Hydrothermal Conversion of Titanated FAU to AEI Zeolite and Its Enhanced Catalytic Performance for NOx Reduction

Titanium and aluminum-co-incorporated AEI zeolites ([Al, Ti]-AEI) with various Si/Ti ratios were obtained from the hydrothermal conversion of titanated faujasite ([Al, Ti]-FAU). X-ray diffraction, SEM/EDX, diffuse reflectance UV-Vis, and FT-IR measurements revealed the formation of highly crystalline [Al, Ti]-AEI zeolite with titanium species having a tetrahedral coordination state and a homogeneous distribution. Interestingly, this [Al, Ti]-AEI zeolite could not be produced from an amorphous hydrogel, suggesting the high potential of using [Al, Ti]-FAU as a starting material for [Al, Ti]-AEI formation. The thermal stability of the [Al, Ti]-AEI zeolite was strongly dependent on the amount of Ti incorporated within the framework. The [Al, Ti]-AEI zeolite with a high titanium content (Si/Ti = 24) exhibited high thermal stability, and its framework structure was maintained even after calcination at 1000 degrees C for 1 h. We also investigated the catalytic performance of a Cu-loaded AEI zeolite catalyst for the selective catalytic reduction (SCR) of NOx by ammonia (NH3-SCR), and discovered that the Cu-loaded AEI catalyst exhibited a higher NO conversion than the Cu-loaded Ti-free AEI catalyst. These results strongly indicate that the hydrothermal conversion of titanated zeolite is very effective for the synthesis of useful Ti-incorporated zeolite, which cannot be easily synthesized using the conventional hydrothermal synthetic route with amorphous hydrogel as a starting material.