Abstract
This paper introduces a concentrated di-carboxylic acid (DCA) hydrolysis process for the integrated production of thermally stable and carboxylated cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). The DCA hydrolysis process addressed several issues associated with mineral acid hydrolysis for CNC production, such as cellulose loss and acid recovery. The surface and morphological properties of the cellulose nanomaterials resulting from the DCA hydrolysis process can be tailored simply by controlling the severity of DCA hydrolysis. To further reduce cost, a lowtemperature (≤80 ℃) hydrotropic chemical process using p-toluenesulfonic acid (p-TsOH) was also introduced to rapidly fractionate raw lignocelluloses for the production of lignin containing cellulose nanofibrils (LCNFs) and lignin nanoparticles (LNPs). The LCNF surface hydrophobicity and morphology can be tailored by controlling the fractionation severity, i.e., the extent of delignification. The lignin also improved the thermal stability of LCNFs. LNPs can be easily separated by diluting the spent acid liquor to below the p-TsOH minimal hydrotropic concentration of approximately 10%. p-TsOH can also be easily recovered by re-concentrating the diluted spent liquor after lignin precipitation. We believe that these two novel processes presented here have the potential to achieve true sustainable, economic, and tailored production of cellulose nanomaterials, suitable for a variety of applications.
