Simultaneous microwave-assisted phosphotungstic acid catalysis for rapid improvements on the accessibility and...

Improving the cellulose accessibility and reactivity in an efficient and convenient way has become the focused issue in the field of dissolving pulp manufacturing. We herein demonstrate a simple yet efficient strategy, namely a simultaneous microwave (MW)-assisted phosphotungstic acid (PTA) catalysis (MW-PTA_sim). The MW-PTA_sim treatment was efficient to improve Fock reactivity from 49.1 % to 85.8 % and decrease viscosity from 561 to 360 mL/g within 10 min, which was superior to the single MW treatment and the sequential MW-PTA_seq treatment. Besides, the MW-PTA_sim treated fiber had rougher and more fibrillated surfaces with an enhanced fiber accessibility, showing increased specific surface area (SSA) from 1.43 to 6.31 m²/g, mean pore diameter (MPD) from 6.92 to 11.20 nm and water retention value (WRV) from 101 % to 172 %. These positive enhancements are mainly due to a synergy that MW-enhanced rotation of PTA mediums was served as "spinning cutters" to attack the fibers, plus MW-accelerated PTA transfer and catalytic hydrolysis further improved the fiber accessibility. Moreover, PTA also demonstrates a high reusability and chemical stability. This process offers an effective and sustainable alternative for manufacturing a premium dissolving pulp.