Comparison of monopersulfuric acid and sulfuric acid as prehydrolysis reagents for high-purity cellulose production from Japanese cedar via soda–anthraquinone (soda–AQ) cooking and totally chlorine-free (TCF) bleaching

Prehydrolysis/soda–anthraquinone (AQ) cooking has emerged as a promising strategy for the production of high-purity cellulose; however, optimization of the prehydrolysis stage is still required. In this study, monopersulfuric acid (MPS) was evaluated as a prehydrolysis reagent for the production of cellulose from Japanese cedar ( Cryptomeria japonica ) via prehydrolysis/soda–AQ cooking and compared with sulfuric acid (H 2 SO 4 ) under equivalent acid dosages. At high acid dosage, MPS-treated wood showed lower residue yield than H 2 SO 4 -treated wood, whereas H 2 SO 4 treatment resulted in higher Klason lignin content after prehydrolysis. Nitrobenzene oxidation further confirmed lower vanillin yields in H 2 SO 4 -treated wood than in MPS-treated wood, indicating that lignin condensation was suppressed when MPS was used for prehydrolysis. Sugar analysis of the prehydrolysis liquor (PHL) showed that at low H 2 SO 4 dosage (4.8%), MPS and H 2 SO 4 treatments afforded comparable untreated total sugar contents. However, at high dosage (≥ 24%), the untreated total sugar content was lower in MPS-treated PHL, suggesting oxidative transformation or degradation of released carbohydrates. When soda–AQ cooking was conducted after MPS treatment, the resulting pulp showed lower kappa number, improved oxygen-bleaching response, and higher brightness of the final totally chlorine-free (TCF) bleached pulp (83.0% ISO) compared with soda–AQ cooking performed after H 2 SO 4 treatment or without prehydrolysis. However, the brightness differences among the pulps became smaller after the subsequent TCF bleaching sequence, despite the higher brightness of MPS/soda–AQ pulp after oxygen bleaching. Although pulp viscosity did not reach dissolving-pulp grade specifications, the bleached pulp exhibited high glucan purity (≈96%) indicating applicability for high-purity cellulose applications. Overall, the results demonstrate that MPS/soda–AQ is a viable, sulfide-free and chlorine-free route for obtaining cellulose with high glucan content from Japanese cedar. These findings position MPS/soda–AQ cooking as a new biorefinery process for producing high-purity cellulose streams rather than conventional dissolving pulp for advanced material applications from domestic softwood resources in Japan.