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Energy & Fuels 2008, 22, 4146–4150
Mesophase from Anthracene Oil-Based Pitches ´ lvarez, J. Sutil, R. Santamarı´a, C. Blanco, R. Mene´ndez, and M. Granda* P. A Instituto Nacional del Carbo´n, Consejo Superior de InVestigaciones Cientı´ficas (CSIC), Post Office Box 73, OViedo 33080, Spain ReceiVed June 23, 2008. ReVised Manuscript ReceiVed September 1, 2008
This work deals with the preparation of the mesophase from two pitch-like materials obtained from anthracene oil by oxidative thermal condensation (AOP-1) and the subsequent thermal treatment and distillation of AOP-1 (AOP-2). The mesophase was obtained by the controlled pyrolysis (440-470 °C and different periods of residence times) and subsequent sedimentation of the samples. In the case of the pitch prepared by oxidative thermal condensation, a dynamic pressure of 5 bar was applied during the pyrolysis. The pressure was a critical parameter, and its influence was also investigated. The results show that AOP-1 requires higher temperatures and/or residence times to develop mesophase than AOP-2. After sedimentation, a sample consisting of mainly mesophase was produced in all of the cases. The characterization of the mesophases by means of techniques, such as elemental and thermogravimetric analysis and optical microscopy, showed that anthracene oil-based derivatives are appropriate precursors for producing QI-free mesophase with suitable properties for the fabrication of a wide range of carbon materials.
1. Introduction It is well-known that carbonaceous mesophase has been extensively used in a wide variety of applications, such as the manufacture of carbon materials of high density and high strength,1,2 catalyst carriers,3 or high specific surface-active carbons for batteries,4,5 among others.6 The mesophase can be prepared from a variety of sources,7,8 with coal-tar pitch9-11 and petroleum pitch12-14 being the most common. An alternative source is provided by highly aromatic fractions, such as anthracene oil.15,16 This product is a mixture of polycyclic aromatic hydrocarbons of 3-5 rings obtained as the heaviest * To whom correspondence should be addressed: Instituto Nacional del Carbo´n, CSIC, Department of Chemistry of Materials, P.O. Box 73, Oviedo 33080, Spain. Telephone: +34-985-11-89-78. Fax: +34-985-29-76-62. E-mail:
[email protected]. (1) Hu, Y. S.; Adelhelm, P.; Smarsly, B. M.; Hore, S.; Antonietti, M.; Maier, J. AdV. Funct. Mater. 2007, 17 (12), 1873–1878. (2) Lopez-Galilea, I.; Garcia-Rosales, C.; Pintsuk, G.; Linke, J. Phys. Scr., T 2007, 128, 60–65. (3) Mora, E.; Blanco, C.; Pajares, J. A.; Santamaria, R.; Menendez, R. J. Colloid Interface Sci. 2006, 298 (1), 341–347. (4) Wen, K. Y.; Marrow, T. J.; Marsden, B. J. Carbon 2008, 46 (1), 62–71. (5) Ramos-Fernandez, J. M.; Martinez-Escandell, M.; Rodriguez-Reinoso, F. Carbon 2008, 46 (2), 384–386. (6) Ge, M.; Shen, Z. M.; Chi, W. D.; Liu, H. Carbon 2007, 45 (1), 141–145. (7) Granda, M.; Santamaria, R.; Menendez, R. Chem. Phys. Carbon 2003, 28, 263–330. (8) Brooks, J. D.; Taylor, G. H. Carbon 1965, 3 (2), 185–193. (9) Perez, M.; Granda, M.; Santamaria, R.; Morgan, T.; Menendez, R. Fuel 2004, 83 (9), 1257–1265. (10) Rocha, V. G.; Granda, M.; Santamaria, R.; Blanco, C.; Diestre, E. I.; Menendez, R. J. Anal. Appl. Pyrolysis 2005, 73 (2), 276–283. (11) Marsh, H.; Walker, P. L. Chemistry and Physics of Carbon: A Series of AdVances; Thrower, P. A., Ed.; Marcel Dekker: New York, 1979; Vol. 15, Chapter 3, p 229. (12) Marsh, H.; Martinez-Escandell, M.; Rodriguez-Reinoso, F. Carbon 1999, 37, 363–366. (13) Greinke, R. A. Chemistry and Physics of Carbon: A Series of AdVances; Thrower, P. A., Ed.; Marcel Dekker: New York, 1994; Vol. 24, Chapter 1, p 1. (14) Honda, H. Carbon 1988, 26 (2), 139–159.
