Simultaneous mechanical refining and phosphotungstic acid catalysis for improving the reactivity of kraft-based dissolving pulp

Improvements on reactivity and viscosity control of the prehydrolysis kraft (PHK) dissolving pulp in an efficient and sustainable way is of both fundamental and practical interest. In this study, we proposed a novel concept of using a simultaneous treatment consisting of mechanical refining (R) and phosphotungstic acid (PTA) catalysis (defined as R-PTA(sim)) for this purpose. Results showed that the simultaneous process (R- PTA(sim)) was more effective in improving Fock reactivity, from 47.2 to 83.5%, while the sequential process (initial refining, followed by PTA catalysis, defined as R-PTA(seq)) increased from 47.2 to 77.2%. The viscosity of resultant pulps was 411mL/g and 428mL/g for the R- PTA(sim) and the R-PTA(seq), respectively. The explanations are: (1) the PTA catalysis induces cellulose depolymerization and morphological changes of fibers, and improves the mechanical refining efficiency, (2) mechanical refining facilitates the diffusion/adsorption of PTA into cellulose fibers and further enhances the PTA catalysis, (3) an enhanced synergistic effect occurs in simultaneous treatment. It was demonstrated that PTA has a high chemical stability and recyclability/reusability. This concept can offer a new pathway for sustainable manufacturing high- quality dissolving pulp. [GRAPHICS]