含钴锰基水滑石衍生复合氧化物的制备及其催化氧化VOCs性能研究

发布时间：2018-03-09 21:03

本文选题：水滑石　切入点：复合氧化物　出处：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：全国环境污染形势越来越严重,解决环境问题迫在眉睫。挥发性有机化合物(Volatile organic compounds,VOCs)作为大气污染物之一,不仅破坏生态环境,而且影响了人们的健康。催化氧化技术是解决空气VOCs污染问题最有效途径之一,且不会产生二次污染物,其关键问题是研制低成本、高效、稳定性好的催化剂。水滑石(Layered Double Hydroxides,LDHs)衍生得到的复合氧化物具有多孔性、高比表面积、协同效应、酸碱双功能性及晶粒高度分散等特性,在环境催化领域表现出良好的应用潜力,是制备催化反应器的主要功能组件,尤其是整体式薄膜材料。本论文旨在通过制备含Co/Mn的LDHs衍生得到多元复合氧化物催化剂,详细研究了其形貌、表面结构和化学性质,揭示了催化剂结构与催化氧化性能之间的关系;最终通过原位生长法制备ab面垂直于基底整体式薄膜催化剂。具体研究内容和结果如下:(1)Co-Al复合氧化物的结构调控及其催化氧化VOCs性能通过简单地控制反应溶剂(水、甲醇和乙醇)和氨释放剂(氨水、六次甲基四胺和尿素)合成了不同形貌的Co-Al LDHs,包括弯曲片、不完整六边形片和绒球状,比较了其氧化物对典型VOCs(苯)催化氧化性能。结果表明,采用乙醇和尿素的条件所得的绒球状的CoAl氧化物催化性能最好,在230℃下苯的转化率为99%。(2)氧化物结构缺陷及其催化氧化VOCs性能在纯氧气气氛下,将Co2+(3d7)氧化为Co3+(3d6)成功制备了CoⅡCoⅢLDHs,煅烧后得到缺陷结构氧化物。通过激光拉曼光谱、H2-TPR、TPD和XPS表征氧化物结构缺陷(酸性位点、氧缺陷和表面价态分布),并与Co-Al氧化物比较对苯和甲苯的催化性能。原位氧化法制备的氧化物催化氧化苯、甲苯完全转化的温度分别为210℃和220℃,具有丰富的结构缺陷,诱导产生良好的低温还原性、表面路易斯酸性位点和活性氧(Oads)。(3)复合组分协同效应与催化氧化性能关系通过分别引入Co、Ce掺杂Mn-Al LDHs成功制备了三元的LDHs,经煅烧形成一系列层状复合氧化物。研究表明,LDHs主层板的金属元素种类和比例影响了复合氧化物晶型结构、比表面积、还原能力和表面物种分布,并进一步探讨锻烧温度对结构的影响。在Co-Mn-Al催化剂体系中,当Co:Mn=1:2时,比表面积最大为128.04m2 g-1,孔径分布更集中,晶粒最小,催化氧化苯转化90%的温度(T90)为238℃;在低温条件下(350℃)锻烧得到的氧化物结构更完整、比表面积高,但在高温条件下(550℃)得到的氧化物催化性能最好(T90=208℃),组分协同效应增强。在Ce-Mn-Al氧化物催化剂体系中,Ce元素掺杂Mn-Al形成固溶体促进了 CeO2和MnOx的协同效应、增大Mn4+/Mn3+和晶格氧(Olatt)比例,进一步促进催化氧化苯性能。(4)整体式薄膜催化剂催化氧化VOCs性能研究基于上述研究结果,采用原位生长技术在铝箔上制备出一系列垂直生长的Co-Mn-Al LDHs,并以此为前驱体制备了整体式Co-Mn-Al氧化物薄膜催化剂,考察了对苯的催化氧化性能。研究结果表明,整体式Co-Mn-Al薄膜催化剂的最优样品催化氧化苯的T90为240℃,比二元的Mn-Al和Co-Al薄膜催化剂的T90分别降低了 25℃和60℃。整体式薄膜的结构比粉体更复杂,单位质量的反应速率明显优于最优的粉体催化剂,整体式薄膜的Oads/Olatt约为0.916,而粉体的Oads/Olatt约为0.55。金属基整体式催化剂成功应用于催化VOCs,为催化反应器的制备奠定了一定实践基础。
[Abstract]:The situation in the country is more and more serious environmental pollution, to solve environmental problems imminent. Volatile organic compounds (Volatile organic, compounds, VOCs) as one of the air pollutants, not only damage the ecological environment, but also affect people's health. Catalytic oxidation technology is to solve the air pollution problem is one of the most effective ways to VOCs, and will not have two key pollutants. The problem is the development of low cost, high efficiency, good stability of catalyst. Hydrotalcite (Layered Double Hydroxides, LDHs) derived composite oxides obtained with porous, high surface area, synergistic effect, acid base bifunctionalized and highly dispersed grain characteristics, showed good application potential in the field of environmental catalysis, is the main function of system preparation of catalytic reactor components, especially monolithic thin film materials. The purpose of this paper is derived from multiple complex oxides were prepared by Co/Mn containing LDHs The catalyst on the surface morphology, structure and chemical properties, reveals the relationship between catalyst structure and catalytic oxidation performance; finally through the preparation of AB in situ growth perpendicular to the substrate surface integral film catalyst. The specific research contents and results are as follows: (1) the performance of the structure and regulation of catalytic oxidation of VOCs composite oxide by Co-Al a simple control of the reaction solvent (water, methanol and ethanol) and ammonia release agent (ammonia, six methyl four amine and urea) with different morphologies Co-Al LDHs were synthesized, including bending sheet, incomplete hexagonal