Control of Al Distribution in the CHA-Type Aluminosilicate Zeolites and Its Impact on the Hydrothermal Stability and Catalytic Properties

The CHA-type aluminosilicate zeolites were synthesized in the presence of the N, N, N -trimethyl-1-adamantammonium cation from different starting materials, including fumed silica, aluminum hydroxide, and the FAU-type zeolite, with their proportions varied. In this work, the proportion of “Q 4 ( n Al)”, Si(OSi) 4- n (OAl) n and “Q 3 ( n Al)”, Si(OSi) 3- n (OH)(OAl) n, in the total framework Si atoms, which can be estimated by the solid-state 29 Si MAS NMR technique, has been applied to an index for Al distribution. When the proportion of the Al source derived from the FAU-type zeolite was increased, the proportion of Q 4 (2Al) was increased. Thus, we found a facile method for controlling the Al distribution in the CHA-type zeolite by varying the starting materials. Finally, the impacts of the Al distribution on the hydrothermal stability and catalytic properties in the methanol to olefins (MTO) reaction were investigated.