Pre-sulfidation issue of pre-hydrogenation catalysts
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Sulfidation of the pre-hydrogenation system in the reforming unit is generally carried out using the DMDS injection method for wet sulfidation. I would like to discuss whether sulfur-containing naphtha can be used as a sulfurizing oil for direct sulfidation, and what level of sulfur content in the sulfur-containing naphtha is appropriate
The pre-sulfiding of gasoline hydrogenation catalysts requires a sulfur content in the oil of >200 ppm; it is estimated that the requirements for pre-sulfiding in reformation and pre-hydrogenation are not very different
Use naphtha? Isn’t it diesel?
Pre-sulfurization with sulfur-containing naphtha can be used, but we haven’t used it here. DMDS is used every time. Using DMDS, the hydrogen sulfide concentration in the circulating hydrogen must be maintained at above 1,000 v-ppm at all times, with the goal of keeping it above 3,000 v-ppm. It is estimated that using sulfur-containing naphtha should be similar to using DMDS.
Sulfur-containing naphtha can be used as the sulfurizing oil for direct sulfiding; it just takes longer. In the case of a one-pass hydrogen process, the hydrogen sulfide content in the hydrogen sent out will be slightly higher. Based on our production experience, there is no major problem if sulfiding is not carried out!
It doesn’t seem very feasible. Pre-sulfurization is a reaction process in which the oxidized catalyst reacts with H2S, producing water. The effectiveness of pre-sulfurization can be determined by comparing the amount of sulfur calculated after the pre-sulfurization process is complete with the theoretical amount of sulfur provided by the catalyst manufacturer； At the same time, system water cut measurement is compared with the water generated by theoretical calculations to assess the effectiveness of pre-sulfurization. Presulfurization essentially converts the oxidized catalyst into a sulfided catalyst with higher activity and stability. If you pre-sulfurize using high-sulfur naphtha directly, it is equivalent to using a hydrogenation feed with high sulfur content, and this does not result in any improvement in catalyst activity!
We had failed in vulcanization before, and it felt the same way (the difference wasn’t significant)
The sulfur in naphtha may not necessarily react with the catalyst, and its concentration is difficult to control; it’s better to use DMDS instead.
This post was last edited by Green Lotus on 2018-9-10 at 15:17. Shandong Daqi uses the technology developed by the Fuyan Research Institute to produce a safe and environmentally friendly vulcanizing agent called FSA-55, which serves as a substitute for DMDS. FSA-55 has a flash point above 110°C, and it features a mild odor as well as a low decomposition temperature. It has now been applied in Binzhou, Zibo, and Sichuan, and its performance has received positive feedback from customers!
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