限域结构钌金属及合金纳米粒子催化剂材料的制备及催化加氢性能研究
发布时间：2018-10-25 07:10
【摘要】：金属Ru基催化剂在诸多催化反应中获得广泛应用,特别是在芳香族化合物的加氢反应中显示优异的催化性能。近年来,研究者发现微观限域结构对金属纳米粒子与其周围环境的相互作用方式及催化性能具有重要影响,由此指导人们设计出新型金属纳米及合金催化剂材料,充分发挥贵金属的催化效能,满足贵金属催化剂高效利用的实际需求。本论文基于类水滑石(LDHs)主体层板的限域效应,采用尿素分解法首先制备了 RuMgAl-LDHs催化剂前体,然后通过氢气气氛下还原处理得到限域于LDHs层板中的金属Ru纳米粒子催化剂材料。进而,采用原位生长法在γ-Al203载体上合成出NiRuAl-LDHs前体,通过氢气还原处理制备了负载型NiRu双金属合金催化剂材料。采用XRD、HRTEM、XPS及STEM-EDS等多种手段对限域结构Ru纳米粒子及NiRu合金的晶相组成、表面价态、形貌等进行表征和分析,进而推测了,探讨了微量Ru的掺杂对金属Ni的还原行为的影响。最后分别将Ru纳米粒子催化剂及NiRu合金催化剂应用于苯和裂解汽油模拟物的加氢反应中,测试催化剂的活性、选择性及稳定性,并探讨了催化剂结构与反应性能的构效关系。主要的实验内容和结果如下:(1)采用尿素分解法制备了高结晶度的RuMgAl-LDHs催化剂前体,Ru离子均匀分布于水滑石层板中。然后,通过控制氢气还原处理温度制备了限域于LDHs层板中的金属Ru纳米粒子催化剂材料。采用HRTEM、STEM等表征研究表明,Ru纳米粒子趋向于向LDHs边缘区域聚集。此聚集趋势在恒定pH法制备的小晶粒RuMgAl-LDHs前体中表现的更为明显,由此制得选择限域于LDHs边棱部位的复合型纳米金属Ru/LDHs催化剂材料。将由不同还原温度制备的Ru/LDHs样品应用于催化苯加氢生成环己烷反应中,在90 ℃,5 MPa H2的反应条件下,100℃还原样品催化性能最佳。主要源于过低的还原温度不能保证Ru粒子的边缘迁移,而过高的还原温度使得Ru颗粒在边缘聚集长大,降低了金属分散性。(2)以γ-Al2O3作为载体,采用原位生长法在其上合成了NiRuAl-LDHs前体,通过450 ℃下氢气还原处理制备了负载型NiRu双金属合金催化剂材料。STEM-EDX、XPS、TPR等测试结果表明,NiRu双金属形成了合金结构,微量Ru的添加提高了 Ni2+的还原度,降低了 Ni粒子尺寸。将制备的不同Ru含量的负载型NiRu合金催化剂应用于苯乙烯催化加氢反应中。结果表明,微量Ru的掺杂明显提高了 Ni催化剂的加氢反应性能。推测Ru的添加提高了 Ni金属分散性;同时,产生的溢流氢促使了催化性能的提高。
[Abstract]:Metal Ru catalysts have been widely used in many catalytic reactions, especially in hydrogenation of aromatic compounds. In recent years, researchers have found that the microstructure has an important influence on the interaction mode and catalytic performance between metal nanoparticles and their surrounding environment, thus guiding people to design new metal nanoparticles and alloy catalyst materials. Give full play to the catalytic efficiency of noble metals, meet the actual demand of high efficiency utilization of noble metal catalysts. In this paper, based on the limiting effect of hydrotalcite-like (LDHs) main plate, the precursor of RuMgAl-LDHs catalyst was prepared by urea decomposition method, and then the metal Ru nanoparticle catalyst material was prepared by reduction treatment in hydrogen atmosphere. Furthermore, the precursor of NiRuAl-LDHs was synthesized on 纬-Al203 carrier by in situ growth method, and the supported NiRu bimetallic catalyst material was prepared by hydrogen reduction. The crystal phase composition, surface valence state and morphology of limited structure Ru nanoparticles and NiRu alloys were characterized and analyzed by means of XRD,HRTEM,XPS and STEM-EDS, and the effect of trace Ru doping on the reduction behavior of Ni was discussed. Finally, Ru nanoparticles and NiRu alloy catalysts were applied to the hydrogenation of benzene and pyrolysis gasoline simulants, the activity, selectivity and stability of the catalysts were tested, and the structure-activity relationship between catalyst structure and reaction performance was discussed. The main experimental contents and results are as follows: (1) the precursor of RuMgAl-LDHs catalyst with high crystallinity was prepared by urea decomposition method. Ru ions were uniformly distributed in hydrotalcite laminates. Then, metal Ru nanoparticles were prepared by controlling the