Process for producing levulinic acid

Claim 1

A PROCESS FOR THE PRODUCTION OF LEVULINIC ACID COMPRISING DIGESTING IN AN AQUEOUS DIGESTION MEDIUM UNDER PRESSURE AT A TEMPERATURE ABOVE 100*C. A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF A HEXOSE AND A MATERIAL YIELDING A HEXOSE UNDER THE CONDITIONS OF DIGESTION, SAID DIGESTION MEDIUM HAVING SALTS DISSOLVING THEREIN FURNISHING ALUMINUM IONS, CHLORIDE IONS, SULFATE IONS AND IONS OF AT LEAST ONE ALKALI METAL SELECTED FROM THE GROUP CONSISTING OF SODIUM AND POTASSIUM, THE ALUMINUM CONTENT BEING AT LEAST 1.9% BASED ON THE WEIGHT OF SAID MEDIUM, THE CHLORIDE CONTENT BEIN AT LEAST 1.8% BASED ON THE WEIGHT OF SAID MEDIUM, THE SULFATE CONTENT BEING AT LEAST 6.5% BASED ON THE WEIGHT OF SAID MEDIUM AND THE ALKALI METAL CONTENT BEING AT LEAST 1.2% BASED ON THE WEIGHT OF SAID MEDIUM WHEN ONLY SODIUM IS PRESENT, AT LEAST 2.0% WHEN ONLY POTASSIUM IS PRESENT AND WHEN BOTH SODIUM AND POTASSIUM ARE PRESENT, THE CONCENTRATION OF EACH BEING SUCH THAT THE SUM OF THE PERCENT OF SODIUM DIVIDED BY 1.2 AND THE PERCENT OF POTASSIUM DIVIDED BY 2.0 IS AT LEAST ONE, THE TOTAL SALTS CONTENT OF SAID DIGESTION MEDIUM BEING FROM 18 TO 50% BASED ON THE WEIGHT OF SAID MEDIUM, SAID DIGESTION MEDIUM CONTANING NO MORE THAN 25%, BASED ON THE TOTAL SALT CONTENT, OF SALTS SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM CHLORIDE, ZINC CHLORIDE AND MIXTURES THEREOF, EXTRACTING LEVULINIC ACID FROM SAID DIGESTION MEDIUM WITH AN ORGANIC SOLVENT FOR SAID LEVULINIC ACID WHICH IS SUBSTANTIALLY IMMISCIBLE WITH SAID MEDIUM, AND RECOVERING LEVULINIC ACID FROM SAID ORGANIC SOLVENT.