Cellulose Degradation, acidic

Solution Process. With the exception of fibrous triacetate, practically all cellulose acetate is manufactured by a solution process using sulfuric acid catalyst with acetic anhydride in an acetic acid solvent. An excellent description of this process is given (85). In the process (Fig. 8), cellulose (ca 400 kg) is treated with ca 1200 kg acetic anhydride in 1600 kg acetic acid solvent and 28—40 kg sulfuric acid (7—10% based on cellulose) as catalyst. During the exothermic reaction, the temperature is controlled at 40—45°C to minimize cellulose degradation. After the reaction solution becomes clear and fiber-free and the desired viscosity has been achieved, sufficient aqueous acetic acid (60—70% acid) is added to destroy the excess anhydride and provide 10—15% free water for hydrolysis. At this point, the sulfuric acid catalyst may be partially neutralized with calcium, magnesium, or sodium salts for better control of product molecular weight. 

Chemical degradation of cellulose — Levulinic acid + Xylitol... 

In an inciteful discussion of insect-microbe relationships, Jones (10) postulated that insect-microbial associations, known to involve catabolic (e.g. cellulose-degrading) and anabolic (e.g. biosynthesis of vitamins, sterols, and amino acids) processes necessary to the survival of the host, could also include detoxification abilities. Most investigations in this area have been limited (11). Nevertheless, some studies indicate detoxification of terpenoids (12,... 

Cellulose degradation in an acetic acid environment. Studies in Conservation, 45, 201-10. 

Major biotechnological uses of the biomass carbohydrate moiety have attracted worldwide attention. Controlled cellulose degradation by cellulases may produce materials for important multifarious applications carbohydrates that can be used in the food and beverage industries, cellulose microfibril fragments for non-caloric food additives, hyperabsorbent cellulose fibers from fragmented cellulose microfibrils which can be used in biomedical, commercial and house-hold absorbent materials. Biomass-derived glucose syrups can also be used as carbon source in industrial fermentations for the production of antibiotics, industrial enzymes, amino-acids, and bulk chemicals. 

Wood hydrolysis has been limited to cellulose degradation by cellulase enzymes. These en mes are typically low activity and highly inhibited by the glucose product. As mentioned above, mild acid pretreatment has been found to be an important first step in the biomass utilization process. The pretreatment is used both to break down the hemicellulose to sugars and to disrupt the lignocellulosic structure and tlie crystallinity of the cellulose. 

Care is taken to ensure that the digestion liquor does not become too acid, otherwise cellulose degradation during the pulping step can become more significant. 

Excess base is used to ensure that the pH is kept at or below 12, to ensure that hypochlorite, OCl (and not hypochlorous acid, HOCl), is the bleach active species (see Fig. 15.10), and to stabilize the hypochlorite ion for this purpose. Both the C and H, stages are designed to operate at pHs well clear of neutral to minimize the concentration of undissociated hypochlorous acid and attendant cellulose degradation. Hypochlorite ion is a less powerful oxidant than chlorine and hence more suitable for later bleach stages. Hypochlorite oxidizes and dissolves the chlorinated residues from the chlorination stage, the so-called... 

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