Environmental benign synthesis of Nano-SSZ-13 via FAU trans-crystallization: Enhanced NH₃-SCR performance on Cu-SSZ-13 with nano-size effect

Small pore zeolites with chabazite structure have been commercialized for selective catalytic reduction (SCR) of nitrogen oxides (NO_x) with ammonium (NH₃) from diesel exhaust. However, conventional zeolite synthesis processes detrimental effects on the environment due to the consumption of large amount of water, organic templates. Thus, this study proposed a green synthesis process with addition of minimal amount of water, structure directing agent and shortened steps to prepare nano-sized SSZ-13 (0.12 μm) using trans-crystallization strategy and exhibited enhanced performance for NO_x removal after copper ion-exchange. The operation temperature window (NO_x conversion >90 %) as well as the SO₂ and H₂O resistance over the green-route prepared nano-sized SSZ-13 (178−480 °C) outperformed the conventional SSZ-13 (29.8 μm, 211−438 °C) mainly due to the much shorter diffusion path. This clearly implied that the mass transportation was key for NH₃-SCR of NO_x on such small pore zeolite catalysts, which was further confirmed via an in-depth mass transportation calculation process. These results demonstrate that the Cu-nano-sized SSZ-13 prepared by the environmental benign route has great potential to act as a new generation of deNO_x catalyst for diesel exhaust and provided a guideline for researchers to develop new methods to synthesize nano-catalysts for air pollution control.