Ferrierite lattice

Leherte et al. (38-40) reported a series of MD calculations for water molecules adsorbed in the ferrierite framework. The ferrierite lattice is modeled with a Si/Al ratio of 8, with the siting for aluminum atoms taken from ab initio calculations. (The T4 site is preferentially substituted.) Four unit cells were included and the lattice and intramolecular water parameters kept rigid. Three different water concentrations were considered 23, 33, and 41 molecules in 4 unit cells. 

Since frequently the properties of ferrierites are compared with some synthetic materials (MFI, STT, MWW), which frameworks are different from FER-type, a short survey of their structural properties will be givea These properties will facilitate the conparative analysis, particularly connected with the location of exchanged ions in their lattice. The presentation will be limited only to synthetic conqxmnds that are mentioned along the chapter, particularly in correlation with ferrierite structural and catalytic properties. A definitive survey of these materials can be found in the Atlas of Zeolite Framework Types [07B4]. 

Fig. 10. Nai 5TMA15[Al3Si33072] -6 H2O ferrierite. (a) Temperature dependences of lattice parameters of as-synthesized and (b) calcinated sample, (c) Data for H-ferrierite. Empty circles refer to cooling [89F1],...

A partial dealumination of ferrierite increasing the bulk Si/Al ratio (determined by EDAX) from 4.6 to 7.0 was found upon treatment with SiCl4 at 550°C [152]. However, the few presented data did not evidence isomorphous substitution and do not give any structural information about the product Considering the small pore openings of the two-dimensional channel system of ferrierite, it is probable that the observed dealumination is accompanied by a gradual lattice collapse. 

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