ABSTRACT
Industry ..............................................................................................254 7.3 Manufacture of Pyridine Nitriles .......................................................259 7.3.1 Ammoxidation of 2P to 2CP ..................................................259 7.3.2 Ammoxidation of 3P to 3CP ..................................................260 7.3.3 Vanadium Phosphate Based Catalysts ...................................261 7.3.4 Other Catalyst Compositions .................................................263 7.3.5 Ammoxidation of 4P to 4CP ..................................................266 7.4 Manufacture of Pyrazine Nitriles ......................................................268 7.4.1 Ammoxidation of 2MP to 2CPy ............................................268 7.5 Mechanistic Aspects ..........................................................................271 7.5.1 Mechanism of Vapor Phase Ammoxidation over
V2O5-Containing Catalysts ................................................................272 7.5.2 Mechanism of Toluene Ammoxidation over VPO Catalysts...... 274 7.6 Summary and Outlook .......................................................................276 Acknowledgments .......................................................................................278 Keywords ....................................................................................................278 References ...................................................................................................278
The conversion of various olefins, aromatic and hetero-aromatic compounds in the presence of air (oxygen) and ammonia towards their corresponding nitriles in a continuous process is termed as ammoxidation or ammonoxidation or oxidative ammonolysis [ 1]. It is a rather simple one-pot reaction leading from hydrocarbons or hetero-aromatics to nitriles that are mainly used as intermediates for the production of a wide variety of industrially important chemicals. Outstanding examples are the manufacture of acrylonitrile from propene, xylene dinitriles from p-and m-xylene, 2-cyanopyrazine from 2-methylpyrazine, nicotinonitrile from 3-picoline, etc. Scheme 7.1 shows the general stoichiometry of an olefinic and aromatic or hetero-aromatic reactant to their corresponding nitriles, respectively. The one-step reaction runs after a first H-abstraction via an allyl-and benzyl-like species formed in an activation step. Subsequently, an aldehyde stage is formed that reacts with an activated ammonia surface species towards a N-containing intermediate (imine [ 2, 3] or amine/amide [4, 5]) that is further oxidatively dehydrogenated to form the desired nitrile.
