Heterogeneous Catalysis in Supercritical Fluids: The Enhancement of Catalytic Stability to Coking

超临界流体中的多相催化：焦化催化稳定性的增强

• 批准号: EP/D503892/1
• 负责人: Joseph Wood
• 金额: $ 24.91万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD503892%2F1
• 关键词: Heterogeneous; Catalysis; Supercritical; Fluids; Enhancement

Catalytic reactions are used across a wide range of industrial manufacturing applications from petrochemicals to fine chemicals. Basically, a catalyst is a material added to speed up the reaction, without being changed itself. In heterogeneous catalytic reactions, the catalyst consists of solid pellets loaded with metal active ingredients, which speed up the reaction in the gas or liquid phase. They are called 'supported metal catalysts'. Pd/alumina catalysts are an example of such a class of catalysts, which consist of an alumina support with a high surface area (200-300 m2/g) containing many small pores of the order of typically 1-50 nm in diameter. Within the catalyst pores, the Pd metal is deposited in clusters, which act as the active sites that catalyse reactions. During their lifetime catalysts deactivate, that is lose some of their ability to increase the rate of reaction. There are several reasons why this may happen, for example the reactants become transformed into unwanted side products, which stick to the catalyst surface. Over a period of time and under elevated temperatures these species effectively burn on to the catalyst surface to form carbonaceous deposits called coke. This has the effect of covering or deactivating the active metal sites, and also blocking the pores or hindering the passage of reacting molecules from the bulk fluid outside the catalyst to the active sites within the catalyst pellet.Chemical Engineers are interested in ways to reduce catalyst deactivation so as to use the catalyst for as long as possible. This research proposal is concerned with doing just that. In particular, we seek to use supercritical fluids as special solvents for conducting catalytic reactions, since previous work has suggested that catalysts may deactivate less rapidly under such conditions. Supercritical fluids are substances which are heated and pressurised above a certain temperature and pressure called the critical point, which is a property of the substance itself. Above this point there is no longer a clear liquid and gas phase, but a single supercritical phase that has some of the properties of both. For example in supercritical fluids reactants display fast rates of diffusion like a gas, and dissolve other materials as well as a liquid can. We propose to exploit these advantages to help remove coke from the catalyst surface, by operating the reaction in a supercritical solvent such as C02. By carefully adjusting the pressure and temperature, the coke will be dissolved and transported in C02 so that less is deposited inside the catalyst and the useful lifetime is extended. We will select a suitable catalyst to carry out reactions in a conventional reactor packed with the catalyst, then perform the same test reaction under supercritical conditions. This will allow us to compare the coke deposition under the two sets of conditions, based on the same reactant conversion or operating time during the reaction. Two reactions of industrial relevance have been selected: isomerisation of hexene and hydrogenation of naphthalene.Characterization tests will be carried out to determine how the catalyst pore structure changes between the fresh unused catalyst, and the catalyst used under sub and supercritical conditions. Standard characterization tests will be used to determine the pore size distribution, but more sophisticated analyses will reveal information such as the pore shape and show the distribution of pores of different sizes. From these characterisation tests a computer model of catalyst structure and behaviour will be developed, allowing for diffusion of reactants into the pores, reaction rate and coke deposition. By running the model under different input conditions, the optimal catalyst pore structure and reactor operating conditions such as temperature and pressure will be selected. The overall objective of the project will be to recommend suitable conditions to maximise catalyst

催化反应用于从石油化工到精细化工的广泛工业制造应用。基本上，催化剂是一种添加以加速反应的材料，本身不会发生变化。在非均相催化反应中，催化剂由负载有金属活性成分的固体颗粒组成，其加速气相或液相中的反应。它们被称为“负载型金属催化剂”。Pd/氧化铝催化剂是这类催化剂的一个实例，其由具有高表面积（200-300 m2/g）的氧化铝载体组成，所述氧化铝载体含有许多直径通常为1-50 nm量级的小孔。在催化剂孔内，Pd金属以簇的形式沉积，其充当催化反应的活性位点。在催化剂的使用寿命期间，催化剂会失活，也就是说失去了一些提高反应速率的能力。可能发生这种情况的原因有几个，例如反应物转化为不需要的副产物，这些副产物粘附在催化剂表面。经过一段时间和高温下，这些物质有效地燃烧到催化剂表面，形成称为焦炭的碳质沉积物。这具有覆盖或失活活性金属位点的效果，并且还阻塞孔隙或阻碍反应分子从催化剂外部的本体流体到催化剂颗粒内的活性位点的通道。化学工程师对减少催化剂失活的方法感兴趣，以便尽可能长地使用催化剂。这项研究计划就是要做到这一点。特别是，我们寻求使用超临界流体作为进行催化反应的特殊溶剂，因为以前的工作表明，催化剂可能会在这种条件下失活不太迅速。超临界流体是被加热和加压到一定温度和压力以上的物质，称为临界点，这是物质本身的性质。在这一点以上，不再有一个明确的液相和气相，而是一个单一的超临界相，具有两者的一些性质。例如，在超临界流体中，反应物显示出像气体一样的快速扩散速率，并且溶解其他材料以及液体。我们提出利用这些优点，通过在超临界溶剂如CO2中操作反应来帮助从催化剂表面除去焦炭。通过仔细调节压力和温度，焦炭将溶解并在CO2中运输，使得更少的沉积在催化剂内部并延长使用寿命。我们将选择合适的催化剂，在装有催化剂的常规反应器中进行反应，然后在超临界条件下进行相同的试验反应。这将使我们能够比较两组条件下的焦炭沉积，基于相同的反应物转化率或反应期间的操作时间。选择了两个与工业相关的反应：己烯异构化和萘加氢。将进行表征试验，以确定新鲜未使用的催化剂与在亚临界和超临界条件下使用的催化剂之间催化剂孔结构的变化。将使用标准表征测试来确定孔径分布，但更复杂的分析将揭示诸如孔形状等信息，并显示不同尺寸的孔的分布。从这些表征测试中，将开发催化剂结构和行为的计算机模型，允许反应物扩散到孔隙中，反应速率和焦炭沉积。通过在不同的输入条件下运行该模型，将选择最佳的催化剂孔结构和反应器操作条件，如温度和压力。该项目的总体目标将是推荐合适的条件，以最大限度地提高催化剂

项目成果

Modelling of pore structure evolution during catalyst deactivation and comparison with experiment

• DOI: 10.1016/j.ces.2010.07.027
• 发表时间: 2010-10
• 期刊: Chemical Engineering Science
• 影响因子: 4.7
• 作者: Peter I. Chigada;Jiawei Wang;B. Al-Duri;J. Wood;S. Rigby

Improving the interpretation of mercury porosimetry data using computerised X-ray tomography and mean-field DFT

• DOI: 10.1016/j.ces.2011.02.031
• 发表时间: 2011-06
• 期刊: Chemical Engineering Science
• 影响因子: 4.7
• 作者: S. Rigby;Peter I. Chigada;Jiawei Wang;S. Wilkinson;Henry Bateman;B. Al-Duri;J. Wood;S. Bakalis;T. Miri

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

超临界条件下 Y 型沸石和 ZSM5 催化剂上 1-己烯异构化过程中的失活

• DOI: 10.1021/ie101876f
• 发表时间: 2011
• 期刊: Industrial & Engineering Chemistry Research
• 影响因子: 4.2
• 作者: Hassan F

Prolonging catalyst lifetime in supercritical isomerisation of 1-hexene on Pt/Al2O3.

延长 Pt/Al2O3 上 1-己烯超临界异构化的催化剂寿命。

• 发表时间: 2008
• 作者: J Wang