Zeolites (SCR Systems)
Microporous aluminosilicate minerals used as catalyst substrates in Selective Catalytic Reduction (SCR) systems to reduce NOx emissions from diesel engines.
Overview
Zeolites are microporous crystalline aluminosilicate materials with a highly ordered porous structure that provides an enormous internal surface area, making them ideal catalyst substrates and adsorbents. In automotive Selective Catalytic Reduction (SCR) systems, copper-exchanged (Cu-zeolite) or iron-exchanged (Fe-zeolite) variants are coated onto ceramic honeycomb substrates to catalyse the reaction between injected AdBlue (aqueous urea solution) and exhaust NOx, converting it to harmless nitrogen and water. Zeolite SCR catalysts are the primary technology enabling modern diesel vehicles to meet Euro 6 and US EPA Tier 3 NOx emissions standards. They are also used in cold-start hydrocarbon traps and as molecular sieves in HVAC and fuel systems.
Automotive Applications
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Properties
Category
Type
Zeolite Catalyst Substrate
Available Colors
Available Forms
Key Properties
- High Surface Area
- Microporous Structure
- Thermal Stability (up to ~750°C)
- NOx Reduction Efficiency >95%
- Hydrothermal Durability
- Tunable Pore Size
Technical Specifications
Density
2.0–2.3 g/cm³
Temperature Resistance
Up to ~750°C (hydrothermal stability)
Sustainability
Sustainability Rating
Zeolites are synthesised from abundant silica and alumina sources and do not contain precious metals, making them lower-cost than PGM catalysts. Their role in NOx reduction significantly reduces ground-level air pollution. Spent zeolite catalysts are typically landfilled, though research into regeneration and recycling is ongoing.