具有特殊形貌的介孔氧化硅的合成及其作为催化剂载体的应用研究

发布时间：2018-07-11 21:19

本文选题：介孔氧化硅 + 纳米花　；参考：《华南理工大学》2015年硕士论文

【摘要】：纳米花状的介孔氧化硅不仅具备介孔材料的一般特点,如比表面积高,结构规整有序,水热稳定性好和无毒、表面易于修饰等特点,而且其径向开放的多级孔道结构极大的促进了底物分子的传质和扩散,是制备催化剂的理想载体。本文采用溶剂热法,以十六烷基溴化吡啶(CPB)为表面活性剂,在水、环己烷和戊醇组成的油水体系中合成了颗粒均匀,粒径为200 nm,比表面积高达502 m2·g-1的多级孔道结构的介孔氧化硅纳米花(mesoporous silica nanoflower,MSNF)。通过改变油水体积比、TEOS的浓度和水热温度,探究了反应条件对纳米花形貌的影响。我们发现,环己烷对纳米花形貌具有决定性的影响。此外,我们探究了加入第二模板剂对纳米花形貌的影响并初步研究了采用硬模板法设计合成棉花球状氧化硅。通过SEM、TEM、XRD、TG、FTIR、N2吸脱附等测试对合成的氧化硅材料的形貌和结构进行了表征,并对MSNF的形成过程进行了合理的推理和阐述。以MSNF为载体,采用浸渍-H2还原法制备了mono-Pd、mono-Au和Pd Au0.2催化剂样品,并用于催化苯酚加氢的性能研究,研究了Au对Pd的添加效应。实验表明,Pd Au0.2的催化活性是单金属Pd和商业Pd/C的4倍和13倍。为了探究不同载体的双金属效应,我们选取了XC-72R、MCM-41、SBA-15、MCM-48为载体,制备一系列单金属和Pd Au0.2双金属催化剂用于催化苯酚加氢反应。结果表明,以XC-72R为载体制备催化剂,Au的添加降低了Pd基催化剂的催化性能。与之相反,采用Si O2为载体制备的催化剂,Au的添加明显提高了催化剂的催化性能。以下是不同介孔Si O2为载体制备的催化剂的催化性能排序:SBA-15MSNFMCM-48MCM-41。以MSNF为载体,采用浸渍-H2还原法制备了Pd Irn双金属催化剂并首次用于催化硝基苯加氢反应。探究了不同Pd/Ir摩尔比对催化剂性能的影响,筛选出Pd Ir比例最优的催化剂样品(nIr/nPd=0.4)。实验结果表明,与mono-Pd和mono-Ir相比,在保持对苯胺的高选择性(98%)的基础上,Pd Ir0.4/MSNF在0.5h内对硝基苯的转化率高达100%,分别是mono-Pd和mono-Ir的5倍和33倍。通过TEM、H2-TPR、XRD等测试,我们发现Ir的添加可以有效减小催化剂的粒径,提高催化剂的抗团聚性能。
[Abstract]:Nano-flower-like mesoporous silica not only has the general characteristics of mesoporous materials, such as high specific surface area, orderly structure, good hydrothermal stability and non-toxic, surface easy to modify and so on. Moreover, its radial open multilevel pore structure greatly promotes the mass transfer and diffusion of substrate molecules, and is an ideal support for the preparation of catalysts. In this paper, a solvothermal method with cetylpyridine bromide (CPB) as surfactant was used to synthesize homogeneous particles in an oil-water system composed of water, cyclohexane and pentanol. The mesoporous silica nanorods with a diameter of 200nm and a specific surface area of 502m2 g ~ (-1) were obtained from the mesoporous silica nanorods (mesoporous silica nanoflower MSNF). By changing the concentration of TEOS and hydrothermal temperature, the effect of reaction conditions on the morphology of nano-flowers was investigated. We found that cyclohexane has a decisive effect on the morphology of nano-flowers. In addition, we investigated the effect of the addition of the second template on the morphology of the nano-flowers and studied the design and synthesis of cotton spherical silica by hard template method. The morphology and structure of the synthesized silicon oxide materials were characterized by the desorption and desorption tests, and the formation process of MSNF was reasoned and explained. Mono-Pdlmono-Au and PD Au0.2 catalysts were prepared by impregnation -H2 reduction method on MSNF-supported, and were used to study the catalytic properties of phenol hydrogenation. The effect of au on PD addition was studied. The results show that the catalytic activity of Pd Au0.2 is 4 and 13 times higher than that of single metal PD and commercial PD / C. In order to investigate the bimetallic effect of different supports, a series of monometallic and PD Au0.2 bimetallic catalysts were prepared on XC-72RNMCM-41 SBA-15MCM-48 to catalyze the hydrogenation of phenol. The results showed that the addition of au on XC-72R catalyst decreased the catalytic performance of PD based catalyst. On the contrary, the addition of au on Sio _ 2 supports can obviously improve the catalytic performance of the catalyst. The following is the order of catalytic performance of different mesoporous Sio _ 2 supported catalysts: 1 SBA-15 MSNFMCM-48MCM-41. PD Irn bimetallic catalyst was prepared by dipping H2 reduction method with MSNF as the carrier and was used for the hydrogenation of nitrobenzene for the first time. The influence of PD / ir molar ratio on catalyst performance was investigated. The best PD / ir ratio was obtained (nIrr / nPd0. 4). Compared with mono-Pd and mono-Ir, the conversion of PD Ir0.4 / MSNF to nitrobenzene in 0.5 h was 100 times higher than that of mono-Pd and mono-Ir, which was 5 and 33 times higher than that of mono-Pd and mono-Ir, respectively, on the basis of maintaining high selectivity for aniline (98%). By means of Tem H2-TPRO XRD, we found that the addition of ir can effectively reduce the particle size of the catalyst and improve the agglomeration resistance of the catalyst.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.2;O643.36

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