(644c) Cellulose Acetate Production Using Deep Eutectic Solvent Pulping and Totally Chlorine Free Bleaching

Cellulose acetate is a high-value cellulose derivative that requires high-purity (85-90%) viscous grade pulp as a substrate. Deep eutectic solvents (DES) have gained recent attention due to their potential to serve as alternatives to conventional pulping processes their low cost, ease of preparation, eco-friendliness, and high recoverability. DES treatments of lignocellulosic biomass have previously been shown to allow for viscous grade pulp production, however the potential of these pulps to be converted into high-value products has not been explored. In the present work, aspen wood was pulped using a choline chloride-based DES followed by a totally chlorine free (TCF) bleaching sequence comprised of alternating NaOH and H₂O₂ treatments. DES pulping resulted in 85.8% lignin removal compared to the untreated aspen wood. This was increased to 98.1% delignification after bleaching. The bleached DES pulp exhibited 87.8% cellulose content with 1.4% residual lignin and 2.7% xylan and an overall yield of 29.3% from the raw feedstock. Acetylation was then successfully carried out and the product was evaluated based on the degree of substitution (DS) and acetate filtration characteristics in comparison to commercial cellulose acetate samples. Results showed for the first time that DES pulping can facilitate the production of viscous grade pulp suitable for cellulose acetate production. This lab-scale demonstration indicates the potential scalability of DES-based processes for future industrial applications for the pulp and paper industry.