A Facile Route to Large-Pore Zeolites

A Facile Route to Large-Pore Zeolites

Author: David Smith

Zeolites are microporous crystalline aluminosilicate materials, which can be used for selective catalysis, absorption, and ion exchange. Large-pore zeolites, such as those incorporating 12-membered ring (12MR) channels, are of interest for processing bulky hydrocarbons and biomass-derived species. A single large-pore zeolite, FAU, dominates 95 % of the synthetic zeolite market. However, the search for new, equally effective large-pore zeolites is an area of much research activity.

By using simple quaternary organic structure-directing agents based on tetramethylimidazole, Mark Davis and colleagues, California Institute of Technology (Caltech), Pasadena, USA, have developed a range of aluminosilicate materials. The products have a ITQ-27 or IWV (two-dimensional large-pore aluminosilicate) structure, which consists of a 2D pore system containing 12MRs and 14MRs.

Unlike previously reported IWV materials, in which the Si/Al ratio was limited, the Davis group prepared materials with Si/Al = 14.8–23.2 under hydroxide-mediated conditions and Si/Al up to 82 under fluoride-mediated conditions. The products displayed catalytic activity in the hydroisomerization of n-hexane, with similar product distributions to those obtained over the well-established ZSM-12 zeolite, indicating a similar effective pore size.


 

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