Jul-2012

Recoup money from your spent catalyst

How you can reap additional revenues from spent platinum process catalysts. Virtually all refining, petrochemical and chemical processors throughout the Middle East use precious metal-bearing catalysts to facilitate reactions and for controlling or abating toxic or noxious emissions.

Kevin Beirne
Sabin Metal Corporation

Article Summary

Metal-bearing catalysts typically contain platinum group metals (PGMs), which include platinum, palladium, ruthenium and rhodium, although some catalytic processes also employ other precious metals such as rhenium, gold and silver.

Precious metal-bearing catalysts are configured in many different forms including monolithic structures, beads, pellets, powders or extrudates (Figure 1); no matter what their composition, process catalysts have limited productive lives before they lose their efficacy and must be replaced with fresh stock.

Useful lives of precious metal-bearing catalysts vary, depending upon how and where they are employed. When these catalysts can no longer function effectively, users send them to a precious metals refiner to recover and refine their remaining precious metals. Precious metals refiners use a number of different techniques to recover PGMs and other precious metals from spent catalysts; some are different than others depending upon specific chemistry, application and other factors. However, all refiners must address certain key issues such as point-to-point logistics and transportation (many times across oceans and continents), accurate materials documentation, process efficiencies, environmental compliance, process turnaround times and many other considerations that have a direct affect on returned values to catalyst owners.

While each of these functions is important in the overall recovery/refining process, sampling spent catalysts is the most critical element in the entire process, since it requires achieving a virtually homogenous mass from a spent catalyst lot from which individual samples are subsequently removed for laboratory analysis.

Without accurate sampling methods, it is virtually impossible for any precious metals refiner to determine the precious metals content remaining in a spent catalyst lot. However, generating a homogenous mass for sampling is much easier said than done; spent processing catalysts and their carriers (these typically include soluble or insoluble alumina, silica/alumina or zeolites) are far from homogenous because of accumulated process contaminants of various densities, such as sulphur, carbon, solvents and water.

Because sampling is such a critical element in the overall refining/recovery process, catalyst owners should look carefully at a prospective refiner’s procedures, policies and equipment.

100% sampling is essential
One such policy (absolutely essential to help maximise returns) is the sampling of 100% of a spent PGM-bearing catalyst lot vs sampling a representative quantity only. Ideally, a continuous catalyst sampling system (Figure 2) that produces consistent, reproducible, statistically valid samples should be located at the refiner’s facility.

The system should generate samples that represent — as accurately as possible — multi-ton lots of spent catalysts that are typical for hydrocarbon and petrochemical plants. Even specialised equipment for capturing dust should be available for subsequent sampling of remaining dust from this process. The sampling system should generate individual lot samples for the catalyst owner, the refiner, an umpire (a mediator to settle disputes), and reserve samples.

The refiner should also permit the catalyst owner or its representative to observe the sampling process at all times.

Once sampling procedures are completed, representative samples must be assayed to measure their precious metals content. Precious metals refiners must perform assays with state-of-the-art laboratory instruments and procedures in order to achieve the highest possible level of accuracy. Typical assaying equipment and techniques include atomic absorption spectroscopy and inductively coupled plasma (ICP) emission spectroscopy (Figure 3), x-ray fluorescence, volumetric, gravimetric and fire assay techniques. Determination as to which combination of equipment and techniques should be used is based upon the types of materials being assayed.

Many organisations recover and refine PGMs and other precious metals from spent catalysts. While they all essentially perform the same function, it is important to be aware of some considerable differences between them, as these can have a significant impact on returns and, critically, affect the risk of litigation through exposure to local or foreign environmental and regulatory governing authorities. Therefore, it is in the catalyst owner’s best interest to learn as much as possible about the precious metals refiner under consideration. For example, information regarding how the refiner processes spent catalysts and what equipment and procedures it uses should be on hand. Particular areas of interest include the refiner’s process contamination removal methods, material sampling and assaying methods, environmental protection policies and procedures; compliance with international trade and logistics policies; and (perhaps most important) the refiner’s reputation with its long-term customers. All of these issues and more will have an impact on the relationship established with the precious metal refiner.