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 “Q4(nAl)”, Si(OSi)4-n(OAl)n and “Q3(nAl)”, Si(OSi)3-n(OH)(OAl)n, in the total framework Si atoms, which can be estimated by the solid-state 29Si 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 Q4(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.