Cobalt molybdate, dehydrogenation

Johnston, K. P., Hydrogenation-Dehydrogenation of Pyrenes Catalyzed by Sulphided Cobalt-Molybdate at Coal Liquefaction Conditions. Fuel, 1984. 63 pp. 463 168. 

Keywords nickel molybdate, cobalt molybdate, nickel cobalt molybdate, propane oxidative dehydrogenation, propylene production... 

Catalysts based on transition metal molybdates, typically bismuth, cobalt and nickel molybdates [2-6], have received recent attention. Of the transition metal molybdates, those based on nickel, and in particular the stoichiometric NiMo04, have attracted the greatest interest. NiMo04 presents two polymorphic phases at atmospheric pressure a low temperature a phase, and a high temperature P phase [2,7]. Both phases are monoclinic with space group dim. These phases differ primarily in the coordination of molybdenum which is distorted octahedral in the a phase and distorted tetrahedral in the P phase. The P phase has been shown to be almost twice more selective in propene formation than the a phase for comparable conversion at the same temp>erature [2]. A similar effect has been noted for oxidative dehydrogenation of butane, with the P phase being approximately three times more selective in butene formation than the a phase [8]. The reason for the difference in selectivities is unknown, but the properties of the phases are known to be dependent on the precursors from which they are derived. Typically, nickel molybdates are prepared by calcination of precipitated precursors. 

Alumina catalysts activated by additions of dehydrogenating catalysts, e.g., nickel oxide, copper oxide or sulfide, zinc oxide or sulfide, cobalt selenide, zinc phosphate, cadmium tungstate, mixtures of the oxides of zinc and tungsten, of cadmium and molybdenum, etc., are claimed to be superior in the formation of acetaldehyde from mixtures of steam and acetylene at 350° to 400° C.l-la Zinc oxide catalysts may be activated in a similar way by the addition of small amounts of molybdates or molybdic acid, and are effective at 300° to 350° C.121b... 

Agafonov, Yu.A., Nekrasov, N.V., and Gaidai, N.A. Kinetic and mechanistic study of the oxidative dehydrogenation of isobutane over cobalt and nickel molybdates. Kinet. Catal. 2001, 42, 821. 

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