Kinetics of hydrodenitrogenation of SRC-II liquids and synfuel-simulating blends

The kinetics of hydrodenitrogenation (HDN) of two blended feeds (blend A, a SRC-II middle-heavy distillate blended with 4.76 wt % of 1,10-phenanthroline and blend B, a synfuel-simulating reference blend containing tetralin, 85.5, phenanthrene, 3.5, and 1,10-phenanthroline, 11.0 wt %), were measured in an autoclave reactor at four temperatures between 300–375 °C, using sulphided 3Co-8Mo and 3Ni-8Mo catalysts prepared by stepwise addition of the Co or Ni promoter to Mo-impregnated γ-Al 2O 3. Linear increase in nitrogen removal as a function of time was found at each reaction temperature, indicating pseudo-zero-order HDN kinetics for both feeds. Faster hydrogen consumption is observed with both catalysts in the early stage of the HDN process, in agreement with previous kinetic studies of isomeric benzoquinolines, phenanthridine and carbazoles, showing rapid initial hydrogen consumption by hydrogenation of both N-heterocyclic and carbocyclic aromatic rings prior to the less-consuming C-N hydrogenolysis steps. The hydrogen consumption for HDN of blend A at 350–375 °C is in the range of 8.0–10.3 moles of H 2 per N g atom removed. This is drastically higher than the ideal H 2 consumption of 3–4 moles H 2 per N g atom removed, calculated on the basis of selective hydrogenation of N-heterocyclic rings only, followed by C-N hydrogenolysis. Results obtained indicate the need for catalysts of augmented C-N hydrogenolysis selectivity for more efficient HDN of heavy oils and synfuels.