TEMPO-NaOCl-NaBr氧化体系氧化再生纤维素的动力学研究

研究了2，2，6，6—四甲基哌啶氧化物自由基(TEMPO)—NaOCl—NaBr氧化体系氧化再生纤维素的动力学。研究结果表明TEMPO—NaOC1—NaBr氧化体系对再生纤维素的氧化可近似地用关于纤维素基质的一级反应动力学来描述。在本研究所用的TEMPO浓度范围内，氧化反应速率与TEMPO的浓度成正比。在较低浓度时，氧化反应速率与NaBr用量也成正比，但浓度较大时，氧化反应速率基本不随NaBr浓度增大而增大。温度对氧化反应速率常数的影响符合Arrhenius方程的规律，由此求得的粘胶纤维的表观活化能为66．2kJ／mol。这里还讨论了反应液pH值，纤维素的形态和结晶度对氧化反应速率的影响。

Kinetic Study on TEMPO-mediated Selective Oxidation of Regenerated Cellulose

The kinetics of the TEMPO-mediated oxidation of regenerated celluloses has been studied. It is revealed that the oxidation reaction of the regenerated celluloses by 2,2,6,6-tetramethyl-piplidine-1-oxyl radical (TEMPO)- NaBr- NaOCl system can be approximately described in a first-order kinetics with respect to substrate. In the concentration range used the rate constant k is directly proportional to the concentration of TEMPO while is proportional to the concentration of NaBr in a relatively lower range and tends to level off at higher concentration. The effect of temperature on the rate constant can be well described by Arrhenius equation, the apparent activation energy measured is about 66.2 kJ/mol. The effect of the pH of reaction solution, the crystallinity and morphology of the substrates on the oxidation rate is also discussed.