Cellulose nanocrystals prepared via formic acid hydrolysis followed by TEMPO-mediated oxidation

Abstract

Cellulose nanocrystals (CNCs) as a renewable and biodegradable nanomaterial have wide application value. In this work, CNCs were extracted from bleached chemical pulp using two stages of isolation (i.e. formic acid (FA) hydrolysis and 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) mediated oxidation) under mild conditions. In the first stage, FA was used to remove hemicellulose, swell cellulose fibers, and release CNCs. The FA could be readily recovered and reused. In the second stage, the CNCs isolated by FA were further modified by TEMPO-mediated oxidation to increase the surface charge of CNCs. It was found that the modified CNCs with more ordered crystal structure and higher surface charge had better redispersibility and higher viscosity in aqueous phase. Therefore, the modified CNCs could be more effective when used as rheology modifier in the fields of water based coating, paint, food etc.

Preparation and characterization of thermally stable cellulose nanocrystals via a sustainable approach of FeCl3-catalyzed formic acid hydrolysis

“…(1) (Yu et al 2013) and crystal size (D hkl ) was estimated using the Scherrer Eq. (2) (Li et al 2015a) shown as follows:…”

“…At last, the obtained CNC suspensions (the consistency was about 1 %) were stored in a cold room (4°C) for further treatments or tests. The yields of the obtained products were calculated based on the volume and solid content of the resultant F-CNC suspensions (Li et al 2015a). …”

“…Also, the reported yield of CNCs via sonochemical assisted hydrolysis were low (2-5 % in water and 10 % in aqueous maleic acid) and the yield of CNCs prepared by sulfuric acid hydrolysis was in the range of 30-75 % depending on the starting material and the hydrolysis conditions (Chen et al 2015). In our previous work, CNCs were obtained by the use of formic acid (FA, 98 %) hydrolysis, and the FA could be easily recovered and reused (Li et al 2015a). In order to further reduce the FA concentration and lower the process cost, in this study FeCl 3 as a catalyst was added in FA hydrolysis for the preparation of CNCs and the FA concentration could be lowered from 98 % to 80 % (98 % FA (BASF): about $1200/t; 85 % FA (BASF): about $450/t).…”

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

“…However, in order to improve the efficiency of hydrolysis, higher temperature and longer reaction time are necessary because of the weak acidity of organic acid. Li and coworkers reported a two-step strategy to produce CNCs from bleached chemical pulp under mild conditions [80]. In the first stage, formic acid (FA) was used to hydrolyze the amorphous region of cellulose and release CNCs.…”

Sustainable Design for the Direct Fabrication and Highly Versatile Functionalization of Nanocelluloses

“…This possibility is further supported by the recent production of NCC in 42-70% yield from bleached chemical hardwood pulp (silver birch (Betula pendula)) using formic acid in combination with HCl. [33] Despite this information, we began to investigate NFC fabrication using an organic acid process. [30,34] For recent oxalic acid pretreatment of kraft bleached Eucaluptus pulp in combination with disk milling for fabrication of NFC, see ref.…”