Process for obtaining xylitol from natural products containing xylan

Claim 2

Process for preparing xylitol which consists essentially of: a. acid hydrolyzing a xylan containing material to produce a solution containing xylose and acetic acid; b. recovering unhydrolyzed organic residues by filtration. c. removing hydrolyzing acid; d. removing most, if any, proteins, tannins and pectins from said solution by contacting the same with an adsorbent; e. evaporating said purified solution under vacuum to a viscous, virtually water-free syrup, thereby removing substantially all of the acetic acid in said solution; f. diluting said syrup with water and adjusting the pH of the resulting diluted solution to a value of from about 6.5 to about 7.5; g. hydrogenating xylose in said diluted solution in the presence of a Raney nickel hydrogenation catalyst under pressure to produce a solution containing xylose; and h. recovering xylitol from the xylitol containing solution.

Claim 3

Process for preparing xylitol which consists essentially of: a. acid hydrolyzing a xylan containing material to produce a solution containing xylose and acetic acid; b. removing unhydrolyzed organic residues by filtration; c. removing hydrolyzing acid; d. removing most, if any, proteins, tannins and pectins from said solution by contacting the same with an adsorbent; e. evaporating said purified solution at a temperature not in excess of 70°C under vacuum to a viscous, virtually water-free syrup thereby removing substantially all of the acetic acid in said solution; f. diluting said syrup with water and adjusting the pH of the resultant diluted solution to a value of from about 6.5 to about 7.5; g. without any acid removal step performed on said syrup or the resultant diluted syrup, hydrogenating the xylose in said diluted solution in the presence of a Raney nickel hydrogenation catalyst under pressure to produce a solution containing xylitol; and h. recovering xylitol from the xylitol containing solution.

Claim 4

Process for preparing xylitol which consists essentially of: a. acid hydrolyzing a xylan containing material to produce a solution containing xylose and acetic acid; b. removing unhydrolyzed organic residues by filtration; c. removing hydrolyzing acid; d. removing most, if any, proteins, tannins and pectins from said solution by contacting the same with an adsorbent; e. evaporating said purified solution at a temperature not in excess of 70°C under vacuum to a viscous, virtually water-free syrup thereby removing substantially all of the acetic acid in said solution; f. diluting said syrup with water and adjusting the pH of the resultant diluted solution to a value of from about 6.5 to about 7.5; g. without any acid removal step performed on said syrup or the resultant diluted syrup, hydrogenating the xylose in said diluted solution in the presence of a Raney nickel hydrogenation catalyst under pressure to produce a solution containing xylitol; and h. recovering xylitol from the xylitol containing solution.

Claim 5

Process of claim 1, wherein one or more oxides or carbonates of calcium or magnesium are used to adjust the pH of the xylose containing solution.

Claim 6

Process of claim 1 wherein the hydrogenation is carried out at about 15 to about 150 atmospheres gauge pressure and about 70° to 150°C.

Claim 7

Process of claim 1 wherein a purification with active charcoal is carried out before and after the hydrogenation.

Claim 8

Process of claim 1 wherein residual ions are removed by cation or anion exchangers after the hydrogenation.

Claim 9

Process of claim 1 wherein the xylitol containing solution is concentrated by evaporation to a syrupy consistency and the syrup diluted with ethanol, the weight ratio between ethanol and total water amounting to approximately 4 to 5 : 1.