Regarding the issue of catalyst sulfidation

Hydrocracking catalysts containing molecular sieves (especially those with a high content of molecular sieves) exhibit high hydrocracking activity after sulfidation. Since the cracking reaction is a highly exothermic process, in order to prevent it from becoming too intense, appropriate measures must be taken to deactivate the catalyst before the feed oil is introduced. This helps to suppress its excessive initial activity and prevents any potential rise in temperature during the feeding process, thereby ensuring the safety of the catalyst, equipment, and personnel. Among them, the use of low-nitrogen start-up oil and the injection of anhydrous liquid ammonia are effective passivation methods to suppress the initial activity of the catalyst. After the injected anhydrous liquid ammonia is adsorbed by the catalyst, it can effectively suppress the initial activity of the catalyst. However, as the reaction temperature rises and the operating time increases, the ammonia adsorbed on the catalyst gradually desorbs and is lost, allowing the catalyst to regain its normal activity. Requirements for the initial activation passivation oil: Distillation range dry point:

I understand this, but I want to know why the flow rate of aniline injected during sulfidation needs to be calculated based on the nitrogen content in diesel. Why is that? Please explain.