Supported catalysts are widely used in many industries. Manufacturing these catalysts is complex and manufacturing processes are influenced by many interdependent parameters. Although the performance and activity of catalysts are the most critical properties, their structures and design are also critical to their effectiveness. Previous work has shown that drying of catalysts can lead to the redistribution of metal and this in turn can affect the performance of the catalyst. At the same time, drying processes are often designed and scaled up by trial-and-error so it is desirable to have predictive models of the drying process. Previous experimental and modeling work has shown how the adsorption (of metal on the catalyst support) can significantly influence metal distributions at lower concentrations. It was also observed that at higher concentrations, adsorption was no longer the controlling factor, and solution properties began to control the metal distribution characteristics. Solution properties like density, viscosity, surface tension and volume ratio of metal all change as the metal concentration increases and these properties can in turn affect the distribution of metal during drying. In previous work, a drying model was developed that takes into account six different parameters to account for changes in solution properties as the concentration of metal increased. In this work, we carry out a parametric analysis, for nickel nitrate hexahydrate on a γ-alumina support, to investigate the relative importance of these parameters in accounting for metal redistribution during drying at high concentrations. A detailed analysis on each of the solution parameters, in terms of the drying rate and redistribution of metal, showed that only three of the parameters were important: the volume ratio of metal, the vapor pressure, and the solubility of the metal in the solution. Based on this, we have created a reduced parameter model with fewer parameters. This model can be used for different metal precursors without doing multiple expensive and time-consuming experiments. We tested this reduced parameter model using a new metal precursor (cobalt nitrate hexahydrate) on the same support, and modeling and experimental results for the new metal precursor are presented in this paper. We show that the reduced parameter model does not show appreciably different results from the more complex drying model and the results are in qualitative agreement with the experimental results.
ASJC Scopus subject areas
- Chemie (insg.)
- Chemische Verfahrenstechnik (insg.)
- Wirtschaftsingenieurwesen und Fertigungstechnik