The Study On The Oxidation And Degradation Of Microcrystalline Cellulose By Ultrasonic-TEMPO

This research explored the optimum process conditions of various influence factors of TEMPO-NaClO-NaClO2 oxidation system and ultrasonic-TEMPO oxidation and degradation of microcrystalline cellulose mainly through the measuring and analysising of carboxyl content and degree of polymerization of cellulose. Studying on the carboxyl content and the degree of polymerization kinetics of the cellulose oxidative degradation from the two methods,explored the reaction order of the change in carboxyl content and the kinetics equations of the change in polymerization degree, compared the changing rule of the parameters, analysed the effect of ultrasound on oxidative degradation of cellulose.Researched the effection of ultrasound in oxidation degradation of microcrystalline cellulose in TEMPO oxidation system by analyzing the surface morphology, the internal groups and the stability of the structure, the crystal structure of the cellulose before and after oxidative degraded with TEMPO and ultrasonic coupling TEMPO with the scanning electron microscope(SEM), FTIR spectrum, X-ray diffraction, carbon analysis of nuclear magnetic resonance (NMR)The main research contents and results were as follows:1.The optimum conditions of TEMPO-NaClO-NaClO2 oxidation system was:reaction time was 24h, reaction temperature was 50℃, the additive amount of NaC102 was 10-20mmol,the addition amount of TEMPO was 1-1.5mmol,the additive amount of NaClO was 20-30mmol.On the basis of the study, the optimum conditions by ultrasound-TEMPO oxidation system was:ultrasonic time was 2h, ultrasonic power was 450w, ultrasonic temperature was 50℃.2. Through the research on dynamics of carboxyl content and the degree of polymerization of the cellulose, the dynamic equation of carboxyl content was:Qt= P0 (1-e-kit); dynamics equation of degree of polymerization was: Dt=(D0-D∞)[e-(k1+k2)t+e-k3t-e-(k1+k3)t]+D∞, k1, k2, k3 was the kinetic parameters. We can know the change roles of carboxyl content and degree of polymerization with the reaction time.The cavitation of trasonic is the main influence factor for cellulose oxidation and the thermal effects of trasonic is the main influence factor for cellulose degradation.