doi:10.1016/j.jcis.2005.11.051
Copyright © 2005 Elsevier Inc. All rights reserved.
Chemical activation of carbon mesophase pitches
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E. Mora1, C. Blanco
, 
, J.A. Pajares, R. Santamaría and R. Menéndez
Department of Materials Chemistry, Instituto Nacional del Carbón, CSIC, Apartado 73, 33080 Oviedo, Spain
Received 27 October 2005;
accepted 24 November 2005.
Available online 27 December 2005.
Abstract
This paper studies the chemical activation of mesophase pitches of different origins in order to obtain activated carbons suitable for use as electrodes in supercapacitors. The effect that the activating agent (NaOH, LiOH, and KOH), the alkaline hydroxide/pitch ratio, and the activation temperature had on the characteristics of the resultant activated carbons was studied. LiOH was found to be a noneffective activating agent, while activation with NaOH and KOH yielded activated carbons with high apparent surface areas and pore volumes. The increase of the KOH/pitch ratio caused an increase of the chemical attack on the carbon, producing higher burnoffs and development of porosity. Extremely high apparent surface areas were obtained when the petroleum pitch was activated with 5:1 KOH/carbon ratio. The increase of the activation temperature caused an increase of the burnoff, although the differences were not as significant as those derived from the use of different proportions of activating agent.
Graphical abstract
N2 adsorption isotherms of carbons activated with different KOH-to-pitch ratios indicate that the increase of the proportion of KOH causes a significant increase in the development of porosity accompanied by the widening of the micropores.
Keywords: Mesophase; Activation; Surface area; Porosity; Immersion calorimetry
Fig. 1. N2 isotherms of carbons activated with NaOH and KOH.
Fig. 2. N2 isotherms of carbons activated with different KOH-to-pitch ratios.
Fig. 3. XRD spectra of carbons activated with different KOH-to-pitch ratios and the mesophase pitch before activation.
Fig. 4. N2 isotherms of carbons activated at different temperatures.
Table 1.
Main properties of the mesophase pitches used for activation
Notes. C/H, atomic ratio; SP, Mettler softening point (°C); TI, toluene insoluble content (%); NMPI, N-methyl-2pyrrolidone insoluble content (%); CY, Alcan carbon yield (%); MC, mesophase content (vol%).
Table 2.
Activation yields and immersion enthalpies of carbons activated with different alkaline hydroxides
Notes. AY, activation yield; −ΔHi, immersion enthalpy.
Table 3.
Textural parameters of carbons activated with NaOH and KOH
Notes. SBET, BET apparent surface area; Vtot, total volume of pores; VN2, volume of micropores; Vme, volume of mesopores; E0, characteristic energy; L, average pore diameter; Smi, microporous surface area.
Table 4.
Activation yields and immersion enthalpies of carbons activated with different KOH-to-pitch ratios
Notes. AY, activation yield; −ΔHi, immersion enthalpy.
Table 5.
Textural parameters of carbons activated with different KOH-to-pitch ratios
Notes. SBET, BET apparent surface area; Vtot, total volume of pores; VN2, volume of micropores; VCO2, volume of narrow micropores; Vme, volume of mesopores; E0, characteristic energy; L, average pore diameter; Smi, microporous surface area.
Table 6.
Activation yields and immersion enthalpies of carbons activated at different temperatures
Notes. AY, activation yield; −ΔHi, immersion enthalpy.
Table 7.
Textural properties of carbons activated at different temperatures
Notes. SBET, BET apparent surface area; Vtot, total volume of pores; VN2, volume of micropores; VCO2, volume of narrow micropores; Vme, volume of mesopores; E0, characteristic energy; L, average pore diameter; Smi, microporous surface area.
Corresponding author. Fax: +34 985 297662.
1 Actual address: Department of Physics, The Ohio State University, 191 West Woodruff Ave., Columbus, OH 43210, USA.
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