Zirconium phosphate, pillaring

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. 

Advancements in the preparation of new PLS s nearly parallels that of the zeolite and zeolite-like phases. Initially the pillared smectite clays were investigated but the quest for new materials with new properties led to e qiloring the pillaring of other layered phases. These include, most notably, the layered zirconium phosphates, double hydroxides (hydrotalcites), sihcas and metal oxides. The parallel paths of discovery in new material compositions for the layered phases and the microporous (zeoUte) phases are summarized in Table 1. A conq>arison between the pore architectures of the zeohtes and the two dimensional PLS is shown in Table 2. 

Zirconium phosphate derivatives have been investigated for a number of applications. Thio-phosphate derivatives,542 as well as [PhNH3]2[Zr(P04)3],545 have been employed as ion-exchange media. Similarly, a variety of materials derived from pillared Zr phosphates offered promise as selective ion-exchange materials.546-549... 

We have prepared other mixed composition pillared compounds irtiich have as their non-pillaring group the hydroxyl moiety, and thus are simply relatives of zirconium phosphate in which the layers are spread at a fixed distance apart. These products behave as expected in titration and ion-exchange experiments, and will not be further discussed here. 

Al, - Novel alumina-pillared y-zirconium phosphate materials have... 

Clays have also been pillared with polyoxometalate ions, such [(PW11VO40)4-].261 Other layered materials can also be pillared. Zirconium phosphate has been pillared with chromium(III) oxide.262 A layered titanate has been pillared with silica.263 The need for a separate pillaring step has been avoided in the preparation of some porous lamellar silicas which are structurally similar to pillared clays.264 Eight to twelve carbon diamines were used with tetra-ethoxysilane in ethanol with added water to make them in 18 h at room temperature. The template was recovered by solvent extraction before the silica was calcined. 

Hitherto the most successful pillaring has been carried out on smectite type clays. The original research on pillaring included several series of unsuccessful experiments on mica, vermiculite and the sheet silicic acid minerals magadiite, silhydrite and kenyaite. Recently renewed attention has focused on these and other alternative sheet structures. They include rectorite, zirconium phosphates, tetrasilicic micas, hydrotalcites and silicic acids, the general structural features of which are shown in Figure 4. 

Zirconium phosphates have been extensively investigated as intercalation hosts (531. and the catalytic properties of some pillared zirconium phosphates has been reviewed by Clearfield (541. 

Figure 13 Idealized schematic representation of mixed component pillared zirconium phosphate derivatives (a) p-phenylene-diphosphonate/monohydrogen phosphate (b) 4,4 -biphenylphosphonate/HP04. (From Ref. 75b.)...

Zirconium phosphate, besides the traditional intercalation processes, has been used to produce pillared compounds, such as those involving mixed Fe-Cr oxides [3]. Furthermore, it has been shown [4] that the protonic conductivity of a-zirconium phosphate can be enhanced by the formation of a composite with alumina or silica, an example of synergic cooperation between the oxides and phosphates which are the main classes of compounds highhghted in the book. 

These layered phosphates do not swell in water. Therefore, the layers were first spread apart by intercalation of butylamine. In this condition the AI13 species was exchanged for the alkylammonium ion to form pillared products [19]. Table 12-1 gives a summary of some of the results obtained with zirconium phosphate. It is observed that the surface areas of the aluminum... 

Our dried sample (250 C in vacuo) of chromia pillared zirconium phosphate gave a surface area of 119 m2/g (40 point N2 sorption BET isotherm, see Figure 12-5). Of this total, 73 m2/g was present as micropores. A t-plot analysis showed that the pores ranged from 8-14 A in diameter. The larger mesopores had a mean diameter of 38 A, with a very narrow spread of pore dimensions. 

Figure 12-5. BET nitrogen sorption isothenn of chromium-pillared zirconium phosphate.

During the preparation of this manuscript it came to our attention that a very similar technique had been utilized to prepare chromia pillared a-zirconium phosphate [28]. Very large interlayer spacings were achieved with very high surface areas. Thus, this exfoliation... 

Effect of pillar length on interlayer spacing in pillared a-zirconium phosphate. Reproduced with pemission from l66 . 

In heterogeneous catalysts, the tailored and pillared cavity is an essential property as it enables the movement of reactants to inner catalytic sites. The mass transfer of reactants and products inside the pores is mainly influenced by the interaction of the internal walls of the channel with organic molecules, and can consequently be controlled by the difference in polarities. To ensure such properties, anchored ruthenium hybrid zirconium phosphate-phosphonates coated with hydrophobic linear double-stranded polystyrene over the inner surface of the Zr layers were prepared by the first complexation of Ru and then molding of inorganic backbone method, and used as the catalyst in the ATH of o-, m- and p-substituted acetophenones (Fig. 42) [121]. This catalyst showed good catalytic activity and enantioselectivity (73.6-95.6 % ees) in the aqueous reduction with FA-TEA as the hydrogen donor, and could retain its catalytic properties after five runs in the case of acetophenone. 

Ti3P6027] 5[NH3CH2CH2NH3] 2[H30], mesoporous titanium phosphate molecular sieves, alumina pillared y-zirconium phosphates, ( Al,... 

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