| 摘要 |
Lignin contained in a cellulosic or lignocellulosic pulp product is removed by contacting the product with a gaseous medium containing ozone in the presence of a liquid agent which is a lower fatty acid, such a formic, acetic or propionic acid, having only a low solvent capacity for lignin; as a consequence of this treatment, lignin which is present in the product will be converted into a lignin derivative that has an increased sealability in the fatty acid and can be removed quantitatively by extraction from the lignocellulosic material. Purified pulp can thus be obtained with increased processing efficiency and without most pollution problems of prior art processing methods because the fatty acid used as the main constituent of the processing liquid in all stages of pulp production can be circulated counter-currently through the stages of the process with purification of the acid for recirculation only after its use in the digestion step where the normal starting materials of pulp production, i.e. wood or annual plants, are treated according to the acetosolve process at ambient pressure and temperatures of below 120.degree. to form a raw pulp product. |
