Experiences with Scaling-Up Production of TEMPO-Grade Cellulose Nanofibrils

The USDA Forest Products Laboratory (FPL) has worked toward production of cellulose nanofibrils (CNF) to a level suitable for supplying for many preliminary research and development projects. In particular, this chapter discusses the process steps involved in scaling the production of CNF from grams in the laboratory to pilot batch sizes up to 4 kg, namely the reaction, washing, dispersion, separation and freeze drying. The carboxylation of the pulp nanofibril surface was carried out using the catalyst TEMPO with two reaction protocols utilizing hypochlorite at pH 10 and sodium chlorite at pH 7. Various methods for mechanical dispersion, of oxidized pulp fibers into individual nanofibrils are also compared. Currently, aqueous suspension and freeze-dried TEMPO-grade cellulose nanofibrils produced using hypochlorite are available through the University of Maines Process Development Center (along with other cellulose nanomaterials). However, end-use applications will ultimately dictate the process optimization of chemistry and dispersion that are engineered into producing CNF with particular properties.