Al-pillared clays

Brindley and Sempels (1), Vaughan et al. (2) and Shabtai (3) have shown that the experimental conditions of Al intercalation influences the physicochemical properties of the clay. The nature, amount and spacial distribution of the pillars change the thermal stability, texture and acidity of the pillared clays. For example, Rausch and Bale (4) have reported that the OH/Al ratio modifies the structure of the Al complex and that monomeric [Al(0H)x(H20)6-x] " or polymeric [A1i304(0H)24(H20)i2] species can be obtained. Clearfield (5) demonstrated that the polymerisation state of Zr species depends on the temperature, concentration and pH of the solutions. In any case, the height of pillars is largely controlled by the polymerisation state of the intercalated complexes. However, in order to maintain the accessibility of the inner surface, the density or spacial distribution of the pillars has to be controlled. This parameter has been studied by Flee et al (5), and Shabtai et al (7) for Al pillared clays and Farfan-Torres et al (8) for zirconium. 

Nanosized sulfated tin oxide (STO) particles dispersed in the micropores of Al-pillared clay (STO/Al-P), were used by Mishra and co-workers [91] as an environmentally benign, recyclable and efficient catalyst for the solvent-free synthesis of 3,4-dihydropyrimidin-2(l//)-ones 42 using a domestic microwave oven. The protocol offers advantages in terms of simple experimentation, reusable catalyst, excellent yields, short reaction times, and preclusion of toxic solvents (Scheme 31). 

Sowmiya M, Sharma A, Parsodkar S et al (2007) Nanosized sulfated Sn02 dispersed in the micropores of Al-pillared clay as an efficient catalyst for the synthesis of some biologically important molecules. Appl Catal A Gen 333 272-280... 

Chiral (Salen)Mn complex Al pillared clay Encapsulation /... 

Figure 13. Reaction pathway in the disproportionation of 1,2,4-trimethylbenzene using Al-pillared clays [79],...

Al-pillared clays thermally stable up to 750 C have been prepared from easily available starting materials a natural clay, namely the saponite, and a commercial aqueous solution of Chlorhydrol. 

Starting from a natural clay, the saponite, Al-pillared clays have been easily ... 

In 2004, Jiang, et al. studied the esterification of n-pentanol with benzoic add using Al-pillared clay (PILC) supported 5042" /Ti02 superacid catalyst (Fang et al., 2010), and find that it is known that the generation of super acid sites in the system of 5042 /MJDy solid superacid is necessarily promoted by the sulfur of the metal oxides, the more acid sites formed, the higher catalytic activity exhibited. Therefore, Al-PILC carrier can effectively enhance the catalytic activity. 

B. Al-Pillared Clays Derived from High-Charge-Density Clays... 

Table 5 Adsorption Properties of Al-Pillared Clay Minerals...

This scheme bears also resemblance to what is reported for clays or pillared clays [110]. Molecular water on strong Al sites is normally assumed as a source of acidity in clays, hi [Al]-pillared clays [152], a band was observed with the features of AIOH(II) species, i.e., a stretching mode at 3660 cm and a shift upon CO interaction of ca. 200 cm This species arises from the simultaneous presence of the Al pillar and the silica sheet in clays, so it is again proposed to be an Si-O-Al-OH species. 

Guelou, E., Tatibouet, J. and Barrault, J. (2010). Fe-Al-Pillared Clays Catalysts for Wet Peroxide Oxidation of Phenol, in A. Gil, S. Korili, R. TmjiUano, et al. (eds). Pillared Clays and Related Catalysts, Springer, Heidelberg, Germany, pp. 201—224. 

Timofeeva, M., Khankhasaeva, S., Chesalov, Y., et al. (2009). Synthesis of Fe,Al-pillared Clays Starting from the Al,Fe-polymeric Precursor Effect of Synthesis Parameters on Textural and Catalytic Properties, AjPjpZ. Catal. B-Environ., 88, pp. 127-134. 

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