【作者】 李德华；

【导师】 周继承；

【作者基本信息】 湘潭大学 ， 化学工程， 2008， 硕士

【摘要】 金,由于化学惰性和难于高分散,长时间以来被认为没有催化活性。自1987年发现负载型金催化剂对CO低温氧化具有优异的催化性能以来,金催化剂以其特有的低温高活性,湿度增强效应等特点,引起了各国学者的关注。随后的研究发现金催化剂在NO还原、CO低温氧化、选择氢化、水蒸汽转换、烃类氧化等很多反应中都具有较理想的催化活性。金催化剂的催化活性与其颗粒粒径大小密切相关,在小于10nm才表现出高的催化活性,但是对其催化活性中心的研究还不充分。因此关于如何制备出低负载量、高活性及结构稳定的纳米金催化剂,研究其活性结构及反应机理,仍然是纳米金催化剂研究的重要课题。本文针对纳米金催化剂高活性和结构稳定的特点,利用分子筛独特的孔道效应所具有的择形催化能力,将催化剂的活性组分纳米金负载在TS-1、MCM-41等分子筛上,设计、制备和筛选出催化性能良好的负载型纳米金催化剂,对催化剂样品进行了XRD、FT-IR、SEM以及TEM等表征分析。以环己烷氧化反应和甲苯氧化反应为模型反应,利用这些催化剂载体的疏水亲油性、孔道效应以及择形作用来抑制氧化反应中副反应的进行,提高纳米金催化剂的催化性能,同时获得较高的环己烷转化率、目的产物选择性和甲苯液相氧化反应的转化率。将这种新型催化材料与环己烷氧化、甲苯氧化的反应规律相结合,采用环境友好的氧气氧化法,探求绿色环保型环己烷和甲苯氧化生产工艺。本论文使用自己设计制备的氧化催化剂评价装置,详细考察了纳米金催化剂制备方法、制备过程中各因素对其物化性质的影响及对其催化性能的影响;系统研究了这些纳米金催化剂对环己烷氧化和甲苯氧化的催化性能,优化了环己烷氧化和甲苯氧化反应的工艺条件。得到以下结果:1、TS-1是纳米金催化剂的优良载体,其孔道效应和择形催化性能提高了环己烷氧化和甲苯氧化反应中目标产物的选择性。以TS-1为载体制备出的Au/TS-1催化剂具有较高的催化活性,转化频率数可以达到9161h^-1。2、催化剂制备方法对纳米金催化剂的催化性能有很大的影响。水热合成法和沉积-沉淀法是两种较优的负载型纳米金催化剂的的制备方法,其制备的纳米金催化剂均具有高活性、结构稳定的特点,且催化剂使用4次后,其催化活性基本不变。XRD、FT-IR、SEM、TEM等表征结果显示,Au/TS^-1等以TS-1为载体的催化剂仍具有类似TS-1的结构特征,活性中心金以纳米尺度高度分散于载体表面上,其颗粒大小在6 nm左右。Au/ MCM-41催化剂上的活性中心金同样以纳米尺度高度分散于载体表面上,其颗粒大小5nm左右。3、采用沉积-沉淀（DP）的方法制备了负载型催化剂Au/TS-1在环己烷氧化反应中具有优异的催化活性。当加入0.02g Au/TS-1 Au的负载量为1%的催化剂、压力为1.0MPa时,在150℃下反应2.5h,环己烷的转化率最高可达到11.20%,环己酮、环己醇和环己基过氧化氢的总选择性达到89.60%。4、以无机钛硅为原料采用一步水热合成法得到的Au/TS-1,在甲苯氧化反应中,具有较为良好的催化性能,在保持一定转化率时还有较高苯甲醛的选择性,反应后催化剂容易分离,再生效果良好。在压力为1.0MPa,165℃下反应3h,甲苯转化率可达20.54%,而苯甲醛的选择性为44.74%,苯甲酸的选择性为54.77%的优异结果。更多还原

【Abstract】 Gold in bulk has often been regarded to be poorly active as a catalyst for it’s chemical inert and poor dispersion. Since 1987, it has found that supported nano-gold catalyst showed high catalytic performance on low-temperature CO oxidation, nano-gold catalyst with high catalytic activity and enhancement of humidity aroused the attention of scholars. Subsequent studies found that it turns out to be surprisingly active in many reactions, such as reducion of NO、low-temperature CO oxidation、selective hydrogenation、WGSR、hydrocarbon oxidation et al. The catalytic activity of gold catalyst closely related with the gold particle size, only when gold is small enough(<10nm), it turns out to be surprisingly active. But the study about the catalystic center is not adequate. In recent years, new methods for preparation of catalyst with low loadings, high activity and high stability and research into the structure of the active phase in gold catalyst and the reaction mechanism have continued to be widely studied.This paper aimed to the nano-gold catalyst with and structural stability of the characteristics, and the unique use of zeolite channels by using the shape-selective catalytic capacity, the nano-gold was supported on the molecular sieve such as TS-1、MCM-41, design、selection and preparation of surpported nano-gold catalyst with a good catalytic performance. Samples of the catalyst characterized by XRD, FT-IR, SEM and TEM . The toluene oxidation reaction and cyclohexane oxidation reaction was used as model reactions to evaluate the catalytic performance, these catalysts lipophilic and the effect of shape-selective channels were used to control the co-reaction, the catalytic nano-gold catalyst performance was enhanced through the synergies with nano-gold, for the more, cyclohexane、benzene conversion rate and products selectivity were improved. This new catalytic materials related with cyclohexane、toluene oxidation reaction, used environmental friendly oxygen oxidation, to explore green-toluene and cyclohexane oxidation process. The own designed evaluation device was used to investigate the influence of factors in preparation process on physicochemical properties and the catalytic activities on toluene oxidation and cyclohexane oxidation. Technology conditions were optimized in cyclohexane oxidation and toluene oxidation. The results and conclusion have been obtained as follows:1、TS-1 is a good nano-gold catalyst support, TS-1 with special structure and shape-selective catalysis performance have the ability to improve the selectivity of cyclohexane oxidation and toluene oxidation. The Au/TS-1 catalyst was prepared with the TS-1 as the support which had a high catalytic performance, and the conversion of frequency(TOF) can reach 9161 h-1.2、Prepare method has great effect on the performance of nano-gold catalyst. Hydrothermal synthesis method and Deposition-precipitation method are good methods for the preparation of surpported nano-gold catalysts which have a high catalytic performance and steady structure. The catalytic activity of these catalysts had only a slight decrease after reused for three times. Based on structural characterization by XRD、FT-IR、SEM and TEM, The result showed that these Au/TS-1 catalysts have the similar formation of an MFI-structure, the size of gold particles as active centers highly dispersed on the surface of support is about 6 nanometers on Au/TS-1 and 5 nanometers on Au/MCM-41.3、Au/TS-1 catalyst, which was prepared by deposition-precipitaion method, showed high catalytic performance on cyclohexane selectivitive oxidation. The results showed that this catalyst had 11.20% cyclohexane conversion and 89.60% selectivity at 0.02g Au/TS-1(w(Au)%=1%)、150℃for 2.5h under the pressure of 1.0Mpa.4、Au/TS-1 catalyst was prepared supported by hydrothermal synthesis method and used as catalyst in selective oxidation of toluene to benzaldehyde in liquid phase. It was found that toluene oxidation produced benzaldehyde of 44.74% selectivity , benzoic acid of 54.77% selectivity and 20.54% conversion after reaction of 3 hours using Au/TS-1 as catalyst at 165℃under the pressure of 1.0MPa.更多还原