Transformation of Extra-Large Pore Germanosilicate CIT-13 Molecular Sieve into Extra-Large Pore CIT-5 Molecular Sieve

Abstract

The 14- and 10-membered ring germanosilicate Ge-CIT-13 (*CTH) is transformed into the 14-membered ring germanosilicate Ge-CIT-5 (CFI). The transformation can occur at room temperature but requires the presence of adsorbed water. The *CTH-to-CFI transformation involves rearrangement of germanium-rich double-4-ring units in *CTH to form double-zigzag chains in CFI. The rate of transformation is dependent on the germanium content of the starting Ge-CIT-13 and the humidity of the transforming atmosphere. Other germanosilicates—UTL, IWW, and ITH—do not show this type of transformation because of arrangements of Ge-sites within their d4r units and/or to spatial restrictions regarding the d4r unit arrangement within their interlayer regions. Ge-CIT-5 can be further transformed into 10-membered-ring CIT-15 using ammonium hydroxide solution as the delaminating agent. Postsynthetic alumination of Ge-CIT-5 yielded high-silica CFI-type aluminogermanosilicates having molar Si/Al ratios in the range of 14–230, primarily depending on the acidity of the solution phase.