Efficient and rapid transformation of high silica CHA zeolite from FAU zeolite in the absence of water solvent
High silica CHA zeolite plays important roles for selective catalytic reduction of NOx with NH3 (NH3-SCR), but its synthesis is not highly efficient due to the use of relatively high-cost structural directing agent (SDA) of N,N,N-dimethylethylcyclohexylammonium hydroxide (TMAdaOH) and relatively long crystallization time under hydrothermal conditions. Herein we report an efficient and rapid synthesis of high silica CHA zeolite with good crystallinity and uniform crystals (CHA-ST), which has been achieved from interzeolite transformation of high silica FAU zeolite in the absence of water solvent but the presence of zeolite seeds and the bromide form of SDA. The absence of water solvent in the synthesis significantly improves the zeolite yield by avoidance of the dissolution of aluminosilicate species in aqueous media, while the addition of zeolite seeds remarkably enhances the crystallization rate under solvent-free conditions. In addition, this route allows for using low-cost bromide form of the SDA. Catalytic tests in the NH3-SCR show that copper-exchanged CHA-ST (Cu-CHA-ST) exhibits comparable catalytic properties to those of Cu-SSZ-13 obtained from the conventional hydrothermal route.