reduction temperature of hydrogen in LDHs laminates. HRTEM,STEM analysis showed that Ru nanoparticles tend to aggregate to the edge of LDHs. This aggregation trend is more obvious in the small grain RuMgAl-LDHs precursor prepared by the constant pH method. Therefore, the composite nanometallic Ru/LDHs catalyst material limited to the edge and edge of LDHs was prepared. The Ru/LDHs samples prepared at different reduction temperatures were used to catalyze the hydrogenation of benzene to cyclohexane. Under the reaction conditions of 90 鈩，
本文编号：2292999
[Abstract]:Metal Ru catalysts have been widely used in many catalytic reactions, especially in hydrogenation of aromatic compounds. In recent years, researchers have found that the microstructure has an important influence on the interaction mode and catalytic performance between metal nanoparticles and their surrounding environment, thus guiding people to design new metal nanoparticles and alloy catalyst materials. Give full play to the catalytic efficiency of noble metals, meet the actual demand of high efficiency utilization of noble metal catalysts. In this paper, based on the limiting effect of hydrotalcite-like (LDHs) main plate, the precursor of RuMgAl-LDHs catalyst was prepared by urea decomposition method, and then the metal Ru nanoparticle catalyst material was prepared by reduction treatment in hydrogen atmosphere. Furthermore, the precursor of NiRuAl-LDHs was synthesized on 纬-Al203 carrier by in situ growth method, and the supported NiRu bimetallic catalyst material was prepared by hydrogen reduction. The crystal phase composition, surface valence state and morphology of limited structure Ru nanoparticles and NiRu alloys were characterized and analyzed by means of XRD,HRTEM,XPS and STEM-EDS, and the effect of trace Ru doping on the reduction behavior of Ni was discussed. Finally, Ru nanoparticles and NiRu alloy catalysts were applied to the hydrogenation of benzene and pyrolysis gasoline simulants, the activity, selectivity and stability of the catalysts were tested, and the structure-activity relationship between catalyst structure and reaction performance was discussed. The main experimental contents and results are as follows: (1) the precursor of RuMgAl-LDHs catalyst with high crystallinity was prepared by urea decomposition method. Ru ions were uniformly distributed in hydrotalcite laminates. Then, metal Ru nanoparticles were prepared by controlling the reduction temperature of hydrogen in LDHs laminates. HRTEM,STEM analysis showed that Ru nanoparticles tend to aggregate to the edge of LDHs. This aggregation trend is more obvious in the small grain RuMgAl-LDHs precursor prepared by the constant pH method. Therefore, the composite nanometallic Ru/LDHs catalyst material limited to the edge and edge of LDHs was prepared. The Ru/LDHs samples prepared at different reduction temperatures were used to catalyze the hydrogenation of benzene to cyclohexane. Under the reaction conditions of 90 鈩，
本文编号：2292999
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