Tailored and Integrated Production of Carboxylated Cellulose Nanocrystals (CNC) with Nanofibrils (CNF) through Maleic Acid Hydrolysis

This study demonstrates the feasibility of tailored and integrated production of carboxylated cellulose nanocrystals (CNC) with nanofibrils (CNF) from bleached pulp fibers through hydrolysis using a recyclable dicarboxylic acid. Hydrolysis experiments were conducted using ranges of 15-75 wt% maleic acid concentrations, 60-120 degrees C temperatures, and 5-300 min reaction times. Maleic acid esterified cellulose resulted in carboxylated CNC and CNF. Furthermore, the acid-hydrolysis solubilized xylan and depolymerized cellulose, which substantially reduced the energy input for the production of CNF through subsequent mechanical fibrillation. A combined hydrolysis factor (CHF), a measure of hydrolysis severity, was developed to map xylan dissolution and cellulose depolymerization over the entire reaction space. It was found that CHF can be used to predict the morphological and chemical properties of the resultant CNC and CNF, independent of the individual reaction process variables. This is important for process scale-up design in order to tailor the properties of CNC and CNF for specific applications. With the low temperature hydrolysis and low energy input in mechanical fibrillation, along with the recyclability of maleic acid, the presented process has promise of achieving commercial success in the low-cost and sustainable production of CNC and CNF.