Broadening synthetic scope of SSZ-39 zeolite for NH3-SCR: A fast and direct route from amorphous starting materials

The inevitable use of FAU-type zeolites and long synthesis time bottleneck the mass production of SSZ-39 zeolite, a next-generation catalyst for selective catalytic reduction of NOx by ammonia (NH3-SCR). Herein, fast synthesis of SSZ-39 zeolites directly from colloidal silica and sodium aluminate is achieved with various reactant compositions, including a cost-effective low organic structure-directing agent-consuming condition and a scarcely reported KOH-containing condition. The reactant alkalinity and NaOH content are critical to the phase selectivity and fast crystallization, and partially replacing Na+ with K+ can eliminate the formation of gmelinite impurity. With optimized conditions, synthesis can be completed within 4 h without aging process in an autoclave, and even within 80 min by fast heating in a tubular reactor. Outstanding hydrothermal stability and NH3-SCR activity of the Cu-exchanged samples prove such fast and direct synthesis route a promising way to efficiently produce high-quality SSZ-39 zeolites for further applications.