On the issue of heavy metal contamination in catalysts

It’s hard to say about the standards, but the catalyst activity will definitely decline. One can’t wait until the catalyst is almost completely ineffective before replacing it; it’s better to replace it in small amounts over time, so that the operation of the device remains stable. Frequent dressing changes can cause operational fluctuations.

What are the heavy metals that cause contamination in catalytic cracking catalysts? What criteria must be met to consider it poisoning? What are the symptoms after poisoning? Is it only possible to solve the problem with a large amount of replacement catalysts? Iron, nickel, copper, vanadium, and so on ； The toxic effects of various metals on catalysts vary; these values are generally expressed in ppm. For example, the threshold for iron that a catalyst can tolerate is no more than 8000 ppm ； After poisoning, activity decreases and the yield drops; in cases where poisoning is severe due to various metals, it can also be distinguished from the color of the catalyst ； After catalyst poisoning, one approach is to increase the amount of passivator added, and the other is to replace a large quantity of balance agent (that is discharged from the regenerator during normal production) or to purchase balance agent externally. Using a large amount of fresh replacement material is uneconomical and can cause fluctuations in production.

1. What are the heavy metals that cause contamination in catalytic cracking catalysts? What are the symptoms after poisoning? Heavy metal contamination of catalysts: http://bbs.hcbbs.com/thread-597130-1-1.html (Source: Haichuan Network) / 2. What standards must be met for it to be considered poisoning? Catalyst heavy metal pollution index: http://bbs.hcbbs.com/thread-40415-1-1.html (Source: Haichuan Net) 3. Is it only possible to solve the problem by replacing the catalyst in large quantities? As mentioned above, replacing the agent frequently is one of the methods; it’s a balancing agent that matches the model – you’re right. Another option is to add a passivator, which helps to passivate heavy metals; if the pollution isn’t too severe, adding this passivator can resolve the issue. The passivator also contains the heavy metal Sb, so more is not always better. You can refer to the following papers to help with understanding: http://www.doc88.com/p-2751613011896.html http://www.doc88.com/p-005903196323.html

The content of heavy metals in the catalyst generally should not exceed 5000 ppm per metal, and the total amount of the five types of heavy metals should not exceed 20000 ppm. The passivator only has an inhibitory effect on the heavy metal nickel. Of course, using displacement balancers is also a method with relatively low costs; to resolve the problem fundamentally, it is necessary to control the salt content and heavy metal levels in the raw materials.

The heavy metal pollutants causing catalyst poisoning include mainly iron, nickel, copper, vanadium, and sodium. The criterion for catalyst poisoning is primarily determined by analyzing the activity of the catalyst; a **decrease in the catalyst’s activity indicates severe poisoning. The color of the catalyst also changes during sampling – it should be white under normal conditions. The color varies after poisoning; some are red. It can also be seen on the DCS screen that the product distribution has changed, with an increase in gas and coke and a decrease in liquid-phase products. Catalyst poisoning phenomenon: Due to the loss of catalyst activity, thermal cracking becomes dominant, resulting in an increase in gas volume and char formation. As a consequence, the amount of rich gas increases, the reaction pressure rises, and the bed temperature rises in the regeneration system due to oxygen-enriched combustion. The color of the catalyst sampled during outdoor operations differs from the normal color. After catalyst poisoning, the feed must be properly electrodesalted before it can be fed into the catalytic unit. On the other hand, the processing volume should be reduced first; some of the catalyst from the two reactors is removed, and then catalyst is added to maintain operation. The activity of the catalyst is analyzed, and small amounts of catalyst are added based on the results of these analyses.