Knowledge Management System Of Institute of process engineering,CAS
|Thesis Advisor||陈运法, 潘吉庆|
近年来，雾霾已成为一个严重的大气污染问题，许多工业过程中排放的挥发性有机化合物（Volatile Organic Compounds，VOCs）是造成臭氧污染和雾霾的主要因素。同时，VOCs会对人体产生一系列不良影响，如头痛、呼吸道和皮肤刺激、甚至诱发癌症等。催化氧化技术是VOCs降解最有效的方法之一，氧化锰具有多种晶体结构以及丰富的氧化价态，展现出独特的氧化还原性能，有利于催化氧化过程中表面氧的利用和气态氧的活化，被广泛应用于催化领域。本论文制备了不同结构和组分的锰基复合氧化物，并进一步考察了其对典型VOCs（如苯 、甲醛等）的催化氧化性能，通过组分和结构控制，探索了催化剂的构效关系。主要研究结果如下：（1）钙钛矿型LaMnO3催化剂制备及对苯的催化性能通过溶胶-凝胶法、硬模板法、微乳法、沉淀法分别制备了不同形貌且结晶性良好的LaMnO3。结果表明，以二氧化硅KIT-6为模板制备的LaMnO3比表面积最大（108.8 m2 g-1），保留了模板的多孔道结构，其在催化氧化苯上展现最好的性能（T90% = 237 ºC，质量空速60000 mL g-1 h-1），不同方法制备LaMnO3的催化性能排序为：硬模板法 > 溶胶-凝胶法 > 沉淀法 > 微乳法，分析结果表明比表面积和孔结构是影响LaMnO3催化活性的关键因素。（2）含尖晶石相Cu-Mn复合氧化物制备及对苯的催化性能采用溶胶-凝胶法制备出一系列含尖晶石相的纳米铜锰氧化物Cu3-xMnx（x = 0、1、1.5、2、2.5、3），探索了尖晶石相形成对催化苯活性的影响，CuMn2由尖晶石相CuMn2O4和Mn2O3组成，尖晶石相的形成带来了更大的比表面积、更小的孔径和更多的晶格氧，使得催化氧化苯的活性和稳定性有显著提升，CuMn2展现出最优的低温催化性能（T90% = 186 ºC）。结果表明，CuMn2O4对促进电子传输和晶格氧的迁移起着至关重要的作用。 （3）CeO2@MnOx核壳结构催化剂制备及对苯的催化性能由Ce-MOF（Metal Organic Framework, MOF）部分热解得到含CeO2的纳米管，再通过氧化还原自沉积包覆上锰氧化物，成功制备不同锰铈比的CeO2@MnOx核壳结构催化剂，探究了其催化氧化苯的性能。其中，Mn/Ce摩尔比为2.03的CeO2@MnOx中氧化锰包覆均匀，形成了高比表面积（203.8 m2 g-1）、介孔分布均匀的中空核壳结构，此外，还具有良好的低温H2-还原性、丰富的氧空位和酸位点、高含量的Ce3+、Mn4+和吸附的氧物种，这有利于催化活性的提高，该催化剂在质量空速（Weight Hourly Space Velocity, WHSV）60000 mL g-1 h-1下催化100 ppm苯的性能最佳（T90% = 148 ºC），低温催化氧化苯的性能优于最新报道的贵金属催化剂。（4）整体式催化剂制备及其微波下催化氧化甲醛的性能采用简单的浸渍法制备了一系列堇青石负载（LaMnO3、LaMnO3/CeOx、LaMnO3/ZrCeOx、CuOx/MnOx）整体式催化剂（尺寸10×10×5 cm3）。测试结果表明，整体式催化剂具有良好的微波吸收能力，其中堇青石负载LaMnOx整体吸收微波效果最好，在微波功率300 W下7分钟可升温到200 ºC；堇青石负载CuOx/MnOx催化剂在微波功率300 W下催化速率最快；堇青石负载LaMnO3/ ZrCeOx催化剂催化降解甲醛效果最佳，有望在100 ºC下快速降解1ppm甲醛（体积空速，20000 h-1）。;In recent years, haze has become a serious air pollution problem. Volatile Organic Compounds (VOCs) emitted by many industrial processes are a major factor of ozone pollution and. Meanwhile, VOCs can cause a range of adverse effects on human body, such as headaches, respiratory and skin irritation, even causing cancer. Catalytic oxidation technology is one of the most effective methods of VOCs treatment. Manganese oxides have unique redox properties due to its various crystal structures and abundant oxidation states, which is beneficial to the utilization of surface oxygen and activation of gaseous oxygen during the process of catalytic oxidation, so it is widely applied in the field of catalysis. In this thesis, manganese-based composite oxides with different structures and components are prepared by different methods, and further investigate their performance on catalytic oxidation of typical VOCs (such as benzene and formaldehyde). By means of composition and structure regulation, the relationship between structure and performance is explored. The main research results are as follows:(1) Preparation of perovskite LaMnO3 catalyst and its catalytic performance for benzeneLaMnO3 with different morphologies and good crystallinity was prepared by sol-gel method, hard template method, microemulsion method and precipitation method respectively. LaMnO3 prepared with silicon dioxide KIT-6 as template had the maximum specific surface area (108.8 m2 g-1). The multichannel structure of template was well preserved and its performance of catalytic oxidation for benzene was the best (T90% = 237 ºC，WHSV = 60000 mL g-1 h-1). The catalytic performance of LaMnO3 prepared by different methods were ranked as follows : hard template method > sol-gel method > precipitation method > microemulsion method, and the results of analysis indicate that specific surface area and pore structure were the key factors affecting the catalytic activity of LaMnO3.