pre-vulcanization

No, there’s no need to consider this issue

The feedstock for diesel hydrodesulfurization pre-fluidization is usually straight-run diesel; as long as the nitrogen content is within the specified range, there are no issues. Even if some ammonium salts crystallize, adding water after pre-sulfurization will wash away these ammonium salts. However, in diesel cracking hydrogenation, ammonia is injected during pre-sulfurization to protect the cracking agent; therefore, water is injected during pre-sulfurization to prevent ammonium salt crystallization.

Ammonia injection during cracking is used to passivate the catalyst, preventing it from having excessive activity at the beginning of the sulfidation process and avoiding excessive temperature rises in the catalyst bed. Additionally, water is generated as a result of reactions that occur during the pre-sulfidation process; since this stage lasts not very long, the possibility of salt formation is low. Generally, zhiliuy is used for sulfidation when the plant starts up

Injecting ammonia during the pre-sulfurization of the hydrocracking unit serves to deactivate the cracking agents, preventing the feedstock from cracking at high temperatures in the later stages of pre-sulfurization; this would otherwise result in the production of large amounts of olefins, which in turn would cause the highly active hydrogenation catalysts that have just been pre-sulfurized to carry out intense hydrogenation reactions, leading to overheating of the catalyst bed. During sulfidation, the circulating hydrogen is in a high-sulfur, high-ammonia environment, so the crystallization rate cannot be measured using the standards applied in normal production phases. Moreover, during pre-sulfidation, the temperature of the hot high-pressure gas phase is lower than that in regular production, being significantly below the crystallization temperature of ammonium salts; therefore, water must be added during hydrocracking.

No way, we didn’t start injecting water once the unit was in operation

Low-sulfur, low-nitrogen diesel used for presulfurization does not suffer from ammonium salt clogging, but a small amount of ammonium salts is formed.

“Xunkai Catalysts boasts a comprehensive range of hydrogenation catalyst products, including those based on Raney nickel, supported nickel, copper-zinc, copper-silicon systems, as well as catalysts on precious metal carriers – both in powder form and for fixed-bed use. These catalysts have been successfully applied in processes such as hydrogenation, dehydrogenation, reductive amination, and desulfurization across industries including those involved in 1,4-butanediol, caprolactam, fatty alcohols, organic amines, butyl octanol, HPPO, petroleum resins, dye intermediates, as well as pharmaceutical and pesticide intermediates. For technical inquiries, please contact Manager Mei at 17701646014