Copper-exchanged SUZ-4 zeolite catalysts for selective catalytic reduction of NOx†

Abstract

Copper-based SSZ-13 (Cu-SSZ-13, CHA topology) zeolite catalysts have been commercialized towards the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR), but the applications of Cu-SSZ-13 catalysts are still limited by the great challenge of high-cost organic templates. To this end, zeolite catalysts with other topologies have been attempted to substitute SSZ-13 to achieve the target of low cost and high performance. Herein, a series of SUZ-4 zeolites (SZR topology), structurally related to the FER topology, are successfully synthesized by using tetraethylammonium hydroxide (TEAOH) as the organic template. Compared to SSZ-13 zeolites synthesized by the addition of N,N,N-trimethyl-1-adamantylammonium hydroxide (TMAdaOH), the obtained SUZ-4 zeolites show higher economic benefits. Moreover, copper-exchanged SUZ-4 (Cu-SUZ-4) zeolites exhibit comparable NH₃-SCR performance to commercial Cu-SSZ-13. Particularly, the NO conversion of the Cu-SUZ-4-2 zeolite with optimal Cu loading is above 90% in the temperature range of 250–550 °C at high gaseous hourly space velocity (200 000 h⁻¹). After hydrothermal ageing (HTA), the NO conversion of Cu-SUZ-4-2-HTA is close to 90% in the temperature range of 300–550 °C, indicating its high hydrothermal stability. The present work provides an alternative catalyst that can potentially substitute SSZ-13 with high NH₃-SCR catalytic properties and low cost.