Fabrication and properties of peroxide cellulose from coniferous and deciduous wood for chemical processing

Abstract

Acid prehydrolysis does not impede subsequent peroxide delignification, increases the mass fraction of α-cellulose, and improves the reactivity of cellulose but does not ensure a high degree of modification. Aqueous prehydrolysis is less effective. Cold alkaline modification of coniferous (spruce) prehydrolysis peroxide cellulose is highly effective and increases the mass fraction of α-cellulose to 97.5%. Deciduous wood is delignified and modified more easily than coniferous wood. Deciduous (birch) cellulose with up to 99% mass fraction of α-cellulose can be obtained by peroxide cooking with acid prehydrolysis, finishing, and cold alkaline modification. The process regimes developed allow processing highly modified coniferous and deciduous cellulose with properties as good as sulfate cord cellulose with minimal technogenic environmental pollution.The necessity of sharply curtailing the amount of harmful industrial emissions has stimulated a search for new methods of manufacturing and processing cellulose which would satisfy environmental protection requirements. Low-temperature catalyzed oxidative delignification of wood by hydrogen peroxide is one of the most promising methods. This method of manufacturing cellulose allows eliminating sulfur compounds from the manufacturing process. The reagents used are not hazardous to the environment. The process is conducted at temperatures below 100°C and atmospheric pressure.Specific requirements for chemical purity, macromolecular homogeneity, reactivity, etc., are imposed on cellulose for chemical processing. To satisfy these requirements, it is necessary to use process operations and regimes for obtaining peroxide soluble cellulose.Statistical methods of experiment design, mathematical modeling, evaluation, and optimization were used in all stages of the study. Mathematical processing was conducted with tools from the Statgraphics Plus v.5 applied software package.The peroxide method includes cooking ground plant raw material with a solution of hydrogen peroxide in the presence of a multicomponent catalyst a mixture of tungstic acid or its salts, molybdic acid or its salts, and a mineral acid.The effect of the basic process factors in catalyzed delignification of wood by hydrogen peroxide on the yield and properties of cellulose was investigated in the first stage and the optimum cooking parameters were determined with a generalized optimization parameter. The conditions of the study were as follows: peroxide stage temperature of 89.2°C, duration of 2.5 h; concentration of sulfuric acid in solution of 0.025 M; concentration of sodium hydroxide in alkaline extraction of 42 g/dm 3 ; duration of alkaline stage of 1.5 h. The cellulose obtained in the optimum conditions contained 88% α-cellulose, 8% hemicelluloses, and 4% lignin [1].The properties of the peroxide cellulose were close to the properties of unbleached sulfite cellulose on such indexes as the α-cellulose and lignin content and degree of polymerization (DP), but are inferior to industrial cellulose with respect t...