Assessing the surface sites of the large pore 3-dimensional microporous material H-ITQ-7 using FT-IR spectroscopy and molecular probes

H-ITQ-7 ((Si + Ge)/Al= 103) has been synthesized and submitted to thorough characterization, in particular with respect to the acidic properties. The H-ITQ-7 material, being one of very few known zeolite or zeotype materials with a three dimensional large pore channel structure, is of particular interest due to its structural similarities with the well studied and industrially relevant H-beta zeolite. By using a variety of molecular probes (H2O, CH3OH, CO, and pyridine) in combination with FT-IR spectroscopy, detailed insights regarding the acidic character of the various surface sites have been obtained. The use of several probes is required, as complementary knowledge is gained. Al containing H-ITQ-7 possesses strong Bronsted acid sites of at least two families that are clearly seen to interact differently with both CH3OH and CO. The spectral features observed upon adsorption of H2O and CH3OH indicate that the Bronsted acid sites of H-ITQ-7 are of strength comparable to those of H-beta. However, the spectra recorded upon adsorption of the more sensitive CO probe suggest that the acid strength of the Bronsted sites of H-ITQ-7 is slightly lower than those of several other acidic zeolites. H-ITQ-7 is an active catalyst in the conversion of methanol to hydrocarbons at 400 degrees C, a reaction that requires strong Brensted acidity, and the product shape selectivity observed indicates that the pores of H-ITQ-7 are slightly more restricted than those of H-beta. (C) 2010 Elsevier Inc. All rights reserved.