Hydrodenitrogenation of decahydroquinoline, cyclohexylamine and o-propylaniline over carbon-supported transition metal sulfide catalysts

Carbon-supported transition metal sulfide (TMS) catalysts were prepared by impregnation of an activated carbon support with aqueous solutions of first-, second-, and third-row (group V-VIII) transition metal salts followed by drying and in situ sulfidation. Their activity for the hydrodenitrogenation of decahydroquinoline (5.2–5.5 MPa, 623–653 K), cyclohexylamine (4.8-5.5 MPa, 543–653 K), and o-propylaniline (5.1–5.5 MPa, 593–653 K) was tested in microautoclaves. When plotted versus the position of the transition metal in the Periodic System, the conversions of all three N-containing reactants to hydrocarbons over the first-row transition metal sulfides formed U-shaped curves with a minimum at Mn, while V had the highest conversion. The decahydroquinoline and cyclohexylamine conversions to hydrocarbons over the second- and third-row TMS formed volcano curves with maxima at Rh and Ir, respectively. Disproportionation reactions were found to be important side reactions in the cyclohexylamine hydrodenitrogenation. The activities of the second-row transition metal sulfides for the conversion of o-propylaniline formed a volcano curve with a maximum at Ru or Rh sulfide, whereas the activities of the third-row transition metal sulfides formed a strongly distorted volcano curve. All catalysts and especially Re sulfide had a very high selectivity for propylbenzene