PROCESS FOR THE DELIGNIFICATION OF CELLULOSE CONTAINING RAW MATERIALS

摘要

In the disclosed three step process for the delignification of cellulose containing raw material, the cellulose extraction is achieved by using an extraction solution of concentrated acetic acid at elevated temperature and pressures. The obtained acetic acid wet cellulose is treated in a second step with the aforementionned extraction solution and an added amount of nitric acid with a subsequent washing or extraction with water or with the extraction solution. In a third process step, the obtained acetic acid wet cellulose is treated with an ozone containing gas. The use of halogenous additives or bleaching agents is no longer required for this process. The process provides for a residual lignin content of less than 1% per weight, even if the yielded cellulose was extracted from coniferous wood which is hard to delignify.