Synthesis, Characterization, and Catalytic Properties of Pillared Montmorillonite with Aluminum/Cerium Polyoxycations

Abstract

This paper describes the preparation of pillared montmorillonite by means of mixed aluminum and cerium oligomers. When cerium was incorporated into the materials, the basal spacing increased up to 26 Å. Nuclear magnetic resonance studies indicated total absence of tetrahedral aluminum in the polyoxycations incorporated between the clay sheets. These results indicate that AlCe-pillared montmorillonite incorporates inorganic polyoxycations with a chemical nature different from that of the aluminum polyoxycation or Keggin ion [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ . The texture of the materials showed a high specific surface area and porosity, with generation of pores at the limit between the microporous and mesoporous zones. The number and strength of the acid sites in these materials were also high. The catalytic behavior of the materials in the hydrocracking and hydroisomerization reaction of n-heptane was compared with that of materials obtained from the same montmorillonite and intercalation of the Keggin ion. The AlCe-pillared samples showed increased conversion and improved the selectivity toward the products of cracking.

Development of Pillared Clays for Wet Hydrogen Peroxide Oxidation of Phenol and Its Application in the Posttreatment of Coffee Wastewater

“…Cerium (Ce) was introduced into pillared clays with Al and Al-Fe, improving the metallic dispersion properties, increasing the pillars resistance [124][125][126], and favoring the redox properties of the active metallic phase [48,127]. The catalysts obtained by the pillaring of Colombian bentonite with Al-Fe or Al-Ce-Fe are highly efficient for the reaction of phenol oxidation in diluted aqueous media in moderate conditions of temperature and pressure (25 • C and atmospheric pressure).…”

Catalytic wet peroxide oxidation of phenol over Ce-Zr-modified clays: Effect of the pillaring method

“…Indeed, it has been shown that pillared clay with different basal spacing and microporosity was prepared with mixed cation pillaring [3][4][5][6][7]. In addition, previous works [7,8] report that the incorporation of species of Ce favors catalytic activity (CWPO reaction) of the pillared clays, probably because the cerium oxide formed in the solids enhances the textural properties of the solid, the dispersion and/or the redox properties of active species [9,10].…”

Effect of Transition-Metal Cations on the Adsorption of H2S in Modified Pillared Clays

“…From their first syntheses during the late 1970s, − PILCs (pillared interlayered clays) have attracted a lot of attention and have been the subject of numerous studies. They are generated through the exchange of the small charge-compensating cations (usually alkali) of the clays, situated between the negatively charged clay layers, with metal polyoxycations. , Calcination at 400 °C or higher temperatures leads to the dehydration and dehydroxylation of hydroxycations and their conversion to metal oxide pillars separating the clay layers. ,, Hence, for example, pillaring a clay with Al implies first the intercalation of the Keggin ion [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ 8,9 and then the formation of Al 2 O 3 pillars as a result of heat treatment. − …”

“…Pillaring of clay with metal oxides results in the appearance of new and interesting properties. First, the presence of these large pillars instead of alkali cations in the clay interlayer space causes the development of micropores (pores with a width smaller than 20 Å). ,,− Another valuable feature of PILCs is their acidity, whether it is of the Brønsted or of the Lewis kind. Even though clays originally have Brønsted acidic character, introducing metal oxide pillars, especially aluminum, brings Lewis acid sites .…”