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Catalytic converter recycling: key questions answered by PMR chemist Martin Paradis

Recovered automotive catalytic converters contain precious metals including platinum, palladium and rhodium.
Recovered automotive catalytic converters contain precious metals including platinum, palladium and rhodium.

The recycled catalytic converter industry has been constantly evolving over the last 25 years. Traditionally, converter buyers would have three grades in mind: small, medium and large. At Montreal-based PMR Inc., a dedicated catalytic converter recycling specialist and a leading converter information provider and toll refining purchaser in North America, they now have over 65 grading categories and over 20,000 serial numbers. 

PMR is a vendor of precious metals, including platinum, palladium and rhodium, which are sold directly to end users. The company makes purchases based on recovered precious metals contained in catalytic converters, and offers an extensive online database that provides up-to-the-moment pricing for more than 20,000 individual pieces.

One of the big questions regularly asked by automotive recyclers is: how does a catalytic converter recycling company value the material it receives from suppliers and put a fair market price on it for the subsequent sale? The answer to this question is as varied as the companies involved in buying and selling recovered catalytic converters. 

Ultimately, the value of materials depends on the technical abilities and knowledge of each company involved. In the end there is only one way to put a true value to scrap converters and that is to de-can, process, sample and assay the ceramic material that is contained inside them. ("Assay" is defined here as the process of analyzing a substance to determine its precise composition.)

This process can be complex. There are very few converter companies, such as PMR, that have in-house laboratories. For some companies, just having a laboratory does not always ensure that converter precious metal values are accurate. Processing, sampling and assaying ceramic catalyst requires very precise formulas to be followed and applied to get the correct readings from lab machines. If the internal assay formulas are not correct, the ceramic or converters can either be undervalued or overvalued. 

With over 20 years in analytical chemistry, Martin Paradis recently brought his investigative and methodical experience to the PMR catalyst laboratory. Starting his career as a lab technician and analyst, Paradis progressively developed his knowledge, taking on positions in metrology and instrumentation, and now manages the research and development side of PMR's lab. Paradis' degree in analytical chemistry, accompanied by his many accreditations and certifications in natural science, has enabled him to enhance, run and manage the PMR laboratory, which is dedicated to the assaying of catalyst materials.

Following are answers to some of the most frequently asked questions that PMR receives from recyclers about the assay process for end-of-life catalytic converters.

What is an assay and what information is produced from 
a catalyst assay result?

In laymen's terms, an assay is the process of analyzing a substance to determine its precise composition. Platinum Group Metals (PGM) in spent catalysts can be analyzed very accurately, even in low concentrations. The measurement used to express the concentration of PGMs in spent catalysts is parts per million (ppm). All converters in the global recycling stream end up being sold on assay, as it is the only process that defines the number of troy ounces (unit of measure used for weighing precious metals) derived from each precious metal within automotive catalyst. Those metals include platinum, palladium and rhodium.

What are typical methods 
of analysis?

PGMs are typically analyzed by spectroscopy, where different analytical methods are available. X-Ray Fluorescence Spectroscopy (XRF) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) are the most frequently used methods. Different methods require different instruments and different ways to prepare the sample, which are chosen according to specific criteria, such as sample type, specifications, time, costs, etc.

The most common instrument for analysis is the benchtop XRF as it is easy to use and reasonable in cost. Nevertheless, expertise and proficient knowledge is needed for machine calibration to produce correct results. There has been significant enhancements and developments in recent years that have highly improved the accuracy of these machines. Consequently, proper calibration and sampling with XRF can provide a very good reading of materials.

The most common instrument used in laboratories, including PMR's, is the ICP-OES, which requires exceptional skill and expertise in analytical chemistry for machine use and sample preparation. This instrumentation provides excellent accuracy but is also extremely costly and time consuming.

Regardless of the chosen method, the most important factor that will influence the rest of the process, including the chosen instrumentation, will be the sample itself. Sampling is extremely important as it needs to be representative and in the appropriate form to produce accurate results. Sample particle size can affect homogeneity, which is an important factor in producing accurate readings.

Which is better: ICP or XRF?

From a technological point of view, both methods are different, and each have their advantages. XRF is fast, inexpensive and sample preparation is simple. When properly calibrated, modern XRF instruments yield excellent results. ICP-OES is very accurate, can detect very low concentrations of PGMs and requires a very small sample to obtain results. XRF is a reliable and quick alternative to ICP-OES, and both methods are very good for PGM analysis. Most laboratories will use multiple methods and different catalyst technologies to conduct both a preliminary and final analysis on every tested sample.

How confident are you in the reliability of your results?

At PMR, we have a state-of-the-art laboratory using the most modern and sophisticated technologies and instruments to guarantee the best possible results for our customers. Our team of trained and dedicated chemists ensures that every analysis is done in a timely, accurate and professional manner. The confidence we have in our methods is highlighted through our transparent practices, which allow customers to access their samples up to three months post analysis to check any result with a third-party laboratory.

What specific questions should recyclers ask when processing converters and analyzing assay results?

The above information surely debunks some of the common misconceptions concerning analytical processes related to catalyst assays. Bearing in mind the information shared, questions to consider if you are currently processing your converters and receiving assay results would be how transparent are the results that you are getting? In your final report, are you being shown total recovered PPMs and troy ounces per metal? Is your carbon percentage by material type made visible? More importantly, who is conducting the analysis of your sample and do they have the certified degrees and expertise to provide you with an accurate and transparent result?

This article was originally published in the May/June 2021 edition of Recycling Product News, Volume 29, Number 4.

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