Poisoning of catalytic cracking catalysts
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I would like to ask: what are the symptoms and characteristics of poisoning of catalysts by calcium, iron, vanadium, and nickel, and how can they be distinguished from one another?
No one answered, so I’ll take it on myself. Please don’t give up, all the experts and moderators out there – help me out!
This post was last edited by liurf1975 on 2011-4-23 20:55. Nickel attaches to the surface of the catalyst in an oxidized state; it plays a role in dehydrogenation during catalytic reactions, which reduces the catalyst’s selectivity, increases the yield of coke, and raises the hydrogen/methane ratio in the dry gas. However, nickel does not damage the molecular sieve and has little effect on the catalyst’s activity. Vanadium: The vanadium present in the feedstock deposits on the catalyst, increasing the hydrogen/methane ratio in the dry gas. In addition to causing dehydration, it also damages the structure of the catalyst and reduces its activity. Vanadium is oxidized on the catalyst to form V2O5, which destroys the active centers of the catalyst. Vanadium reacts with aluminum to form low-boiling eutectics, which lower the melting point of the catalyst’s structure; this damages the catalyst’s micropores and lattice, reduces its specific surface area, leads to a sharp decline in activity, and results in permanent deactivation. Sodium: When sodium deposits on the catalyst, it can neutralize the acidity of the catalyst, reducing its activity. It can also form low-boiling eutectics with vanadium and aluminum, thereby damaging the catalyst’s structure and decreasing its stability. Calcium and iron: Calcium also has effects similar to those of sodium; iron that results from equipment corrosion has no impact on catalysts, but iron in combined forms is just as harmful as vanadium.
Reply to 4# liurf1975: Thank you. I’m not sure how to determine whether it’s V poisoning or Na.Fe poisoning in the case where there is a high yield of dry gas coke and reduced catalyst activity Because the symptoms caused by poisoning don’t differ much
Several types of metal poisoning often occur simultaneously; it is advisable to determine the levels of various metals in the body in order to determine which type of metal poisoning is more severe. The activity of the catalyst decreases over time as it is used, and fresh material must be continuously added to maintain a certain level of activity.
I’ve learned a lot; it’s been very enlightening. Thank you!
This post was last edited by liurf1975 on 2011-4-24 at 17:26. It’s about identifying exactly what type of poisoning it is – that is, conducting an analysis! Parameters such as heavy metal content, specific surface area, and activity!
Vanadium poisoning is the most severe issue, but generally, imported oils contain high levels of vanadium; domestic oils, on the other hand, have high nickel content. Vanadium has a significant impact on activity, leading to a decrease in dry gas and coke production as well as an increase in reprocessed oil. However, nickel, iron, and calcium do not necessarily lead to an increase in reprocessed oil, unless levels above 10,000 also result in a decrease in activity; calcium contamination can affect the porosity of the catalyst by making its surface sticky.