Modification of MCM-22 zeolite through sequential post-synthesis treatments. Implications on the acidic and catalytic behaviour

Glycerol dehydration catalyzed by MWW zeolites and the changes in the catalyst deactivation caused by porosity modification

“…4B). A band near 1540 cm −1 was related to the formation of pyridinium cations (PyH + ), reflecting the presence of Brønsted acid sites, while a band centered at 1450 cm −1 corresponded to pyridine chemisorbed on Lewis acid sites (Py-L) [18]. The highest PyH + /Py-L ratio (1.6) was obtained for the parent MCM-22 zeolite, suggesting that this material contained a greater number of Brønsted acid sites compared to the modified zeolites.…”

“…[18]. Briefly, 5.0 g of MCM-22P and 28.2 g of CTABr (hexadecyltrimethylammonium bromide, Sigma-Aldrich) were mixed with 97.4 g of deionized water, followed by addition of 61.2 g of a 20 wt.% solution of TPAOH (tetrapropylammonium hydroxide, Sigma-Aldrich).…”

“…The three zeolites have different porosities and belong to the same MWW framework family [8,[17][18][19][20]. MCM-36 is a pillared layered structure built of inorganic layers with inorganic pillars appended on both sides of the sheets.…”

Transformation of ethylbenzene-m-xylene feed over MCM-22 zeolites with different acidities

“…The particular structure of the zeolite MCM-22 holds out interesting opportunities for modification by different methods like dealumination [13][14][15][16], change in the Si/Al ratio [17,18], etc. In the present work modified MCM-22 zeolites with varying composition of the building lattice elements and diverse number and strength of the acid sites were used for the selective transformation of EB in presence of m-xylene at high temperature and atmospheric pressure.…”

Mesopore modification of beta zeolites by sequential alkali and acid treatments: Narrowing mesopore size distribution featuring unimodality and mesoporous texture properties estimated upon a mesoporous volumetric model

“…Note that, upon alkaline treatments, zeolites with different structures and framework compositions commonly represent their different desilication behavior, which directly affects the mesoporous formation related to porous geometry. One consequence of this is to bring non-uniform mesopore size distribution in the modified zeolite crystals, and that the pore sizes for a few of them were inclined to extend towards the macroporous scale, as exemplified by zeolites beta [24], mordenite [25], ZSM-12 [26], ZSM-22 [27], and MCM-22 [28]. Apparently, such characteristics of forming textural pores in an extensively sized scope seem likely to discord with the structure-property-function relationship required for heterogeneous catalysis [29].…”