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Solid-state NMR and ESR studies of activated carbons produced from pecan shells

Permanent URL:
http://handle.nal.usda.gov/10113/43983
Abstract:
A large number of solid-state NMR and ESR experiments were explored as potential tools to study chemical structure, mobility, and pore volume of activated carbon. We used a model system where pecan shells were activated with phosphoric acid, and carbonized at 450 °C for 4 h with varying amounts of air flow. Through the use of different NMR experiments (e.g., CP-MAS, SPE-MAS, and DD-MAS) several structural parameters were calculated such as mole fraction of bridgehead aromatic carbons, number of carbons per aromatic ring system, and number of phenolic carbons per aromatic ring system. The relaxation time measurements (T1, TCH, and THIP) were indicative of the relative mobility of different structural units. ESR spectra showed the presence of π-type aromatic free radicals in the carbonized samples with a slight shift in g value with increasing oxidation. The combined NMR and ESR data give a consistent picture of the carbon structure and the carbonization process, which is not easily available otherwise. In addition, the 1H NMR data on adsorbed water are shown to be consistent with the trends in the amount of pore volumes for different samples of activated carbons.
Author(s):
Cheng, H.N. , Wartelle, Lynda H. , Klasson, K. Thomas , Edwards, John C.
Subject(s):
pecan shells , nuclear magnetic resonance spectroscopy , activated carbon , air flow , phosphoric acid , electron paramagnetic resonance spectroscopy , adsorption , water , chemical structure , nonfood plant products
Format:
p. 2455-2469.
Note:
Includes references
Source:
Carbon 2010 Aug., v. 48, no. 9
Language:
English
Year:
2010
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
File:
Download [PDF File]
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.