首页> 外文期刊>Journal of Analytical & Applied Pyrolysis >Boiling point of levoglucosan and devolatilization temperatures in cellulose pyrolysis measured at different heating area temperatures
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Boiling point of levoglucosan and devolatilization temperatures in cellulose pyrolysis measured at different heating area temperatures

机译:在不同加热区域温度下测得的左旋葡聚糖的沸点和纤维素热解中的脱挥发分温度

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Fast heating conditions are known to improve the yields of volatile products in cellulose pyrolysis. The mechanism, however, is not yet well understood. For better understanding of the cellulose fast pyrolysis, the devolatilization temperature was directly measured during the pyrolysis of cellulose. An in situ measurement method employing a very fine thermocouple was first developed. A sample in a ceramic boat was pushed into the heating area, preheated at 430-700 ℃ under the flow of N_2 (150 mL/min). Employing this method, the boiling point (385 ℃) of levoglucosan, the major volatile product derived from cellulose fast pyrolysis, was measured directly for the first time, and was found to reduce to 345 and 292 ℃ under reduced pressures of 0.5 and 0.1 atm, respectively. High heating area temperatures increased the selectivity of levoglucosan evaporation by shortening the period required for the completion of evaporation. With these results in mind, pyrolysis of cellulose powder (Ceolus FD-F20) was studied using a similar procedure. The results obtained under the reduced pressures suggested that the depolymeriza-tion of cellulose, not evaporation of the volatiles products, is the rate-determining step for the pyrolytic devolatilization of cellulose. Interestingly, the depolymerization temperature varied depending on the heating area temperature as 360-385 ℃ (for 430-500 ℃) and 400-450 ℃ (for 500-700 ℃) (the values in the parentheses: heating area temperatures). The char morphology also changed; the pyrolysis conditions provided powder-like and film-like char materials, respectively. According to these results, the effects of heating area temperature on the cellulose pyrolysis mechanism are discussed, focusing on the behavior of cellulose crystallites.
机译:已知快速加热条件可提高纤维素热解过程中挥发性产物的产率。然而,该机制尚未被很好地理解。为了更好地理解纤维素快速热解,在纤维素热解过程中直接测量脱挥发分温度。首先开发了一种采用非常精细的热电偶的现场测量方法。将陶瓷舟皿中的样品推入加热区域,在N_2(150 mL / min)的流动下于430-700℃预热。采用这种方法,首次直接测量了纤维素快速热解衍生的主要挥发性产物左旋葡聚糖的沸点(385℃),发现在0.5和0.1 atm的减压下分别降至345和292℃。 , 分别。较高的加热区域温度通过缩短完成蒸发所需的时间,提高了左葡糖聚糖蒸发的选择性。考虑到这些结果,使用相似的方法研究了纤维素粉末(Ceolus FD-F20)的热解。在减压下获得的结果表明,纤维素的解聚而不是挥发产物的蒸发是纤维素热解挥发的速率决定步骤。有趣的是,解聚温度根据加热区域温度而变化,分别为360-385℃(对于430-500℃)和400-450℃(对于500-700℃)(括号中的值:加热区域温度)。炭的形态也改变了。热解条件分别提供了粉末状和膜状炭。根据这些结果,讨论了加热区域温度对纤维素热解机理的影响,重点是纤维素微晶的行为。

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