ADSORPTION PREFERENCES OF NH3 ON V2O5 CATALYSTS - THEORETICAL-ANALYSIS OF A CRITICAL STEP IN AMMOXIDATION PROCESSES

Metal oxides utilized as mild oxidation catalysts are industrially important in ammoxidation processes. This reaction involves the activation of NH3, and subsequent oxidation produces a nitrile product. The most important nitriles are obtained by ammoxidation of propylene, toluene, xylenes, and pyridines. Our work focuses on adsorption and activation processes for ammonia on model V2O5(010) surfaces. Extended Huckel/tight-binding calculations have been used to characterize both the active sites of the catalyst and the nucleophilic and electrophilic surface oxygen species. For several oxidation processes, nucleophilic oxygen species are implicated in selective processes, and electrophilic species produce nonselective carbon oxides. Our studies have also evaluated known low-energy adsorption sites and described bonding interactions between surface/adsorbate and coadsorbate interactions. An analysis of such interactions is essential, as competitive adsorption processes are critical for ammonia activation. © 1990, American Chemical Society. All rights reserved.