Tungstate catalysts

In treating cracked stocks such as steam cracked naphtha or visbreaker naphtha, which are highly olefinic in nature, nickel molybdate or nickel tungstate catalysts are generally employed. These catalysts have much higher activity for olefin samration reactions than does cobalt molybdate. 

One problem associated with the peroxotungstate-catalyzed epoxidation system described above is the separation of the catalyst after the completed reaction. To overcome this obstacle, efforts to prepare heterogeneous tungstate catalysts have been conducted. De Vos and coworkers employed W catalysts derived from sodium tungstate and layered double hydroxides (LDH - coprecipitated MgCU, AICI3, and NaOH) for the epoxidation of simple olefins and allyl alcohols with... 

Tunable uv-vis lasers, 23 144 Tuneable separation systems, 22 654 Tung oil, 9 143, 149, 150, 20 814-817 Tungstate catalysts, 22 48 Tungstates, 25 381-382 properties of, 25 382t Tungsten (W). See Nickel-chromium-molybdenum (tungsten) alloys, 25 349-376... 

Fig. 4.22 Halide- and halogenated solvent-free biphasic epoxidation with 30% aqueous H202 using tungstate catalysts.

Fig. 4.23 Oxidative cleavage of cyclohexene using tungstate catalyst.

Among the large variety of catalytic methods available for the epoxidation of alkenes, those based on tungstate catalysts hold a prominent place when it comes to industrial relevance. Several positive features of W-based catalyst systems explain their popularity in industry ... 

Oxidations, including epoxidations, with tungstate catalysts can be run with inexpensive and "green aqueous H2O2 as the terminal oxidant. 

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