氟掺杂铈钛复合催化剂催化臭氧化烟气脱硝过程机制研究

Focusing on the low-temperature flue gas emitted from industrial furnaces, sintering machine and catalytic cracking unit, the hydroxyl radicals from catalytic ozonation was applied to react with NO into HNO3, achieving low-cost and high-efficiency NO removal. Breakthrough existing research ideas of catalytic ozonation catalysts by way of enhancing NO removal by promoting the production of hydroxyl radicals through increasing oxygen vacancies, the fluoride doped cerium-titanium composite catalysts have been prepared. Our previous studies have revealed that the amount of oxygen vacancies over catalyst surface was promoted by fluoride doping. The production of hydroxyl radicals and NO removal were apparently enhanced. To further this investigation, we propose here to state the formation mechanisms of oxygen vacancies over fluoride doped catalysts, the formation of hydroxyl radicals by the reaction among ozone, water and oxygen vacancies, the properties of diffusion-reaction coupling of hydroxyl radicals and the reaction mechanisms between NO and hydroxyl radicals into HNO3 by photoluminescence, electron paramagnetic resonance and in-situ infrared spectrum, achieving the preparation method of catalytic ozonation catalysts, promoting the researches of new flue gas denitrification with low costs, high efficiency and wide applications.

本项目针对工业炉窑、烧结机、催化裂化装置等排烟温度偏低的烟气，采用臭氧催化转化为羟基自由基，然后与NO反应生成HNO3的方法，实现低成本、高效NO的脱除。突破现有臭氧转化催化剂的研究思路，以增加氧空位强化羟基自由基生成提高催化剂活性为目的，制备氟掺杂铈钛复合催化剂。前期结果表明，氟掺杂铈钛复合催化剂表面呈现更多的氧空位，羟基自由基的生成和NO的脱除明显提高。在此基础上，借助光致发光光谱、电子顺磁共振及原位红外等表征技术，探明氟掺杂铈钛复合催化剂氧空位的形成机制，臭氧和水与氧空位作用生成羟基自由基的机理，羟基自由基的扩散-反应耦合特性，以及羟基自由基与NO反应过程中的作用及消亡等演化规律，获得催化臭氧化催化剂的制备方法，推进低成本、高效率、适用面广的烟气脱硝新工艺技术研发。

针对氟掺杂铈钛复合催化剂催化臭氧化烟气脱硝过程机制，研究了氟掺杂脱硝催化剂的催化活性，明确了脱硝的主要活性物质是羟基自由基；对催化剂的结构特性进行了研究，确定了氟掺杂铈钛复合催化剂中氟掺杂的位点是-Vo-Ce3+-F--，明晰了氟掺杂改善了表面氧空位和表面羟基生成，从而促进羟基自由基生成的机制；研究了表面羟基的O-H键性能、电子传递特性以及总流量/旁路气流量和预热温度，厘清了羟基自由基中O-H键弱化，从而导致其从催化剂表面脱附的机制；开展了羟基自由基的扩散-反应耦合特性研究，明确了羟基自由基的扩散-反应耦合时间为0.428 s；研究了NO与∙OH反应转化为HNO3的过程机制及烟气中SO2对该反应过程的影响，确定了羟基自由基与NO作用生成HNO2，其继续与羟基自由基作用生成HNO3的机理，以及SO2对该反应无影响。