Mo-V-Sb-Nb mixed oxides

Figure 1.18 Survey and expanded V 2p and Mo 3d XPS spectra form a Mo-V-Sb-Nb mixed oxide catalyst after calcination in nitrogen (a) and air (b) atmospheres [145]. The data indicate a lesser degree of oxidation in nitrogen, a result that was correlated with the promotion of reactions leading to the production of propene and acrylic acid rather than acetic acid, the main product obtained with the fully oxidized sample. (Reproduced with permission from Elsevier.)...

This section presents a summary and comparison of four different projects carried out at Leverhulme Centre for Innovative Catalysis, University of Liverpool, UK on propane (amm)oxidation over Mo-V-Sb-Nb mixed oxides, V- and W-modified Keggin structure HPCs and Ga exchanged H-ZSM-5. These three examples represent the main groups of catalytic materials for propane oxidation to acrylic acid (see Section 13.3). The results, which will be discussed here, on the effect of the different redox and acid-base properties on the reaction, aim at bringing further insight into the catalytic transformation of propane. Introduction of steam or ammonia to the propane oxygen mixture over some of the catalysts is demonstrated to be a crucial parameter for more selective reaction. 

Therefore, the combined presence of (i) correct crystalline structure, (ii) partial reduction of the transition metal oxides, and (hi) low Lewis acidity, are crucial elements for successful propane oxidation to acrylic acid over Mo-V-Sb-Nb mixed oxide catalyst. 

Novakova, E.K., Vedrine, J.C., and Derouane, E.G. Propane oxidation on Mo-V-Sb-Nb mixed-oxide catalysts, 1. Kinetic and mechanistic studies. J. 

The use of Mo-V-containing catalysts for ethane ODH was studiedafter the important catal3dic results on MoVNbO catalysts by Union Carbide researchers in 1978. ° However, no improvement was observed on this type of catalyst More recently, ethylene yields of around 75% (at reaction temperatures in the 350-450°C range) have been reported employing Mo-V-Te-Nb mixed-oxide-based catalysts. The catalytic behavior in this type of catalyst is directly related to the presence of the so-called M1 phase (Fig. 24.2c). i27-i30,207,208 replacement of Te by Sb improves... 

Guerrero-Perez, M., Al-Saeedi, J., Gnliants, V., et al. (2004). Catalytic Properties of Mixed Mo-V-Sb-Nb-O Oxides Catalysts for the Ammoxidation of Propane to Acrylonitrile, Appl. Catal. A Gen., 260, pp. 93-99. 

Al-Saeedi, J.N. and Guliants, V.V. (2002) High-throughput experimentation in multicomponent bulk mixed metal oxides Mo-V-Sb-Nb-O system for selective oxidation of propane to acrylic acid. Appl. Catal. A Gen, 237, 111. 

Al-Saeedi, J.N., Guliants, V.V., Guerrero-Perez, O., and Banares, M.A. Bulk structure and catalytic properties of mixed Mo-V-Sb-Nb oxides for selective propane oxidation to acrylic acid. J. Catal 2003, 215, 108-115. 

The second most active and selective mixed oxide catalyst for the propane oxidation to acrylic acid is based again on Mo-V-Te-Nb-Ox, in which Te is substituted by Sb [61]. Test results on this catalyst suggested that Sb-based catalyst is less active and selective than its Te analog, but the overall performance was still quite good (16% acrylic acid yield). Takahashi et al. [63] proposed further improvements to this catalyst system by introducing potassium into the catalyst, resulting in raise of the yield to 25%. 

Acetonitrile can be produced by catalytic ammoxidation of ethane and propane over Nb-Sb mixed oxides supported on alumina, with selechvities to acetonitrile of about 50-55% at alkane conversions of around 30% [133]. In both cases, CO forms in approximately a 1 1 molar ratio with acetonitrile, owing to a parallel reaction from a common intermediate. When feeding n-butane, the selectivity to acetonitrile halves. Bondareva and coworkers [134] also studied ethane ammoxidation over similar types of catalyst (V/Mo/Nb/O). 

NiO doped by 56 different metal centers Mixed-metal oxides containing V, Fe, Mo, Cr, Ta, Nb, Mn, Sb and Bi Ti-sdicates... 

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