Bismuth molybdate catalyst stability

III. Stability of the Multicomponent Bismuth Molybdate Catalyst Depending on the Bulk Diffusion of Oxide Ion... 

The establishment of the structures and thermal transformations of the catalytically active phases of bismuth molybdate resulted in research directed toward investigating the stability of the structure under reducing conditions. Fattore et al. (38) investigated an unsupported bismuth molybdate catalyst with composition Bi2032.66M0O3 during propylene... 

FIGURE 4 Designs of Raman cells that, for selected reactions, deliver catalyst performance data corresponding to those of an ideal reactor, (A) C.G. Hill [Adapted from Snyder T.P., and Hill C.G.,/ Catal. 132, 536 (1991) Stability of Bismuth Molybdate Catalysts at Elevated-Temperatures in Air and under Reaction Conditions, copyright (1991), with permission from Elsevier (377)], (B) G. Mestl [source, M.A. Banares],... 

In the preceding section, we explained that the bulk diffusion of oxide ion plays an important role in the enhancement of the catalytic activity of the multicomponent bismuth molybdate systems. Here, another important role of the oxide ion migration in increasing the stability of the catalyst system is introduced. 

FIGURE 13 Raman-GC recorded during propene oxidation on bismuth molybdate with simultaneous activity measurement (A) Raman spectra (Reprinted from J. Catal. 132,536 (1991), Snyder T.P., Hill C.G., Stability of bismuth molbydate catalysts at elevated temperatures in air and under reaction conditions, copyright (1991) with permission from Elsevier) (Snyder and Hill, 1991) (B) simultaneous conversion and selectivity (based on Snyder and Hill, 1991). 

Bismuth cerium molybdates were prepared by coprecipitation using aqueous solutions of (NH ) Mo 02, (NH,)2Ce(N0 ), and Bi(NO ) 5H2O. The catalysts were supported on oiO (20% by weight) using an ammonium stabilized silica sol. Samples for diffraction analysis were unsupported. Samples were calcined in air at 290 and 425°C for three hours each followed by 16 hours at 500, 550, or 600 C. X-ray powder patterns were obtained using a Rlgaku D/Max-IIA X-ray diffractometer using Cu K radiation. 

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