钯银、铂锡纳米晶及其催化性能研究

发布时间：2018-11-20 15:40

【摘要】：贵金属钯、铂催化性能优异,是工业生产中重要的金属催化剂。为解决钯、铂储量稀少的问题,我们发展了胶体化学方法制备了钯银、铂锡纳米晶,并将其分别用于催化加氢反应及电催化甲酸氧化反应,其优异的催化性能使钯、铂资源的高效利用成为可能。双金属纳米晶的催化性质与纳米晶尺寸、形貌、组成等结构因素密切相关,因此,发展高效催化剂依赖于对反应的深入理解和可控的纳米合成技术。本论文通过可控的改变钯银、铂锡纳米晶的组成,显著地提高了催化剂的活性和反应的区域选择性,并经过系统的表征手段加深了对催化剂结构-性质关系的认识。制备了优异的脱氯加氢催化剂——钯银合金纳米晶。在十八胺体系,合成了一系列具有不同比例,尺寸均一的钯银合金纳米晶。通过对不同时间钯银合金纳米晶产物的表征,我们研究了纳米晶的生长过程。此系列纳米晶的催化活性在催化4-氯苯酚的脱氯加氢反应中展现了显著的组成依赖性,明确了钯、银在催化加氢过程中的不同作用,为设计更好的环境保护催化剂提供了依据。制备了尺寸均一的不同组成的铂锡纳米晶,并将其应用于α,β不饱和醛的羰基选择性加氢反应中。X射线表征揭示铂锡纳米晶的结构随着锡含量增加发生的变化:由氧化锡“补丁”的铂锡合金转变为氧化锡“补丁”的铂团簇。在肉桂醛的催化加氢过程中,随着锡含量的增加,目标产物不饱和醇的选择性增加,而催化活性呈现出先增加后降低的特点。实验证明铂在反应中起到解离氢的作用,而密度泛函理论计算表明氧化锡中的氧缺陷在促进羰基吸附中起到了决定性作用。此课题研究了“组成-结构-性质”的关系,为生物质转化催化剂的合成提供了思路。探索了低温一步合成铂锡金属间化合物技术,制备并研究了凹面立方体和多缺陷立方体的Pt3Sn形成的机理。不同形貌的Pt3Sn显示出不同的电催化甲酸氧化活性,由于结合了金属间化合物的稳定性和缺陷的活性,多缺陷立方体Pt3Sn的活性与抗中毒性最好。此项研究改善了金属间化合物形貌控制研究稀少的现状,为金属间化合物的催化应用提供了物质基础。
[Abstract]:Noble metal palladium and platinum have excellent catalytic performance and are important metal catalysts in industrial production. In order to solve the problem of scarce storage of palladium and platinum, we developed colloidal chemical methods to prepare palladium silver and platinum tin nanocrystals, and used them for catalytic hydrogenation and electrocatalytic formic acid oxidation respectively. The efficient utilization of platinum resources is possible. The catalytic properties of bimetallic nanocrystals are closely related to the structural factors such as size, morphology and composition of nanocrystals. Therefore, the development of efficient catalysts depends on in-depth understanding of the reaction and controllable nanosynthesis technology. By changing the composition of Pd-Ag and Pt-Sn nanocrystals, the activity of the catalyst and the regional selectivity of the reaction were improved significantly, and the relationship between the structure and the properties of the catalyst was further understood by means of systematic characterization. Palladium silver alloy nanocrystalline was prepared as an excellent catalyst for dechlorination hydrogenation. In octadecylamine system, a series of palladium silver alloy nanocrystals with different proportion and uniform size were synthesized. The growth process of palladium silver alloy nanocrystals was studied by characterization of nanocrystalline products at different times. The catalytic activity of this series of nanocrystals in the dechlorination hydrogenation of 4-chlorophenol showed a significant component dependence, and the different roles of palladium and silver in the catalytic hydrogenation process were clarified. It provides a basis for the design of better environmental protection catalyst. Pt-Sn nanocrystals with uniform size were prepared and applied to 伪. In the carbonyl selective hydrogenation of 尾 -unsaturated aldehydes, X-ray characterization revealed that the structure of platinum and tin nanocrystals changed with the increase of tin content: from the "patch" of tin oxide to the platinum cluster of "patch" of tin oxide. In the process of catalytic hydrogenation of cinnamaldehyde, the selectivity of unsaturated alcohols increased with the increase of tin content, while the catalytic activity increased first and then decreased. The experimental results show that platinum plays a role of dissociation hydrogen in the reaction, and density functional theory shows that oxygen defects in tin oxide play a decisive role in promoting carbonyl adsorption. The relationship between composition, structure and property is studied in this paper, and the synthesis of catalyst for material transformation is provided. The technology of one-step synthesis of platinum-tin intermetallic compounds at low temperature was explored. The formation mechanism of Pt3Sn for concave cube and multi-defect cube was prepared and studied. Different morphologies of Pt3Sn showed different electrocatalytic formic acid oxidation activity. Because of the combination of intermetallic compound stability and defect activity, multi-defect cube Pt3Sn had the best activity and anti-toxicity. This study improves the present situation of morphology control of intermetallic compounds and provides a material basis for the catalytic application of intermetallic compounds.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O643.36;TB383.1

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