催化加氢中钼基纳米材料的载体效应

发布时间：2018-02-24 00:25

本文关键词： 碳化钼氢化氧化钼铂族金属金属-载体相互作用选择性加氢表面调控　出处：《暨南大学》2017年硕士论文　论文类型：学位论文

【摘要】：金属-载体相互作用是影响负载型金属催化剂性能的重要因素之一。通过调控该作用,可以调变催化加氢反应的活性、选择性和稳定性。在芳硝基化合物、α-β不饱和醇的加氢转化反应中,金属-载体相互作用往往能起到关键作用。本论文通过研究钼基碳化物、氧化物纳米材料的独特载体效应,揭示载体表面物理化学性质与载体作用的关系;并通过改变载体性质调控金属-载体相互作用,进而优化Ni、Pt等金属的催化加氢活性、选择性及稳定性。论文主要工作和结果如下:一、基于碳化钼(Mo_2C)与Ni的金属-载体相互作用,以Mo_2C纳米线为载体制备高分散的Ni基催化剂,提高硝基苯甲酸的催化加氢活性,进而通过碳包覆优化催化剂稳定性。工作发现,Mo_2C与Ni的强相互作用可以显著降低Ni纳米颗粒的尺寸(~nm),相比SiO_2、碳纳米管等传统载体,分散度得到显著提高,因此Ni/Mo_2C表现了高的催化活性。进而,针对反应溶剂中水容易导致Ni流失并失活,工作通过简易的碳包覆策略提高了Ni/Mo_2C的稳定性。其中,具有合适包覆量的Ni/Mo_2C@C在酸性环境(pH~3)中连续四次反应后仍然保持高的活性。二、以氢化氧化钼(H-MoO_x)为载体设计Pt-Sn双金属催化剂(Pt-Sn/H-MoO_x),同时提高芳硝基化合物(如硝基苯乙烯)催化加氢活性和选择性。工作证明H-MoO_x的载体作用提高了Pt、Pt-Sn的分散度,从而表现了优异的活性;Pt-Sn双金属颗粒表面上Sn原子分隔了Pt原子,改变了硝基苯乙烯的吸附模式,从而提高了加氢选择性。该催化剂在多种芳硝基化合物,如硝基苯乙烯、卤代硝基苯、硝基苯甲酸等的选择性加氢反应中均表现了优异的选择性。三、以氢化氧化钼(H-MoO_x)为载体,研究Pt-M/MoO_x(M=Fe、Co、Ni、Cu、Zn)催化剂在肉桂醛选择性加氢中的应用。在30oC和1MPa氢气的条件下,最优比例的Pt-Fe/MoO_x对肉桂醛选择性高于90%,同时保持了极高的活性。工作发现过渡金属M通过其氧化物掺杂而改变Pt活性表面,并配合载体效应、电子效应和空间位阻,同时提高了催化剂在肉桂醛选择性加氢中的活性和选择性。本论文工作证明了钼基纳米材料作为催化剂载体,与金属催化中心具有强的相互作用。利用该相互作用,设计Ni、Pt高分散金属负载型催化剂,大幅提升催化加氢活性、选择性。本论文提出金属载体相互作用与修饰负载金属相结合的策略,多元化调控催化剂催化性能,为高性能催化剂设计提供了新思路。
[Abstract]:The metal-carrier interaction is one of the important factors affecting the performance of supported metal catalysts. Selectivity and stability. The metal-carrier interaction often plays a key role in hydrogenation of aromatic nitro compounds and 伪-尾 unsaturated alcohols. The relationship between the physicochemical properties of the support surface and the action of the carrier was revealed, and the catalytic hydrogenation activity of metals such as NiPt was optimized by adjusting the metal-carrier interaction by changing the properties of the carrier. Selectivity and stability. The main work and results are as follows: 1. Based on the interaction between Mo _ 2C and Ni, highly dispersed Ni based catalysts were prepared on Mo_2C nanowires to improve the catalytic hydrogenation activity of nitrobenzoic acid. Furthermore, the stability of the catalyst was optimized by carbon coating. It was found that the strong interaction between Mo 2C and Ni could significantly reduce the size of Ni nanoparticles and increase the dispersion of Ni nanoparticles compared with the traditional carriers such as SiO2, carbon nanotubes and so on. Therefore, Ni/Mo_2C exhibited high catalytic activity. Furthermore, water in the reaction solvent could easily lead to Ni loss and inactivation, and the stability of Ni/Mo_2C was improved by simple carbon coating strategy. The Ni/Mo_2C@C with suitable coating amount remained high activity after four consecutive reactions in acidic environment pH ~ (3). A Pt-Sn bimetallic catalyst, Pt-SnR / H-MoOxC, was designed on the basis of molybdenum hydroxide and H-MoOX as the carrier, and the catalytic hydrogenation activity and selectivity of aromatic nitro compounds (such as nitrobenzene ethylene) were improved simultaneously. It was proved that the supported action of H-MoOx increased the dispersion of Pt-Sn. Thus, Sn atoms separated Pt atoms on the surface of Pt-Sn bimetallic particles, which changed the adsorption mode of nitrobenzene ethylene and improved hydrogenation selectivity. The selective hydrogenation of halogenated nitrobenzene and nitrobenzoic acid showed excellent selectivity. Thirdly, the application of Pt-M / Moo _ xM _ (Moo _ x) -FeCoCU _ (Cu) Zn) catalyst in selective hydrogenation of cinnamaldehyde was studied with molybdenum hydroxide and H-MoOx as the carrier, the catalyst was used in selective hydrogenation of cinnamaldehyde at 30oC and 1MPa hydrogen. The optimum ratio of Pt-Fe/MoO_x to cinnamaldehyde was higher than 90%, while keeping a high activity. It was found that transition metal M changed the active surface of Pt by doping its oxides, and coordinated with carrier effect, electron effect and steric hindrance. At the same time, the activity and selectivity of the catalyst in selective hydrogenation of cinnamaldehyde were improved. A highly dispersed metal-supported catalyst was designed to greatly improve the hydrogenation activity and selectivity. In this paper, a strategy of combining metal carrier interaction with modified supported metal was proposed to control the catalytic performance of the catalyst. It provides a new idea for the design of high performance catalyst.
【学位授予单位】：暨南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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