Solid zirconium phosphates

The solubility of zirconium phosphate, Zr0(H2P04)2, has been studied by von Hevesy and Kimura [25HEV/KIM] in hydrochloric acid solutions. The zirconyl ion does not exist in aqueous solution nor in the solid state (see Section V.2.2) and, as such, the above solid is most likely Zr(HP04)2 H20(cr). The solid was found by these authors to give a saturated solution (as Zr(HP04)2 H20(er)) of 0.00012 M in 6.01 M HCl and 0.00023 M in 10 M HCl. The dissolution of the solid can be described by Reaction (V.70)  

Using the measured data and taking into account chloride complexation, the logarithm of the solubility constant for Reaction (V.70) is - (16.4 0.7) in 6.01 M HCl and - (18.5 1.3) in 10 M HCl. Correction of these data to zero ionic strength using the ion interaction coefficients between Zr and with Cl (Appendix B) leads to the following solubility constant at zero ionic strength  

From the selected Gibbs energy and enthalpy of formation values and the entropy of the constituent elements in their standard states (Zr, O2, H2 and P Chapter IV and Section V. 1.1.2.1), the selected entropy of Zr(HP04)2-H20(cr) is  

the value reported by Filippova and Chemodanov [75FIL/CHE] is more positive than those listed in Table V-33 by a similar amount as found for Zr(HP04)2 H20(cr) and is also rejected by this review. The selected enthalpy of formation for a-Zr(HP04)2 is  

Karyakin et al. [98KAR/CHE] also determined the enthalpy of formation of 3-Zr(HP04)2. Both a- and P-Zr(HP04)2 are monoclinic and differ only in their lattice parameters. The value determined by [98KAR/CHE] is  

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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]. 

Layered inorganic solids have been used for site isolation, for example, nickel phosphine complexes confined within the interlayer spaces of sepiolite have been used as olefin hydrogenation catalysts [63], and similarly there has been the encapsulation of metal complexes into zirconium phosphates [64], The principal idea is illustrated in Figure 5.8. The metal complex can be encapsulated by covalent means (a) or by non-covalent interactions (b). 

Later, Yoshida et al. reported the dehydration of fructose to HMF in a batch-type reactor under subcritical water (sub-CW) and with different zirconium phosphate solid acid catalysts at 240°C (Scheme 7) [77]. Over amorphous zirconium phosphate, 80% of fructose was converted after 120 s affording HMF with a selectivity of 61%. Interestingly, no side product stemming from the rehydration of HMF was detected in this case. However, soluble polymers and furaldehyde were detected as side products. Remarkably, zirconium phosphate solid catalysts were stable under subcritical water conditions and were reused without any loss of their activity. 

Addition of a soluble Zr(IV) salt to phosphoric acid results in the precipitation of a gelatinous amorphous solid. The stoichiometric crystalline zirconium phosphate can be prepared by refluxing zirconium phosphate-gel in concentrated phosphoric acid [5]. The procedures for synthesis of zirconium phosphate have been described in detail elsewhere [6]. 

It has been reported (4,5) that solid electrolyte sensors using stabilized zirconia can detect reducible gases in ambient atmosphere by making use of an anomalous EMF which is unusually larger than is expected from the Nernst equation. However, these sensors should be operated in a temperature range above ca. 300°C mainly because the ionic conductivity of stabilized zirconia is too small at lower temperatures. On the other hand, solid state proton conductors such as antimonic acid (6,1), zirconium phosphate (8), and dodecamolybdo-phosphoric acid (9) are known to exhibit relatively high protonic conductivities at room temperature. We recently found that the electrochemical cell using these proton conductors could detect... 

Slade, R.C.T., Forano, C.R.M., Peraio, A. and Alberti, G. (1993) A JH NMR relaxation-time study of dynamic processes in zirconium phosphates of differing crystallinities and in related compounds. Solid State Ionics, 6, 23-31. 

It must also be pointed out that other basic materials have been synthesized which present no surface oxygens and hydroxyls, but other types of active sites whose exact nature remains controversial. These type of solids are, for example, impregnated imides and nitrides on zeolites and alumina, amorphous oxynitrides obtained by treatment with ammonia or aluminium orthophosphate, zirconium phosphate, aluminium vanadate or galloaluminophosphate, and KF supported on alumina/1,3,41 One of the main advantages of these solids with respect to basic oxides is their resistance to carbon dioxide or water. 

Zirconium phosphate. Reject. Test if all phosphate has been precipitated by the addition of a drop of the zirconium(IV) nitrate reagent. Add about 0-5 g solid NH4C1, heat to boiling, add a slight excess of dilute NH3 solution (i.e. until the odour of NH3 is permanent in the boiling solution), boil for 2-3 minutes and filter. ... 

