Characterization of Wood Chars Produced at Different Temperatures Using Advanced Solid-State 13 C NMR Spectroscopic Techniques
2012; American Chemical Society; Volume: 26; Issue: 9 Linguagem: Inglês
10.1021/ef300947s
ISSN1520-5029
AutoresXiaoyan Cao, Joseph J. Pignatello, Yuan Li, Charisma Lattao, Mark A. Chappell, Na Chen, Lesley F. Miller, Jingdong Mao,
Tópico(s)activated carbon and charcoal
ResumoTemperature is one of the controlling factors determining the chemical structure of char. We employed advanced solid-state 13C NMR techniques to characterize maple wood and its chars produced under N2 at temperatures from 300 to 700 °C. Our results indicated that 300 °C char was primarily composed of residues of biopolymers such as lignin and cellulose. Carbohydrates are completely lost for char prepared at 350 °C. At 400 °C, the char lost most of the ligno-cellulosic features and consisted predominantly of aromatic structures. By 500 °C, sp3-hybridized carbon had all but disappeared. Protonated aromatic carbons increased up to 400 °C chars but then decreased. Aromatic C–O groups decreased, whereas nonprotonated aromatic carbons, especially bridgehead carbons, increased as temperature increased. The minimum aromatic cluster sizes estimated from spectral analysis increased from 8 carbons in 300 °C char, to 20, 18, 40, 64, and 76 carbons, respectively, in 350 °C, 400 °C, 500 °C, 600 °C, and 700 °C chars. 1H–13C long-range dipolar dephasing displayed the same increasing trend of aromatic cluster sizes of wood chars with increasing temperature. We show for the first time quantitative changes of different aromatic C forms and aromatic cluster size as a function of heat treatment temperature.
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