Xylan extraction strategies and the performance of the resulting high purity cellulose fiber to swelling and dissolution

Abstract

In this study, we investigated the influence of hemicelluloses removal treatment on the reactivity of the resulting pulp. The idea was to develop treatment strategies consisting of mechanical refining (different refining technologies), chemical treatment (CCE), and xylanase treatment that enabled both quantitative xylan removal as well as good reactivity to dissolution without the need for additional post-extraction treatments (cellulose activation) to improve reactivity. Cellulose post-extraction treatments result in additional production costs. The reactivity of the extracted pulps was evaluated based on the degree of swelling in NaOH and dilute cupriethylene diamine solution (CUEN), the solubility in 8% NaOH at -10 °C, and the Fock reactivity. The result obtained showed that hemicelluloses removal strategies that included mechanical refining treatment led to better pulp reactivity than unrefined pulp. The best result was obtained with refined pulp extracted with 6% soda (cellulose II not detected). In addition, we obtained a Fock reactivity ranging from 60 to 70%. The good correlations found between fiber swelling, solubility in caustic soda, and Fock reactivity suggest that the tedious Fock test could be substituted by the much simpler swelling and solubility measurements. The negative impact of cellulose II on pulp reactivity is due to the higher number of hydrogen bonds formed under dewatering and drying. This problem would most likely be averted in the ideal case where pulp dissolution is integrated into the pulp mill.