纳米铈基复合氧化物孔材料催化降解氯代有机污染物的性能及机理研究

The exhaust containing chlorinated organic volatile compounds (CVOC) presentspersistent environmental pollution. Catalytic elimination of organic chlorinatedhydrocarbons is most economical and reliable, because of the conversion at lowtemperature and high selectivity. In this proposal, solvent and water thermal synthesis,surfactant self-assembly will be used for preparing CeO2 nano-materials with differentmorphologies and lattice faces. The effect of nano-CeO2 mricrostructure on the abilityto adsorb and activate oxygen, adsorption strength of Cl species and hydrolysis will beinvestigated. Through the introduction of Ru and some transitional metal oxides, the Cebasematerials can be modified with several levers so as to create the combination ofseveral active sites for different reactions, realize the removal of Cl species from thecatalyst surface, and exchange Cl species with active oxygen. Therefore, a strong adsorption of Cl species produced during CVOC decomposition resulting in the deactivation whish is serious question can be overcome. At the same time, the activities for CVOC oxidation at low temperature and HCl oxidation will be promoted and the activity for chlorination of CVOC will be inhibited. As a result, the chlorination may not proceed over Ce-based catalysts even in the presence of a small amount of Cl2. CVOC can be converted into HCl, H2O, and CO2 with high selectivity. And the system for stable catalytic elimination of CVOC at low temperature is established. If the project in proposal is successful, new method and think for catalytic elimination of CVOC at low temperature is provided for our country. And this project can obtain patents completely.

含氯代有机污染物（CVOCs）的削减技术及控制原理研究是目前环境化学领域的研究热点之一。本研究拟针对目前降解CVOCs催化剂性能上的缺陷，设计合成出兼具"形貌效应"、"孔结构效应"及"掺杂效应"的纳米Ce基复合氧化物孔材料，通过对该材料表面组成、形貌、结构的调控，优化出低温高活性、稳定性好、降解产物安全的新型高效催化剂。综合利用多种分析技术，特别是原位动态表征技术，获取反应过程中的活性中心、电子转移、中间物种和反应过渡态等重要信息；探索合成条件与形貌、孔结构形成及高度暴露活性晶面之间的规律，系统研究催化性能与催化剂的组成、晶面、孔结构之间的依赖关系；从微观层次深入研究界面催化的反应机理。本课题的研究将为CVOCs污染物的控制技术提供一种新的方法和理论依据。

Cl-VOCs是一类比较常见的大气污染物，对生态环境和人类健康有重要的危害性，催化燃烧法是降解该污染物的最有效技术之一。针对项目研究的关键科学问题，通过系统研究，得到了以下规律性的认识：1. 与CeO2相比，CeO2-MOx对TCE的催化降解活性均明显提高，降解活性顺序为4Ce1Cu＞4Ce1Cr＞4Ce1Mn＞4Ce1Fe＞4Ce1Co＞4Ce1Ni＞4Ce1V＞CeO2。CeO2-CrOx表现出优异的深度氧化性能，几乎没有产生副产物C2Cl4，这与该复合氧化物中CeO2和CrOx之间的强相互作用，导致大量具有强氧化能力的Cr6+物种的产生有关。CeO2-CrOx对其它不同分子结构的Cl-VOCs也表现出优异的深度氧化性能。 2. 分子筛复合改性的(Ce,Cr)xO2/zeolite催化剂对DCE的降解活性顺序为(Ce,Cr)xO2/HZSM–5＞(Ce,Cr)xO2/H–BETA＞(Ce,Cr)xO2/H–USY＞(Ce,Cr)xO2/H–MOR，明显高于单组分催化剂，且(Ce,Cr)xO2/zeolite表面生成副产物C2H3Cl的浓度也明显减少，酸性、氧化性和孔道结构之间的协同催化效应显著提高了(Ce,Cr)xO2/zeolite对Cl-VOCs的催化降解性能。3. 不同酸性氧化物MOy复合改性的(Ce,Cr)xO2/MOy催化剂对Cl-VOCs的降解活性顺序为(Ce,Cr)xO2/Nb2O5＞(Ce,Cr)xO2/TiO2＞(Ce,Cr)xO2/WO3＞(Ce,Cr)xO2/MoO3＞(Ce,Cr)xO2/La2O3＞(Ce,Cr)xO2/V2O5。MOy（Nb2O5、TiO2和WO3）与 (Ce,Cr)xO2之间存在明显的协同催化效应，明显促进了该复合催化剂对DCE的催化降解性能。4. 研究了反应体系中水和苯的存在对CeO2-CrOx、(Ce,Cr)xO2/HZSM–5及CeO2-CrOx-Nb2O复合催化剂催化降解性能的影响、催化剂的耐受性以及催化剂的失活原因。5. 合成了具有不同形貌的CeO2-MnOx复合氧化物，暴露 {110} 和 {100} 晶面的rod-CeO2-MnOx剂具有最好的催化性能，这与它具有较多的氧空穴以及表面活性氧物种的流动性增加有关；富锰可改善催化剂的氧化还原性能以及对CB的催化降解活性，且几乎没有多氯苯或聚氯苯等副产物产生。