The Effect Of Recycling TEMPO Catalytic System On Pulp Oxidation

Cellulose is a kind of organic polymer which is inexhaustible, friendly to environment, and it can be used to prepare nanofibers. Nowadays, many researchers have studied on nanofibers prepared by TEMPO oxidation because of it!s advantages, such as mild reaction condition, efficient reaction and good selectivity. Carboxyl content, one of the indicator of TEMPO oxidation, influences the quality and yield of nanofibers.In order to reduce the environment pollution and realize the cleaner production of TEMPO oxidized cellulose, it studied the effect of recycle catalyst of TEMPO-mediated oxidation system and researched the impact of TEMPO dosage, the concentration of inorganic salt, oxidation product on reaction rate and carboxyl content.The results were as follows:Recycle catalyst of TEMPO-mediated oxidation system was feasible. After the spent liquor was recycled four times, the carboxyl content was ruduced to 90% of the original content and the reaction time prolonged over one hour. It also indicated that relatively high carboxyl content was obtained without the introduction of additional catalytic agents. With the increase of cycle times, the decrease of reaction rate can be partly explained by the reduce of TEMPO dosage, the concentration of inorganic salt and the accumulation of oxidation product.The carboxyl content was similar when the TEMPO catalyst mediated was added to system as supplement, it resulted from part of TEMPO was absorbed in recycle.As the fact that NaClO was converted into NaCl during the oxidation, the inorganic salt concentration in the reaction solution increased with the increase of cycle times. After the spent liquor was recycled four times, the carboxyl content was ruduced to 93% of the original content and the reaction time was two times of the first reaction time.Moreover, the oxidized xylan was used as accumulation of oxidation product in the filtrate. The results showed that the reaction rate and carboxyl content were reduced significantly.With the pulp concentration increase from 1% to 6%, the reaction decreased by 35%, the carboxyl content declined from 1.55mmol/g to 1.0mmol/g. With the increase of oxidant amount, the reaction rate was almost invariant and carboxyl content was increased.The properties of handsheet made from TEMPO oxidized cellulose were connected with pH and the method of drying.