Hemicellulose, catalytic hydrolysis

Xylitol is synthesized by reduction of D-xylose catalytically (40), electrolytically (41), and by sodium amalgam (42). D-Xylose is obtained by hydrolysis of xylan and other hemicellulosic substances obtained from such sources as wood, com cobs (43), almond shells, hazelnuts, or olive waste (44). Isolation of xylose is not necessary xylitol results from hydrogenation of the solution obtained by acid hydrolysis of cottonseed hulls (45). 

Furoic acid (furan-2-carboxylic acid, or pyromucic acid) is used as a bactericide, and the furoate esters are used as flavoring agents, as antibiotic and corticosteroid intermediates. It is obtained by the enzymatic or chemical/catalytic aerobial oxidation of furfural (2-furalaldehyde) the latter is the only unsaturated large-volume organic chemical prepared from carbohydrates today. D-Xylose and L-ara-binose, the pentoses contained in the xylan-rich portion of hemicelluloses from agricultural and forestry wastes, under the conditions used for hydrolysis undergo dehydration to furfural. 

Predicting Catalytic Effect of Acid on Hemicellulose Hydrolysis... 

Table II lists derivatives of D-glucuronic acid which have been obtained by catalytic oxidation. A ready preparation of 3-0-methyl-D-glucuronic acid is by the oxidation of l,2-0-isopropylidene-3-0-methyl-D-gluco-furanose and subsequent hydrolysis of the product." 4-0-Methyl-D-glucuronic acid, a compound of considerable interest because of its occurrence as a fundamental unit in hemicelluloses" and polysaccharides," cannot be obtained by the simple catalytic oxidation of methyl 4-0-methyl-D-glucopyranoside. f...

As described in the previous section. Brown et al. obtained an aromatic yield of 1% in the catalytic fast pyrolysis of milled wood lignin with ZSM-5 at 600°C, which was considerable lower than the yields obtained from cellulose and hemicellulose [286]. Also, the coke yield from lignin (59%) was much higher. Huber et al. used the lignin residue obtained after H SO hydrolysis of maple wood as a substrate for pyrolysis in a fluidized-bed reactor with spray-dried ZSM-5 at 600°C [298]. Next to lignin, this substrate also contains humic residue, a compound also composed of phenolic entities. An aromatic and olefin yield of only 2% and 1% was obtained, compared to respective yields of 15% and 7% from pure maple wood. The coke yield from the solid residue (69%) was also much higher than the coke yield from maple wood (32%). 

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