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The objective of this study is to prepare multilayered catalysts by successive impregnation and to develop mathematical models for the catalyst preparation, including isothermal successive impregnation and non-isothermal drying. Independent experiments have been designed to determine the parameters used in the mathematical model, including adsorption-desorption equilibrium constant, maximum surface concentration, adsorption rate constant, and effective diffusion coefficient. The mathematical model with independently determined parameters can be used to predict the active metal distribution inside the porous catalyst support.
Alumina supported catalysts have been prepared by various impregnation methods, including single impregnation of nickel, single impregnation of molybdenum, co-impregnation of nickel and citric acid, co-impregnation of molybdenum and nickel, and successive impregnation consisting of single impregnation of molybdenum followed by co-impregnation of nickel and citric acid. The resulting internal metal profiles have been determined by Electron Probe Microanalysis (EPMA), and the total metal contents by Atomic Absorption Spectrometry (AAS). Consistence of active metal profiles between the proposed successive impregnation model and the EPMA data have shown that the mathematical model can be used as a tool in designing the preparation procedures of multilayered catalysts.
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