Characterization and morphological control of β zeolite synthesized in a fluoride medium

Abstract

The formation and morphological control of beta zeolite was investigated in a fluoride medium. 29Si MASNMR spectra showed that the chiral siliceous β framework was free of the connectivity defects. For F-W-β, F-Pt-β and F-Pd-β, a visible mesoporous size distribution at 17.4-17.9 Å was detected. The relative coverage of surface -OH groups decreased in the sequence: H-β > H-ZSM-5 > F-Al-β > F-W-β > F-Pd-β > F-Pt-β > F-Si-β(1) > F-Si-β(2). The synthesis in a fluoride medium resulted in a higher resolution of all the IR vibration environments of framework elements. The spontaneous nucleation in a fluoride medium induced the formation of especially uniform crystalline morphology, while the presence of β seeding resulted in a mixed morphology. Prolonging the crystallization time remarkably increased the crystal size of siliceous β. TEOS as the silica source resulted in the formation of a single-crystal zeolite β, but aerosil-200 silica induced a multi-crystal β.