COLL 177 |
| Azzeddine Lekhal, Benjamin Glasser, and Johannes G. Khinast. Chemical and Biochemical Engineering Department, Rutgers University, 98 Brett Road, Engineering Building/ Busch Campus, Piscataway, NJ 08854 |
| In our work we focus on the understanding of the influence of pH and ionic strength during the drying of impregnation catalysts. During this process, a redistribution of the catalyst occurs, which is a complex function of the drying conditions, the properties of the impregnating solution and the support material. To account for the pH and ionic strength effects, in our model the metal adsorption is described by the Revised Physical Adsorption (RPA) model developed by Regalbuto’s group. The results show that the impact of drying is strong when the initial pH of the liquid solution is below the point of zero charge (PZC). In such a case, the catalyst accumulates at the particle surface when the convective flow is strong and at the particle center when the solute-metal diffusivity is high. A comparison of our model with a drying model that assumes a constant adsorption equilibrium constant shows that the variations of pH and ionic strength cannot be ignored when the initial adsorption constant is low and the pH below the PZC. In such cases, the adsorption constant increases over several orders of magnitude when pH effects are accounted for. |
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The Science and Engineering of Catalyst Preparation
2:00 PM-5:25 PM, Monday, March 29, 2004 Marriott -- Orange County 3, Oral
Division of Colloid and Surface Chemistry |