Patent ID: 8709769

Claim:
A process for the production of a residue containing sugars from a cellulosic material, said process comprising the steps of: (i) hydrolyzing said cellulosic material with an aqueous acid to produce a hydrolysate; (ii) extracting acid and water from said hydrolysate with a water-miscible organic extraction solvent to yield (a) a first aqueous acidic solution containing said extraction solvent and (b) the residue containing sugars; (iii) evaporating said extraction solvent from said first solution to yield (a) a second aqueous acid solution containing no more than 10% wt. of said extraction solvent and (b) gaseous extraction solvent; (iv) condensing said gaseous extraction solvent for recycling; and, optionally, (v) concentrating said second aqueous acid solution for recycling; wherein said extraction solvent is liquid at the temperature and pressure of step (ii), has a boiling point of from 25 to 60° C. at a pressure in the range 1 to 8 bar, comprises a solvent having a boiling point at 1 bar of below 20° C., and is such that water-soluble oligosaccharides are precipitated from solution by its addition in step (ii).