Influence of swelling on the efficiency of TEMPO reaction, nanofibril production and characterization

Abstract

This paper studies the effect of three swelling pretreatment processes (glycerol, alkaline, and molten salt hydrate) to improve the efficiency of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs). The novelty of this research lies in the presentation of a new approach that increases the process`s sustainability. The new pretreatment results in the reduction of both chemical reagents and energy consumption. Results demonstrate that pulps pretreated with molten salt hydrate exhibit a crystallinity index up to 50 % lower than the original fibers, while the carboxyl groups obtained during oxidation increase up to 30 %. The increase in oxidation efficiency allows us to obtain a highly fibrillated CNF with a 50 % dose reduction of TEMPO and NaBr at the same time that the energy consumption (kWh/kg) is reduced by 15%.