Energy & Fuels 1998, 12, 949-957
949
Carbon Precursors from Anthracene Oil. Insight into the Reactions of Anthracene Oil with Sulfur Adela L. Ferna´ndez, Marcos Granda, Jenaro Bermejo, and Rosa Mene´ndez* Instituto Nacional del Carbo´ n, CSIC, Apartado 73, 33080 Oviedo, Spain
Pablo Bernad Departamento de Quı´mica Organometa´ lica, Universidad de Oviedo, 33071 Oviedo, Spain Received February 5, 1998. Revised Manuscript Received June 24, 1998
An anthracene oil with a boiling point of 250-370 °C was reacted with sulfur (5-20 wt %) at 250-300 °C for 2 h. The extent of anthracene oil conversion to a carbon precursor (pitch-like material) was monitored from the weights of the residues obtained by thermogravimetric analysis at 350 °C (R350), the temperature at which the anthracene oil residue is zero. Anthracene oil readily reacts with sulfur, the initial concentration of sulfur being the main controlling parameter of the reaction. The anthracene oil components showed different reactivities with sulfur, as determined by gas chromatography of the toluene-soluble fraction, and also followed different mechanisms because of their different structures. Studies by probe mass spectrometry of the pure compounds revealed the type of reaction mechanisms involved in the process. The amount of sulfur incorporated into the reaction products determined the optical texture of the resultant cokes.
Introduction Anthracene oil is a tar fraction that distills between 250 and 370 °C. It is mainly composed of polycyclic aromatic hydrocarbons (PAH) with 2-4 aromatic rings. The major constituent compounds are phenanthrene, anthracene, fluoranthene, and pyrene. Conversion of the molecules of anthracene oil to larger-sized molecules offers the possibility of using anthracene oil as a precursor for carbon materials, with the subsequent economic upgrading of the anthracene oil. Pitch-like materials can be prepared by polymerizing the constituents of anthracene oil. The process of polymerization can be either thermal or chemical. Results obtained with model compounds1,2 show that thermal polymerizations of PAH occur at temperatures near to 500 °C and at high pressures. Russian researchers3 have obtained needle coke from anthracene oil by thermal treatment at 455 °C and 7 MPa for 4 h. This treatment requires expensive facilities and a high energy consumption, with a subsequent increase in the price of the final product. Chemical polymerization of anthracene oil could be possible under less severe conditions by means of Friedel-Crafts type catalysts,4-7 air-blowing,8,9 or addition of sulfur. * To whom correspondence should be addressed. (1) Lewis, I. C. Carbon 1980, 18, 191-196. (2) Greinke, R. A.; Lewis, I. C. Carbon 1984, 22, 305-314. (3) Cheshko, F. F.; Pityulin, I. N.; Pyrin, A. I.; Shustikov, V. I. Coke Chem. 1995, 7, 36-44. (4) Rey Boero, J. F.; Wargon, J. A. Carbon 1981, 19, 333-340. (5) Otani, S.; Oya, A. Bull. Chem. Soc. Jpn. 1972, 45, 623-624. (6) Mochida, I.; Kudo, K.; Fukuda, N.; Takeshita, K. Carbon 1975, 13, 135-139. (7) Mochida, I.; Shimizu, K.; Korai, Y.; Otsuka, H.; Fujiyama, S. Carbon 1988, 26, 843-852.