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. ... 

In an application of the Paal-Knorr pyrrole synthesis, the synthetic equivalents 3 of 1,4-ketoaldehydes were prepared by the radical addition of ketones 4 to vinyl pivalate. Treatment of the intermediates 3 with amines gave pyrroles 5 <03SL75>. Other new extensions of this popular pyrrole synthesis include the preparation of a number of pyrroles from hexane-2,5-dione and amines under solvent-free conditions in the presence of layered zirconium phosphate or phosphonate catalysts <03TL3923>, and the development of a solid-phase variant of this reaction <03SL711>. Likewise, the preparation of iV-acylpyrroles from primary amides and 2,5-dimethoxytetrahydrofuran in the presence of one equivalent of thionyl chloride has also been reported <03S1959>. 

An alternative method for producing mass spectra of solid samples which shows promise for the analysis of zeolites and related materials is the plasma desorption technique recently reported by Schwiekert et al. [71,72]. This technique uses a less energetic means of ionizing the solid than laser ablation, and initial indications are that negative ion spectra from materials like zirconium phosphate may reflect the connectivity as well as the stoichiometry of the solid analyzed to a greater degree than laser ablation. 

M. Casciola, F. Marmottini, and A. Peraio. AC conductivity of alpha-layered zirconium-phosphate in the presence of water vapour at 100-200°C. Solid State Ionics 61, 125-129 1993. 

In contrast to the conventional approach whereby various organic groups are subsequently bound to a previously prepared surface, we have been synthesizing a broad series of anchored, layered-structure solids by precipitating the pre-derived phosphonate salts with tetravalent metal ions. The two-dimensional backbone has the zirconium phosphate structure however, substituted for hydroxylic groups are the desired organics, oriented away from the basal surfaces in a bilayered fashion in the interlayer region. 

Ikeda, S., Kondo, T. Kato, S., Ito, K., Nomura, K. and Fujita, Y. (1995) Carbon dioxide sensor using solid electrolytes with zirconium phosphate framework (2). Properties of the CO, gas sensor using Mgi.i5Zr4P5 7810.30,4 as electrolyte. Solid-State Ionics, 79, 354—7. 

P. Costamagna, C. Yang, A.B. Bocarsly and S. Srinvasan, Nafion 115/zirconium phosphate composite membranes for operation of PEMFCs above 100 °C, Electrochim. Acta, 2002, 47, 1023-1033 C. Yang, S. Srinivasan, A.S. Arico, P. Creti, V Baglio and Y Antonucci, Electrochem. Solid-State Lett., 2001, 4, A31-A34. 

The catalytic properties of metal-zirconium phosphate solid has also been investigated (21, 349). The catalysts were prepared by the ion exchange of zirconium phosphate with copper, nickel, and chromium ions. Cataljdic dehydration of 2-propanol was studied at 160°-350°C, with zirconium phosphate itself giving the highest activity, yielding 97% propylene at 230°-240°C. Introduction of Cu +, Ni +, and Cr " decreased the dehydrating properties, and also decreased the catalytic isomerizing properties when tested with the cyclohexane-methylcyclopentane isomerization. The introduction of copper and nickel improved the dehydration properties of zirconium phosphate when tested on ethylbenzene. 

In the course of this chapter we will treat a number of other novel materials as well. Solids such as zirconium phosphates also possess layered structures and represent some of the newest materials being explored as heterogeneous catalysts. Although the zirconium phosphates have not yet been as widely studied by NMR as the clays, we review here some of the salient work done so far. This subject promises to be a thriving area of research in the near future. 

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.)...

These authors studied the enthalpy of dehydration of zirconium phosphate and arsenate, in the temperature range 95 to 140°C and 90 to 110°C, respectively, by measuring the partial pressure of water vapour over the solid phases using a tensimetric method. The reaction studied was ... 

Zinc hydrides, 931 Zinc naphthalocyanine preparation, 993 Zinc pseudohalides, 981 solid state, 985 Zirconium phosphate ion exchange resins, 720... 

A further experiment was done to look at oxidant concentration in the solid and in solution (Table 4). It was found that, even after thorough washing, the peracetic acid formed was very much concentrated in the solid. This would explain why zirconium phosphate inhibits the formation of free peracetic acid, as it suggests that peracid is formed but held in the interlayers. The selectivity to dihydroxy products may then be attributed to adsorption selectivity. This is our current understanding of the mechanism. 

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