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On the science of catalyst preparation: Platinum impregnation over oxides and zeolites.

机译：关于催化剂制备的科学：铂在氧化物和沸石上的浸渍。

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In this study, the preparation of silica-, alumina- and zeolite-based platinum catalysts through noble metal adsorption from aqueous solution is investigated. The Revised Physical Adsorption Model (RPA), derived from first principles without adjustable parameters and solely based on electrostatic interaction between metal complexes and an oxide support surface, was refined through a detailed individual consideration of ionic strength. In conjunction with a proton transfer model, the RPA model was used to simulate platinum (CPA) adsorption over alumina to a very reasonable degree without the use of adjustable parameters. It is shown how the model can in general be used to design a catalyst preparation method and how it was applied to an industrial platinum catalyst preparation problem, where the noble metal was to be selectively placed onto only one support material (zeolite) in the presence of another (silica).; Furthermore, the coordination chemistry of hydrogen hexachloroplatinate (IV) (CPA) in aqueous solution as well as in complexes adsorbed over alumina and its impact on catalyst preparation procedures are investigated using EXAFS. In disagreement with most available speciation models, the chlorine-oxygen ligand exchange process in aqueous solution was found to proceed to a fully oxygen coordinated, chlorine-free complex in dilute solutions at long times and high pH. The chlorine coordination number increases with lowered pH and raised chloride and CPA concentrations. Similarly, the speciation of adsorbed complexes also depends on the chloride concentration in the system, but is mainly a function of the local pH in the adsorbate layer at equilibrium. Given the wide pH shifts observed when large amounts of metal oxide are contacted with aqueous noble metal solutions (as it is commonly practiced in industrial catalyst preparation), the platinum coordination chemistry and thus the chlorine content of the final catalyst are directly influenced by the preparation conditions.
机译：在这项研究中，研究了通过从水溶液中吸附贵金属来制备二氧化硅，氧化铝和沸石基铂催化剂。修订后的物理吸附模型（RPA）是从没有可调整参数的第一原理出发，仅基于金属配合物与氧化物载体表面之间的静电相互作用而得出的，通过详细考虑离子强度来进行改进。结合质子传递模型，RPA模型用于在不使用可调参数的情况下，以非常合理的程度模拟氧化铝上的铂（CPA）吸附。显示了该模型通常如何用于设计催化剂的制备方法，以及如何将其应用于工业铂催化剂的制备问题，在该问题中，将贵金属仅在存在的情况下选择性地仅放置在一种载体材料（沸石）上另一个（二氧化硅）。此外，使用EXAFS研究了六氯铂酸氢盐（IV）（CPA）在水溶液中以及吸附在氧化铝上的配合物中的配位化学及其对催化剂制备程序的影响。与大多数现有的物种模型不同，水溶液中的氯-氧配体交换过程在长时间和高pH条件下在稀溶液中进行为完全氧配位，无氯的络合物。氯的配位数随着pH值的降低以及氯化物和CPA浓度的增加而增加。类似地，吸附的配合物的形态也取决于系统中氯化物的浓度，但主要是平衡状态下吸附物层中局部pH的函数。考虑到当大量金属氧化物与贵金属水溶液接触时观察到的宽广的pH值变化（这在工业催化剂制备中很常见），铂的配位化学以及最终催化剂的氯含量直接受到制备的影响。条件。

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