Acid hydrolysis cellulose

Cellulose acid hydrolysis is an entry point for a biorefinery [139]. Recently, heterogeneous catalytic depolymerization of cellulose has received much attention [10, 140, 141). Solid materials modified with sulfonic acid groups have been widely attempted for cellulose hydrolysis. SuUbnated mesoporous sihcas [142], suUbnated carbon materials [69, 143-145], suUbnated carbon-siUca nanocomposites [146], and styrene-based sulfonic acid resins [147] have all been reported for sugar hydrolysis. 

Cellulose is the main component of the wood cell wall, typically 40—50% by weight of the dry wood. Pure cellulose is a polymer of glucose residues joined by 1,4-P-glucosidic bonds. The degree of polymerization (DP) is variable and may range from 700 to 10,000 DP or more. Wood cellulose is more resistant to dilute acid hydrolysis than hemiceUulose. X-ray diffraction indicates a partial crystalline stmcture for wood cellulose. The crystalline regions are more difficult to hydrolyze than the amorphous regions because removal of the easily hydrolyzed material has Htde effect on the diffraction pattern. 

Fig. 7. Combined sulfur during preparation of cellulose acetate hydrolysis of sulfate and esters (6). Acetylation schedule A, mixer charged with linters and acetic acid B, minor portion of catalyst added C, began cooling to 18°C D, acetic anhydride added and continued cooling to 16°C E, significant portion...

Abatzoglou, N. and Chornet, E. (1998) Acid hydrolysis of hemicellulose and cellulose. Theory and Applications, in Polysaccharides, Marcel Dekkes, New York, pp. 1007-1045. 

In 1886, Brown11 discovered an organism which formed extremely tough membranes when cultivated m suitable nutrient solutions containing carbohydrates such as D-fructose, D-mannitol or D-glucose ethanol, sucrose or starch did not support membrane formation by this organism which Brown called Bacterium xylinum ) (Acetobacter xylinum). The membranes were readily soluble in cuprammonium hydroxide solution and yielded a dextrorotatory sugar upon acid hydrolysis. These properties and the results of combustion analysis led him to believe that the membrane was cellulose. 

The reaction between cellulose and acrylamide was studied by quantitative, chromatographic separation of the substituted D-glucoses obtained on acid hydrolysis of the reaction product,320 followed by an analysis by Spurlin s method.249 Although, apparently, no check was made on the stability of the ethers to the conditions of hydrolysis, it might be expected that the ethers would isomerize only under basic conditions. The ratios of the relative equilibrium-constants for reaction at 0-2, 0-3, and 0-6 were 9 1 19, and these are attributable to the high, relative stability of the primary ether, together with the low reactivity of 0-3, also observed in rate-controlled reactions. 

Scholler A process for making glucose from wood by acid hydrolysis of the cellulose component under pressure. Invented by H. Scholler in Germany in 1929. Operated in Germany in the 1920s and in Russia in the 1970s. 

It is obvious that acid hydrolysis methods leave a number of unsolved problems and many minor disagreements to be ironed out. In general, however, the available results suggest that the natural celluloses consist chiefly of crystalline material which is only slowly eroded by acids. The non-crystalline fraction appears to be relatively more susceptible to hydrolysis than the crystalline fraction and to have a greater capacity to absorb moisture. In other words, the non-crystalline fraction is probably more reactive than the crystalline material, as Mark14 has suggested. In this connection the fact should not be overlooked that the surface layer of the crystallites is probably amorphous and hence relatively more reactive than the underlying layers. 

Relatively pure xylan isolated from the holocellulose of aspen (Populus) wood is said to contain 85% of xylose residues.78 One of the characteristic properties of xylan is its ease of hydrolysis. Because it hydrolyzes much more readily than cellulose, mild acid treatment may be employed to bring about preferential hydrolysis of xylan from plant material. Xylose is ordinarily prepared in the laboratory by direct sulfuric acid hydrolysis of the native xylan in ground corn cobs.74 Hydrolysis in hydrochloric acid proceeds rapidly, but decomposition to furfural also occurs to some extent.76 A commercial method for the production of D-xylose from cottonseed hulls76 and straw77 and from corn cobs17 78 has been described. 

Acid hydrolysis of cellulosic materials that include some hemicellulose, produces D-xylose, D-glucose, and cellobiose, as well as 11, 2-furalde-hyde (5), levulinic acid, formic acid, and acetic acid. In order to lessen the contamination due to hemicellulose, acid hydrolysis is generally performed in two steps dilute sulfuric acid (1%) at 80-120° followed by 5-20% sulfuric acid at 180°. The initial stage removes most of the pentogly-cans (pentosans). 

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