Zirconium phosphate amorphous

ZrPA = Zirconium phosphate amorphous, TiPA = Titanium phosphate amorphous, SnPC = Tin phosphate crystaiiine, ZrWP = Zirconium/tungsto. phosphate, MeCN = Acetonitrile, AcOH = Acetic acid, CX = Cyclohexanone, CP = Cyclopentanone, PIN = Pinacolone, AP = Acetophenone, 6-HCA = 6-Hydroxycaproic acid, e-Cap. = e-Caprolactone, Polymer = Polycaprolactone of unknown molecular weight, DVL = S-Valerolactone, t-BA = t-Butylacetate, PhA = Phenyl acetate, PhOH = Phenol,... 

The main interest in zirconium phosphates relates to their ion-exchange properties. If amorphous zirconium phosphate is equiUbrated with sodium hydroxide to pH 7, one hydrogen is displaced and ZrNaH(P0 2 3H20 [13933-56-7] is obtained. The spacing between the zirconium layers is increased from 0.76 to 1.18 nm, which allows this phosphate to exchange larger ions. 

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 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. 

The Lewis acidity of Zr in amorphous zirconium phosphate has been exploited for the Baeyer-Villiger oxidation of ketones with H202 as the oxidant (209). Excellent results are obtained for reaction in acetic acid. However, it is difficult to distinguish between the contributions of in situ formed peracetic acid and an inorganic Zr peracid. In the reaction in acetonitrile, the yields of oxidized products are modest ... 

There are several forms of metal(IV) phosphates, including amorphous, crystalline, and pellicular. However, here only the preparation of amorphous zirconium phosphate is described. Phosphoric acid (10 % w/w. 162 ml) was added to zirconyl chloride octahydrate (14.4 g in 112 ml of demineralized water), and stirred at room temperature for 4 h. The resulting gel was washed repeatedly with demineralized water (3 x 500 ml) and centrifuged each time. 

Early work on the exchange properties of amorphous zirconium phosphate has been summarized by Amphlett (29). In addition, Ahrland et al. (13,15) have studied the exchange behavior of representative fission product ions, for which they found an affinity order of UO, Ce, Y " ", Sr +, Cs+, Rb+, Na+, when amorphous gels of high P04/Zr ratios were used. The separation of certain transplutonium ions (250) on amorphous... 

It was recognized that the hydrolytic stability of amorphous zirconium phosphate left something to be desired (14, 36,123), although certain ratios seem to be more stable than others in water at 25°C. The... 

In general, the crystalline form does not hydrolyze to the extent that the amorphous form does (19,123, 237), although ion exchange which is accompanied by an increase in distance between the layers makes the crystalline form more susceptible to hydrolysis (23). Since the j8 and y forms of zirconium phosphate are more open, exchange of cations such as Cs+ and Ba +, which are excluded in the a form, can occur in these forms. Since one hydrogen is opposed to the other, the theoretical capacity of 7.06 meq/gm is not achieved. 

Inorganic ion exchangers fall roughly into two groups crystalline, such as the ammonium salts of the 12-heteropolyacids, and amorphous, such as zirconium phosphate. One example from each group will be described. 

Crystalline zirconium phosphate was prepared by the method described by Clearfield and Thakur. Thermal activation was carried out at 100, 200, 300, 400 C. A portion of the amorphous material used to make the crystalline zirconium phosphates was retained for evaluation. Catalysts were characterised using titrimetric methods to measure acidity and x-ray diffraction to examine crystallinity. Thermogravimetric analysis (TGA) was used to determine phase changes on heat treatment. 

Five catalysts were assessed for activity in phenol hydroxylation. These were amorphous zirconium phosphate and the four crystalline samples heated at 100, 200, 300 and 400°C. The best catalyst in terms of conversion of phenol to catechol and hydroquinione was the crystalline sample heated at 100°C. This gave typically >90% selectivity to dihyroxybenzenes at 12% conversion of phenol and 2 1 mole ratio of phenol to Reactivity decreased with high activation temperatures. 

The existing method for preparing crystalline zirconium phosphate is firstly to precipitate the amorphous form from a mixture of phosphonic acid and zirconyl chloride and secondly to reflux the amorphous form in 12M phosphoric acid for several days after washing the amorphous form free of chloride. This gives the a-form. Not only is this a time consuming process, but the amorphous form is difficult to filter. We aimed to develop a one step process to the crystalline material by using crystal habit modifiers. 

Synonyms Zirconium orthophosphate Properties Wh. amorphous powd. highly insol. in water dec. on heating Uses Ion-exchange catalyst Manuf./Distrib. Southern Ionics http //www.southernionics. com Zirconium phosphate acid form CAS 13772-29-7 Empirical ... 

Amorphous zirconium phosphate a-Zr(HP04)2 (Chapter 5.7) is an excellent sorbant for use in renal dialysis [6], Radioactive Cr P04 is a neoplastic suppressant and is much used in cancer treatment. The heteropoly anion PaWigOg is a potent inhibitor of viral DNA but other more complex anions of this type may prove to be of greater use (Chapter 5.7). Radioactive P has uses in medicine (Chapter 13.5). 

Moreover, composite membranes based on S-PEEK-WC can be obtained by incorporating an amorphous zirconium phosphate suUbphenylenphosphonate gel with a fixed 20 wt% content. They, indicated as Zr(SPP)/S-PEEK-WC, absorb less water and methanol than the pure S-PEEK-WC and the methanol absorption does not increase significantly with temperature on the contrary of the pure S-PEEK-WC, especially in the case of high DS. The Zr(SPP)/S-PEEK-WC methanol permeability is lower than that of Nafion due to its microstructure with narrow and highly branched channels, which are responsible for the lower methanol crossover. 

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