Co3-xMxO4尖晶石型复合氧化物的结构调变及催化氧化性能研究

Emission of volatile organic compounds (VOCs) is becoming a more and more prominent problem in China in recent years, which cause serious air pollution and pose great threat to people’s health and life, so the emission control and the degradation of VOCs are strongly required. Catalytic total oxidation of VOCs is considered as one of the most efficient ways for VOCs degradation and tricobalt tetraoxide (Co3O4) appears as a promising catalyst due to its low cost, high activity, and good resistance to chlorine poison. In this research, we attempt to develop a high-performance Co3-xMxO4 spinel mixed oxide by using layered double hydroxides (LDHs) as precursor, in which the doping metal ions (Mn+) are incorporated into the Co3O4 spinel lattice to replace part of tetrahedral Co2+ and/or octahedral Co3+ sites. One of our goals is to establish a facile method based on LDHs for the controlled synthesis of spinel mixed oxides. In this respect, LDHs are synthesized by co-precipitation, and then decomposed to form spinel mixed oxides. The influence of LDHs chemical composition, synthesis procedure, and thermal treatment conditions on the spinel formation would be studied in detail. It is expected that a spinel mixed oxide with high specific surface area, good thermal stability, uniform morphology and size, and controllable structure and composition can be obtained. A detailed characterization of the prepared catalysts would be conducted to get information about the nano/micro-structure and physicochemical properties of the spinel mixed oxides such as distribution and chemical state of Co and doping metal ions, crystallite size, surface state, redox property, and so on. Also, a systematic study on the catalytic activity, selectivity, and stability for total oxidation of VOCs (including chlorinated VOCs) would be performed by using a variety of model compounds. The influence of VOCs type, co-existence of multi-component VOCs, and presence of water on the catalytic performance would be investigated. Based on the results of structural characterization and catalytic test as well as in situ measurements, the structure-performance relationship and reaction mechanism would be carefully discussed to understand the doping effect of metal ions. It can be expected that the findings in this research would provide useful information for the design and preparation of novel efficient and cost-effective catalysts and their application in VOCs total oxidation.

挥发性有机物(VOCs)是导致大气环境恶化的主要污染物，催化氧化是一种节能、环保、高效的净化技术，Co3O4具有优异的催化性能和抗氯中毒能力，具有良好的应用前景。本项目拟以层状复合氢氧化物(LDHs)为前驱体设计制备具有尖晶石结构的Co3-xMxO4复合氧化物，通过调控LDHs的化学组成、形貌尺寸和热处理条件，研制出具有比表面积高、热稳定性好、形貌和尺寸均匀、结构和组成可控的尖晶石复合氧化物，采用各种表征技术对尖晶石的纳微结构、表面状态、还原性能等性质进行详细表征，并结合VOCs模型化合物催化氧化性能评价，弄清楚影响尖晶石形成的关键因素，认识金属离子Mn+对Co3O4的结构和性质的掺杂效应，揭示Co3-xMxO4组分之间的相互作用及其对催化性能的调变机制，从而形成基于LDHs的Co3-xMxO4尖晶石的设计、制备和调控方法，为高性能实用型VOCs氧化催化剂的研制提供理论基础和原型技术。

挥发性有机物(VOCs)是导致大气环境恶化的主要污染物，催化燃烧是一种节能、环保、高效的净化技术，Co3O4具有优异的催化性能，具有良好的应用前景。本项目以层状复合氢氧化物(LDHs)为前驱体制备Co3-xMxO4尖晶石型复合氧化物，通过调控LDHs的化学组成、形貌尺寸和热处理条件，研制具有热稳定性好、形貌和尺寸均匀、结构和组成可控的尖晶石，采用各种表征技术对尖晶石的纳微结构、表面状态、还原性能等性质进行表征，并结合VOCs模型化合物催化燃烧性能评价，探讨掺杂金属离子Mn+对Co3O4的结构和化学性质的调变作用，揭示Co3-xMxO4组分之间的相互作用及其对催化性能的影响。主要结果如下：(1)发展以甲醇/水混合溶液为溶剂、氢氧化钠溶液为沉淀剂、在温和碱性条件下定量合成Co2+‒Co3+ HTlcs类水滑石的新方法。利用甲醇提高溶解氧浓度，促进Co离子氧化，采用氢氧化钠作沉淀剂使Co离子完全沉淀，大大提高HTlcs产率。(2)以钴铜类水滑石为前驱体制备Co3-xCuxO4尖晶石，铜占据四面体和八面体位置，形成部分反式尖晶石结构。掺杂Cu削弱Co–O键，显著提高Co还原性能和晶格氧迁移能力，显示出强相互作用，提高甲烷催化燃烧活性，Co2.7Cu0.3O4表现出良好的低温活性、稳定性和抗水汽性能。(3)以CoAl类水滑石为前驱体制备Co3-xAlxO4尖晶石，对甲烷催化燃烧表现出优异的高温活性和稳定性。掺杂Al不仅能有效抑制Co3O4烧结长大，而且可显著抑制Co3O4分解生成CoO，大大提高热稳定性。该结果为解决Co3O4高温易烧结、热稳定性差等问题提供新思路，有望突破Co3O4应用技术瓶颈，在高温催化燃烧领域得到应用。这些研究结果对发展基于LDHs的Co3-xMxO4尖晶石的设计制备和结构性能调控方法奠定了基础，为高性能实用型VOCs燃烧催化剂的研制提供理论基础和原型技术。