Studies Of Wheat Straw Xylanase-soda Chemi-mechanical Pulping

Developing wheat straw soda Chemi-mechanical pulp (ACMP) is an important method of the utilization of agricultural residues and overcoming the shortage of the raw material in the pulp and paper industry. Bio-chemimechanical pulping is an efficienct way of reducing waste water pollution in pulping. The function of hot water pretreatment, xylanase pretreatment and hot water-xylanase pretreatment prior to soda treatment during chemi-mechanical pulping of wheat straw along with xylanase pretreatment prior to hydrogen peroxide bleaching of wheat straw xylanase soda chemi-mechanical pulp (H-X-ACMP) were investigated in this thesis.It mainly achieves the following results:1. The suitable temperature of pretreating wheat straw with hot water was 90°C. Compared to the ACMP, H-ACMP respectively increases 7% and 5% in tensile index and tear index of chemi-mechanical pulp.2.The suitable conditions of pretreatment wheat straw with xylanase were the enzyme dosage 15 IU/g (on oven dry wheat straw and xylanase activity), pretreatment time 90-120min.Compared to the ACMP, X-ACMP respectively increase 40% and 16% in tensile index, tear index of chemi-mechanical pulp. Pretreatment with xylanase after hot water treatment of wheat straw, it was more effective than pretreatment with hot water and xylanase, Compared to the ACMP, H-X-ACMP respectively increase 75%å’Œ 19.5% in tensile index, tear index of chemi-mechanical pulp.For the same physical strength ,it could decrease the 30% of the soda consumption.3. Pretreatment with xylanase prior to H₂O₂ bleaching during bleaching led to effectiveness of H₂O₂ bleaching improving, and brightness of bleached pulp increasing 5.5%ISO(compared to the control). The suitable conditions of xylanase pretreatment were xylanase dosage of 12 IU/g( oven dry wheat straw), the time of 120min. Furthermore, the pulp could be bleached to 74.6% ISO brightness level by using XP₅a P₅a bleaching sequences.4. Compared to the ACMP, H-X-ACMP the R50, R102, R203 fractionations fiber could be increased by hot water and xylanase pretreatment of wheat straw, and softness and fibrillation of fiber could also be improved, it was mainly the reason for H-X-ACMP possess upper physical strength. H-X-ACMP could be sued to the paperboard of higher strength.5.FTIR and 2D-HMQC NMR spectroscopy of wheat straw dioxane lignin analysis results showed: pretreatment with xylanase led to -OH and -OCH₃ increasing, wheat straw and soda chemi-mechanical pulp of wheat straw were activated during breaking off covalent bond and xylan from the lignin-carbohydrate-eomplexes (LCC) was partially degraded and removed in enzyme stage by enzyme attacks lignin-carbohydrates linkages such as ether or glycoside linkages. Xylanase pretreatment created advantage condition that wheat straw and soda chemi-mechanical pulp of wheat straw were treatmented by the subseguently chemicals.