Au1-xM'x/3DOM MOy (M' = Pd, Pt; M = Cr, Mn, Co, Fe)的可控制备及催化CO和VOC氧化的性能研究

Carbon monoxide and volatile organic compounds (VOCs) are pollutants to the atmosphere. Catalytic oxidation is an effective pathway to eleminate CO and VOCs, in which the catalyst is the key issue. Supported noble metal alloys (Au1-xM'x, M' = Pd, Pt) and porous transition metal oxides (MOy, M = Cr, Mn, Co, and Fe) are active for the oxidation of CO and VOCs. Using the traditional methods, however, one cannot obtain Au1-xM' with uniform particle sizes and porous MOy. Using the gas bubble-assisted polyvinyl alcohol-protected ruduction method, one can fabricate the noble metal alloys Au1-xM'x with a particle size of 2-4 nm; whereas via the hard-templating approach with poly(methyl methacrylate) or ploystyrene microspheres as template, one can prepare three-dimensionally ordered macroporous (3DOM) MOy. In this proposal, we shall adopt the hard-templating and gas bubble-assisted polyvinyl alcohol-protected ruduction methods to prepare 3DOM MOy and Au1-xM'x/3DOM MOy catalysts,respectively. A number of characterization techniques will be used to determine the physicochemical properties of the materials, and their catalytic activities for the oxidation of CO and VOCs will be evaluated. By so doing, we can elucidate the "structure-performance" relationship, clarify the involved catalytic mechanisms, and establish the corresponding catalytic reaction kinetic models. It is envisioned that the results obtained in the proposed project will provide a useful guidance on designing novel catalytic materials with high performance and developing the relevant catalytic technologies, and the utilization of such new and effective catalysts in eliminating the typical atmospheric pollutants at low temperatures will give rise to improvement in atmospheric environment quality.

CO和挥发性有机物(VOC)污染大气环境。催化法是消除CO和VOC的有效途径，催化剂是核心。负载Au1-xM'x（M' = Pd, Pt）和多孔过渡金属氧化物MOy（M = Cr、Mn、Co、Fe）对CO和VOC氧化显示催化活性。传统方法难获得粒径均匀的Au1-xM'x和多孔MOy，但采用聚乙烯醇保护的鼓泡还原法可制得粒径为2-4 nm的Au1-xM'x，而采用硬模板（如聚甲基丙烯酸甲酯等）法可制得三维有序大孔（3DOM）结构的MOy。本课题拟采用硬模板法和聚乙烯醇保护的鼓泡还原法分别制备3DOM MOy和Au1-xM'x/3DOM MOy，利用若干技术表征催化剂物化性质，研究其对CO和VOC氧化的催化行为，揭示构效关系，探明催化作用机制，建立反应动力学模型。研究结果可为新型高性能催化材料设计和相关催化技术建立提供有益指导，而新型高效催化剂应用于低温消除CO和VOC污染物则可改善大气环境。

经过研究三维有序大孔（3DOM）金属氧化物及负载纳米合金催化剂的可控制备、表征及其对典型挥发性有机物（VOC）和CO氧化反应的催化性能，得到如下研究成果：（1）利用硼氢化钠辅助的液相还原法制备了一系列的纳米贵金属及其合金（Au、Pd、AuPd、PtPd等），采用浸渍法将贵金属颗粒负载到具有3DOM结构的过渡金属氧化物（Co3O4及Mn2O3等）上，该系列催化剂对于CO和VOC的氧化反应显示了良好的催化活性与稳定性，这与其具有较高的吸附氧物种浓度以及合金中存在的电子转移效应有关；（2）利用聚甲基丙烯酸甲酯或者KIT-6硬模板法制备了一系列三维有序大孔复合金属氧化物（La0.6Sr0.4MnO3、CoCr2O4等）和一系列三维有序介孔金属氧化物（Mn2O3及Cr2O3等），以其为载体，负载纳米合金。该系列催化剂对于VOC和甲烷的氧化反应显示了良好的催化活性与稳定性。这与贵金属与载体之间存在的强相互作用有关；（3）利用硼氢化钠辅助的液相还原法制备了具有壳‒核结构或者异质结构的二元金属或三元金属纳米晶（Pd@Co及AuPdCo等）及其负载型催化剂。所得催化剂与传统材料相比，对典型VOC和甲烷的催化氧化性能有了较大幅度的提高，这与其具有较多的吸附氧物种、具有较好的低温还原性能以及双金属特定的几何构型等因素有关。