Preliminary results from decahydroquinoline hydrodenitrogenation runs show that Bronsted acidity by itself will not catalyze carbon-nitrogen bond scission. The C-N bond cleavage must therefore be catalyzed by an active site, which consists of a transition metal ion in close proximity to an acid site. It appears that hydrodenitrogenation requires both an acidic and a basic site for the Hoffman E/sub 2/ elimination reaction to occur. Several catalysts have been prepared and tested, including Bronsted and Lewis acid catalysts without metal, and silica-alumina and ..gamma..-alumina impregnated with molybdenum, vanadium, nickel or iron. Our results show that the nitrogen removal rate was highest for molybdenum on ..gamma..-alumina catalyst and the rate decreased with lower Mo concentrations. Aluminum borate and aluminum borate phosphate catalysts (with or without nickel) were prepared to develop novel catalysts that would selectively coordinate the nitrogen atom and remove it without excessive hydrogenation. Results show that the support plays an important role in the nitrogen-removal process. Hydrodenitrogenation of aniline has been studied over a presulfided Ni-Mo/..gamma..-Al/sub 2/O/sub 3/ catalyst, and a reaction network has been proposed. Aniline hydrodenitrogenation appears to involve partial hydrogenation of the benzene ring to reduce aromatic resonance with the nitrogen atom, thus reducing the C-N …