Aluminum-pillared montmorillonite

Microwave irradiation has also been applied to the preparation of Fe203/S04-superacid [20, 21] and high-surface aluminum pillared montmorillonites [20],... 

Recent advances in this technology include the use of 2 1 clays converted to hydrophobic forms through the introduction of surfactants in the interlayer. For example, Boyd et al. (1991) introduced cationic chain surfactants into 2 1 clay minerals. Such clays were demonstrated to have high affinity for hydrophobic organic chemicals. Additionally, polyethylene oxides (PEOs) have been intercalated into aluminum-pillared montmorillonite (Montarges et al., 1995). Because PEOs have a... 

Pillaring solutions. Conventional Al203-pillared montmorillonite and interstratified illite/montmorillonites were prepared using an aluminum chlorohydrate (ACH) solution having an Al-concentration of 0.25 M and an OH/Al-ratio of 2.5, prepared by dilution of a commercial ACH-solution (Locron L, Hoechst). The solution was aged for 20 hr. after dilution, prior to use for preparation of pillared products. 

Aluminum oxide pillared smectites. The effect of steam deactivation (18 hr, 100% steam) of conventional Al203-pillared montmorillonite on surface area and cracking performance is shown in Table I. 

Selectivity in the dehydration of olefins is improved with pillared clays. Clays with aluminum oxide or mixed aluminum and iron oxide pillars converted isopropyl alcohol to propylene with more than 90% selectivity.256 A small amount of isopropyl ether was formed. When zeolite Y is used, the two products are formed in roughly equal amounts. A tantalum-pillared montmorillonite converted 1-butanol to butenes at 500°C with 100% selectivity at 41% conversion.257 The product contained a 17 20 16 mixture of 1 -butene/c/s-2-butene/fra/ s-2-butene. No butyraldehyde or butyl ether was formed. A pillared clay has been used for the alkylation of benzene with 1-dodecene without formation of dialkylated products.258 The carbonylation of styrene proceeded in 100% yield (6.50).259... 

Sziicz et al. [32] prepared a series of substrates with different Pd contents (Pd-nanophase reactors) by depositing Pd nanoparticles on the surface and in the micropores of a montmorillonite pillared with aluminum oxide. The N2 adsorption and SAXS data showed that the deposition of Pd nanoparticles inside the micropores decreased the specific surface area and the porosity of the substrate. A values determined from SAXS experiments increased with increasing amounts of deposited Pd. In particular, the value of A increased from 2.76 for nonmodified pillared montmorillonite to 2.83 for montmorillonite containing 2.09 % Pd and 2.9 for the substrate containing 2.53 % Pd. 

The photocatalytic activity of Ti02-montmorillonite in the reduction of with oxidation of triethanolamine (261) and the oxidation of several aliphatic alcohols have also been reported (259). The photodegradation of dichloro-methane, which is not readily degraded or hydrolyzed in an aquatic environment, to hydrochloric acid and carbon dioxide using titanium-exchanged montmorillonite, titania-pillared montmorillonite, and titanium-aluminum polymeric cation pillared montmorillonite has been reported (261). 

Pillared montmorillonites were used to oligomerize propylene at 30-50 atm [68]. One of the catalysts was pillared with a mixed aluminum-zirconium polymer. The PILCS were much less active than H-zeolite omega or an aluminosilicate catalyst. However, the selectivity for gasoline was greater. The Al-Zr PILC exhibited a high selectivity for aromatics and less coke formation than the Al-PILC. The observed behavior was attributed to the large niimber of Lewis acid sites relative to Br nsted acid sites and to the microporosity of the PILCS. 

It is a matter of some significance catalytically to be able to ascertain whether the aluminum present in a natural clay or its synthetic analogue is in a state of octahedral substitution (as in montmorillonite) or whether there is some tetrahedral substitution (as in beidellite). 27A1 MAS NMR readily provides the necessary answers. For example, Diddams et at. (462) in a study of the synthesis, characterization, and catalytic performance of synthetic beidellites and their pillared analogues, monitored the fate of AI from the gel precursor to the sheet silicate and to its pillared state by 27A1 MAS NMR (see... 

Textural characterization of montmorillonite pillared with aluminum/lanthanum polyoxycations... 

Many other materials, including synthetic aluminas, aluminum carbonates, aluminum silicates, magnesium silicates, various forms of attapulgite and sepiolite (81-83), alumina-pillared acid-activated montmorillonite (84), synthetic mica mont-morillonite, HY-zeolite, zirconium phosphate (85), mica, kaolin, and synthetic hectorite (86), have been evaluated for their ability to purify virgin fats and oils, but none were as good as acid-activated bentonite. 

Oscar M. Julio L. Carmen P. et al. Characterization and catalytic properties of montmorillonite pillared with aluminum/ lanthanum. Appl Cataly. A Gen. 2006, 314, 23-31. 

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