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

Abstract

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.

Pillared HMCM-36 zeolite catalyst for biodiesel production by esterification of palmitic acid

“…It is interesting to note that this band was not clearly appeared in case of MCM-22 sample, this is probably due to very low concentration of isolated Si-OH species on the external surface of this sample [23]. A band at 3618 cm −1 , which can be assigned to strong Brönsted acidic bridging hydroxyl groups (Si OH Al) [24] can be observed in both the samples, however the intensity of this peak is relatively higher in MCM-36 sample than MCM-22.…”

“…Zeolites can be used as shape-selective catalysts due to their well-defined pores with minimum kinetic diameters similar to the size of small organic molecules [2]. However, for some chemical processes, these catalysts are required to catalyze reactions involving larger, bulkier molecules.…”

Layered Materials with Catalytic Applications: Pillared and Delaminated Zeolites from MWW Precursors

“…mesoporous interlayered galleries [108,109]. These MCM-36 derivatives could even be considered as acid-base bifunctional materials which would contain enhanced Lewis acidity, generated by pillaring with aluminum oxides, additional Brönsted acid sites of higher strength than the sites in the zeolitic layers, assigned to the silica-alumina clusters in the interlayer galleries, and base properties by the incorporation of alkaline earth oxide aluminates (MgO/BaO-Al 2 O 3 ) into the interlayer space [110,111].…”

Alkylation of benzene with propylene over MCM-36: A comparative study with MCM-22 zeolite synthesized from the same precursors

“…3. ), which can be attributed to the presence of weak acidic sites and relatively strong acid sites (mainly Brönsted acidity), respectively [9,[17][18]. Compared with MCM-22, the area of high temperature peak for MCM-36 decreases obviously, indicating that the amount of the Brönsted acidic sites decrease considerably.…”