低浓度VOCs光解-液相光催化氧化协同效应及机制研究

It is difficult to reduce low-concentrated VOCs during air pollution control in China. To improve the photocatalytic oxidation (PCO) activity towards VOCs degradation and avoid its deactivation, a novel process of aqueous PCO combined with photolysis pretreatment is proposed in this study. The combined process is used to oxidize benzene, a typical VOCs. Mesoporous TiO2 modified by transition metals is well designed and prepared. Its PCO activity and performance of ozone utilization for benzene degradation are evaluated. The catalytic structure-function relationship is established to clarify the key structural parameters. The synergistic effect between photolysis and aqueous PCO on benzene oxidation is intensively studied and its mechanism is illustrated. The impact of operating parameters is investigated to find out the key factors responsible for the increased VOCs removal. Based on these results, the kinetics models for VOCs oxidation in this process are proposed. In addition, the test on the durability and suitability of the process is carried out. Eventually, a novel simple method will be successfully developed for the efficient and stable removal of low-concentrated VOCs. It can greatly improve PCO activity and stability. The results can also provide theoretical and experimental basis for the application of the developed method.

低浓度VOCs是我国当前大气污染治理的难点。针对光催化氧化VOCs过程催化剂失活、效率低等科学问题，本项目拟发展一种光解-液相光催化氧化新方法。以苯为模型VOCs，调控制备过渡金属改性介孔TiO2功能催化剂，考察其液相光催化氧化活性及有效利用光解副产物臭氧性能，建立催化剂构效关系，明确关键的结构参数。研究VOCs降解过程中气相光解与液相光催化氧化的协同效应，阐明VOCs高效稳定净化的作用机制。考察反应工艺参数对VOCs协同净化性能的影响规律，明确其核心控制因素，建立低浓度VOCs降解动力学模型，研究该体系在不同种类VOCs和工况条件下的适应性与持久性。该研究为改善VOCs光催化氧化性能提供简单有效途径，能形成一种高效稳定的低浓度VOCs净化新方法，并为实现其应用提供理论和理论依据。

低浓度VOCs是我国当前大气污染治理的难点。针对传统气固光催化氧化VOCs过程中催化剂易失活、效率低等关键技术问题，本项目提出了一种光解-液相光催化氧化的新方法。实验中以甲苯为目标污染物，调控制备了介孔TiO2、F-TiO2、Mn/TiO2和P25/ZSM-5等催化剂，考察了这些催化剂在不同体系中的光催化氧化性能，探索了催化剂的构效关系。以P25为催化剂研究了体系中在光解与液相光催化氧化的协同效应，通过中间产物分析明确了甲苯在体系中的氧化降解路径。实验发现，这一体系中存在着协同效应，光解先将污染物氧化降解，氧化后的中间产物在液相光催化体系中更容易被进一步氧化降解，大大提高了污染物的降解性能。同时还能利用液相的湍动，减少中间产物在催化剂表面的累积，有效避免催化剂失活。通过负载Mn及ZSM-5负载来强化P25在光解-液相光催化氧化体系中对甲苯的氧化降解性能，发现负载Mn对VUV/P25体系氧化降解甲苯性能正向影响不大或存在负面影响；ZSM-5用作载体时对P25应用于光解-液相光催化氧化降解气态甲苯有强化作用，不仅提升了甲苯去除效果，还降低了O3副产物出口浓度。但O3副产物在该体系中无法被完全消除，可在后处理中实现。以P25/ZSM-5为催化剂考察了制备工艺参数和关键反应参数对甲苯氧化降解的影响规律，明确了该体系的适应性与持久性，能够高效持续地氧化降解VOCs。本项目研究提出了一种高效稳定的低浓度VOCs净化新方法，为改善大气质量提供有力科学和技术支撑。