Paramolybdate

Undoubtedly the first major polyanion formed when the pH of an aqueous molybdate solution is reduced below about 6 is the heptamolybdate [M07O24] , traditionally known as the paramolybdate ... 

Catalysts were normally prepared by double impregnation of the alumina support, first with ammonium paramolybdate solution to give 12 wt% MoO (8% Mo) after 500°C calcination, then with cobalt... 

Fig. 10 Two possible orientations of paramolybdate ([M07O24] ) in the interlayer of LDHs. Reprinted with permission from [143]. Copyright American Chemical Society...

Preparation of Sodium Paramolybdate. Pour 20 ml of a sodium molybdate solution into a 100-ml beaker. Heat the solution and introduce freshly precipitated molybdic acid into it in small portions with stirring until it stops dissolving. Filter the solution and evaporate it in a water bath until crystallization of a sample taken begins. 

Acidification of the leach liquor with sulfuric acid produces solutions containing Mog0264-, which is extracted into a solution of tertiary amine hydrogen sulfate as described previously. Loaded organic phases are stripped with aqueous ammonia to give solutions from which ammonium paramolybdate can subsequently be crystallized ... 

Calcination of the ammonium paramolybdate yields molybdenum(VI) oxide of high purity 208... 

In the Mo/Al catalyst, the precursor is normally ammonium paramolybdate, which has the formula (NH4)6Mo7024. The Mo... 

Figure 8 Acidic and basic impregnation of Al2 03 with ammonium paramolybdate...

The 6-heteropoly compounds of molybdenum have been studied extensively and are well understood. Typical examples are the 6-molybdotellurate anion, [TeMo6024]-6, and the 6-molybdochromate(III) anion, [CrMo6024H6]-3. These are usually prepared by the reaction of ammonium paramolybdate with a soluble salt of the central atom7. Some of these are stable only in very mild acid solution and caution should thus be exercised in preparing them. 

Fig. 5. Structure of the paramolybdate ion IM07O24I 6-Here seven MoOg octahedra share edges to make the complete unit...

The 9-heteropolymolybdates are prepared by oxidizing a solution of a simple divalent salt of the central atom and a soluble paramolybdate M6Mo7024 with persulfate, peroxide, or bromine water141,142. ... 

The P+s anions are prepared from molybdic acid and a metaphosphate or pyrophosphate. Manganese, cobalt, and copper form solutions of the divalent cations with paramolybdate anion. 

Similarly numerous complex salts are derived from tungsten such as the para- and meta-tungstates, the structures of which are, however, not yet completely elucidated. They are associated with the heteropolyacids, for example, (NH4)6 [Mo(Mo04)6].4H20, ammonium paramolybdate. 

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