Selective oxidation and ammoxidation

Being one of the reactants in some of the important selective oxidation and ammoxidation reactions, NH can be a simple probe molecule to... 

Among the oxide catalysts, bismuth molybdates that catalyse selective oxidation and ammoxidation of propylene to yield acrolein and acrylonitrile have received considerable attention (Grasselli Burrington, 1981) ... 

Selective Oxidation and Ammoxidation of Propylene by Heterogeneous Catalysis Robert K. Grasselli and James D. Burrington... 

Intensive studies on the mechanism of oxidation and ammoxidation have been carried out.900 939957-960 All selective oxidation and ammoxidation catalysts are... 

Further examples of attempts to replace olefins by alkanes as a starting materials, as in the maleic anhydride process, are the development of processes for selective oxidation and ammoxidation. Examples are processes for acrolein, acrylic acid (Table 2, entry 19) and acrylonitrile (Table 2, entry 20) using propane as a feedstock... 

Grasselli, R. K., Advances and future trends in selective oxidation and ammoxidation catalysis, Catal. Today, 49,141,1999... 

Selective Oxidation and Ammoxidation of Propylene by Heterogeneous Catalysis Robert K. Grasselli and James D. Burrington Mechanism of Hydrocarbon Synthesis over Fischer-Tropsch Catalysts P. Biloen and W. M. H. Sachtler Surface Reactions and Selectivity in Electrocatalysis... 

Kinetic Isotope Effects in Selective Oxidation and Ammoxidation Reactions... 

Depending on the preparation route of the VOHPO4 O.5H2O precursor and the gas atmosphere in which the precursor-to-catalyst transformation is performed, catalysts of various structures and compositions are obtained. However, these catalyst structures have a common property that is essential for effective catalytic performance in both selective oxidation and ammoxidation reactions, namely neighboring species that are coupled by effective spin-spin exchange inter-... 

Synthetic zeolites have gained importance as industrial catalysts for cracking and isomerization processes, because of their unique pore structures, which allow the shape-selective conversion of hydrocarbons, combined with their surface acidity, which makes them active for acid-catalyzed reactions. Many attempts have been made to introduce redox-active TMI into zeolite structures to create catalytic activity for the selective oxidation and ammoxidation of hydrocarbons as well as for SCR of nitrogen oxides in effluent gases (69-71). In particular, ZSM-5 doped with Fe ions has attracted attention since the surprising discovery of Panov et al. (72) that these materials catalyze the one-step selective oxidation of benzene to phenol... 

Tin(IV) oxide is used in various heterogeneous catalyst mixtures, e.g. Sn02/V20s for oxidation of arenes to carboxylic acids and anhydrides, and Sn02/Sb20s for selective oxidation and ammoxidation of propylene to acrolein, acrylic acid, and acrylonitrile. 

Vanadium phosphates have been applied to a number of selective oxidation and ammoxidation reactions, although the partial oxidation of n-butane to maleic anhydride remains the most widely studied reaction for these catalysts. Even though the first patent for this reaction was filed over 40 years ago, there are stQl a large number of papers published on this system every year. 

Bismuth Molybdate Catalysts. The Raman spectra of the bismuth molybdates, with Bi/Mo stoichiometric ratios between 0.67 and 14, have been examined using the FLS approach (see Section 3.2). " The bismuth molybdates fall into an unusual class of compounds, the ternary bismuth oxide systems Bi-M-0 (where M = Mo, W, V, Nb, and Ta) which exhibit a variety of interesting physical and chemical properties. Of commercial importance, the bismuth molybdates are heterogeneous catalysts for selective oxidations and ammoxidations (the Sohio process), for example, propylene ( 311 ) to acrolein (C3H4O) by oxidation or to acrylonitrile (C3H3N) by arrunoxidation. ... 

We shall first show that it is still far fiom clear which are the families of catalysts to be used for the various reactions mainly oxidative dehydrogenation or oxidation to oxygen-containing molecules of ethane, propane or isobutane. Much research is still necessary for understanding the mechanisms leading to high selectivity. In this context, we shall suggest that many concepts inherited from the development in selective oxidation and ammoxidation of olefins are probably of little use. 

Selective Oxidation and Ammoxidation of Propylene by Heterogeneous Catalysis... 

All selective oxidation and ammoxidation catalysts possess redox properties. They must be capable not only of reduction during the formation of acrolein or acrylonitrile, but also subsequent catalyst reoxidation in which gaseous oxygen becomes incorporated into the lattice as to replenish catalyst vacancies (Scheme 2). As mentioned earlier, the incorporation of such redox properties into solid state metal oxides was one of the salient working hypotheses on which the development of the Sohio ammoxidation process was based (2). Later, Keulks (70) confirmed the involvement of lattice oxygen in propylene oxidation by using as a vapor phase oxidant. The results showed that the incorporation of O into the acrolein (and CO2) increases with time (Fig. 11), which is consistent with the above redox mechanism. 

SELECTIVE OXIDATION AND AMMOXIDATION OF PROPYLENE ACID SITE ... 

Scheme 11. Mechanism for selective oxidation and ammoxidation of propylene over bismuth molybdate. From (27).

Attention should be drawn It) the use of tin o.xide systems as heterogeneous catalysts. The oldest and most extensively patented systems are the mixed tin-vanadium oxide catalysts for the oxidation of aromatic compounds such as benzene, toluene, xylenes and naphthalene in the. synthesis of organic acids and acid anhydride.s. More recently mixed tin-antimony oxides have been applied to the selective oxidation and ammoxidation of propylene to acrolein, acrylic acid and acrylonitrile. 

R.K. Grasselli (1986) Journal of Chemical Education, vol. 63, p. 216 - Selective oxidation and ammoxidation of olefins by heterogeneous catalysis . 

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