fraction in coal tar distillation.17,18 From an industrial point of view, anthracene oil is qualitatively consistent with a wellknown chemical composition (free of metals and primary QI particles). The primary application of anthracene oil is to produce carbon black. Recently, Fernandez et al.19 reported the preparation of new pitches from anthracene oil at pilot plant scale. This novel industrial procedure for processing anthracene oil consists of the oxidative treatment of the anthracene oil as a first step that gives rise to more reactive species20 and then subjecting to thermal treatment to give rise to the final pitch. The resulting pitches obtained in this way show suitable properties for their use as binder or impregnating agents. Because these pitches are novel products, no studies have been carried out to determine their thermal behavior or their real potential as precursors of graphitizable carbons. The capacity of these materials to develop mesophase is a crucial step that needs to be investigated. In this study, two anthracene oil-based derivatives with different degrees of polymerization were used as the mesophase precursor. The mesophase was obtained by thermal treatment in the temperature range of 440-470 °C at different residence times and pressures. The mesophase was then concentrated and separated by sedimentation.21 The chemical composition, pyrolysis behavior, and
(15) Bermejo, J.; Fernandez, A. L.; Granda, M.; Rubiera, F.; Suelves, I.; Menendez, R. Fuel 2001, 80 (9), 1229–1238. (16) Fernandez, A. L.; Granda, M.; Bermejo, J.; Menendez, R. Carbon 2000, 38 (9), 1315–1322. (17) Fernandez, A. L.; Granda, M.; Bermejo, J.; Menendez, R. Carbon 1999, 37 (8), 1247–1255. (18) Lauer, J. C.; Hernandez, D. H. V.; Cagniant, D. Fuel 1988, 67 (9), 1273–1282. (19) Fernandez, J. J.; Alonso, F. Light Met. 2004, 499–502. (20) Dominguez, A.; Blanco, C.; Santamaria, R.; Granda, M.; Blanco, C. G.; Menendez, R. J. Chromatogr., A 2004, 1026 (1-2), 231–238. (21) Mora, E.; Blanco, C.; Santamaria, R.; Granda, M.; Menendez, R. Carbon 2003, 41 (3), 445–452.
10.1021/ef800499x CCC: $40.75 2008 American Chemical Society Published on Web 10/09/2008
Mesophase from Anthracene Oil-Based Pitches
microstructure of the mesophase samples were studied by means of elemental and thermogravimetric analysis and optical microscopy.
Energy & Fuels, Vol. 22, No. 6, 2008 4147 Table 1. Main Characteristics of the Parent Anthracene Oil and Anthracene Oil-Based Pitches elemental analysis (wt %) sample
2. Experimental Section 2.1. Raw Materials. In this study, two novel anthracene oilbased derivatives (AOP-1 and AOP-2) were used. AOP-1 was obtained by the oxidative thermal condensation of industrial anthracene oil (AO). AOP-2 was obtained by the thermal treatment of AOP-1 and its subsequent distillation to increase its softening point to ∼110 °C. These samples were produced and supplied by Industrial Quı´mica del Nalo´n, S.A. 2.2. Mesophase Preparation. The mesophase was prepared by a sequential process that involves the thermal treatment of the pitch and a subsequent hot sedimentation step. The thermal treatment was carried out in an autoclave of 150 mm height and 85 mm diameter, using a stirrer at 100 rpm. In a typical experiment, 300 g of sample was used. AOP-1 was thermally treated in the temperature range of 440-470 °C for residence times of 2-4 h at a dynamic gaseous pressure of 5 bar under a nitrogen flow of 10 L/h. AOP-2 was thermally treated in the temperature range of 440-450 °C for residence times of 1-5 h under a nitrogen flow of 10 L/h. In this case, no pressure was applied during the treatment. The resultant reaction products were partially anisotropic pitches consisting of polymerized pitch (isotropic phase) and mesophase. In a subsequent step, the mesophase was separated from the isotropic phase by sedimentation at 420 °C for 1 h, using the same autoclave. The mesophase samples were labeled MX-T-t, where X is 1 in AOP-1 and 2 in AOP-2, with T indicating the temperature of the treatment and t indicating the residence time. 2.3. Sample Characterization. Elemental Analysis. The carbon, hydrogen, sulfur, and nitrogen contents of the samples were determined with a LECO-CHNS-932 microanalyzer. The oxygen content was obtained directly using a LECO-VTF-900 furnace coupled to the microanalyzer. The analyses were performed with 1 mg of sample ground and sieved to
