Single Catalyst Pellet Performance in Exothermic Multiphase Reaction Systems

许多商业上重要的化学品都是由 挥发性和非挥发性组分在 负载型催化剂 这些行动中有很大一部分是 有机化合物的氧化和氢化 贵金属和镍催化剂。 这种反应是一种 特种化学品生产的重要一步（用于 例如苯胺和巴豆醛）和生物化学品（用于 实例氢化植物油和木糖）。 此外 这些反应通常是多相的， 快速（质量传输有限）和相当放热。 的 反应热可导致液相汽化， 在催化剂颗粒孔内和外表面上。 充气中发生的气相催化反应 孔隙可导致颗粒内的大的上升 温度和压力。 整体费率也可能提高 基本上由于相变和气相 催化反应 不良高温偏移 (hot斑点）。 这些 单颗粒现象使设计和控制复杂化， 多相催化反应器 更好地了解 这些系统的新型多相反应器操作和 可以开发设计，其中的有益影响 非等温现象被利用或有害的 避免了影响。 PI正在计划一个基本的实验和建模 单载体催化剂颗粒性能的研究 在放热多相反应体系中。 单 颗粒或甚至单个孔隙水平通常决定了总体的 反应器行为 两个涉及环己烯的实验 计划在负载钯丸粒上氢化。 在 在第一个实验中，将小球悬浮在试管中， 与流动的液膜和环形气流接触。 的 总体、速率、外部润湿程度、颗粒质量和 颗粒温度将被监测为各种体积 情况变了 总速率的依赖性， 温度上升，以及内部和外部的程度 在本体条件下的润湿将被确定为相 改变发生了。 在第二个实验中， 扩散池和反应池将被开发用于更多的研究 详细描述了粒子内温度分布。 单 颗粒的一面被液体润湿，另一面被 油门 气体中温度上升的巨大差异- 填充液体的催化剂颗粒提供了一种探测 气体或液体填充孔的位置。 发展和 数值解的几个有关模型的单一， 将携带部分润湿和填充的催化颗粒 出去 研究应提供基本数据， 最终用于多相反应器设计。

Many commercially important chemicals are produced by the reaction of a volatile and a nonvolatile component on a supported catalyst. A large fraction of these actions are oxidations and hydrogenations of organic compounds over precious metal and nickel catalysts. Such reactions are an important step in the production of specialty chemicals (for example aniline and crotonaldehyde) and biochemicals (for example hydrogenated vegetable oils and xylose). In addition to being multiphase in nature, these reactions are typically fast (mass transport limited) and quite exothermic. The reaction heat can lead to liquid-phase vaporization both within the catalyst pellet pores and on the external surface. The gas-phase catalytic reaction occurring in the gas-filled pores can result in a large rise in the intraparticle temperature and pressure. The overall rate may also increase substantially as a result of the phase change and gas-phase catalytic reaction. Undesirable high temperature excursions (hot spots) within a catalytic reactor may result. These single pellet phenomena complicate the design and control of multiphase catalytic reactors. With a better understanding of these systems new types of multiphase reactor operations and designs can be developed in which the beneficial influence of the nonisothermal phenomena is exploited or the detrimental impact is avoided. The PI is planning a fundamental experimental and modelling study of the behavior of a single supported catalytic pellet in an exothermic multiphase reaction system. The single pellet or even single pore level often dictates the overall reactor behavior. Two experiments involving cyclohexene hydrogenation on a supported palladium pellet are planned. In the first experiment the pellet is suspended in a tube and contacted by a flowing liquid film and annular gas flow. The overall, rate, degree of external wetting, pellet mass, and the pellet temperature will be monitored as various bulk conditions are changed. The dependence of the overall rate, temperature rise, and the degree of internal and external wetting on the bulk conditions will be determined as phase change occurs. In the second experiment a novel multiphase diffusion and reaction cell will be developed to study in more detail the intraparticle temperature profile. The single pellet is wetted on one face by the liquid and on the other by the gas. The large differences of temperature rise in gas- and liquid-filled catalyst pellets provides a means of probing the location of gas- or liquid-fill pores. Development and numerical solution of several pertinent models of the single, partially wetted and filled catalytic pellet will be carried out. The research should provide fundamental data to be ultimately used in multiphase reactor design.