乙醇法制浆木素沉淀现象及机理

Study on the Phenomenon and Mechanism of Lignin Precipitation during Ethanol Pulping

研究了快速冷却洗涤法乙醇浆纤维表面木素的形貌学特征，定性比较了洗涤过程中纤维表面术素含量的变化，阐明了乙醇法制浆木素沉淀的现象与机理，揭示了乙醇浆易于漂白的原因。SEM分析结果显示，木素颗粒主要分布在纤维表面，通过对木素颗粒的形貌学特征观察发现，分布在纤维表面的木素颗粒呈球形，粒径分布在0．5～2．0μm，洗涤过程中木素颗粒的数量和大小逐渐减少减小，但是经历四段洗涤的乙醇浆纤维上仍然清晰町见木素颗粒。木素乙醇溶液的乙醇浓度低于42％或者温度降低时，木素发生沉淀，沉淀／吸附在纤维表面，XPS分析结果证明，纤维表面存在木素。结果表明，蒸煮和洗涤过程中溶解木素在纤维上的二次吸附和沉淀是快速冷却洗涤法乙醇浆忙伯值高的原因，沉淀小素具有与溶解木素相似的性质。乙醇浆易于漂白。

Morphological character of lignin particles on the fiber surface was observed and the contents of lignin on the fiber surface in different washing stage were also compared qualitatively. The phenomenon and mechanism of lignin precipitation on the fibers were elucidated, and the reason for easy bleaching of the ethanol pulp was revealed. Results of SEM and XPS showed that a great deal of lignin particles are obvious on the fibers after pulping and each washing stage in a four-stage washing sequence. Lignin precipitation occurs when the ethanol concentration of a lignin ethanol solution reduces or the temperature drops in the pulp washing process. It was concluded that high kappa number of ethanol pulp is mainly due to the precipitation of the dissolved lignin from the pulping liquor, which accounts for the easy bleach- ing of the ethanol pulp.