GB354820A - Improvements in or relating to the treatment of carbohydrates - Google Patents

Abstract

Cellulosic material is impregnated with non-volatile inorganic acid of such low concentration and at such low temperatures that no substantial hydrolysis occurs, and is then treated so as to concentrate the acid to a strength sufficient to transform the cellulose into soluble cellulose, dextrins, or sugars. Preferably, however, this reaction is arrested before the formation of sugars, and a further hydrolysis may then be effected with dilute acid at higher temperatures and pressures. In the first hydrolysis, only a small quantity of acid is used, for instance less than 100 per cent, and preferably 5 to 10 or 50 per cent, of the weight of the cellulose, which may be in the form of wood chips, sawdust; sulphite, sulphate, or mechanical pulp; cotton cellulose, linters, or reconstituted cellulose. Sulphuric acid of 20-50 per cent strength may be sprayed on to the raw material, or this material may be soaked and then pressed to expel excess of acid. The treatment with dilute acid may be effected at 0-25 DEG C., and may be continued for 1-20 hours or more. Concentration of the acid may then be effected by subjecting the material to vacuum or a current of gases such as carbon dioxide, nitrogen, or air, at a temperature preferably below 100 DEG C., but varying inversely with the proportion of acid present. When an acid strength of 65-80 per cent is attained, the material may be allowed to stand at low or ordinary, but preferably at higher, temperatures, say 30-35 DEG C., for a period of 20 minutes to 4 hours. Water may then be added to bring the acid strength to 1/2 -2\ba1/2 per cent, especially between 1/2 and 1 per cent, and the mixture is then heated, preferably under pressure or reflux, for about 6-8 hours. Sulphuric acid may afterwards be removed by means of chalk.ALSO:Cellulosic material is impregnated with nonvolatile inorganic acid of such low concentration and at such low temperatures that no substantial hydrolysis occurs, and is then treated so as to concentrate the acid to a strength sufficient to transform the cellulose into soluble cellulose, dextrins, or sugars. Preferably, however, this reaction is arrested before the formation of sugars, and a further hydrolysis may then be effected with dilute acid at higher temperatures and pressures. In the first hydrolysis, only a small quantity of acid is used, for instance less than 100 per cent, and preferably 5 to 10 or 50 per cent, of the weight of the cellulose, which may be in the form of wood chips, sawdust; sulphite, sulphate, or mechanical pulp; cotton cellulose, linters, or reconstituted cellulose. Sulphuric acid of 20-50 per cent strength may be sprayed on to the raw material, or this material may be soaked and then pressed to expel excess of acid. The treatment with dilute acid may be effected at 0,25 DEG C., and may be continued for 1-20 hours or more. Concentration of the acid may then be effected by subjecting the material to vacuum or a current of gases such as carbon dioxide, nitrogen, or air, at a temperature preferably below 100 DEG C., but varying inversely with the proportion of acid present. When an acid strength of 65-80 per cent is attained, the material may be allowed to stand at low or ordinary, but preferably at higher, temperatures, say 30-35 DEG C., for a period of 20 minutes to 4 hours. Water may then by added to bring the acid strength to 1/2 -2\ba1/2 per cent, especially between 1/2 and 1 per cent, and the mixture is then heated, preferably under pressure or reflux, for about 6-8 hours. Sulphuric acid may afterwards be removed by means of chalk.