Scholler process, dilute-acid

Most simple oligosaccharides are quantitatively hydrolyzed by boiling dilute acid. Cellulose by contrast is hydrolyzed very slowly, and even on extended hydrolysis at higher temperatures, the maximum yield of recoverable sugar is very low. This was explained by Luers ( ) who showed the cellulose hydrolysis in dilute acid involves consecutive first-order reactions of somewhat similar rates for the production and the decomposition of sugar. This observation formed the basis for the development of the Scholler percolation process. This process, which involves removal of sugar from the digester as it is formed, resulted in twice the yield obtainable by batch hydrolysis. 

On the basis of the above methods, two classes of industrial processes have been developed, namely the Bergius-Rheinau process, based on the use of concentrated hydrochloric acid at ordinary temperatures, and the Scholler-Tornesch process, in which very dilute sulfuric acid is used at temperatures of 170-180°C (338-356°F). The latter method in an improved form is known as the Madison process, based on work done at the U.S. Forest Products Laboratory in Madison, Wisconsin. A number of modifications have been developed, including four in Japan. 

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