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Catalyst recycling

Catalyst recycling: Shredding catalysts and selectively recovering precious metals

Processing of ceramic and metallic catalysts for platinum, palladium and rhodium

Used catalysts contain economically important platinum group metals such as platinum, palladium, and rhodium. To ensure the reliable recovery of these metals during refining, the catalyst must first be pre-crushed, finely ground, and homogenized to a defined standard. Crucial factors include reproducible digestion of the monolith, a representative sample, and a machine chain tailored to the material. Depending on the design—ceramic cordierite monolith or metallic support—the material behavior, dust generation, abrasiveness, and sample preparation requirements will vary.

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Why is the defined processing of catalysts so important?

Mechanical processing is the crucial preparatory step for analysis, evaluation, and precious metal recovery. The goal is not only volume reduction but, above all, the production of a homogeneous, representative sample for laboratory use, refining, and quality control. For ceramic monoliths, reproducible comminution, dust control, and uniform fineness are paramount. For metallic catalysts, additional attention must be paid to the casing, support structure, and material separation. A staged process chain improves the comparability of batches and creates a reliable basis for subsequent pyrometallurgical or hydrometallurgical processes.

Material data of used catalysts

Used catalytic converters typically consist of a ceramic honeycomb structure based on cordierite or a metallic support. A high-surface-area washcoat, usually aluminum oxide-based and often supplemented with cerium and zirconium oxides, is applied to the substrate. The economically relevant precious metals are platinum, palladium, and rhodium. For reprocessing, the monolithic structure, brittleness, dust behavior, any metal coating, and the required homogeneity of the sample are crucial.

PropertyValue
MaterialUsed vehicle catalytic converters
Alternative termsAutocatalyst, vehicle catalyst, spent catalyst
Carrier/substrateusually a ceramic monolith made of cordierite, alternatively a metallic support
TexturedHoneycomb-shaped monolith with many channels
Active washcoattypically aluminium oxide with cerium oxide and zirconium oxide components
Economically relevant metalsPlatinum (Pt), Palladium (Pd), Rhodium (Rh)
Material behaviorCeramic monoliths are brittle, metallic supports are tougher.
AbrasivenessApplication-dependent; relevant for tool wear in the case of ceramics.
Dust behaviorThis must be taken into account when processing dry crushing.
Relevance to the processA homogeneous sample and defined fineness are crucial for analysis and precious metal recovery.

Typical process in catalyst recycling

Mechanical processing typically begins with opening the casing and removing the monolith. This is followed by a staged comminution process until the material reaches a fineness suitable for homogenization, sampling, and refining. It is crucial that the precious metals are evenly distributed throughout the material and that the sample remains representative. Only then do analytical testing and hydrometallurgical or pyrometallurgical recovery steps take place.

Process stepObjectiveTypical machine / methodResult
Opening the case / DecanningSeparate the monolith from the metal casingmanual or mechanical pretreatmentexposed monolith or defined fraction
Pre-shreddingReduce volume and create manageable piece sizesJaw crusher or suitable pre-crusherlumpy material in the mm to cm range
Intermediate shreddingCreate a uniform grain distribution for subsequent processesRotor mill or hammer milldefined intermediate fraction
fine grindingproduce homogeneous powder for analysis or refiningdisc mill, ball mill or other fine millfinely ground material
HomogenizationBalance precious metal distributionMixing / Homogenizingrepresentative overall sample
Sample divisionGenerate a laboratory or retention sampleRotary sample divider or riffle dividerreproducible subsamples
Analysis / Refining PreparationDetermine metal content or feed into subsequent processLaboratory analysis, pyro- or hydrometallurgical processingreliable data or defined input material

Typical process parameters

The specific design depends on the construction, monolith material, metal content, desired analytical parameters, and the downstream refining process. In practice, feed sizes, intermediate particle size, final fineness, throughput, and sample mass are selected to ensure reliable operation and reproducible samples.

ParameterTypical area / Note
Task sizeDepending on the catalyst design and pre-separation, often several centimeters up to approximately 100 mm.
Intergranule after pre-crushingtypically a few mm to about 20 mm
Final finenessDepending on the application, from coarse granules to fine powder.
throughputfrom laboratory areas to continuous pilot plant or production quantities
Sample sizedepending on the analysis and batch size
material conditionDry processing is standard; special cases can be treated with cryogenic support.
Dust extractionExtraction and safe material handling recommended
The goal of fine grindinghomogeneous and representative sample for analysis or refining
Important selection criteriaSubstrate type, metal housing, target grain size, wear, cleanability, throughput
Next stepLaboratory analysis, pyrometallurgical or hydrometallurgical recovery

Variants, procedures and alternatives

Ceramic monolith vs. metallic support

Ceramic catalysts are usually brittle and can be ground down in stages. Metallic supports often require adapted pretreatment because the housing, film structure, and material separation affect the process.

Dry processing vs. cryogenic support

Dry processing is the standard for sample preparation and recycling. Cryogenic assistance can be useful when thermal stress, dust behavior, or material adhesion need to be reduced.

Laboratory sample vs. pilot or production batch

In the laboratory, representativeness and analytical performance are paramount. At the pilot plant or production scale, throughput, wear, dust management, and continuous material logistics also become important.

Which machines are suitable for catalyst recycling?

For recycling used catalysts, a staged machinery chain is usually advisable. The initial stage involves the reliable coarse reduction of the monolith or already decanted fractions. This is followed by fine grinding to produce a homogeneous powder sample. For reproducible analysis and evaluation processes, defined homogenization and sample division are then crucial. The specific selection depends primarily on the catalyst design, target particle size, sample size, dust behavior, and desired throughput.

Technical questions about catalyst recycling

Use LITech AI for typical technical questions regarding the processing of used catalysts, the selection of the appropriate machine, target particle sizes, homogenization, sample preparation and precious metal recovery.

FAQ on catalyst recycling

This usually refers to used vehicle catalytic converters with a ceramic or metallic substrate and precious metal coating made of platinum, palladium and rhodium.

Typical steps include opening the casing, removing the monolith, pre-crushing, fine grinding, homogenization, sample division, and subsequent analysis or refining.

For this application, jaw crushers or other pre-crushers are often used, followed by rotor mills, hammer mills or disc vibrating mills, as well as sample dividers for homogenization.

Typical are intermediate stages in the millimeter range and final finenesses from coarse granules to fine powder – depending on analysis, sampling and subsequent refining process.

Precious metals are not always evenly distributed. Only a homogeneous sample provides reliable analytical values ​​and dependable information about the economic metal content.

The focus is on platinum, palladium, and rhodium. Depending on the catalyst type and process, other components can also be considered separately.

It can be useful if heat generation, caking or certain material changes during grinding are to be avoided.

It serves for laboratory analysis, batch evaluation, process development and as a defined feedstock for pyro- or hydrometallurgical precious metal recovery.

Klaus Ebenauer

Ing. Klaus Ebenauer

info@litechgmbh.com
+43 1 99 717 55

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