2021

Lehto, Joni; van Heiningen, Adriaan; Patil, Ravikant; Louhelainen, Jarmo; Alén, Raimo

For recovering value-added wood-based organic material prior to delignification, sodium borohydride (NaBH4) and hydrogen peroxide (H2O2) pretreatments under alkaline conditions were performed before soda pulping of sugar maple (Acer saccharum) chips with sodium hydroxide (NaOH). In this investigation, it was determined whether the pulp yield could be increased by partly stabilizing the hemicelluloses by these pretreatments, and simultaneously obtains lower pulp kappa numbers. The results indicated that when aiming to the same kappa numbers (i.e., kappa numbers 14.3-20.5), roughly 3% higher pulp yield could be achieved if the chips were pretreated with alkaline 0.5% NaBH4 solutions, compared to those produced without such pretreatment or pretreated only with NaOH (i.e., without NaBH4). In contrast, pretreatments conducted with alkaline 2.5% H2O2 did clearly lower pulp yields at the same kappa number range (14.0-22.7) when compared to the reference cooks conducted with NaOH pretreated materials. However, an increase in the H2O2 charge of the pretreatment from 2.5% to 5.0% had a clearly beneficial effect, as the pulp yield and kappa numbers after pulping of 5.0% H2O2 pretreated pulps were comparable to the reference cooks.