Aqueous fractionation of biomass based on novel carbohydrate hydrolysis kinetics

In a multi-function process for hydrolysis and fractionation of lignocellulosic biomass to separate hemicellulosic sugars from other biomass components comprising extractives and proteins;

• a portion of a solubilized lignin;
• cellulose;
• glucose derived from cellulose;
• and insoluble lignin from said biomass, the improvement comprising:
• a) introducing either solid fresh biomass or partially fractioned lignocellulosic biomass material containing entrained water or acid at pH<5.0 into a reactor and heating to a temperature from about 185° C. to about 205° C.;
• b) allowing the reaction to proceed to a point where about 60% by weight of the hemicellulose has been hydrolyzed, in the case of water only for about 6-10 minutes, or in the case when acid is present for about 5-10 minutes for complete dissolution;
• c) adding a dilute acid liquid at a pH below about 5.0 at a temperature of up to about 205° C. for a period ranging from about 5 to about 10 minutes when water is used in step b);
• d) quenching the reaction at an average temperature of up to about 140° C. to quench all degradation and hydrolysis reactions;
• and
• e) introducing into said reaction chamber and simultaneously removing from said reaction chamber, a volumetric flow rate of dilute acid at an average temperature of up to about 140° C. to wash out the majority of the solubilized biomass components, to obtain improved hemicellulosic sugar yields and prevent recondensation reactions from occuring.