大孔氧化物负载贵金属合金纳米粒子的合成及其催化氧化含卤VOC的性能研究

Volatile organic compounds (VOC) are pollutants to the atmosphere. Catalytic oxidation is an effective pathway to eleminate VOC, in which the catalyst is the key issue. Supported noble metals are active for the low-temperature oxidation of VOC. Using the traditional methods, however, one cannot obtain noble metal alloys with uniform particle sizes. Using the polyvinyl alcohol (PVA)-protected reduction method, one can fabricate the noble metal alloys with a particle size of 2-4 nm; whereas via the hard-templating approach with poly(methyl methacrylate) (PMMA) microspheres as template, one can generate three-dimensionally ordered macroporous (3DOM) supports. In this proposal, we shall adopt the PMMA-templating and PVA-protected reduction methods to prepare 3DOM M3Oz (M3 = Ce, Ti, Sn, W) and M1yM2/3DOM M3Oz (M1 or M2 = Au, Pd, Pt, Ru), respectively. Numerous characterization techniques will be used to determine the physicochemical properties of the materials, and their catalytic activities for the oxidation of typical halogen-containing VOC (e.g., 1,2-dichloroethane, trichloroethylene, and 1,2-dichlorobenzene) 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 the utilization of such new and effective catalysts in eliminating the typical halogen-containing VOC will give rise to improvement in atmospheric environment quality.

挥发性有机物(VOC)污染大气环境。催化法是消除VOC的有效途径，催化剂是核心。负载贵金属对VOC氧化显示优良的低温催化活性。传统方法难以获得粒径均匀的贵金属合金，但采用聚乙烯醇（PVA）保护的还原法可制得粒径为2-4 nm的贵金属合金，而采用聚甲基丙烯酸甲酯（PMMA）微球硬模板法可制得三维有序大孔（3DOM）结构的氧化物载体。本课题拟采用PMMA硬模板法和PVA保护的还原法分别制备3DOM M3Oz （M3 = Ce, Ti, Sn, W）和M1yM2/3DOM M3Oz （M1、M2 = Au, Pd, Pt, Ru），利用若干技术表征催化剂物化性质，研究其对典型含卤VOC（如1,2-二氯乙烷、三氯乙烯和1,2-二氯苯等）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提供指导，而新型高效催化剂应用于消除含卤VOC可改善大气环境。

经过研究纳米双金属和多孔催化剂的可控制备、表征及其对典型含氯挥发性有机物（CVOC）氧化反应的催化性能，得到如下研究成果：（1）采用了聚合物微球PMMA模板法和硼氢化钠还原法制备了Ru/三维有序大孔(3DOM) SnO2催化剂，研究了其对于三氯乙烯（TCE）氧化反应的催化性能。结果表明，反应体系引入少量H2O气可以有效减少多氯副产物（如CH2Cl2、CH3COOH和C2H2Cl2）的形成，促进氯离子在催化剂表面的脱附，提高HCl选择性；（2）采用PMMA模板法和硼氢化钠还原法制备了双金属RuM (M = Au, Pd或Pt)负载的RuM/3DOM CeO2催化剂，在空速为20,000 mL/(g h)时，0.93Ru2.87Pd/3DOM CeO2具有最高的催化活性（T50%和T90%分别为237 oC和298 oC）和最低的表观活化能为34 kJ mol−1。Ru物种有利于TCE氧化过程中副产物HCl和Cl2的生成和还原，其中四氯乙烯是主要副产物。Ru2.87Pd/3DOM CeO2催化剂优异的催化性能可被归结于具有较高的吸附氧物种浓度以及具有较强的TCE吸附和活化能力；（3）制备了一系列AuPdy/3DOM CeO2催化剂。其中2.85AuPd1.87/3DOM CeO2在空速为20,000 mL/(g h) 的反应条件下，对于TCE氧化具有最好的催化活性（T90% = 415 oC）。此外，3DOM CeO2负载AuPd合金催化剂表现出更好的抗氯、抗水中毒性能。这可被归结于Au原子和Pd原子、AuPd合金和载体3DOM CeO2之间存在的强相互作用以及表面酸性和高浓度表面吸附氧的协同作用；（4）采用液相还原法和水热合成法制备了不同酸碱性质的多孔载体（介孔Al2O3和MgO和微孔HZSM-5）负载双金属纳米RuCo纳米颗粒催化剂，并研究了该系列催化剂对1,2-二氯乙烷（1,2-DCE）的氧化反应和反应机理。RuCo/HZSM-5表现出最高的催化活性（T90% = 281 oC，TOFNoble metal = 3.6x10-3 s-1，反应速率在270 oC时为 18.7 μmol/(gNoble metal s）。同时该催化剂具有较好的抗氯中毒性能，这与其较强的氧化还原能力、合适的酸度，对1,2-DCE具有较好的吸附性能有关。