Study On The Selective Oxidation Of C₆-hydroxyl Group In Cellulose

Development and utilization of renewable natural cellulose resources has attracted great attention cellulose in the world. Preparing of carboxyl-containing fiber materials is an important aspect of cellulose resource utilization.Nitroxide catalyst is an organic molecule, because of the reaction efficiency, mild reaction conditions, high selectivity, has been widely used to study the oxidation of alcohols, and the choice of material in this thesis nitrogen oxygen free radicals, the article build nitrogen free radical oxidation system to study the catalytic oxidation of cellulose.First, choosing stable nitrogen free radical oxidation system to oxidize cellulose C6hydroxyl.Oxidation products of infrared spectrum and solid-state13C NMR spectrum analysis shows that oxidation reaction occurs on the cellulose C6-hydroxyl, hydroxyl is oxidized to carboxylic acid sodium salt, with dilute acid treatment can regenerate as carboxylic acid, and other hydroxyl on cellulose molecules unit oxidizing phenomenon, the results show that stable nitrogen free radical oxidation systems of has very high selectivity.Research the reaction condition of stable nitrogen radical system to oxidation system. Compared the TEMPO/NaBr/NaCIO,4-acetamide-TEMPO/NaBr/NaClO,4-hydroxy-TEMPO/NaBr/NaCIO three stable nitrogen free radical oxidation system’s reaction rate, the results show that the V-TEMPO/NaBr/NaClO>V4-acetamide-TEMPO/NaBr/NaClO>4-hydroxy-TEMPO/NaBr/NaClO·Choosing TEMPO/NaBr/NaCIO catalytic oxidation system as an example, studying the influence of different raw materials on the reaction rate, the results show that the TEMPO/NaBr/NaCIO catalytic oxidation system of regenerated cellulose oxidation rate is highest, after the oxidation rate of alkali treatment raw material, oxidation rate of natural fiber is the slowest. Studying the factors influencing the product carboxyl content, the result is:the NaClO> pH> temperature> nitrogen oxygen free radical content, the optimum reaction process of reaction system are as follows:raw material of2g, NaClO15ml, pH=9.5, temperature15℃, stable nitrogen oxygen free radical3tendency.Second, with unstable nitrogen free radical oxidation system to catalytic oxidation cellulose, the result of infrared spectrum and solid-state13C NMR spectroscopic show:the oxidation reaction occurs on the cellulose C6-hydroxyl, the product is carboxylic acid sodium salt, with dilute acid treatment can regenerate carboxylic acid, the results show that unsteady nitrogen free radical oxidation system for the oxidation of cellulose C6hydroxyl has very high selectivity.Research the oxidation conditions of unsteady nitrogen free radical system to oxidation system. Compared the oxidation rate of NHPI/anthraquinone, NHPI/four lead acetate,NHPI/ammonium cerium nitrate for oxidation of regenerated cellulose, the results showed that the VNHPI/anthraquinone> VNHPI/four lead acetate> VNHPI/ammonium cerium nitrate.The influence of NHPI/anthraquinone/NaBr/NaClO oxidative regenerated cellulose on oxidation rate, the highest oxidation rate is cotton fiber, the oxidationof natural fiber is the slowest. NHPI/anthraquinone/NaBr NaCIO was optimized oxidation process of regenerated cellulose,choose carboxyl content as examining index, the factors influencing the carboxyl content is dosage of sodium hypochlorite> temperature> NHPI dosage> pH value, NHPI/anthraquinone/NaBr/NaClO best reaction process of catalytic oxidation system are as follows:raw material of2g, NaC1O15ml, pH=10.5, temperature25℃, dosage of NHPI3tendency.