The effect of basic nitrogen on gasoline hydrorefining
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I am an operator in gasoline hydroprocessing. Recently, water-soluble slightly alkaline substances have frequently appeared in the light gasoline, resulting in an alkaline nitrogen content of around 100–150 ppm in the crude oil used as feed for the production of this gasoline. The crude oil is first processed in a pre-hydrogenation reactor and then fractionated at the top of a distillation tower to obtain light gasoline. The operating temperature at the pre-hydrogenation inlet is 165 degrees, with a pressure of 2.4 Mpa. In the distillation tower, the temperature at the bottom of the tower is 160 degrees while it is 70 degrees at the top. The total sulfur content in the light gasoline is around 10 ppm. In my opinion, the low removal rate of basic nitrogen may be due to the pre-hydrogenation reaction; when basic nitrogen is mixed with water, it becomes alkaline. I’ve racked my brains but can’t figure it out; I earnestly ask the experienced master for guidance.
When was the pre-hydrogenated oil analyzed once?
No sampling was taken for analysis after pre-hydrogenation but before distillation. An analysis was done a long time ago, showing that the total sulfur content was around 200. The total sulfur content of the crude oil is around 600.
The lighter the component, the fewer nitrides it contains; therefore, the nitride content in light gasoline should be very low. It’s possible to take a sample for testing, and I don’t think it’s caused by basic nitrogen.
In our case, nitrogen seems to act as a catalyst poison; generally, pre-hydrogenation is used to saturate small amounts of olefins and to thicken light sulfur compounds
Gasoline hydrogenation should not have nitrogen removal capability, or it should have a very weak such capability; the problem needs to be addressed at the source. What are the components of the feed to your catalytic unit? Atmospheric residue or wax oil? Find ways to reduce the total nitrogen in the catalytic feedstock.