Recoverable acrylamide-vinylamine copolymer immobilized TEMPO mediated oxidation of cellulose with good catalytic performance and low cellulose degradation

Abstract

In this work, a recoverable acrylamide-vinylamine copolymer immobilized TEMPO (P(AM-co-VAm)-T) catalyst for selective oxidation of cellulose with good catalytic performance and low cellulose degradation was developed. Firstly, the acrylamide-vinylamine copolymer (P(AM-co-VAm)) was prepared by Hofmann degradation of polyacrylamide (PAM). Then, the condensation reduction reaction between amine groups of P(AM-co-VAm) and carbonyl groups of 4-oxo-TEMPO yielded P(AM-co-VAm)-T. P(AM-co-VAm)-T was used as a catalyst for selective oxidation of C6 primary hydroxyl groups of cellulose to carboxyl groups. The carboxyl content of obtained oxidized cellulose was up to 1.114 mmol/g, which was equivalent to 76% of the free TEMPO level. This macromolecular catalyst was easily recycled and the recycling performance was excellent. Interestingly, it was found that P(AM-co-VAm)-T could effectively reduce the degradation of oxidized cellulose. The corresponding degradation degree was 21%-27%, which was much lower than the degradation degree of free TEMPO (61%-66%) and other macromolecular TEMPO catalysts, such as polyacrylic acid immobilized-TEMPO (41%-53%) and polyamidoamine supported TEMPO (28%-44%). P(AM-co-VAm)-T with positive charge and suitable size could effectively inhibit the formation of C6 aldehydes and C2/C3 ketones, which was the main reason that it could signi cantly inhibit cellulose degradation.

The Implementation and Controversy of VAM in American Primary and Secondary Schools

“…Researchers in different fields conduct research from different perspectives, so as to constantly find the problems of value-added evaluation. On the other hand, this kind of controversy enables educational decision-makers to hear different voices and make more sober and objective decisions about whether to adopt and how to adopt [26]. States are also responding to the controversy.…”

Toward cleaner production of nanocellulose: a review and evaluation

“…Due to the lower catalytic capacity of Fe@MagTEMPO, only 90% carboxyl content to that of free TEMPO can be achieved at a higher temperature (65 °C) for a longer time (3.5 h). In addition, Sun et al 122 proposed acrylamide vinyl amine copolymerization immobilized TEMPO (P(AM- co -VAm)-T), which achieved 76% catalytic performance of free TEMPO and a much lower degradation degree of cellulose. The positive charge and appropriate size of P(AM- co -VAm)-T avoided the formation of C6 aldehydes and C2/C3 ketones by side reactions, thus inhibiting the degradation of cellulose.…”