Conversion of cellulose

Supercritical fluid solvents have been tested for reactive extractions of liquid and gaseous fuels from heavy oils, coal, oil shale, and biomass. In some cases the solvent participates in the reactions, as in the hydrolysis of coal and heavy oils with water. Related applications include conversion of cellulose to glucose in water, dehgnincation of wood with ammonia, and liquefaction of lignin in water. 

Table 14.1. Methods for conversion of cellulosic agricultural wastes into animal feed...

The mechanism of the conversion of cellulose by the Cytophagaem into viscous mucoproteins of high molecular weight forms an unexplored subject of great interest. 

In addition, cellulose undergoes changes in crystalline structure with relative ease. The most common modification is the conversion of cellulose I (i.e. la and 1/8) to cellulose II. This can be achieved by dissolution and regeneration or by simply treating cellulose I with sodium hydroxide. Cellulose II is usually considered to be more thermodynamically stable than biosynthesised cellulose I. However,... 

Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (such materials as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. In order to use the polysaccharides present in lignocel-lulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or... 

Cost sensitivity studies have shown that the successful commercialization of cellulase-based processes, such as the conversion of cellulose to fermentable sugars, is highly dependent on the cost of enzyme production (i). Because fungal -D-glucosidase (EC 3.2.1.21) is the most labile enzyme in this system under process conditions (2), and k to efficient saccharification of cellulose, this enzyme was targeted for application of stabilization technology, both through chemical modification and immobilization to solid supports. 

Figure 7. Conversion of cellulose I crystallites (left) to those of Na-cellulose I (right), by the action of NaOH. Reproduced with permission from ref. 24 (Copyright John Wiley at Sons, 1987).

Gaden, E.L., Jr., Mandels, M.H., Reese, E.T. and Spano, L.A., Enzymatic Conversion of Cellulosic Materials Technology and Applications. Interscience-Wiley, New York, 1976. 

The importance of time, temperature and acid concentration in the hydrolysis of cellulose with dilute acid was recognized by early investigators and applied in the investigations of Simonsen in 1898. Further study was made by Kressman and reported in U. S. Department of Agriculture Bulletin No. 983. Reviews of the quantitative aspects have been made by Doree. Liiers pointed out that the conversion of cellulose dextrin to D-glucose by dilute sulfuric acid was a monomolecular reaction. The constants of the hydrolysis of wood cellulose have been determined by Saeman. The reaction rate (A ) was found to be expressed by the following equation ... 

Abstract Polyfunctionality of carbohydrates and their low solubility in conventional organic solvents make rather complex their conversion to higher value added chemicals. Therefore, innovative processes are now strongly needed in order to increase the selectivity of these reactions. Here, we report an overview of the different heterogeneously-catalyzed processes described in the literature. In particular, hydrolysis, dehydration, oxidation, esterification, and etherification of carbohydrates are presented. We shall discuss the main structural parameters that need to be controlled and that permit the conversion of carbohydrates to bioproducts with good selectivity. The conversion of monosaccharides and disaccharides over solid catalysts, as well as recent advances in the heterogeneously-catalyzed conversion of cellulose, will be presented. 

The conversion of cellulose and starch into sugar, by To avoid this Rousseau adds ammonia, which is con- ... 

In the area of waste utilization, Fred s program on the heat content, gasification, and carbonization of forest fuel is now recognized as a major step in our understanding of forest fires. The acid-catalyzed pyrolysis of cellulosic waste to afford l,6-anhydro-3,4-dideoxy-)3-D-g/ycero-hex-3-enopyranos-2-ulose ( levoglucosenone ) pointed the way to another method of chemical conversion of cellulosic wastes similar to cat-cracking in the petrochemical industry. 

Cellulose Sulfates and Phosphates. Conversion of cellulose to sulfate or phosphate monoesters produces soluble derivatives. These ester groups are highly hydrated, offer steric interference to molecular fit, and are ionized at all PH levels so they continually produce coulombic repulsion. 

Cellulosic Materials. Over 900 x 106 metric tons of carbohydrate-containing cellulosic wastes are generated annually. The technology for converting this material into ethanol is available, but the stoichiometry of the process is disadvantageous. Even if each step in the process of the conversion of cellulose to ethanol proceeded with 100% yields, almost two-thirds of the mass would disappear during the sequence, most of it as carbon dioxide in the fermentation of glucose to ethanol. This amount of carbon dioxide leads to a disposal problem rather than to a raw material credit (209). 

Reese, E. T. Enzymatic Conversion of Cellulosic Materials, Biotechnol. 

The best pretreatment conditions for obtaining high conversion of cellulose to glucose were 200°C for 5 min after swelling the fibers with 2%... 

Ji N, Zhang T, Zheng M, Wang A, Wang H, Wang X, Shu Y, Stottlemyer AL, Chen JG (2009) Catalytic conversion of cellulose into ethylene glycol over supported carbide catalysts. Catal Today 147 77-85... 

A great amount of time, money and effort is being devoted to the use of cellulose as a feedstock for the production of ethanol. The studies incorporate chemical or enzymatic conversion of the cellulose to glucose and the conversion of this to ethanol with yeast (Saccharomyces) or bacteria (Zymomonas). However, a third process is presently under development at Massachusetts Institute of Technology whereby the direct conversion of cellulose to ethanol is being attempted without a separate hydrolysis step. ... 

A second recent development is increased interest in the conversion of cellulose to fermentable sugar for conversion to alcohol. The enzymatic conversion is thus far not well enough developed to be successful commercially, although break-... 

Fig. 5. Enzymatic conversion of cellulosic materials (Reproduced from Binder, H., Keune, H. Forschung aktuell, Biotechnologie, p. 200, Frankfurt, Umschau 1978)...

Gaden, E. L., et al. (eds.) Enzymatic Conversion of Cellulosic Materials, Technology and Application, New York-Chichester-Toronto, John Wiley 1976... 

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