蛇形微通道内带催化反应边界的弹状流动及加氢反应特性研究

发布时间：2018-02-24 00:14

本文关键词： 微反应器弹状流动物质转化催化剂扰流柱　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着微加工及超精密加工技术的飞速发展,微型设备吸引了众多学者从各个领域对其开展研究。微反应器作为微型设备的一种,因其具有比表面积大、传递效率高、接触时间短、副产物少、安全性高、操作性好、放大设计容易、开发周期短等突出优势被广泛应用于化学、化工、能源、生物、材料等诸多领域。微反应器技术成为了相关领域专家研究的热点。本文针对带有催化剂涂层的气-液-固三相微反应器,以硝基苯加氢反应为研究对象,通过可视化实验对蛇形微通道内弹状流条件下含壁载催化反应的两相流动及物质转化进行了研究。利用化学还原浸渍法制备了纳米Pd/γ-AL2O3催化剂,并在蛇形微通道内壁载了催化剂涂层,通道尺寸为400μm(宽)×220μm(深)×846mm(长);研究了不同气液流量下微通道内弹状流动状态及其对气弹长度、液柱长度、空隙率等两相流动参数的影响,并研究了两相流动与催化反应及物质转化的耦合关系;改进了催化剂制备工艺,研究了其对微通道内硝基苯催化加氢反应的强化作用,研究了不同气液流量下具有扰流柱结构的蛇形微通道内的两相流动状态,分析了扰流柱结构所引起的气弹长度及气弹运动速度变化规律,在不同结构微通道内进行硝基苯催化加氢反应并对比了苯胺的产率;利用micro-PIV技术测量了不同结构微通道内的流场。主要研究结果如下:1)化学还原浸渍法制备的纳米Pd/γ-AL2O3催化剂粒径较小,单质Pd在载体γ-Al2O3上的分散性较好,活性较高,可实现在常温、常压下微通道内进行硝基苯催化加氢反应,并且反应速率较高。2)通过改变气液流量可获得初始气弹及液柱长度不同的弹状流型;在低气相流量下由于反应的进行,微通道内的弹状流有向泡状流转变的趋势;气相流量越大空隙率越大,气弹形变速率越快,液相流量越大空隙率越小,气弹形变速率越小;固定液相流量不变,出口苯胺浓度及物质转化率随气相流量的增加呈现先增大后减小的趋势,并在气体流量为40μl·min-1时,物质转化率达到最大值;固定气相流量不变,出口苯胺浓度与物质转化率随液相流量增加呈逐渐减小的趋势;在一定停留时间范围内,气弹越长,液柱越短,物质转化率越高。3)气弹经过扰流柱结构时气弹长度及气弹运动速度增加,在扰流柱区域内气弹长度及气弹运动速度出现震荡式波动,并且这种波动会随着扰流柱高度增加而增大;不同气液流量下气弹经过扰流柱区域时均出现长度及速度的增加与波动,在大气相流量及小液相流量下增加量与波动更加明显;相同气液流量下,带扰流柱结构的微通道内硝基苯催化加氢反应苯胺的产率高于无扰流柱结构通道。
[Abstract]:With the rapid development of micro-machining and ultra-precision machining technology, micro-equipment has attracted many scholars to study it from various fields. As a kind of micro-equipment, micro-reactor has large specific surface area and high transfer efficiency. Such outstanding advantages as short contact time, less by-products, high safety, good maneuverability, easy amplifying design and short development cycle have been widely used in chemical, chemical, energy, biological, etc. Materials and many other fields. Microreactor technology has become the focus of experts in related fields. In this paper, the hydrogenation of nitrobenzene was studied in gas-liquid-solid three-phase microreactors with catalyst coating. The two-phase flow and material transformation of wall-loaded catalytic reactions in a snake-shaped microchannel were studied by visualization experiments. Nano-sized PD / 纬 -Al _ 2O _ 3 catalysts were prepared by chemical reduction impregnation method. The catalyst coating was carried on the inner wall of the snake-shaped microchannel, and the channel size was 400 渭 m (width) 脳 220 渭 m (depth) 脳 846mm (long). The effects of the slug flow state in the microchannel under different gas-liquid flow rates on the two-phase flow parameters, such as gas elastic length, liquid column length, porosity and so on, were studied. The coupling relationship of two-phase flow with catalytic reaction and substance transformation was studied, and the catalytic hydrogenation of nitrobenzene in microchannel was studied by improving the preparation process of catalyst. The two-phase flow state in a snake-shaped microchannel with a spoiler column structure at different gas-liquid flow rates is studied. The variation of the length of the aerodynamics and the velocity of the air-elastic motion caused by the structure of the spoiler column is analyzed. The catalytic hydrogenation of nitrobenzene was carried out in different microchannels and the yield of aniline was compared. The flow field in different structure microchannels was measured by micro-PIV technique. The main results are as follows: (1) Nano-sized PD / 纬 -Al _ 2O _ 3 catalyst prepared by chemical reduction impregnation method has smaller particle size, better dispersion and higher activity of single PD on 纬 -Al _ 2O _ 3 carrier, and can be realized at room temperature. The catalytic hydrogenation of nitrobenzene was carried out in the microchannel under atmospheric pressure, and the reaction rate was higher. 2) the initial gas bomb and the slug flow pattern with different column length could be obtained by changing the gas-liquid flow rate. The bigger the gas flow rate, the faster the rate of Aeroelastic deformation, the smaller the void fraction of liquid flow, the smaller the rate of Aeroelastic deformation, and the less the flow rate of fixed liquid phase is. The concentration of aniline and the conversion rate of aniline for export increased firstly and then decreased with the increase of gas flow rate. When the gas flow rate was 40 渭 l 路min-1, the mass conversion reached the maximum. The concentration of aniline and the conversion rate of aniline for export gradually decreased with the increase of liquid flow rate, and the longer the gas bomb was, the shorter the liquid column was. The higher the mass conversion rate. 3) the longer the gas bomb and the velocity of the gas elastic motion increase when it passes through the structure of the spoiler column, and the oscillatory fluctuation of the length of the gas bomb and the moving velocity of the gas bomb appears in the region of the spoiler column. And the fluctuation will increase with the increase of the height of the turbulence column, and the increase and fluctuation of the length and velocity of the gas bomb in different gas-liquid flow rate will occur, and the increase and fluctuation will be more obvious under the atmospheric phase flow and the small liquid flow rate. At the same gas-liquid flow rate, the yield of aniline in the micro-channel with spoiler column structure is higher than that in the non-scrambling column structure channel.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052

【相似文献】