Biased Al distribution of high-silica FAU-type zeolite synthesized by fast manner at high temperature

The flexible control of composition and atomic arrangement is the ultimate goal in materials science. The control of the Si/Al ratio and Al distribution in the zeolite framework is a hot research topic in the field of zeolites, particularly for catalytic applications. To date, the direct synthesis of high-silica faujasite zeolites (FAUs) with a Si/Al ratio higher than 5 has been limited so far, which is desired to achieve high catalytic performance in various processes such as fluid catalytic cracking and hydrocracking catalysts. In addition, the Al distribution in high-silica FAU has been rarely discussed. In this study, we rapidly synthesized a high-silica FAU with a Si/Al ratio of approximately 6 using tetrapropylammonium cations and seed crystals at a high temperature of 180 °C for 4 h, by approximately one-tenth of conventional FAU syntheses using an OSDA. In silico analysis, based on the results of solid-state 29Si magic-angle spinning nuclear magnetic resonance spectra, revealed that the obtained FAU had a biased Al distribution compared with previously reported FAUs. We also succeeded in the first synthesis of FAU with biased Al distribution using N,N- dimethyl- 3, 5- dimethylpiperidinium cations that acted as organic structure-directing agents just under high-temperature conditions.