Stages in Catalytic Converter Recycling: Part 1

JULY 2022

Stages in Catalytic Converter Recycling – How Many Stages are there in the Catalytic Converter Recycling Process: PART 1

Toll refining catalytic converters seems a lot more complicated than just selling your units for cash. How does it work anyway? What are the stages in catalytic converter recycling? If you have wondered how it all works, then here we will go back to basics and describe the toll refining method and hopefully shed some light on the topic while also dispelling a few myths. We will also discuss when suppliers get paid in the process and show why that distinction is important.

Acquisition: The first step in the recycling process is, simply enough, acquiring catalytic converters. The methods for this vary based on business model/type, but they boil down to buying cores directly, or processing end-of-life vehicles. No matter which method you use, your converters have to go somewhere! Regardless of what kind of company you sell your converters to, they always end up at a toll refiner.

After a toll refiner receives converters, they are counted or graded (the detail of which varies from company to company). This is an important step in understanding the baseline that will be used for comparison later. How many total units were there? How many were full or half full? How many were DPF/after markets/foil?

Once the converters have been counted, they must be decanned. This means any pipes, shields, and metal shells must be removed. The most important part of this step is dust capture; dust produced during this stage often has twice the concentration of precious metals. It is imperative that whoever does the decanning stage has the proper set-up to capture this dust. Some companies do this step themselves, and there is a persistent myth that doing so increases the value of their material. This is not the case.

When decanning is completed, the loose ceramic contained within the converters must be crushed, milled, and commingled (mixed). The result is a mixture that is homogenous (the same throughout), so any one sample taken is identical to any other.

In preparation for analysis, samples are extracted from the homogeneous mixture. Upon reaching the laboratory, the samples are processed in a way determined by the method of analysis.

1. XRF (X-ray Fluorescence): XRF is the more common method of determining precious metal content within a load/sample of catalytic converters. XRF is a non-destructive technique that measures fluorescent secondary x-rays emitted by the sample. A lab grade XRF machine is not the same as an XRF gun. While they both operate on the same scientific principles, the lab machine can analyze a homogenous sample and provide results for a load of converters, and the XRF gun will give a reading only on the small section at which it is pointed.

2. ICP (Inductive Coupled Plasma): While many companies claim they can sample converters, most of them might have an XRF machine at best, or even an XRF gun. The real “Gold Standard” for toll refining companies is the ICP machine, which is much more precise. The powder sample is converted into a liquid, and the elements contained within are separated. Plasma flame is used to make the elements visible as light, and the precious metal content is measured against the ceramic substrate (by light intensity), indicated as parts per million (PPMs).

With the completion of laboratory analysis, the value of the load of converters is determined by a combination of the PPMs of precious metals, net weight of the ceramic, and the market prices for the metals at the time of sale. It is at this stage that all recyclers are paid, whether the company who assayed the material has a smelter or not. In a follow-up article we will discuss what happens after the assay process, so keep an eye out for part 2!

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