Electrochemical Mediator-Based Delignification Mediator Properties and Process Performance
Electrochemical Mediator-Based Delignification Mediator Properties and Process Performance
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DOI：
10.1149/1.1622407
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发表时间：
2003-12
影响因子：
3.9
通讯作者：
M. Mickel;Hee‐Cheol Kim;S. Noll;N. Hampp
中科院分区：
文献类型：
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作者：
M. Mickel;Hee‐Cheol Kim;S. Noll;N. Hampp
常用的纸浆漂白工艺大多采用含氯药剂与氧漂白相结合。完全无氯漂白工艺可提供高纸浆质量，但工艺成本较高。我们开发了一种环保的基于电化学介体（EMB）的脱木质素工艺，该工艺的化学成本低廉，因为介体在该工艺中被回收。在电化学氧化时，介体紫尿酸形成寿命约为几十分钟的自由基，其氧化木质素。在此步骤中，介体被回收并通过过滤容易地从纸浆中分离。由于紫脲酸自由基在木质素氧化过程中相对于纤维素具有非常高的选择性，因此脱木质素纸浆的质量非常出色。由于水中的自由基寿命延长，电解槽中的外部自由基生成能够集成到现有装置中。在实验室规模的演示中，对 EMB 过程进行了建模。据观察，由于过程中的二次反应，介体会损失。这比中介本身的价格更能决定总成本。对不同的副产物进行了定量分析并确定了它们的来源。这将进一步优化 EMB 流程。
Commonly used pulp bleaching processes mostly employ chlorine-containing agents combined with oxygen bleaching. Totally chlorine-free bleaching processes deliver high pulp qualities, but the processes are more expensive. We have developed an environmentally friendly electrochemical mediator-based (EMB) delignification process which is designed to be cheap in chemical costs because the mediator is recycled in the process. Upon electrochemical oxidation the mediator violuric acid forms a radical with a lifetime on the order of several tens of minutes which oxidizes the lignin. During this step the mediator is recovered and easily separated from the pulp by filtration. The quality of the delignified pulp is remarkable due to the very high selectivity of the violuric acid radical in the oxidation of lignin over cellulose. Due to the extended radical lifetime in water the external radical generation in an electrolyzer enables the integration into existing setups. In a lab-scale demonstrator the EMB process was modeled. It was observed that there is a loss of mediator due to secondary reactions in the process. This much more determines the total costs than the price for the mediator itself. The different side products have been quantitatively analyzed and their origins have been identified. This will enable a further optimization of the EMB process.