Topotactic conversion of Ge-rich IWW zeolite into IPC-18 under mild condition

A facile structural conversion process from Ge-rich IWW-type germanosilicate to its daughter structure IPC-18 zeolite has been developed under mild conditions of water medium and room temperature. The parent IWW zeolite with an extremely low Si/Ge ratio of 1.02, synthesized with 1,4-bis-(dimethyl-1-adamantylammonium)-butane as a novel structural directing agent, was critical for the success of this specific structural transformation. The high Ge content favored the breaking of double-four-ring (d4r) subunits under mild conditions and simultaneously the mild H₂O medium suppressed the Si-assisted structural repairing. The HRTEM images collected along the (001) and (010) orientations of IWW and IPC-18 zeolite revealed the occurrence of structural transformation. The formation of IPC-18 zeolite structure was confirmed by the PXRD patterns and selected area electron diffraction patterns. The obtained IPC-18 zeolite demonstrated promising catalytic performance in the hydration of ethylene oxide to ethylene glycol with a high selective of 96%.