tablets and compared their floccular, typical VOCs (benzene) oxide on the catalytic performance. The results show that the catalytic performance of CoAl oxide by ethanol and urea. The ball shape is better, the transformation rate of benzene at 230 DEG C for 99%. (2) structure defects and properties of oxide catalytic oxidation of VOCs in pure oxygen gas Under the condition, the Co2+ (3D7) Co3+ (3d6) oxidation of Co II Co III LDHs was successfully prepared, obtained after calcination. The oxide structure defects by laser Raman spectroscopy, H2-TPR, TPD and XPS characterization of oxide structure defects (acidic sites, oxygen defects and surface valence distribution), and compared with Co-Al oxide on benzene and toluene catalytic performance. The catalytic oxidation of benzene oxide prepared by in situ oxidation of toluene, complete the transformation temperature were 210 degrees and 220 degrees, with abundant structural defects, induced by good low-temperature reducibility, Lewis surface acidic sites and active oxygen (Oads). (3) composite component collaborative relationship effect and catalytic oxidation performance through the introduction of Co, three yuan LDHs the preparation of Ce doped Mn-Al LDHs were successfully calcined to form a series of layered composite oxides. The research results show that the LDHs main board metal elements influence the type and proportion of composite oxide crystal structure, The specific surface area, reducing power and surface species distribution, and to further explore the effect of calcination temperature on the structure. The Co-Mn-Al catalyst system, when Co:Mn=1:2, the maximum specific surface area is 128.04m2 g-1, the pore size distribution is more concentrated, the smallest grain size, the catalytic oxidation of benzene into 90% temperature (T90) at low temperature is 238 DEG C; under the condition of (350 C) get more complete calcined oxide structure, high specific surface area, but under the condition of high temperature (550 DEG C) oxide catalytic performance to get the best (T90=208 C), group synergy is enhanced. In the Ce-Mn-Al oxide catalyst system, Ce doped Mn-Al solid solution formed to promote synergy effect of CeO2 and MnOx, increased Mn4+/Mn3+ and lattice oxygen (Olatt) ratio, to further promote the performance of the catalytic oxidation of benzene. (4) the performance of VOCs thin film monolithic catalyst for catalytic oxidation based on the above research results, by in situ growth in aluminum foil The preparation of a series of vertical growth of Co-Mn-Al LDHs, and as a whole Co-Mn-Al oxide film prepared precursor, catalytic oxidation of benzene was studied. The results show that the optimal sample by catalytic oxidation of benzene with integral Co-Mn-Al thin film catalyst T90 240 C, two yuan more than the Mn-Al and Co-Al film catalyst the T90 were reduced by 25 degrees and 60 degrees. The monolithic structure of thin film is more complex than the powder, powder catalyst reaction rate was significantly better than the optimal unit quality, the whole film Oads/Olatt is about 0.916, while the Oads/ Olatt powder is about 0.55. metallic monolithic catalyst was successfully applied in the catalytic VOCs. As a catalytic reactor for the preparation of some practical basis.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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