Nitrogen is removed in catalytic hydrotreating by the breaking of the C-N bond producing a nitrogen free aliphatic and ammonia. The breakage of the C-N bond is much more difficult to achieve than the C-S bond in desulphurization. Consequently denitrification occurs to a much lesser extent than desulphurization.
Nitrogen is typically not a significant problem in virgin naphtha. If this were the case, a nickel molybdenum catalyst at higher severity hydrotreating conditions would be required. Nitrogen compounds typically found in straight run naphthas are methylpyrrol and pyridine.
🔴The heat released by the denitrification reactions is also negligible owing to the small amount of nitrogen compound involved.
🟡Nitrogen Compounds: Pyridine, Quinoline, Acridine (Basic Nitrogen), Pyrrole, Indole, Carbazole (Non-Basic Nitrogen)
🟪 Some Point for nitrification reactions:
• 1️⃣HDN is the hydrogenation of organic nitrogen compounds yielding hydrocarbons and NH3.
• 2️⃣HDN has a two-step pathway: Hydrogenation, followed by Hydrogenolysis
• 3️⃣HDN is an exothermic reaction and is favored at high PPH2.
• 4️⃣HDN of nitrogen aromatics compounds is more difficult than of aliphatic compounds
• 5️⃣Under mild conditions HDN can be fully assigned to kinetic factors, at more severe conditions thermodynamics sets in
• 6️⃣Organic (basic) N strongly inhibits HDS and HDA reactions
• 7️⃣HDN rate decreases with increasing molecular weight and steric hindrance
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