Efficient Synthesis of All-silica DDR Zeolite

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.