Process for the two-stage composition of the hemicelluloses of xylane-containing natural products for the purpose of obtaining xylose

DETAILED DESCRIPTION What is claimed is: 1.
In a process for the two-stage decomposition of the hemicelluloses of xylane-containing natural products for the purpose of obtaining xylose solutions, wherein the starting material is treated with an alkali hydroxide solution in the first stage and the obtained residue is subjected in the second stage to a dilute acid treatment, the improvement wherein the treated material is moved continuously in both stages in successive reactors by conveyor devices with different conveying performances, while (a) in the first stage the starting material is brought into contact with an alkali hydroxide solution and the residue conveyed into a subsequent extraction zone is extracted with an extraction liquid, and (b) in a second stage the extraction residue of the first stage is brought into contact with dilute acid and the residue conveyed into a subsequent extraction zone is extracted with another extraction liquid and wherein in at least one of the alkali or the acid treatment, the starting material or the residue is preheated with steam to a temperature of about 100.
degree.
to 150.
degree.
C.
and suddenly the alkali hydroxide solution, or the dilute acid, or one of the extraction liquids colder by about 10.
degree.
to 60.
degree.
C.
is added.
2.
A process according to claim 1 wherein the extraction in at least one of stages (a) or (b) is carried out in counter-current.
3.
A process according to claim 1 wherein the alkali treatment in stage (a) is carried out at pressures of from atmospheric pressure to 3 bar and the acid treatment in stage (b) is carried out at pressures corresponding to temperatures of from 100 to 150.
degree.
C.
4.
A process according to claim 1 wherein in stage (a) an approximate 0.
05 to 0.
5 molar alkali hydroxide solution is used.
5.
A process according to claim 1 wherein the dilute acid treatment in stage (b) is carried out with the acid quantity being dimensioned so that it is just taken up by the solid extraction residue of stage (a).
6