Fabrication of Cu-CHA composites with enhanced NH3-SCR catalytic performances and hydrothermal stabilities

Abstract Cu-SSZ-13 and Cu-SAPO-34, both with CHA topology but different compositions, are highly active NH3-SCR catalysts for the abatement of harmful nitrogen oxides from the exhausts of lean-burn engines. However, the former suffers from high preparation cost and worse high-temperature hydrothermal stability, and the latter is limited by its poor low-temperature hydrothermal stability. Herein, a new Cu-CHA composite (named Cu-CHADNL) containing both microenvironments of SSZ-13 and SAPO-34 was synthesized by employing one-pot synthesized Cu-SSZ-13 as Cu source, seeds and part of Si/Al source. The resultant materials have cubic-like morphology, high Si contents, controllable Cu loadings and uniform Si/P/Al/Cu elemental distributions. Solid state MAS NMR, NH3-DRIFTS and H2-TPR demonstrate the coexistence of aluminosilicate and SAPO zones in the Cu-CHADNL crystals. Notably, Cu-CHADNL exhibits high NH3-SCR activity in wide temperature window and robust resistance against both steaming at 800 °C and soaking in 80 °C water. These advantages are owing to the unique composite microstructures of Cu-CHADNL and suggest the material has huge application potential in deNOx process.