Economically and eco-friendly synthesis of SSZ-13 zeolite using choline chloride as template with the investigation effects of sodium ion and aging

Abstract

Economical and efficient synthesis of small-size SSZ-13 zeolite catalysts with CHA topology is attractive for reducing the nitrogen oxide (NO_x) emissions from diesel vehicles. Herein, SSZ-13 zeolites were prepared using low-cost and environmental-friendly choline chloride (CC) as a template. The effects of additional sodium ions and dynamic stirring aging on the crystallization quality, solid yield and physicochemical properties of the obtained SSZ-13 were investigated by XRD, FT-IR, SEM, N₂ sorption and TG-DTG techniques. The results show that three sodium salts (NaCl, NaF, and Na₂SO₄) and aging steps can improve the relative crystallinity and solid yield of the SSZ-13 zeolites to a certain extent. Meanwhile, it was found that sodium salt and aging process significantly changed the crystal morphology of SSZ-13 zeolite from irregular particle aggregates to regular and uniform cubic crystals. And the crystal size of obtained SSZ-13 zeolites also decreased from ∼3 μm to 250–400 nm (adding sodium salts) or ∼700 nm (adding aging steps), respectively. The decrease in the size of SSZ-13 crystals is mainly attributed to that the addition of additional sodium salts or aging steps promoted the formation of more CHA zeolite nuclei. Additionally, the influence of the Na⁺(NaF) content and aging time on the synthesis of SSZ-13 were explored, and the effect mechanism of additional sodium ions and aging steps in the current synthetic system were also discussed. Finally, the obtained Cu-SSZ-13 samples after Cu²⁺ exchange exhibits good catalytic performance for NH₃-SCR of NO_x reaction, and the NO_x conversion remained over 90 % across a temperature window from ∼200 to ∼500 °C, demonstrating its application potentials in diesel vehicle exhausts purification.