PROCESS FOR TREATING CELLULOSIC MATERIALS WITH GASEOUS HYDROFLUORIC ACID

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).