(135a) The Effect of Drying on the Metal Distribution of Supported Catalysts with High Metal Loadings

Cody Bishop, Anusha V. Noorithaya, Prateek Sarkar, Johannes G. Khinast and Benjamin J. Glasser

Department of Chemical and Biochemical Engineering,

Rutgers University, Piscataway, NJ, 08854

Supported catalysts are essential components in a variety of industrial processes, ranging from catalytic converters to production of new drugs. The demand for these supports is due to their high surface area, high mechanical and thermal stabilities. The performance of a catalytic process is intimately related to the catalyst design which results in various metal profiles - uniform, egg-yolk, egg-shell and egg-white profiles. Although catalyst preparation and catalytic processing have been investigated for many years, many aspects of catalyst manufacturing are still not fully understood. In the industry, catalyst design is usually based on trial and error, which is expensive, time-consuming, and does not offer assurances on the final results.

It is generally believed that the metal profile is controlled by the conditions that are applied during impregnation, however, experiments have shown that drying can also significantly impact the metal distribution within the support. Therefore, to achieve a desired metal profile we need to understand both impregnation and drying. Controlling the impregnation and drying conditions can enhance catalyst performance, and minimize the production of useless batches that have to be disposed, or recycled.

In this work we have investigated the metal distribution during the high concentration impregnation and subsequent drying of supported catalysts. Previous work found that high concentration impregnation (3-4 molar) and drying of Ni/Alumina catalysts yield a uniform metal distribution. At intermediate concentrations (~1 molar), the Ni\Alumina catalysts yielded egg-shell profiles. Theoretical models to simulate the impregnation and drying processes of Ni/Alumina had been previously developed. The high concentration drying model was developed for the higher concentrations of nickel nitrate (above 0.1 M). This included the effects of the metal concentration on the solution density, viscosity, surface tension, vapor pressure and the volume ratio of metal. Good agreement was found between experimental and simulation post-drying metal distributions for this model using nickel nitrate. To make the above model widely applicable to many more metals, we designed a simplified model, the reduced parameter model. A detailed analysis on all the solution properties and adsorption parameters was done using experimentally determined properties of nickel nitrate as a reference. The reduced parameter model was tested using properties and parameters of copper nitrate.

Our experiments have allowed us to better understand the fundamental mechanisms that occur during drying, and to develop a strategy that can generate desired metal profiles. Although the results presented are based on a particular metal/support system, they serve to provide physical insight into the fundamentals of the drying processes.