Processing catalytic converters means recovering the platinum, palladium, and rhodium trapped inside them. A typical converter contains 3 to 7 grams of platinum, 2 to 7 grams of palladium, and 1 to 2 grams of rhodium, all deposited on a honeycomb substrate. Extracting those metals involves a sequence of mechanical and chemical steps: opening the shell, crushing the substrate, testing its metal content, and refining the powder into pure metal.
What’s Inside a Catalytic Converter
The outer shell is steel. Inside sits a honeycomb-shaped substrate, either ceramic or metallic foil, coated with a thin washcoat that contains the precious metals. Ceramic substrates are far more common and shatter into brittle fragments when crushed. Metallic foil substrates are rarer and require a different approach because the foil needs a secondary carrier layer to hold the catalytic coating, making it harder to separate cleanly.
The precious metals are not visible to the naked eye. They’re dispersed at the microscopic level across the enormous surface area of the honeycomb. That’s why you can’t simply melt down a converter and pour off the platinum. The entire substrate has to be reduced to a fine, uniform powder before any meaningful extraction can happen.
De-Canning: Opening the Shell
The first physical step is de-canning, which means cutting open the steel housing to get at the substrate inside. Industrial operations use hydraulic shears or purpose-built crusher tubes. In a crusher tube system, the converter is loaded into a steel cylinder, and a hydraulic piston forces the internal material through a grate at the bottom. The substrate splinters into pieces roughly one to two inches in diameter as it passes through.
Smaller shops sometimes use angle grinders or reciprocating saws to cut the shell lengthwise and peel it apart. The steel casing itself is set aside for scrap metal recycling. What you’re after is the honeycomb material inside.
Crushing and Milling to Powder
The broken substrate chunks then go into a pulverizer, typically a knife-type or chain-type mill, which grinds the ceramic into a fine powder. This step is critical because the precious metals are distributed unevenly throughout the honeycomb. Down to the microscopic level, the material is inhomogeneous, so grinding it into a consistent powder is the only way to get an accurate sample for testing and an even feed for refining.
For XRF analysis (the most common quick-testing method), the powder is further processed using a vibratory disk mill or ring-and-puck mill, then pressed into a pellet with a binding agent. The finer and more uniform the grind, the more reliable the assay results.
Assaying: Finding Out What You Have
Before any refining happens, the powder needs to be assayed to determine exactly how much platinum, palladium, and rhodium it contains. This is the step that determines the value of the batch.
Energy-dispersive X-ray fluorescence (EDXRF) is a widely used method that gives quick, accurate readings of precious metal concentrations. The spectrometer fires X-rays at the pressed pellet, and each element fluoresces at a characteristic energy, allowing the machine to calculate concentrations. Results from EDXRF show good agreement with those from more labor-intensive wet chemistry methods like ICP-OES, making it the preferred screening tool for recyclers handling high volumes.
Fire assay is another common technique, especially for confirming values. A small, precisely weighed sample (an “assay ton” uses 14.58 grams of material) is mixed with a flux and smelted in a crucible. The flux collects the precious metals into a lead button, which is then cupelled (heated on a porous cup at around 1,700°F) until the lead is absorbed or volatilized, leaving behind a tiny bead of pure precious metals that can be weighed.
Refining: Extracting the Metals
Two main approaches are used to pull the precious metals out of the powdered substrate: pyrometallurgy (heat-based) and hydrometallurgy (chemical-based). Large-scale refiners often use both in sequence.
Pyrometallurgical Smelting
In this method, the powder is mixed with a flux at a ratio of roughly 6 parts flux to 1 part material and loaded into a crucible. The crucible goes into a furnace at 2,000°F for about 1.5 hours after the furnace reaches temperature. The flux melts and chemically binds to the base materials (the ceramic, oxides, and other non-precious content), floating them to the top as slag. The heavier precious metals sink to the bottom and collect in a metallic button.
That button then goes through cupellation at around 1,700°F to burn off remaining base metals, leaving behind a concentrated bead of platinum group metals. This bead can be further refined through chemical separation to isolate each metal individually.
Hydrometallurgical Leaching
The chemical route dissolves precious metals out of the powder using strong acids or specialized solvents. Traditional methods use a mixture of hydrochloric and nitric acid (aqua regia) to dissolve platinum and palladium. Newer research has explored deep eutectic solvents, combinations of compounds like choline chloride with organic acids, paired with selective extractants that pull specific metals out of solution. These newer methods aim to reduce the volume of hazardous acid waste generated.
Once dissolved, each metal is separated from the solution through selective precipitation or solvent extraction, where chemical reagents bind to one metal but not the others. The separated metals are then reduced back to solid form, washed, and dried.
Melting and Forming Finished Metal
After extraction and purification, the recovered platinum, palladium, and rhodium are melted and cast into bars, ingots, or sponge (a porous metallic form). These standardized forms make the metal easy to weigh, transport, and sell. Recyclers typically test the final product for purity to confirm it meets industry standards before it re-enters the supply chain for use in new converters, electronics, jewelry, or industrial applications.
Health and Safety Risks
Every stage of processing creates exposure hazards. Cutting open the steel shell generates metal fumes and sparks. Crushing and grinding the ceramic substrate releases fine silica-containing dust that can cause serious lung damage with repeated inhalation. The honeycomb coating also contains trace amounts of cerium, zirconium, and other metal oxides that become airborne during milling.
During smelting, temperatures above 2,000°F can volatilize lead (from flux collectors) and other toxic metals into the air. Hydrometallurgical processing involves concentrated acids that produce corrosive fumes and generate liquid waste containing dissolved heavy metals. At recycling facilities handling similar materials, NIOSH has measured worker overexposures to lead, cadmium, and chromium, sometimes even in areas away from the main processing zone due to dust migration and poor ventilation.
Proper processing requires sealed grinding equipment with dust collection, local exhaust ventilation at smelting stations, acid-rated fume hoods for chemical work, and respiratory protection rated for metal fumes and particulates. Wet cleaning methods should replace dry sweeping, which just re-suspends contaminated dust into the air.
Legal Requirements
Catalytic converter recycling falls under hazardous waste regulations in the United States. The Resource Conservation and Recovery Act (RCRA) governs how hazardous byproducts from refining, including acid waste, slag, and contaminated dust, must be handled, stored, and disposed of. Many states impose requirements stricter than the federal baseline, so the rules vary depending on where you operate.
Beyond waste handling, buying and selling used catalytic converters is increasingly regulated at the state level due to widespread theft. Many states now require recyclers to hold specific licenses, document the source of every converter they purchase, and maintain records that can be audited by law enforcement. Processing converters without proper licensing can result in criminal charges in some jurisdictions, separate from any environmental violations.