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
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
Selection criteria for a precious-metal refiner.
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.
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.