(2) Preparation of Cu-Mn composite oxides containing spinel phase and its catalytic performance for benzeneA series of Cu3-xMnx (x = 0, 1, 1.5, 2, 2.5, 3) copper manganese oxides containing spinel phase were prepared by sol-gel method. The effect of spinel phase formation on the catalytic activity of benzene was investigated. CuMn2 was mainly composed of spinel phase CuMn2O4 and Mn2O3. The formation of spinel phase brought with larger specific surface area, smaller pore size and more lattice oxygen, which significantly improved the activity and stability of benzene catalytic oxidation. CuMn2 exhibited the best catalytic performance at low temperature (T90% = 186 ºC). The results showed that CuMn2O4 played an important role in promoting electron transport and lattice oxygen migration.(3) Preparation of CeO2@MnOx core-shell structure catalyst and its catalytic performance for benzeneCeO2 nanotubes were obtained by partial pyrolysis of Ce-MOF (Metal Organic Framework, MOF), and then coated with manganese oxide by self-deposition through redox. CeO2@MnOx catalysts with different Mn/Ce ratios were successfully prepared to further explore their catalytic performance for benzene oxidation. Among these, when the mole ratio of Mn/Ce was 2.03, manganese oxide coating in the CeO2@MnOx was uniform, forming a hollow core-shell structure with high specific surface area (203.8 m2 g-1) and uniform mesoporous distribution. In addition, it had good low temperature reducibility, abundant oxygen vacancy and acid sites, high content of Ce3+, Mn4+ and adsorbed oxygen species, which contributed to the enhancement of catalytic activity. The catalyst showed the best catalytic performance for 100 ppm benzene at the mass airspeed of 60000 mL g-1 h-1 (T90% = 148 ºC), the low-temperature catalytic performance preceded latest reported precious metal catalysts.(4) Preparation of monolithic catalyst and its catalytic performance for formaldehyde under microwaveA series of cordierite supported (LaMnO3, LaMnO3/CeOx, LaMnO3/ZrCeOx, CuOx/MnOx) catalysts (size 10×10×5 cm3) were prepared by a simple impregnation method. The results showed that all monolithic catalysts had good microwave absorption ability, among which cordierite supported LaMnOx catalyst had the best overall microwave absorption effect and can heat up to 200 ºC in about 7 minutes under the microwave power of 300 W. Cordierite supported CuOx/MnOx catalyst had the highest catalytic rate under the microwave power of 300 W. Cordierite supported LaMnO3/ZrCeOx catalyst had the best catalytic effect on formaldehyde at low temperature, it was expected to completely degrade 1ppm formaldehyde at 100 ºC (volume space velocity, 20000 h-1).
|张敏. 锰基复合氧化物制备及其催化氧化VOCs性能研究[D]. 中国科学院大学,2020.|
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