纤维素热裂解过程动力学的试验分析研究

尽管针对纤维素热裂解动力学方面的研究已开展得比较广泛 ,但其表观动力学的确定仍是一具有争论性的问题 ,从而对纤维素热裂解机理的描述也就各不相同 .本文试图通过纤维素的热裂解动力学研究 ,对此种现象作出合理的解释 ,并给出相应的机理描述 .纤维素热裂解随温度的升高经历了五个不同的阶段 ,其中第三阶段是整个过程的主要部分 ,期间大量挥发分析出并造成明显失重 .试验发现随着升温速率的增加 ,热滞后现象的加重致使纤维素热裂解各个阶段向高温侧移动 ;同时高升温速率对炭的生成具有抑制作用 ,但有利于挥发分的生成 .通过对热裂解主反应区的热重分析 ,采用微商法求得对应的反应动力学参数 ,以 6 0 0 K作为分界点 ,低温段的活化能约在2 6 7k J/ m ol,较高温度段则体现为 174 k J/ mol左右的低活化能 .纤维素热裂解是一传热传质现象 ,与化学动力学机制相互影响、控制的过程 ,试验条件、传热传质过程的影响是造成结论存在差异的内在原因

Research on cellulose pyrolysis kinetics

Despite intensive studies led to on cellulose pyrolysis kinetics,the still remaining controversies on the apparentkinetics different explanations for the cellulose pyrolysis mechanism.The reaction kinetics and pyrolysis mechanism were studied in detail in this work.The cellulose pyrolysis process has five dis- tinct phases as temperature increases.The third phase in which the huge amount of volatile is released causing cellulose weightdecrease,plays a main role in the whole process.The TG curve moves toward the direction of higher temperature as the heating rate increases,because of the increase in thermal lag.Fur- thermore,high heating rate promotes volatile production while inhibits char formation.The apparent acti- vation energy and pre- exponential on the third phase of the cellulose pyrolysis process were calculated by differential quotient method.Using60 0 K as break point,the activation energy in the lower temperature zone was calculated to be2 67k J/mol,but only1 74k J/mol in the higher temperature zone.Cellulose py- rolysis is a complicated process controlled by both kinetics and heat- mass transfer.The various kinetic pa- rameters of cellulose pyrolysis reported by others were mainly due to the different experimental conditions and heat- mass transfer processes.