Control of Acid−Base Properties of New Nanocomposite Derivatives of MCM-36 by Mixed Oxide Pillaring

The layered precursor of zeolite MCM-22 was pillared with SiO 2, Al 2 O 3, MgO−Al 2 O 3, BaO−Al 2 O 3, Al 2 O 3 −SiO 2, MgO−Al 2 O 3 −SiO 2, and BaO−Al 2 O 3 −SiO 2 to generate new derivatives of MCM-36. These nanocomposite materials are characterized by a layered structure consisting of microporous zeolite layers and mesoporous slit-shaped galleries formed by the incorporation of pure and mixed oxides between the zeolitic sheets. Enhanced Lewis acidity is generated by pillaring with (mixed) aluminum oxides. The adsorption of 2.6-di- tert -butyl-pyridine (2.6-DTBPy) demonstrated for all materials an increased accessibility to acid sites at the pore mouth or the outer surface of the zeolite layers compared to MCM-22. For (MgO/BaO)−Al 2 O 3 −SiO 2 −MCM-36 additional Brønsted acid sites of higher strength than the sites in the zeolitic sheets are observed, which are assigned to the silica−alumina clusters in the interlayer galleries. Basic properties were introduced by the incorporation of alkaline earth oxide aluminates (MgO/BaO−Al 2 O 3 ) into the interlayer space. Two basic hydroxyl functions were detected by CO 2 adsorption: (i) Mg(Ba)-OH and (ii) Al IV -OH groups on the spinel-type oxide clusters. The latter basic sites are attributed to hydroxyl groups on aluminum ions in a tetrahedral coordination sphere of the defect spinel-type oxide pillaring clusters.