The nitrogen resistance issue of hydrocracking catalysts
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My company uses FC-12 as its hydrocracking catalyst; the designed nitrogen content in the feedstock is 2200 PPm, while the actual nitrogen content in the feedstock is usually around 3000 PPm. Please share if there are hydrocracking catalysts with higher nitrogen resistance, and whether your company has encountered similar situations.
Is the nitrogen level that high? Is it coker wax oil? We usually go around 700 to 1000
It is coking wax oil. Due to the high nitrogen content in the coking feedstock, the nitrogen content in the coking wax oil is also high.
It doesn’t matter; it depends on the refinement quality you achieve； For typical cracking catalysts, it is required that the nitrogen content after purification be less than 10PPM. Catalyst suppliers will inform you that the catalyst can tolerate a nitrogen content of 30PPM; temporarily exceeding this level is not a problem, but the catalyst cannot operate under such conditions for an extended period of time ； Especially for catalysts with a high content of molecular sieves, if an amorphous catalyst is used, the nitrogen resistance will be better ； Foreign catalysts generally have better nitrogen resistance, but this is not entirely accurate; it is still necessary to pay attention to the nitrogen content after purification.
The nitrogen resistance of hydrocracking catalysts is not very high; an increase in the nitrogen content of the feedstock requires stricter control over hydrodenitrogenation, otherwise the activity of the cracking catalyst will decrease significantly.
Such feedstock is not suitable for hydrocracking; it is more reasonable to subject coker wax oil to wax oil hydrogenation before proceeding with catalytic cracking.
Regarding the issues related to coker wax oil and hydrocracking processing, it should be noted that since coker wax oil (CGO) typically has a high nitrogen content, and some coking units introduce some coke dust into CGO, backwashing facilities are generally installed before the hydrocracking unit. Nevertheless, it is still necessary to control the proportion of CGO in the hydrocracking feed so that it does not exceed around 20%； Regarding the nitrogen resistance of hydrocracking catalysts, catalyst suppliers generally state that the N content in the effluent from the first reactor stage can be kept at no more than 50 or even 100 ppm. However, in actual production, in order to ensure the catalyst’s lifespan and extend its operational period, it is common to keep this value below 20 ppm.
It mainly depends on the nitrogen content in the refined oil; as long as this content is less than 10PPM, the requirements are met. Refined catalysts generally do not get poisoned, whereas it is cracking catalysts that are usually poisoned.
There should be sophisticated reactors; what is the nitrogen content in the refined oil, and what is the level of hydrogen sulfide in the circulating hydrogen? It is possible to increase the hydrogen sulfide content in the circulating hydrogen, which facilitates nitrogen removal