燃煤烟气硫硝碳在改性Cu-MOFs衍生金属氧化物上的吸附行为及协同脱除机制的研究

SO2，NO and CO2 are the main pollutants of coal-fired flue gas, and do harm to the environment. It is the hot topic and great challenge that how to develop the flue gas clean technology from single pollutant control to multi pollutants control. Metal-organic frameworks materials (MOFs) have been extensively paid attention to due to their advantages including high specific surface area, structural diversity and more metal active sites. In this study, Cu-MOF-based derivatives were successfully fabricated through solid-state thermolysis under suitable calcination temperature and air. The microscopic pore structure, surface acid-base activity and lattice transformation process of the prepared metal oxides were investigated comprehensively, and the physical and chemical processes such as adsorption, catalytic reaction and desorption of SO2, NO and CO2 were clearly identified. The adsorptive behavior for single pollutant and multi pollutants on candidate adsorbents will be investigated and compared. In situ Fourier transform infrared spectroscopy and density functional theory based computations will be conducted to research the collaborate and competitive effects between multi pollutants and candidate adsorbents, and reveal the reaction mechanism. The research results will provide important scientific information for the control technology of coal-fired flue gas contaminants in related industries. This project places a very high value on the engineering application.

燃煤烟气污染物SO2、NO和CO2对环境造成了极大的危害。如何将烟气净化过程从单一污染物控制扩展到多种污染物协同脱除是环境科学与技术领域的研究热点。本项目以铜基MOFs（Cu-TDPAT和Cu-BTC）为基础，通过表面沉积过渡金属Mn和稀有金属Ce引入更丰富的催化活性位点，经过热处理构筑具有特殊结构且热稳定性优良的复合金属氧化物，使其具有对SO2、NO和CO2的高效协同脱除能力；考察吸附剂的微观孔隙结构、表面酸碱活性及晶格变换过程，明确对污染物分子的吸附-催化反应-解吸的物理化学过程；阐明对污染物单一组分吸附和多组分共吸附的性能；利用原位时间分辨红外光谱等实验手段和理论计算（DFT）有机结合，跟踪观测并模拟SO2、NO和CO2脱除过程中的中间物种，分析它们吸附、分解及迁移的瞬态过程，揭示竞争协同效应机制。本课题将为相关行业燃煤烟气污染物的控制技术和工程化应用提供重要的科学信息。

煤炭直接燃烧会产生大量SO2、NO、CO2、CO，严重威胁生态环境和人类健康。如何将烟气净化过程从单一污染物控制扩展到多种污染物协同脱除是环境科学与技术领域的研究热点。金属有机骨架材料因其显著的结构优势为同时吸附脱除硫硝碳提供了新的思路，具有可观的竞争优势和应用前景。本项目采用溶剂热法制备一系列Cu-BTC和MOF-74吸附剂，测定其对硫硝碳的单吸附、共吸附和再生性能；通过多种表征方式分析吸附剂的物理化学性质；利用原位红外技术和DFT理论探究硫硝碳分子在吸附剂表面的吸附机制，揭示吸附机理。单金属MOF-74对SO2、NO和CO同时脱除有一定效果，但是其饱和吸附量和吸附选择性都有待提高；双金属Ni0.83Mg0.17-MOF-74的共吸附性能最佳，高温条件抑制其对气体的吸附能力，O2和H2O促进气体的单一吸附能力，共吸附系统促进SO2和CO的吸附而抑制NO的吸附。Thomas模型和Yoon-Nelson模型都能够直观的反映SO2、NO和CO在MOF-74上的吸附过程，多组分气体的拟合结果表明MOF-74吸附床对不同组分气体污染物出口浓度与吸附时间存在固定的关联，对工业放大及生产应用具有实际的指导意义。原位红外结果表明SO2和NO在Ni0.83Mg0.17-MOF-74表面表现活跃，发生较强的化学吸附，CO则以物理吸附为主；O2和H2O的引入改变SO2、NO和CO在吸附剂表面的吸附物种从而促进共吸附；SO2和NO在Ni0.83Mg0.17-MOF-74上相互作用形成中间体[SO3NOx]，进而分解为SOx和NOx。基于DFT研究表明，Mg-MOF-74单独吸附各分子时，裸露的金属位是气体吸附的主要位点，各种气体均以端位形式吸附并被活化，其中SO2的O端吸附比S端吸附更容易发生，NO的N端吸附与O端吸附均可以发生，CO的C端吸附与O端吸附都较难发生。金属位与气体之间的相互作用导致S-O键、N-O键、C-O键显著减弱，促进了气体分子的分裂。吸附剂向气体分子转移的电荷与气体分子键的延长成正比。多分子共吸附时SO2和NO之间的电荷转移增加了共吸附体系的稳定性，CO促进了预吸附SO2的分子结构变化和得电子能力，CO对预吸附NO的竞争吸附能力较弱。SO2&NO&CO同时吸附时，吸附剂对各种分子的吸附作用减弱。本项目将为相关行业燃煤烟气的控制技术和工程化应用提供重要科学信息。