Hydrodenitrogenation

Hydrodenitrogenation

Hydrodenitrogenation (HDN) is a similar process to HDS in which hydrogen is used to remove nitrogen, and for this reason during HDS the nitrogen content of fuels is also reduced. Figure 9.6 shows different types of nitrogen-containing compounds in crude oil and refinery unit products. In addition to reducing the N content in fuels as a finishing process, basic nitrogen compounds such as pyridine and quinoline shown in Figure 9.6 should also be removed as a pretreatment step to protect the acidic catalysts used in processes such as FCC. This is similar to HDS being an important pretreatment process for feedstocks that would be exposed to noble metal catalysts (such as Pt in a catalytic reforming process) that are poisoned by sulfur compounds. Figure 9.7 shows examples of HDN reactions and catalysts used for HDN. Similar to HDN reactions for quinoline, shown in Figure 9.7, pyridine (C₅H₅N) can be reduced to pentane (C₅H₁₂) and ammonia (NH₃) by adding 5 molesH₂ in three steps. The overall HDN reaction for pyridine is C₅H₅N + 5H₂ → C₅H₁₂ + NH₃.

Figure 9.6. Types of nitrogen containing compounds found in crude oil.

Credit: Dr. Semih Eser © Penn State is licensed under CC BY-NC-SA 4.0

Figure 9.7. HDN reactions and catalysts.

Credit: Dr. Semih Eser © Penn State is licensed under CC BY-NC-SA 4.0