A-Zirconium phosphate

The Tokuyama Soda single-step catalyst consists of a zirconium phosphate catalyst loaded with 0.1—0.5 wt % paHadium (93—97). Pilot-plant data report (93) that at 140°C, 3 MPa, and a H2 acetone mole ratio of 0.2, the MIBK selectivity is 95% at an acetone conversion of 30%. The reactor product does not contain light methyl substituted methyl pentanes, and allows MIBK recovery in a three-column train with a phase separator between the first and second columns. 

Inspired by the separation ability of cyclic selectors such as cyclodextrins and crown ethers, Malouk s group studied the synthesis of chiral cyclophanes and their intercalation by cation exchange into a lamellar solid acid, a-zirconium phosphate aiming at the preparation of separation media based on solid inorganic-organic conjugates for simple single-plate batch enantioseparations [77-80]. 

Fig. 1.19 Intercalation of enzymes at the galleries of layered a-zirconium phosphate following a delamination-restacking mechanism.

Metallic phosphates nanoparticles have been identified as potential components of FR systems for PP. Hu and coworkers98 99 have used a-zirconium phosphate (a-ZrP) in combination with IFR based on APP and PER. 

Appreciable ionic conductivity is found in open framework or layered materials containing mobile cations (see Ionic Conductors). Several phosphates have been found to be good ionic conductors and are described above NASICON (Section 5.2.1), a-zirconium phosphates (Section 5.3.1), HUP (Section 5.3.3), and phosphate glasses (Section 5.4). Current interest in lithium ion-conducting electrolytes for battery apphcations has led to many lithium-containing phosphate glasses and crystalline solids such as NASICON type titanium phosphate being studied. ... 

Alberti, G., Casciola, M., and Costantino, U., Inorganic ion-exchange pellicles obtained by delamination of a-zirconium phosphate crystals, J. Colloid Interface Sci., 107, 256, 1985. 

Figure 12 idealized structure of a-zirconium phosphate (a-ZrP) showing one of the zeolitic cavities created by the arrangement of the layers. (From G. Alberti, in Study Week on Membranes (R. Passino, ed.), Pontificiae Acad. Sci. Scripta, Varia, Rome, p. 629, 1976. With permission.)... 

The a-zirconium phosphate has a layered structure in which each layer consists of a plane of zirconium atoms coordinated octahedrally to oxygen. The free space in the sides of the layered structure is large enough to allow a spherical ion of 0.263 nm diameter to diffuse the cavity without any obstruction and is accessible to Li, Na" and K" " [139]. However, the size of the window is smaller than the ionic spheres of Rb (0.296 nm) and Cs (0.338 nm) and an ion sieve effect is encountered with these ions. 

When a small amount of Na is added to solution used to examine the exchange of Cs and H -ion with an a-zirconium phosphate ion exchanger, the Na -ion exchanged can expand interlayer distance. The complete exchange of H for Cs that may occur in the exchanger can be attributed to catalysis by the Na ion. When tertiary ammonium ions are introduced in the layer of the a-zirconium phosphate ion exchanger, the interlayer distance expansion that results is proportional to the length of the carbon chain of the amine. 

Figure 2. The structure of a-zirconium phosphate. The area per site on the basal surface is about 24 A2.

The separation of ammonia from interfering compounds was also based on gaseous diffusion of ammonia from an alkaline medium and absorption by an acidic medium. Walker and Shipman described the isolation of ammonia by the use of a zirconium phosphate cation exchanger. The adsorbed ammonia was displaced from the column by 1.24 M cesium chloride, then oxidized by hypochlorite, reacted with phenol to form a phenol-indophenol complex which was measured at 395 or 625 nm, depending on the concentration range. 

Figure 11 Idealized layer in a-zirconium phosphate, showing the relationship of the hexagonal cell (dashed lines) to the monoclinic cell (solid lines). (From Ref. 72b.)...

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. 

Chang et al. also reported on the intercalation of aniline into zirconium phosphate sulfophenylphosphonate (ZPS), an organo derivative of a-zirconium phosphate [70]. The hydrophilic (—SO3H) groups in ZPS promote swelling of ZPS, which served as a template for aniline. The aniline-ZPS system was then oxidized with ammonium peroxydisulfate to yield a polyaniline-ZPS composite. However, there is no X-ray evidence that has been provided to support the formation of an intercalated phase. 

Sue Sue, H.-J., Gam, K. T., Bestaoui, N., Clearfield, A., Miyamoto, M., Miyatake, N. Fracmre behavior of a-zirconium phosphate-based epoxy nanocomposites. Acta Mater. 52 (2004)... 

---