Aluminum molybdate

In such a case, one must conclude that a real two-dimensional aluminum molybdate is formed. As long as the quantity of aluminum molybdate corresponds to less than a monolayer, no three-dimensional aluminum molybdate forms. 

Abbattista et al. (26) found that phosphorus addition prevents crystallization of the y-alumina phase and the transformation from y- to a-alumina in the system AI2O3 —AIPO4 (Fig. 23). More precisely, Morterra et al. (77) reported that phosphates do not affect the phase transition from low-temperature spinel alumina (y-alumina) to high-temperature spinel aluminas 8 and 6 phases) but delay the transition of 8 and 9 to a-alumina (corundum). Stanislaus et al 46) also reported that phosphorus significantly improves the thermal stabihty of the y-alumina phase in P/Al catalysts. However, the same authors found that the positive effect of phosphorus seems to be canceled in the presence of molybdenum due to the formation of aluminum molybdate. Thermal treatments of MoP/Al catalysts at temperatures >700°C result in a considerable reduction of SSA and mechanical strength. The presence of phosphorus does not prevent the reaction between the molybdenum oxo-species and alumina since the interaction between molybdates and phosphates is weak. The presence of nickel does not obviously affect the positive effect of phosphorus in terms of thermal stability 46). On the other hand, Hopkins and Meyers 78) reported that the thermal stability of commercial CoMo/Al and NiMo/Al catalysts is improved by the addition of phosphorus. 

In this paper, we will discuss results of the oxidation of methanol over a series of molybdates including solid solutions of ferric, chromium and aluminum molybdates and also over a new ferric tungstate phase. The mixed molybdates of iron/chromium, iron/aluminum and chromlum/aluminum were made for the first time in pure well-characterized forms. Results are compared with our earlier work over commercial mixtures of ferric molybdate and molybdenum tri oxide and a number of pure molybdates. ... 

Aluminum molybdate, Al2(MoOi )3 was first prepared by Doyle and Forbes(T2) quickly followed by other workers (Ul,73). DSC measurements by Sleight(52) indicate the structure to be monoclinic below 200°C the structure is isomorphous with chromium molybdate( 1). 

There have been few studies on mixed compounds of iron, chromium and aluminum molybdates. Abidova and co-workers(7 -79) made a somewhat inconclusive study on the mixed Fe/Al/Mo oxide system. Based on DSC and reflectance measurements on the ... 

By far the most successful method of preparation was via an amorphous organic precursor to the required mixed molybdates, following the method of Delmon et al.(jrT). The method has proved successful for the pure iron, chromium and aluminum molybdates, and also for the mixed phases. A detailed outline of the method taking the example of FeCr(Mo0i )3 is as follows ... 

All these molybdates are isostructural with ferric molybdate with an open 3-dimensional network of MO octahedra and M0O4 tetrahedra. A ferroelastic transition exists from the low temperature monoclinic form to the high temperature orthorhombic form. The transition temperature varies from 200 C for pure aluminum molybdate to 385 0 for pure chromium molybdate and 500 C for pure ferric molybdate. For the mixed molybdates, the transition temperature was found to be a linear function of composition as is illustrated in Figure 4 for the mixed iron-aluminum molybdates. 

The XPS analysis (Figure 2) of the average sample from the deeper reactor layer, with no considerable bulk properties changes, indicated fine restructuring of the active phase. The monolayer structure of molybdenum Mo(VI) phase is partially changed to multilayer structure [9,10], while the reduced Mo(IV)/Mo(V) phase remained stable [11]. An indication of nucleation of aluminum molybdate on the surface reveals that a part of molybdenum phase... 

Oxides of copper, molybdenum, and vanadium had a disastrous effect on the carriers. Surface area dropped to less than 10 m2/g, and crushing strength was much less than that of the original sample. Degradation by molybdenum oxide is well known at 600°C aluminum molybdate is formed and decomposes at about 800°C into a-Al203 and M0O3 which sublimates. 

Thus, Mo,H-ZSM-5 samples prepared via SSIE proved to be catalyst precursors which, after activation (reduction, carburization), activated CH4 molecules and produced hydrocarbons such as C2H4, C2H6, CgHg, CgHg, benzene, toluene, and naphthalene. At higher Mo contents, however, (inactive) aluminum molybdates, Al2(Mo04)3, formed by extracting framework Al that led to a loss of crystallinity. 

Other Uses. Photochromic glass contains silver chloride (80) and silver molybdate [13765-74-7] (81) (see Chromogenic materials). An apparatus coated with silver nitrate has been described for the detection of rain or snow (82). Treatment with silver-thiosulfate complex has been reported as dramatically increasing the post-harvest life of cut carnations (83). Silver sulfate has been used in the electrolytic coloring of aluminum (84). Silver sulfate also imparts a yellowish red color to glass bulbs (85). 

Aluminum phthalocyanine (PcAlX) can be prepared from the phthalonitrile and aluminum trichloride either in refluxing quinoline138 13g or without a solvent under addition of ammonium molybdate(VI).137 The chloro compound can be transformed to a hydroxy derivative by treatment with sulfuric acid.58-140 Also, the insertion of aluminum in a metal-free phthalocyanine is possible, for example trialkylaluminum can be used.141,142... 

Although azoles are commonly thought of as only yellow metal inhibitors, they are, in fact, used for corrosion inhibition in a wider range of metals such as steel and aluminum. They also are often incorporated in molybdate-based programs to both provide some synergism and reduce the level of molybdate required. Azoles also are employed in many types of organic-based formulations, where they improve the overall protection of steel and reduce the risk of corrosion of yellow metals due to the corrosive action of some common phosphonates. 

For the extraction of Tc from molybdemun irradiated by neutrons or separated from uranium fission products, inorganic sorbents, especially aliuninum oxide have widely been applied. In preparing a Tc generator from irradiated molybdenum , MoOj is dissolved in cone, nitric acid, the solution is diluted and passed through an aluminum oxide column. The column is then eluted by 0.2 N H2SO4 to extract Tc. If molybdenum is adsorbed by AljOj as molybdatophos-phate instead of molybdate, the exchange capacity of molybdenum increases from... 

Instead of aluminum oxide hydrated Zr02 can be used to adsorb irradiated molybdate. Tc is eluted with 2 M HNO3 . 

Aluminum forms tungstates A12(W04)3 and MA1(W04)2.224 Crystals of A1(W04)3 are orthorhombic as in the sulfate, Al3+ is octahedrally coordinated, with A1—O distances between 186 and 191 pm.225 Aluminum can be introduced into the structures of polytungstates and molybdates to prepare (ArWi2O40)5- and (A1Mo602i)3 for example.226... 

A third catalytic system was proposed more recently and based on vanadium aluminum oxynitrides (VALON) [30]. The maximum acrylonitrile yield reported was about 30%, but with acrylonitrile productivity four times higher than for V/ Sb/W/Al/O catalysts and one order of magnitude than for Mo/V/Nb/Te/O. Other companies have studied and developed proprietary formulations but, in general, catalytic systems belong either to the antimonates family (Rhodia, BASF, Nitto, Monsanto) [31-33] orto the molybdates family. 

Molybdenum disulfide is dispersed in greases and oils for lubrication in volatile carriers it is used to form dry coatings of lubricant. Sodium molybdate is an especially effective corrosion inhibitor on aluminum surfaces and is dissolved in cooling solutions to protect aluminum motor blocks in automobiles. 

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