollen grains is formed. Table 6 shows the results of identification of some compounds present in the material soluble in dichloromethane from the layer of maximally swollen grains and from the gas-saturated zone. It follows from the table that the composition of these compounds in extracts of both zones differs. The compounds missing in the extracts of other pyrolysates are present in the extracts obtained from maximally swollen grains. Fig. 5 shows structural formulas of the identified compounds to be found in maximally swollen grains but not in the gas-saturated zone. There can be found also a compound containing the conjugated C Ogroups (6,6-diphenylbicyclo[3,1,0]hex-3-en-2-one 6,6-diphenyl). The data presented give us a good reason to believe that the compounds, which occur in maximally swollen grains, can facilitate the reaction rate of breakage of ether bonding. It can be expected that the flow of reaction of this type can be substantially accelerated by presence of the material from the layer of maximally swollen grains of the coal under study. 4. Conclusions The test reaction of breakage of ether bonding showed the increase in reaction rate constant by 16.7 times due to the presence of the material of maximally swollen grains of the coal under study in the reaction volume. The research on changes in structure of the pyrolyzed coals, the determination of their resistivity and composition of functional groups in maximally swollen grains by FT–IR spectroscopy along with the identification of substances soluble in dichloromethane by GC–MS revealed the formation of new compounds in this layer. These new compounds can be responsible for increase in catalytic activity of the reaction of breakage of ether bonding. Thus, the material of maximally swollen grains of the coal under study can serve as a providential substitute for expensive catalysers which are used nowadays to carry out the reaction of breakage of ether bonding. References [1]

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