Zeolite DDR is a small pore zeolite with high application potential in catalysis, adsorption and membrane separation . However, its application is greatly limited by lengthy synthesis time. Various approaches, such as fast heating, reactive raw silica source, special mineralizing agent, seeding, and high synthesis temperature were combined to accelerate crystallization kinetics . The obtained DDR samples were systematically characterized by XRD , SEM, NMR and nitrogen adsorption-desorption. The fastest synthesis was realized by combining microwave radiation , and active (NH 4 ) 2 SiF 6 as silica source, in which high quality DDR zeolite with high yield was obtained in only 5 min. Moreover, replacing toxic (NH 4 ) 2 SiF 6 with safe silica sol led to improved process environment-friendliness and longer synthesis time of 10 min. Finally, replacing expensive microwave heating with economical oil-bath heating resulted into efficient synthesis of zeolite DDR in only 15 min, which would facilitate its commercial applications in adsorption, catalysis and membrane separation.
All-silica zeolite DDR was prepared by microwave-aided hydrothermal synthesis and characterized by X-ray diffraction, scanning electron microscopy, infra-red spectroscopy, nitrogen adsorption , elemental analysis and thermal gravimetric analysis . Microwave-aided heating significantly reduced the synthesis time from 25 d to 3 d and crystal size from 8 μm to 2 μm. With the help of seeding, the synthesis time and crystal size were further reduced to 6 h and 0.7 μm respectively. The crystal size decreased with seed content. The fragmentation of seed crystals had positive impact on reducing crystal size and increasing product yield. The aging of mother liquor and decrease of H 2 O/SiO 2 had little impact on crystal size.
危险品化学品经营许可证（带存储）