锰基纳微反应器的结构设计及其催化氧化VOCs的体系构建与机制研究

The volatile organic compounds (VOCs) are one of major environmental pollutants, which are hazardous to the environment and human health. The development of catalyst with high-catalytic activity for catalytic oxidation of VOCs with ozone is an important research area. However, the catalytic oxidation with ozone was limited in VOCs treatment application due to the decrease and inactivation of active sites on the surface of ozone catalyst, easy aggregation properties of catalysts, large steric hindrance, and the slow electron transfer in the oxidation process. The structure of layered MnO2/layered graphene can provide the higher space and BET area, which is beneficial to the synergistic effect on the catalytic oxidation of VOCs with ozone between MnO2 and graphene. Therefore, this project aims at fabrication of layered MnO2 and layered graphene composite (i.e. layer-structured MnO2/graphene hybrid composites) as nano/micro-reactor for catalytic oxidation with ozone, and investigating the feasibility and the optimal experimental conditions of layer-structured MnO2/graphene nano/micro-reactor with highly efficient performance for the catalytic oxidation of VOCs with ozone. In addition, we will study the relationship between the structure of nano/micro- reactor and catalytic activity, and the synergistic effect between MnO2 and graphene for the oxidation of VOCs with ozone. It is expected that these investigations will develop a high effective MnO2-graphene composites as a nano/micro-reactor for oxidation of VOCs with ozone, and enrich the fundamental theory not only for the efficient oxidation of VOCs with ozone but also for the environmental pollutant problems.

臭氧（O3）催化氧化是一项极具发展潜力的治理低浓度VOCs的技术之一。然而在臭氧催化过程中，臭氧催化剂表面活性位点的下降和失活、催化剂易团聚、以及空间位阻大不利于氧化过程中的电子迁移等缺点，制约了其在VOCs治理中的广泛应用。基于层状MnO2和层状石墨烯复合的二维间层结构有利于臭氧和VOCs在MnO2和石墨烯中的有效分配、以及减小空间位阻有助于电子迁移和产物的快速扩散，因此本项目主要研究以MnO2-石墨烯间层结构的构筑及其作为催化臭氧氧化纳微反应器为主要特征的催化臭氧氧化VOCs新方法以及以这一新方法为背景的基础理论和应用问题。通过在分子水平上构筑和调控间层结构和层间距离，研究纳微反应器的间层结构与催化VOCs特性之间的构效关系和协同效应；采用石英晶体微天平(QCM)等技术研究臭氧和VOCs在纳微反应器界面的分配行为；研究纳微反应器催化氧化VOCs的降解产物、降解机制以及环境风险。

本项目制备了以石墨烯为载体的层状二氧化锰负载型金属氧化物（MNS/GNS），并探索其高效去除甲硫醇的机理。通过改进型Hummer法制备了层状石墨烯，采用阴离子表面活性剂将石墨烯分散成稳定的胶体溶液，并与带有正电荷的层状二氧化锰通过静电自组装法复合，成功制备了以石墨烯为载体的层状二氧化锰负载型金属氧化物。通过EDS-Elemental Mapping表征计算出MNS/GNS中锰的负载率48.47 wt.%，X射线衍射谱图同时出现石墨烯与层状二氧化锰的特征峰，表明石墨烯与二氧化锰复合情况较好。SEM和BET结果表明，层状二氧化锰的嵌入，阻止了石墨烯层与层之间的复合，解决了催化剂易团聚、比表面积低的问题，因此MNS/GNS可以较好臭氧催化氧化CH3SH气体。对两种不同载体的催化剂MnO2/Al2O3和MNS/GNS进行了催化活性对比分析。结果表明由于MNS/GNS中的石墨烯良具有较高的比表面积和导电性能等特性，MNS/GNS其单位质量催化剂的去除能力与MnO2/Al2O3相比明显提高，MNS/GNS的催化性能有明显提高。此外，由于石墨烯的极性大和吸附能力强，可以将中间产物优先吸附至石墨烯，使得二氧化锰的活性位点持续与臭氧接触产生活性基团，阻止了催化剂的失活，因此层状MnO2/Graphene催化臭氧处理有机废气具有较高的实际应用价值。