Characterization of high-silica mordenites synthesized by various direct hydrothermal synthesis methods

Influences of various additives on the direct synthesis of high-silica mordenite (MOR) zeolite with tetraethylammonium hydroxide (TEAOH) were studied in detail. The addition of NaF as a fluoride source enhanced the nucleation and crystal growth of MOR zeolite. The addition of NH4NO3 as a mineralizer was also effective for the synthesis of high-silica MOR zeolite. The MOR zeolites synthesized with NaF and NH4NO3 were found to have much less framework defects as compared to those synthesized without additives. Under well-optimized conditions, the highly crystalline and pure MOR zeolite with a Si/Al ratio of ≈ 34 was synthesized by adding seed crystals as well as NaF and NH4NO3.