Hydrodenitrogenation of quinoline and decahydroquinoline has been studied employing several catalysts: Bronsted and Lewis acid catalysts without metal, and silica-alumina, .gamma.-alumina and magnesia impregnated with molybdenum, tungsten, nickel or cobalt. Our results show that nitrogen removal rate was highest for molybdenum on alumina and tungsten on silica-alumina or alumina catalysts. Nitrogen abstraction using .gamma.-alumina support is considerably faster than with magnesia support. Several catalysts have been prepared and tested, with the emphasis on understanding the role of acidity in the carbon-nitrogen bond scission reaction. Hydrodenitrogenation of quinoline has been studied by using Ni, Mo/chlorided or fluorided alumina catalysts, with various halide concentrations. Preliminary results from this study indicate that halogenation of .gamma.-alumina catalysts slightly enhanced the hydrogenolysis activity but showed little effect on the hydrogenation activity. Initial results from phenothiazine hydroprocessing show that carbon-sulfur bonds in the reactant are broken much faster than the carbon-nitrogen bonds. Data relevant to this reaction are being evaluated, utilizing kinetic analysis to give quantitative rates of C-N and C-S bond scission and the extents and rates of hydrogenation. Note: this report contains 5th, 6th, 7th and 8th quarterly reports.