What is SSZ-13 Zeolite?

SSZ-13 catalyst is a high-silica synthetic zeolite with the CHA framework topology — the same cage-based structure as SAPO-34, but with an aluminosilicate composition instead of silicoaluminophosphate. This chemical difference is crucial: as an aluminosilicate, SSZ-13 has abundant framework aluminium sites that readily exchange copper and iron cations, making it the ideal support for supplier-grade metal-exchanged SCR catalysts.

SSZ-13 has 8-membered ring pore openings (~3.8 Å) and chabazite cages that provide an ideal environment for stabilising isolated Cu²⁺ ions. Copper occupies specific cation positions within the six-membered ring of the CHA cage, where it is protected against migration and clustering into inactive CuO particles. This structural stabilisation is the basis for SSZ-13’s signature property: hydrothermal stability that allows Cu-SSZ-13 to survive repeated exposure to temperatures above 800 °C during diesel particulate filter regeneration.

Why Cu-SSZ-13 Is the Diesel SCR Standard

Cu-SSZ-13 became the global benchmark for diesel SCR because it solved the fatal flaw of earlier Cu-exchanged zeolites (Cu-ZSM-5, Cu-Beta): hydrothermal deactivation. When a diesel particulate filter regenerates, the downstream SCR catalyst is exposed to temperatures of 700-850 °C in steam-containing exhaust. Cu-ZSM-5 and Cu-Beta lose significant activity under these conditions because copper migrates and agglomerates into CuO. Cu-SSZ-13 retains >80% of its initial NOx conversion activity after standardised 800 °C/16-hour hydrothermal aging because the CHA cage confines the copper ions.

This combination of low-temperature SCR activity (>90% NOx conversion at 200 °C) and extreme hydrothermal durability has made Cu-SSZ-13 the standard catalyst for on-road diesel vehicles meeting Euro VI, EPA 2010, and China 6 emission standards. Fe-SSZ-13 offers an alternative for high-temperature and sulfur-containing exhaust streams.

For detailed grade selection, metal loading specifications, and SCR performance data, see the SSZ-13 product hub. For CHA framework comparison, see SAPO-34 vs SSZ-13.