A catalytic converter is more than a singular device. It is an engineered assembly comprising several components that must function collectively under extreme conditions. This blog post takes a look Inside the Converter: Components and Materials That Make It Work. The core elements are the substrate, the support mat, the stainless steel housing, and the inlet and outlet cones that join the device to the exhaust system.
The substrate: The engine of conversion
The substrate, often referred to as the monolith, can be made of ceramic or metal. It is structured as a honeycomb matrix to maximise surface area, allowing exhaust gases to make maximum contact with the catalyst coating applied to the walls. Ceramic substrates are most common but are inherently brittle and prone to damage if not handled carefully.
The support mat: Cushioning and sealing
Surrounding the substrate is the support mat, made of inorganic fibres – usually polycrystalline alumina –held together by a binder. The mat engages in multiple critical functions:
- It holds the substrate securely.
- It creates a seal to prevent exhaust gas bypass.
- It cushions against vibration and thermal expansion.
Typical mat properties include weights from 1050 to 6200 g/m², and uncompressed thickness ranging between 1.5 and 10 mm.
Mat variations: Polycrystalline versus intumescent
Comparison between mat types shows that polycrystalline mats provide reliable holding pressure and insulating performance. Intumescent mats, which expand when heated, are less common but used in specific designs requiring adaptive sealing. Polycrystalline fibres are more expensive yet essential for high-performance converters. A German patent describes such mats used for mounting ultra-thin-walled monoliths, reinforcing their relevance in modern designs.
The housing: Structural integrity
The housing, informally referred to as the can, is constructed from stainless steel and provides structural strength and corrosion resistance. These cans or tubes come in varying thicknesses: thicker ones are more robust in forming and less prone to deformation, while thinner ones reduce weight and cost. Thin-walled cans, however, may ripple or collapse if improperly formed. Cones welded to each end of the housing ensure a smooth connection to the exhaust system, maintaining flow and sealing integrity.
Ultimately, every part of the catalytic converter – from fibrous mat to stainless steel housing – must be precisely engineered and selected to withstand high temperatures, mechanical stress, and corrosive conditions. The success of emissions performance depends heavily on the correct material choices in this assembly. For more on recent advances in the development of catalytic converters, read this paper.
Learn more about Jendamark’s canning lines and end-of-line catalytic converter assembly processes here.
