Recovery of Precious Metals in Spent Process Catalysts

Catalysts are important tools in the synthesis of active pharmaceutical ingredients. Recovery of precious-metal catalysts from a pharmaceutical manufacturing process is a factor in cost control and environmental compliance.
Aug 01, 2007
Volume 2007 Supplement, Issue 3

Catalysts, which are used to enhance and expedite chemical reactions, are a necessary part of pharmaceutical processing. That process not only involves using the catalyst in the synthesis of an active ingredient or intermediate but further involves recovery of the catalyst. When the catalyst includes Platinum Group Metals (PGMs), such as platinum, palladium, ruthenium, and rhodium, efficient recovery is particularly important in controlling costs in a manufacturing. Effective selection of a precious-metal refiner in the catalyst recovery process is a factor in achieving those cost savings.

Precious metals in pharmaceutical processing

Precious-metal catalysts are typically supported on carriers. Carbon supports are the most common carrier media for precious metal-bearing catalysts in the pharmaceutical processing industry. Heterogeneous palladium on carbon, platinum on carbon, palladium on alumina, and palladium on calcium carbonate are examples of catalysts and their supports that facilitate hydrogenation of intermediates. These catalysts do not last forever and, when spent, the PGMs from the catalysts need to be recovered. A precious-metal refiner can be used for this function.

Precious-metal recovery and refining

Selection criteria for a precious-metal refiner.
The precious-metals recovery and refining process involves complex procedures and policies that include materials documentation, contamination removal, sampling, assaying, recovery, refining, processing turnaround time, and environmental considerations. A refiner's effectiveness in executing these functions can determine the amount of PGMs recovered from spent catalysts, the turnaround time, and the value returned to a pharmaceutical manufacturer. The monetary value of PGMs varies with their price fluctuations on a given commodities market. To understand the criteria in selecting a precious-metal refiner (see sidebar), it is important to understand the equipment, sampling techniques, and environmental considerations in precious-metal catalyst recovery.

Equipment. Most refiners use a wide variety of equipment to process spent catalysts. This equipment includes rotary and crucible furnaces, kilns, roasters, thermal processors, pulverizers, granulators, screens, blenders, auto samplers, reactors, dissolvers, precipitators, electrolytic cells, and filter presses. In selecting a precious-metals refiner for a partner relationship, a pharmaceutical manufacturer should be aware of some of the key steps within the refiner's process and how the various equipment and tools are applied to spent catalyst lots. Sampling and assaying are two of the more important procedures that help to ensure optimum return of PGMs from spent catalysts.

Sampling techniques. Precious-metal refiners generally use three different sampling techniques: dry sampling, melt sampling, and solution sampling. The choice of method depends on the type of material to be processed and its precious-metal content. Because most catalysts for pharmaceutical processing are based on carbon, dry sampling is often applied to these materials. Dry sampling is the most complex of the three sampling approaches and is used when materials cannot be dissolved in a solution or are not suitable for melt sampling because of their structure. Because it is difficult to achieve true homogeneity by means of dry sampling, refiners using this technique should have expertise and sound judgmental skills. And for maximum sampling accuracy, spent catalysts must be properly prepared prior to dry sampling.

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