The reaction of sulfur with aromatic compounds has not been studied in depth. Its oxidizing effects on toluene have been known since the beginning of this century.10 Sulfur reacts principally with alicyclic and hydroaromatic structures. This reaction was used in the 1960s to measure the amounts of such structures in coals11,12 and later to measure the hydrogen-donor capability of coals, as well as coal- and petroleumderived liquids.13,14 Elemental sulfur has been extensively used as a dehydrogenation reagent in the synthesis of polycyclic aromatic hydrocarbons and their derivatives.15 However, Van Krevelen et al.16 and other researchers17 have shown that at temperatures above 200 °C, sulfur extracts hydrogen from aromatic compounds. Mazumdar et al.18 stated that sulfur reacts with aromatic compounds to give Ar-S-Ar-type com(8) Belkina, T. V.; Privalov, V. E.; Stepanenko, M. A. Coke Chem. 1979, 8, 53-57. (9) Yamaguchi, C.; Mondori, J.; Matsumoto, A.; Honda, H.; Kumagai, H.; Sanada, Y. Carbon 1995, 33, 193-201. (10) Aronstein, M. M. L.; von Nierop, S. A. Recl. Trav. Chim. PaysBas 1902, 21, 448. (11) Mazumdar, B. K.; Chakrabartty, S. K.; Lahiri, A. Fuel 1959, 38, 115-119. (12) Dicker, P. H.; Flagg, M. K.; Gaines, A. F.; Martin, T. G. J. Appl. Chem. 1963, 13, 444-454. (13) Aiura, M.; Masunaga, T.; Moriya, K.; Kageyama, Y. Fuel 1984, 63, 1138-1142. (14) Rahimi, P. M.; Dawson, W. H.; Kelly, J. F. Fuel 1991, 70, 9599. (15) Fu, P. P.; Harvey, R. G. Chem. Rev. 1978, 78, 317-361. (16) van Krevelen, D. W.; Goedkoop, M. L.; Palmen, P. H. G. Fuel 1959, 38, 256. (17) Iyengar, M. S.; Dutta, S. N.; Banerjee, D. D.; Banerjee, D. K.; Rai, S. K. Fuel 1960, 39, 189-192. (18) Mazumdar, B. K.; Chakrabartty, S. K.; Ganguly, S.; Lahiri, A. Fuel 1962, 41, 121-128.
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950 Energy & Fuels, Vol. 12, No. 5, 1998
Ferna´ ndez et al.
Table 1. Experimental Conditions for Reactions of Anthracene Oil with Sulfur and Characteristics of Resultant Products AO-5 wt % S
AO-7.5 wt % S
AO-10 wt % S
AO-20 wt % S
fluorene-10 wt % S phenanthrene-20 wt % S
T (°C)
t (min)
250 250 250 275 275 275 300 300 300 250 250 250 275 275 275 300 300 300 250 250 250 275 275 275 300 300 300 300 300 250 250 250 275 275 275 300 300 300 300 250 300
10 60 120 10 60 120 10 60 120 10 60 120 10 60 120 10 60 120 10 60 120 10 60 120 10 40 60 90 120 5 60 120 5 60 120 5 10 60 120 360 120
TI (wt %)
4.1
13.0
6.3 12.7 17.4
20.0 33.3 42.1
R350 (wt %)
R600 (wt %)
13.9 14.9 13.3 15.3 16.2 16.2 16.2 17.0 15.9 21.9 22.7 22.7 22.7 23.5 21.7 24.5 26.1 27.8 24.2 29.3 31.5 26.8 31.5 31.0 28.6 29.8 33.0 31.8 35.0 38.1 57.2 53.4 38.1 62.1 60.4 40.3 44.8 63.5 71.0 46.6 21.3
8.2 8.2 8.6 9.6 8.4 11.7 10.2 8.8 11.2 14.7 13.3 17.3 14.8 13.3 15.1 14.5 15.8 15.5 17.1 19.4 19.2 18.1 19.0 19.2 19.4 21.2 19.5 21.7 20.4 29.6 38.5 39.0 29.6 39.9 39.7 30.4 34.6 40.3 42.0 17.7 8.1
CY (wt %)
10.3 9.9 10.7 10.8 10.6 15.3 15.3 15.1 16.8 21.1 20.8 20.7 21.7 20.7 21.9 37.6 37.9 31.9 41.5 25.8 16.0
pounds, and Klenn et al.19-21 obtained the respective thiophenes from the catalytic reaction of aromatics and H2S at about 500 °C. Molecular condensation of aromatics with and without the incorporation of sulfur are also reported.10,15,22,23 In general, thermal treatment of pure organic compounds and industrial mixtures of aromatics with sulfur results in significant increases in their softening points and carbon yields.24-28 This paper reports on the reactions of anthracene oil with elemental sulfur at temperatures between 250 and 300 °C, using sulfur concentrations in the range 5-20
wt %. The extent of anthracene oil conversion was determined from the weight of the residues obtained at 350 °C by means of thermogravimetric analysis of the reaction products taken at different reaction times. The reactivity of the principal components in the anthracene oil was monitored by subjecting toluene extracts of the reaction products to gas chromatography. Establishment of the mechanisms involved in the polymerization of the anthracene oil was based on mass spectrometry analyses of the reaction products obtained from selected PAH under the same conditions.
