Alumina and magnesia-alumina have been applied for pillaring the layered precursor of zeolite MCM-22. Calcination of such materials has led to new varieties of MCM-36 molecular sieves. Pillaring with alumina yields mesoporous materials with lower surface areas than those pillared with silica. The pillaring process with alumina strongly depends upon the preparation conditions of the alumina species and requires an elongated aging of the pillaring solutions. Application of magnesia in addition to alumina results in a higher exfoliation of the MCM-22 layers and incorporation of an increased amount of alumina into the materials. MgO 6 Al 2 O 3 as pillaring agent yields a significantly higher mesoporosity in the range of 2-4 nm as compared with Al 2 O 3 . This synthesis method is a promising tool for tailoring the physicochemical properties and the structure of the slit-mesopores in relation to materials typically pillared with silica.
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-butylpyridine (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.
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