Process for the production of alcohol

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 comprising a C2-3 ether 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) and is such that water-soluble oligosaccharides are precipitated from solution by its addition in step (ii).

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, and is such that water-soluble oligosaccharides are precipitated from solution by its addition in step (ii), wherein extraction step (ii) is performed at a temperature within 15° C. and a pressure within 1 bar of the temperature and pressure of hydrolysis step (i), wherein evaporation step (iii) is performed at a temperature within 15° C. and a pressure within 5 bar of the temperature and pressure of extraction step (ii), and wherein condensation step (iv) is performed at a temperature within 15° C. and a pressure within 1 bar of the temperature and pressure of extraction step (ii).