(19) Klemn, L. H.; Karchesy, J. J. J. Heterocyclic Chem. 1978, 15, 561-563. (20) Klemn, L. H.; Karchesy, J. J.; Lawrence, R. F. J. Heterocyclic Chem. 1978, 15, 773-775. (21) Klemn, L. H.; Lawrence, R. F. J. Heterocyclic Chem. 1979, 16, 559-601. (22) Thayer, H. I.; Corson, B. B. J. Am. Chem. Soc. 1948, 70, 23302333. (23) Walker, A.; Baldwin, W. E.; Thayer, H. I.; Corson, B. B. J. Org. Chem. 1951, 16, 1805-1808. (24) Mazumdar, B. K.; Chakrabartty, S. K.; Lahiri, A. Fuel 1959, 38, 112-114. (25) Kipling, J. J.; Shooter, P. V.; Young, R. N. Carbon 1966, 4, 333341. (26) Fitzer, E.; Mueller, K; Shaefer, W. Chemistry and Physics of Carbon; Marcel Dekker: New York, 1971; pp 237-383. (27) van Ufford, J. J. Q.; Vlugter, J. C. Brennst. Chem. 1965, 46, 7-11. (28) Kulalakov, V. V.; Neproshin, E. I.; Fedeneya, E. N. Solid Fuel Chem. 1984, 18, 123-125.
Experimental Section Materials Used. A commercial anthracene oil (AO) with a boiling point from 250 to 370 °C was used as a raw material. Its elemental analysis is given in Table 2. The chemicals, all pure grade (sulfur, Merck washed and purified by sublimation, >99 wt %; fluorene, Fluka, >98 wt %; and phenanthrene, Aldrich, >98 wt %), were used as received. Reaction of Anthracene Oil with Sulfur. Figure 1 is a schematic diagram of the equipment used to study the reactions of AO with sulfur. A 250 g amount of AO placed in a 500 mL glass reactor was heated using an electric mantle. The temperature was monitored via a thermocouple inserted into the reaction mass. The AO was heated in a nitrogen flow of 80 mL min-1 at 5 °C min-1 to the reaction temperature (250, 275, and 300 °C). Once the reaction temperature was estab-
Carbon Precursors from Anthracene Oil
Energy & Fuels, Vol. 12, No. 5, 1998 951
Table 2. Elemental Analysis of Anthracene Oil and Products Derived from Reactions of Anthracene Oil, Fluorene, and Phenanthrene with Sulfur treatment sample
Soa
Tb
5 5 5 5 7.5 7.5 7.5 7.5 7.5 7.5 10 10 10 10 10 20 10 20
none 250 275 300 300 250 275 275 275 300 300 250 275 300 300 300 300 250 300
anthracene oil
fluorene phenanthrene a
elemental analysis (wt %) tc
C
H
S
N
O
120 120 120 240 120 10 60 120 10 120 120 120 20 90 120 120 360 120
91.4 91.1 91.3 91.2 90.8 91.3 90.3 90.8 91.1 90.4 91.0 90.2 91.0 90.5 90.6 90.9 88.3 93.7 78.0
5.7 5.2 5.3 5.3 5.2 5.3 5.2 5.1 5.1 5.0 5.2 5.0 5.1 4.9 4.8 5.0 4.3 5.4 4.5
0.5 1.3 1.1 1.0 1.1 1.0 1.8 1.5 1.4 1.8 1.3 2.3 1.5 2.1 1.8 1.8 4.9 0.3 17.1
1.1 0.9 0.9 1.0 0.9 0.8 1.0 0.9 0.9 0.9 1.0 0.9 0.8 1.0 0.9 0.9 1.0 0.05 0.05
1.4 1.6 1.4 1.5 2.0 1.6 1.8 1.7 1.6 1.9 1.5 1.6 1.6 1.5 1.8 1.4 1.4 0.6 0.4
Initial sulfur concentration (wt %). b Temperature (°C). c Time (min).
Figure 1. Experimental device used to study reactions of anthracene oil, fluorene, and phenanthrene with sulfur. lished, additions of sulfur were made (5, 7.5, 10, and 20 wt %) and temperatures maintained for 120 min. Stirring was used during this treatment in order to mix the AO and sulfur. The reactor was equipped with a condenser to avoid the distillation of light AO components and was also connected to a washing flask to trap any H2S released during the reaction. Samples were taken at 5, 10, 40, 60, and 90 min. After reaction, the material was cooled to room temperature and weighed. Total losses, including H2S, were
