Hoechst Aktiengesellschaft

Benckiser-knapsack Gmbh

Theodor Riehm

Rudiger Erckel

Raimund Franz

Rolf Woernle

Theodor Auel

Wilhelm Spatz

The semi-continuous process according to the invention for hydrolyzing cellulose-containing material (substrate) with gaseous hydrogen fluoride comprises sorption and subsequent desorption of HF in a total of n steps. The substrate is divided into n batches in n reactors (1a, 1b, 1c, . . . ); each batch passes through the n process steps in one reactor (1a, . . . ). Initially, sorption is carried out in the first to the (n/2)th step by the action of HF-inert gas mixtures, having an HF concentration which increases from sorption step to sorption step, at a temperature above the boiling point of HF. Subsequently, desorption is brought about in the ((n/2)+1)th to nth step by treating with heated HF-inert gas mixtures having an HF concentration which decreases from desorption step to desorption step; n is an even number from 4 to 12 and the n steps each take place in the same time segments (periods). The sequence of steps is displaced by one period from each batch to the next batch. During each period, the batch in the first step is connected to the batch in the last step and the batch in the second step with the batch in the penultimate step and the batch in the (n/2)th step with the batch in the ((n/2)+1)th step, by HF-inert gas circulations.

Process for hydrolyzing cellulose-containing material with gaseous

A continuous process for hydrolyzing cellulose-containing material (substrate) with gaseous hydrogen fluoride, HF is sorbed by the substrate at a temperature above its boiling point in n sorption steps and thereafter the sorbed HF is removed from the substrate by heating in n desorption steps. The number n of sorption steps and of desorption steps is identical and the reaction steps mentioned each occur in reactors which are separated from one another in a gas-tight manner. After introduction into the first sorption reactor (1a), the substrate passes consecutively through gas-tight valves into the second (1a) . . . nth sorption reactor and from the latter, optionally via a hold-up reactor (2) into the first, second, . . . nth desorption reactor (3a) and is removed from the nth desorption reactor (3a). The streams of HF gas, which contain an inert carrier gas in addition to HF, are circulated between the first (1a) or second (1b) or . . . (n-1)th or nth sorption reactor and the nth (3a) or (n-1)th (3b) . . . or second or first desorption reactor respectively.

The continuous process for hydrolyzing cellulose-containing material (substrate) is carried out by sorption of gaseous HF in a sorption reaction (1) and subsequent desorption in n steps, which are carried out in n reactors which are separated from one another in a gas-tight manner. The substrate is introduced via a gas-tight valve into the sorption reactor (1), passes through this and then reaches consecutively, through gas-tight valves, a hold-up reactor (2) and the first (3c), second (3b), . . . nth desporption reactor, from which it is then removed. The desorption is carried out in each case by the action of one of the n inert gas streams on the substrate at different temperatures, the particular inert gas stream being enriched with the HF being liberated during desorption. The gas streams, which are enriched to different extents with HF, are allowed to act on the substrate in the sorption reactor (1) in such a manner that the gas streams of low HF concentration act on a substrate having a zero or low concentration of HF and thereafter the gas streams of higher HF concentration act on substrate having higher HF concentration. The total gas stream (8a) produced from the individual gas streams leaves, after completion of sorption, the sorption reactor (1) largely freed of HF and is either conveyed to the desorption steps after dividing up into individual gas streams or it initially passes through the last desorption step (3a) and is thereafter divided up and passed to the other desorption steps in order, after passing through the latter, to be returned to the sorption reactor (1).

A process for producing polyalcohols such as xylite from deciduous wood wherein the wood is hydrolyzed with dilute mineral acid to produce a sugar solution which is deionized and decolorized in an ion exchanger and hydrogenated to produce a polyalcohol solution which is also decolorized and deionized by ion exchange and from which pure polyalcohol is thereafter separated by crystallization, further comprising dispensing with neutralization of the acid in the sugar solution after hydrolysis, deionizing and decolorizing both the sugar solution and the polyalcohol solution in the same ion exchanger, eluting acetic acid taken up by the ion exchanger from the polyalcohol solution and displacing polyalcohol solution from the exchanger with the acid containing sugar solution, washing the ion exchanger with water only after ion exchange of the sugar solution, removing the bulk of the acetic acid from the sugar solution by evaporating the sugar solution to a higher concentration than the concentration customarily utilized for hydrogenation, and rediluting the sugar solution prior to hydrogenation with the exchanger wash water.

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Heidelberg, Germany

Theodor Riehm