Investigation on Measures to Reduce Hydrothermal Deactivation of Equilibrium Catalysts in Catalytic Cracking Units (Incentive Fund)

The reasons for catalyst deactivation are generally classified into three categories: poisoning, sintering and thermal deactivation, and coking and blockage. 1. Inactivation caused by poisoning (1) Temporary poisoning (reversible poisoning): When a toxin adsorbs onto or reacts with the active center, the bonds formed are relatively weak; it is possible to use appropriate methods to remove the toxin, thereby restoring the catalyst’s activity without affecting its properties. This type of poisoning is known as reversible poisoning or temporary poisoning. (2) Permanent poisoning (irreversible poisoning): When a toxin interacts with the active components of a catalyst, strong chemical bonds are formed, making it difficult to remove the toxin using conventional methods in order to restore the catalyst’s activity. This type of poisoning is known as irreversible or permanent poisoning. (3) Selective poisoning: After catalyst poisoning, it may lose its catalytic ability for a certain reaction, but remain catalytically active for other reactions; this phenomenon is known as selective poisoning. In a cascade reaction, if the poison only poisons the active sites that trigger subsequent reactions, it can halt the reaction at an intermediate stage, yielding intermediates in high yield. 2. Deactivation caused by coking and blockage: Carbonaceous deposits on the surface of the catalyst are known as coking. Coking almost always occurs in heterogeneous catalytic reaction processes that use organic substances as reactants and solids as catalysts. The phenomenon in which the pore size decreases (or the pore openings shrink) due to the deposition of carbonaceous substances and/or other materials within the catalyst pores, preventing reactant molecules from diffusing into those pores, is known as clogging. Therefore, clogging is often categorized under coking, and the overall decline in activity is referred to as coking deactivation; it is the most widespread and common form of catalyst deactivation. Typically, carbonaceous deposits can be removed by gasification in reaction with water vapor or hydrogen, so coking and deactivation are reversible processes. Compared to catalyst poisoning, there are far more substances that cause catalyst coking and blockage than catalyst poisons. In actual coking studies, it has been found that catalyst coking involves a rapid initial deactivation, followed by a quasi-steady state in terms of activity. It has been reported that coking deposition occurs mainly during the initial stage (within 0.15 seconds), and it has also been observed that approximately 50% of the carbon formed gets deposited within the first 20 seconds. Coking deactivation is also reversible; by controlling coking during the early stages of the reaction, the activity of the catalyst can be greatly improved. This is precisely why research on coking deactivation is becoming increasingly active. 3. Sintering and thermal deactivation (solid-state transformation): The sintering and thermal deactivation of catalysts refer to the changes in the structure and properties of the catalysts caused by high temperatures. In addition to causing sintering of the catalyst, high temperatures can also lead to other changes, including alterations in chemical and phase composition, semi-melting, grain growth, the encapsulation of active components by the carrier, and the loss of active components due to the formation of volatile or sublimable substances. In fact, at high temperatures, all catalysts will gradually undergo irreversible structural changes; the rate of these changes varies depending on the catalyst. Sintering and thermal deactivation are related to various factors, such as the pretreatment, reduction, and regeneration processes of the catalyst, as well as the promoters and carriers added. Of course, the reasons for catalyst deactivation are complex; the deactivation of each catalyst does not occur solely due to one of the categories mentioned above, but is often caused by two or more factors.

Reply 1# BJYTABC: 1. Maintain a lower regeneration temperature while ensuring an effective burning effect； 2. Use dry gas pre-lift in place of partial steam pre-lift.

In addition to the upper level, it is also necessary to control the amount of misting steam appropriately; high-temperature steam should be used as the stripping steam to minimize the amount of steam entering the regenerator

I hope more sea friends will participate. Haven’t you considered addressing the issue of hydrothermal deactivation of catalysts?

We use UOP technology here, with 2-stage incomplete regeneration. Repeated hypoxia, then repeated hyperoxia. The raw catalyst first enters stage 1, where it undergoes coking at a lower temperature to remove all the hydrogen and part of the carbon. Then, it passes through an external heat exchanger and external circulation to reach stage 2, where the remaining carbon is burned off. Since there is no hydrogen in stage 2, it is possible to control a higher temperature for the coking process there. This not only reduces repeated hydrothermal deactivation but also ensures an effective re-charring effect.

Reply to 6# wuzhangzhu: Great! This is the method of using the regenerative charring process to reduce the hydrothermal deactivation of the equilibrium catalyst. Not bad. Everyone is welcome to speak up actively.