Synthesis and characterization of all-silica DDR zeolite by microwave heating

• Studied the synthesis of all-silica zeolite DDR by microwave-aided heating.
• MW heating significantly reduced the synthesis time and crystal size.
• Submicron DDR crystals obtained in 6 h with MW heating + seeding.

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 H2O/SiO2 had little impact on crystal size.

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