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| PDF : |  17040154.pdf |
| title(En) : | Effect of the Thermal Treatment on Wood Hemicelluloses. IV. Mechanism in Early Stage of Xylan Pyrolysis (in English) |
| author(En) : | Kazumasa Shimizu, Fumiyuki Teratani, Kango Miyazaki |
| information : | Mokuzai Gakkaishi 17(4), 154-159 (1971) |
| assort : | Original Article |
| summary(En) : | The thermal degradation of xylan was studied with both the dynamic heating and isothermal heating(170°, 180° and 190°C) in vacuo. The pyrolysis mechanism was investigated by determining the changes in intrinsic viscosities of the degradation products. The results obtained showed that the chain scission in early stage of pyrolysis occurred at random and obeyed first-order kinetics. The activation energy was 30.7 kcal/mole for the dynamic heating and 32.6 kcal/mole for the isothermal one. Moreover, considering the weight loss and the number of chain scissions per chain in the region of 160° to 230°C in the dynamic pyrolysis, the following mechanism of xylan pyrolysis was suggested: 1) the initiation reaction of random chain scission, 2) the splitting off of monomer units (propagation reaction), 3) the stabilization of chain end (termination reaction). From the change of molecular weight distribution shown by gel permeation chromatography (GPC), it was revealed that the thermal degradation of xylan was caused by random chain scission. |