374
Energy & Fuels 2005, 19, 374-381
Effect of the Polymerization with Formaldehyde on the Thermal Reactivity of a Low-Temperature Coal Tar Pitch Jose´ L. Crespo,† Ana Arenillas,† Jose´ A. Vin˜a,† Roberto Garcı´a,*,† Colin E. Snape,‡ and Sabino R. Moinelo† Instituto Nacional del Carbo´ n (CSIC), Apartado 73, 33080 Oviedo, Spain, and University of Nottingham, Nottingham Fuel & Energy Centre, School of Chemical, Environmental and Mining Engineering (SChEME), University Park, Nottingham NG7 2RD, UK Received May 20, 2004. Revised Manuscript Received October 13, 2004
The influence of polymerization with formaldehyde on the thermal reactivity of a lowtemperature coal tar pitch has been investigated. The mechanism and extent of the polymerization depends on the catalyst used, the greatest extent of polymerization being achieved under basic catalytic conditions. After the polymerization treatment, samples were carbonized at 420 °C and the products were characterized by optical microscopy. According to the results, polymerization with formaldehyde increases the reactivity of the pitch, giving rise to increased carbonization yields and leading to the formation of the mesophase with milder conditions. The polymerization process also affects the morphology of the resultant anisotropic material, giving rise to the formation of irregularly shaped mesophase particles and reducing the optical texture size of the anisotropic domains, giving mosaic texture, especially when basic catalysis is used.
Introduction Many studies have been carried out on the mechanisms of mesophase formation and the behavior during carbonization under different conditions of high-temperature coal tar pitches,1-4petroleum pitches1,3,5-7 and synthetic pitches.8-10However, few studies have been focused on low-temperature coal tar pitches.11,12The latter develop mesophase in a very rapid manner, due to the presence of high contents of heteroatoms and alkyl or aryl substituents in the polyaromatic compounds.12 The mesophase originating from these pitches * Correspondingauthor.E-mail:
[email protected]: +34 985 29 7662. † Instituto Nacional del Carbo ´ n (CSIC). ‡ University of Nottingham. (1) Hu¨ttinger, K. J.; Wang, J. P. Carbon 1991, 29, 439. (2) Mene´ndez, R.; Gray, E. M.; Marsh, H.; Pysz, R. W.; Heintz, E. A. Carbon 1991, 29, 107. (3) Hu¨ttinger, K. J.; Wang, J. P. Carbon 1992, 30, 1. (4) Taylor, G. H.; Pennock, G. M.; Fitz Gerald, J. D.; Brunckhorst, L. F. Carbon 1993, 31, 341. (5) Marsh, H.; Martı´nez-Escandell, M.; Rodrı´guez-Reinoso, F. Carbon 1999, 37, 363. (6) Santamarı´a-Ramı´rez, R.; Romero-Palazo´n, E.; Go´mez de Salazar, C.; Rodrı´guez-Reinoso, F.; Martı´nez-Sa´ez, S.; Martı´nez-Escandell, M.; Marsh, H. Carbon 1999, 37, 445. (7) Torregrosa-Rodrı´guez, P.; Martı´nez-Escandell, M.; Rodrı´guezReinoso, F.; Marsh, H.; Go´mez de Salazar, C.; Romero Palazo´n, E. Carbon 2000, 38, 535. (8) Mochida, I.; Shimizu, K.; Korai, Y.; Otsuka, H.; Sakai, Y.; Fujiyama, S. Carbon 1990, 28, 311. (9) Korai, Y.; Yoon, S.-H.; Oka, H.; Mochida, I.; Nakamura, T.; Kato, I.; Sakai, Y. Carbon 1998, 36, 369. (10) Mochida, I.; Korai, Y.; Ku, C.-H.; Watanabe, F.; Sakai, Y. Carbon 2000, 38, 305. (11) Garcı´a, R.; Arenillas, A.; Crespo, J. L.; Pis, J. J.; Moinelo, S. R. Energy Fuels 2002, 16, 935. (12) Garcı´a, R.; Crespo, J. L.; Martin, S. C.; Snape, C. E.; Moinelo, S. R. Energy Fuels 2003, 17, 291.
displays a high tendency to coalescence, because of both the low viscosity and the low primary quinolineinsoluble content. For this reason, the isolation of good yields of small-sized mesophase spherules (
