【作者】 李雪；

【导师】 徐南平； 范益群；

【作者基本信息】 南京工业大学 ， 化学工程， 2006， 博士

【摘要】 近年来,随着半导体、石油化工等领域对高纯氢气需求的不断增长,氢能源已经广为人们所重视。金属钯及其合金膜由于具有透氢性能良好和耐高温的特点,除了用作氢气分离和纯化器外,还可以用作脱氢、制氢等反应的反应器,实现反应和分离的一体化。但是,从该类材料目前的研究状况来看,所开发的膜材料仍存在一些亟待解决的问题----金属钯膜氢气通量较小、成本较昂贵以及化学稳定性较差。解决上述瓶颈问题的关键在于:将金属膜沉积在多孔支撑体表面,降低金属膜层厚度,开发新的制膜方法与工艺来改善金属膜微观结构。在实验室前期工作的基础上,借助于X射线衍射(XRD)、扫描电镜-元素分析(SEM-EDS)、原子力显微镜(AFM)等分析测试手段对光催化法制备金属钯膜的工艺优化、膜材料的开发做了一些新的探索。在本实验室前期的光催化过程中,溶液内易发生均相反应,从而直接影响钯膜的致密性,同时支撑体TiO2半导体表面的物理化学性质与光催化的效果也息息相关。基于膜材料的微观结构制约其宏观性能,并且是其工艺的综合反映的基本概念,首先对镀液的配置和二氧化钛半导体的物性进行了系统的研究。结果表明,在光催化反应体系中引入络合剂EDTA,可以抑制均相反应的发生、改善金属钯膜的物理化学性质,并且制备了系列片式超薄金属复合钯膜。实验过程中通过添加络合剂,不仅解决了镀液稳定性的关键问题,而且可以控制光催化反应速度,所制得的金属钯膜的晶粒较小;同时EDTA可以改变TiO2的导带结构,增加了基膜二氧化钛的导带边界与金属钯离子还原电势的能级差,有利于促进光催化反应的进行。上述研究对制备性能良好的金属钯膜具有指导性意义。其次,针对光催化制备金属钯膜致密性较差的问题,以光的入射效率对钯膜致密性影响较大为切入点,对光催化制备的方法进行了改进。本文首次将光催化反应在TiO2表面的Pd (II)液膜中进行,而不是在光催化反应槽内进行,并放大为管式外膜。研究结果表明,采用该种方法不仅避免主反应体系的均相反更多还原

【Abstract】 In recent years, the demand for highly pure hydrogen is increasing rapidly due to many fields such as those used in semiconductor manufactures and petrochemical processing. It is well known that Pd and its alloy membranes have been commonly used as hydrogen separators and hydrogenation /dehydrogenation membrane reactors. However, most of the available Pd membranes have not been up to the industrial standards, mainly due to the low hydrogen permeance, high cost, and undesirable mechanical stabilities. Three general approaches may be followed: to be deposited on a porous support, decrease Pd membrane thickness and optimize Pd membrane microstructure.The present study was based on the previous work and aimed in investigating optimizing and exploiting new process for palladium and alloy membranes for hydrogen with aid of XRD, SEM-EDS and AFM analysis. This paper reviews the principle, preparation and characterization of the palladium-based composite membranes and a novel photocatalytic deposition technique in our group is highlighted for membrane preparation. Compared with the previous work in our lab, the photocatalytic reaction rate can be well controlled by adding chelating agents and palladium crystalline grain became fine, which will make the metal membrane denser. Also, the enhancement of the photocatalytic deposition by the addition of EDTA may be caused by the upward shift of the conduction band energy of TiO2 due to the negative charge of the chelating agents.The PCD method was improved and ultra-thin Pd membranes supported on TiO2 outer tubes were prepared by the method, which is interpreted by the photocatalytic reaction at the TiO2 semiconductor/Pd (II) liquid film interface by directly irradiating. The TiO2 supports were prepared by the wet chemical method. And the reaction更多还原