活性焦内SO3/H2SO4极性致迁移及官能团定向分布机制研究

The mechanism of S element conversion, migration and occurrence in activated coke interior is the foundation for regenerative utilization technology of SO2 pollutants caused by coal combustion. The current existing mechanism lack the complete understanding in: the function pathway and morphology of water molecules; the mechanism of sulfuric acid generation and migration. Therefore, the project proposed (1) a new mechanism called "SO3/H2SO4 Polarity creating migration". It is considered that the polar functional groups, distributing in mesopores of activated coke play a significant role in the SO2 removal process. Polar functional groups act as the adsorption centers of polar molecules. Relying on polar effect or hydration, the byproduct SO3 or H2SO4 forming in micropores are able to migrate out of micropores and into mesopores or macropores in the form of liquid; (2) "functional groups oriented distribution mechanism" in activated coke interior. Basic functional groups growing in micropores can make microporous space much hydrophobic. It can promote the SO2 adsorption and oxidation, as well as improving diffusion and transport velocity of water molecules within the micropores. The improving of water molecules transport velocity undoubtedly promotes the byproducts hydration process and the precipitation process in the form of hydration molecules. Reasonable quantities of polar functional groups distributing in mesopores and macropores, especially distributing in the adjacent of micropores and mesopores can strengthen the migration of SO3/H2SO4 from micropores to mesopores. Consequently, sulfur content and the SO2 adsorption rate are largely increased. The implementation of this project will provide important theoretic guide for enhancing activated coke SO2 removal capacity, proposing innovative regeneration technologies and carrying on new environment functional materials research.

S元素在活性焦内的转化、迁移及赋存机制是燃煤SO2污染物资源化利用技术的基础。现有脱硫机理对H2O作用形态及过程；酸性官能团作用机制；硫酸形成及迁移机制缺乏完整认识。为此：（1）提出了活性焦内SO3/H2SO4的极性致迁移机制，认为在活性焦脱硫过程中，分布在中孔内的极性官能团具有重要作用，可成为极性分子的吸附中心，并通过极性作用或水合作用使副产物迁移出微孔并以液相赋存在中孔和大孔内；（2）提出了活性焦内官能团的定向分布机制，使微孔内富含碱性官能团、微孔空间具有一定的疏水性。既有利于SO2的催化氧化作用，又可提高水分子在微孔内的扩散和输运速度，便于副产物水合携出；使中孔及大孔内分布适量的极性官能团，特别是分布在中孔和微孔相邻处，用以强化SO3/H2SO4向中孔的迁移，从而可望同时提高活性焦的硫容和吸附速度。本项目可为提高活性焦脱硫性能、创新再生工艺和开展新型环境功能材料研究提供理论指导。

S元素在活性焦内的吸附、转化、迁移及赋存机制是改善活性焦性能、开发新型再生工艺的理论基础。本项目基于对活性焦脱硫研究中H2O 作用机制以及硫酸形成迁移机制的分析，提出了活性焦内SO3/H2SO4极性致迁移机制以及与之匹配的官能团定向分布机制，围绕关键科学问题“活性焦内SO3/H2SO4 的极性致迁移机制”、“活性焦内官能团的定向分布机制”，主要取得以下成果：.（1）剥离物理、化学结构的耦合影响，揭示污染物分子吸附转化的强化机制。从实验角度基于分子自组装原理制备了孔隙及表面化学结构定量可控的多孔碳材料，解耦了孔隙和官能团对SO2分子吸附的影响。从理论计算角度，采用密度泛函（DFT）量子化学计算揭示了含氧、含氮等活性位对SO2的吸附及催化氧化作用机制。基于上述研究，获得了活性焦分级孔隙内含硫物种极性致迁移机制：目标分子吸附及转化反应发生在微孔中；分布在中孔的极性官能团形成SO3/H2SO4迁移的动力，释放微孔空间及活性位，增强SO2脱除能力。.（2）基于表面官能团与孔隙间依存关系，提出官能团极性定向分布的活性焦制备方法。研究了单一及组合气体活化过程无规则碳、微晶结构、孔隙以及官能团的协同演变机制，提出了“微孔发达、中孔通达”的活性焦制备方法；引入煤结构预处理以及活化后活性焦的后处理工艺提出了“微孔中发展碱性官能团、中大孔中构筑极性官能团”的活性焦制备方法。该方法为匹配极性致迁移机制的高性能脱硫活性焦制备提供技术指导。.（3）发展了基于微波极性选择作用的活性焦快速再生及含硫副产物回收方法。通过热再生过程中活性焦质量损失与脱硫性能的联分析，揭示了“烧失反应”的微观本质。提出了采用水蒸气吹扫和洗脱的复合再生工艺，可延长活性焦循环使用寿命。基于微波均匀快速的场作用特征，发展了微波再生方法，显著降低了活性焦再生时间及再生损耗；微波的极性选择性及内部热点效应，一方面能够使硫酸分子直接解吸；另一方面能够实现含硫物种的还原及单质硫的产生，提高了副产物的资源化利用价值。