Abstract: The biorefinery concept of non-wood lignocellulosic fiber biomass alkaline sulfite pulping (ASP) was proposed in this study. The influences of total alkali charge, sulfurous acid degree, cooking temperature and time on the characteristics of wheat straw extended delignification and lignin sulfonation were investigated. The results indicated that ASP has a high selectivity on extended delignification for wheat straw, and the degree of lignin sulfonation increased with the extending of delignification. The total alkaline charge, sulfurous acid degree, maximum cooking temperature and time at maximum temperature have significant impacts on both extended delignification selectivity and lignin sulfonation degree. A good extended delignification pulp with yield 56.8%, Kappa number 8.8, and viscosity 33.3 mPa·s was obtained under the cooking conditions of the total alkali charge 18.0%, the sulfurous acid degree 85.0%, liquor ratio 3.5, maximum cooking temperature 168 ℃ and 150 minutes at 168 ℃. Meanwhile the lignin sulfonation group content in the black liquor was up to 2.16 mmol/g. Based on the extended delignification selectivity, the lignin sulfonation and the basic pulp properties, ASP has good perspective for wheat straw pulping biorefinery.

Key words: wheat straw, alkaline sulfite pulping, lignin, sulfonic acid group