Abstract
Seven oligomeric fractions of well-defined composition and molecular weight distribution were generated via supercritical extraction from an isotropic petroleum pitch (M-50) and used as precursors for the production of activated carbon fibers. Both isotropic and mesophase-containing fractions were produced, so that the effects of molecular order and molecular weight could be separated. Carbonization weight loss was found to gradually decrease with increasing molecular weight (and oligomeric number), with mesophase content not being a significant factor. Similar behavior was observed for activation weight loss when the precursors were isotropic; however, even modest increases in molecular order significantly retarded the activation process and resulted in dramatic drops in specific pore volume. A 100% dimer precursor fraction with an average molecular weight of 480 Da produced activated carbon fibers with the highest (specific) pore volume, and the highest pore volume in the range desired for hydrogen adsorption (6-7 Å). Even for isotropic precursors, decreases in pore volume with increasing molecular weight were observed. The incremental pore size distribution generated from the nitrogen adsorption data consisted of discrete peaks, which is consistent with the formation of pores by the removal of short micrographene layers, with each layer being formed from an individual oligomeric molecule.
Original language | English |
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Pages (from-to) | 267-277 |
Number of pages | 11 |
Journal | Carbon |
Volume | 52 |
DOIs | |
State | Published - Feb 2013 |
Externally published | Yes |
Funding
This research was supported by the US Department of Energy, Office of Basic Energy Sciences , Division of Materials Sciences and Engineering , under contract DE-AC05-00OR22725 with UT-Battelle, LLC. Additional support was provided by the ERC program of NSF under award number EEC-9731680 . The authors wish to thank Prof. Danny D. Edie for his helpful discussions, and Marlon Morales for his assistance with the WAXD experiments.