Calculation method for FCC catalyst activity
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In catalytic devices, there are fresh catalysts, regenerants, and catalysts awaiting regeneration. During the production process, the activity of the catalysts is tested by external laboratories; however, it’s not clear exactly how this is done or how the calculations are carried out. It is said that this is accomplished through \"microreactor\" experiments, but the question is: what data are obtained from these experiments, and based on what are the calculations made? The catalyst activity we achieve generally exceeds 60. Dear HaiChuan users, could you briefly explain the method for calculating catalyst activity?
The BET method can be used for this purpose, with chemical adsorption energy chosen to determine the active surface area. First, it is necessary to determine what type of catalyst you are working with; if it is an acidic catalyst, NH3 TPD can be used to measure its acidic sites. For basic catalysts, CO, H2, etc., can be used for measurement. To calculate the active surface area from gas adsorption amounts, it is first necessary to determine the stoichiometric relationship of adsorption, that is, how many active sites each adsorbed molecule can cover. For hydrogen adsorption, the stoichiometric coefficient is generally 2; for CO, it is 1 under the same conditions, and 2 in the case of bridge bonding. There is also a method called hydroxyl titration: first, the catalyst is made to adsorb oxygen, followed by hydrogen; the reaction between the adsorbed oxygen and hydrogen produces water, and by determining the amount of hydrogen consumed, the amount of oxygen adsorbed can be calculated, thereby determining the number of oxygen adsorption sites. This latter method is more suitable for measuring catalysts on activated carbon carriers, as activated carbon can adsorb gases such as CO; if the BET method is to be used, it is necessary to choose gases that activated carbon does not adsorb
Thank you. What was mentioned above are common methods for evaluating catalysts in laboratories; universities cover these topics to some extent. However, I still lack experience in calculating the indicators related to microreactor analysis of catalysts. The following is merely theoretical information. --------------- The microactivity of a catalyst is a relative indicator used to measure its ability to facilitate reactions. In the laboratory, microreactivity (MAT) is determined using a method that works as follows: 4.0 g of the catalyst to be tested is placed in a specially designed miniature fixed-bed fluidized reactor. Standard feedstock (usually some type of light diesel) is used, and at a reaction temperature of 482°C, 1.33 g of the feed oil is introduced over a period of 75 seconds. After the reaction is complete, the products are collected. The percentage of the total feed mass that consists of liquid products with a boiling point below 204°C (gasoline), gas, and coke represents the microreactivity (MA) of that catalyst. Microreactor experiments can provide data for evaluating the relative performance of cracking catalysts. Since the experimental results are influenced by catalyst pretreatment, the properties of the feed oil, the testing equipment, and operational parameters, ASTM D-3907 provides detailed specifications for the testing of MA, covering everything from the instrumentation and experimental conditions to the analytical methods. Only devices constructed strictly in accordance with standard specifications can provide reliable microreactivity data. ------------------ May I ask what equipment and instruments are required for this method, and how to establish the experimental procedure?