Lignin hydrolytic reactions

Hydrolytic Reactions. Probably the most important reactions, with regard to their impact on the properties of wood, involve some type of hydrolysis. Both carbohydrates and lignin are affected, and hydrolysis is encountered in almost every kind of wood processing. 

Some results of the modification of lignin sulfonate Ultra B002 by reaction with terephthaloyl chloride are summarized in Table VI. The total hydroxyl content of the lignosulfonates as well as their derivatives are presented in Table VII. The hydrolytic resistance of selected products is evaluated in Table VIII. The results presented in Tables VI-VIII stress several advantages of the derivatives with terephthaloyl chloride. The modified lignin sulfonates were insoluble, or only very slightly soluble, in organic solvents. They were, however, soluble in dimethyl sulfoxide. Ordered structures were identified by X-ray studies (16,17). 

The major chemical changes in wood caused by fiberboard manufacture are secondary side reactions which are both beneficial and detrimental to the final properties achieved. Defibering is accomplished by hydrolytic breakdown of lignin and hemicelluloses under wet acidic conditions combined with high process temperatures. Board conversion and consolidation is attended by pyrolytic reactions which... 

As a broad generalization the cellulose provides impact resistance and tensile strength, the lignin provides stiffness, and both matrix polymers contribute to hardness and compressive strength. Hydrolytic and oxidative processes that depolymerize and solubilize the wood components will affect the wood properties, often to an extent far greater than might be expected from the limited initial reaction. 

The section on degradation of organics deals with paints, plastics, nylon, wood, and architectural organics. The effects of acid deposition on wood and other cellulosic materials are described. Strength losses in wood may be caused by hydrolytic degradation of the hemicelluloses and a sulfonation reaction of the lignin. Thus, the fibrils and matrix structure is affected. Cotton materials can be affected similarly, and soiling will result. The effect of acid deposition of nylon is indicative of a potentially shorter serviceable lifetime for outdoor fabrics. 

Acid or alkaline treatments of particulate feeds have been shown to improve digester gas yields (17.22-25). Acid hydrolysis was not used in our work because severe reaction conditions are required, and there is considerable decomposition of the hydrolytic products under these conditions ( ). Dilute alkaline pretreatment was evaluated because alkali was shown to be more effective in promoting hydrolysis of cellulosic biomass than acid (17,26). It is postulated, for example, that sodium hydroxide breaks down the cross-linked lignin macro-molecules surrounding the cellulose fibers into alkali-soluble lower-molecular-weight units. In this way, the cellulose fibers are exposed for... 

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