Tungstate, methanol oxidation

The sodium tungstate catalyzed oxidation of 1,2,3,4-tetrahydroquinoxaline with 30% aqueous hydrogen peroxide solution in methanol gives quinoxaline. ... 

Also for this reaction, namely esterification plus transesterification, mixed oxides, this time acidic in nature, appear to be the most promising alternative. Tungstated zirconia-alumina (WZA), sulfated zirconia-alumina and sulfated tin oxide were shown to be active in the transesterification of soybean oil with methanol at 200-300 °C and in the esterification of n-octanoic acid with methanol at 175-200 °C. Although the order of activities is different for the two reactions, WZA gives high conversions in both readions and it is stable under the reaction conditions [31]. Titania on zirconia, alumina on zirconia and zirconia on alumina also showed good performances [32, 6]. 

Furuta et al. tested a series of strong solid acids (alumina promoted sulfated zirconia, alumina promoted tungstated zirconia and sulfated tin oxide) for the transesterification of soybean oil with methanol at 200-300°C. Reaction yields over 90% were obtained for the alumina promoted tungstated zirconia at reaction times of 20 h using a flow reactor T = 250°C). The activity of the same catalyst was maintained for up to 100 h. 

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. ... 

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