Regarding the activity of catalytic cracking catalysts

Dude, you should read more books on this topic regularly! Here is my answer for you: A catalyst must have practical significance for industrial production and can be used in industrial-scale manufacturing facilities. They should be able to operate properly over the long term under the actual production conditions of pressure, temperature, reactant concentration, flow rate, and contact time, while maintaining good activity and selectivity, as well as exhibiting excellent stability against overheating and toxic substances. Throughout the entire lifespan of the catalyst, it maintains good compressive strength and resists erosion by air currents without becoming powdered. If catalytic activity declines due to carbon deposition caused by side reactions or the effect of certain toxic substances, it can be regenerated in a relatively simple manner either inside or outside the reactor to restore its activity. 　　1. Activity 　　　　Activity refers to the degree to which a particular catalyst influences the reaction rate. The most commonly used method in industry to indicate catalyst activity is conversion rate; however, space-time yield is also used for this purpose. Theoretically, it is more accurate to measure it using the reaction rate. 　　(1) Conversion rate representation This is the most commonly used method for expressing activity in industry, and it can be further divided into three forms of representation. For the A→B reaction, the conversion rate achieved at a given temperature can be expressed by the following formula: 　　　　XA=（Number of moles of A that have been converted after the reaction, NA / Number of moles of A in the feed, N0A）×100% 　　It can also be expressed in terms of the temperature required to achieve a specified conversion rate. For example, the conversion temperature at which the reaction reaches equilibrium is T_eq, while the temperature at any given conversion rate is T; the amount of reactant A converted remains the same in both cases. The difference between these two temperatures, ΔT = T – T_eq, can be used to represent the activity of the catalyst. If ΔT=0, then such a catalyst is the most ideal catalyst. Usually ΔT>0, and the larger this difference, the lower the catalyst activity ； The smaller ΔT, the better the activity. 　　　　Catalyst activity can also be expressed as the space velocity required to achieve a certain specified conversion rate (such as XA=80%) at a given temperature; the higher the space velocity necessary to reach the specified conversion rate at that temperature, the greater the catalyst’s activity. Some reactions are limited by thermodynamic equilibrium, resulting in low equilibrium conversion rates. To make full use of the raw materials, it is necessary to separate the reaction products, then add fresh raw materials for reuse. The conversion rate of the material passing through the catalyst once is referred to as the single-pass conversion rate. 　　(2) Spatiotemporal yield expression: This is expressed as the number of moles NB of the desired product that can be obtained per unit time t using a catalyst of unit volume V, as given by the following formula: Y = NB / (V · t).

(3) Reaction rate expressions: For a simple reaction of A → B, if V, S, and W represent the volume, surface area, and weight of the solid catalyst respectively, then the reaction rates r are expressed in different forms as follows: rv = (1/V) · (dNA/dt) = (1/V) · (dNB/dt); rs = (1/S) · (dNA/dt) = (1/S) · (dNB/dt); rw = (1/W) · (dNA/dt) = (1/W) · (dNB/dt). The relationship between these three reaction rates is: rv = ρ · Sg ； rs=ρ·rw, where ρ is the bulk density of the catalyst, and Sg is the specific surface area of the catalyst. Among the three representation methods, rs is the most suitable, as it relates the reaction rate, or activity, to the specific surface area of the catalyst; in other words, it represents specific activity. 　　　　It should be noted that activity is related not only to the surface area of contact between the reactants and the catalyst, but also to factors such as the degree of dispersion of the active components and whether they are on accessible surfaces, catalyst lattice defects (voids, gaps, dislocations, grain boundaries), chemical species on the catalyst surface and their electronic structure, coordination number, and local symmetry.

The indicator for characterizing catalyst activity in catalytic cracking is microreactivity! It is carried out in a microreactor using 100 milliliters of feed oil (just for illustration; 100 milliliters isn’t actually required, it’s only used to simplify subsequent calculations), and the conversion rate is calculated as (100 minus the components other than gasoline)/100. The conversion rate of this microreactor is used as an indicator of activity. Why isn’t diesel included in the conversion rate? This is because it was initially used to catalyze the conversion of diesel into gasoline as the end product. This post was last edited by mjl25mp6 on 2008-1-8 09:34.]

Perhaps it’s my lack of ability to express myself clearly; let me rephrase it: I’m not from the oil refining industry, so I don’t fully understand the concept of catalytic activity as discussed by those in the oil refining sector regarding our industrial catalytic cracking units. After all, what is taught in books differs from what is actually applied in industry. As I understand it, in the catalytic cracking units of our refining industry, the catalytic activity is generally in the range of 60-70; does this refer to the conversion rate of crude oil? Is this the current method used in catalytic cracking units to evaluate catalytic activity? I work with refining additives, and I have a basic understanding of refining plants, but I want to learn more. I’ll need to ask for advice from all of you here more often in the future; I hope you can help me a lot, hehe. The individual reviews are finished today; we’ll continue tomorrow. Welcome everyone to offer your valuable suggestions

This post was last edited by kaminocmyhc on 2011-4-2 09:48. The testing methods used now are probably different from those of the past; those were my learning notes when I first started working. However, no matter how advanced the instruments are, they still rely on the same calculation principles; it’s just that they operate faster and provide more accurate data

It is correct that the indicator for characterizing catalyst activity in catalytic cracking is microreactivity, and a standard microreactivity tester must be used. ASTM3907 is adopted internationally. In China, the RIPP method is used. The results of the two methods are quite similar. The activity is tested using standard diesel, and the method for calculating activity is (feed amount – liquid yield at temperatures above 210 degrees) / feed amount. The guy above is right; the calculation of catalytic cracking conversion does not include the diesel yield.

LIKONPEC Automatic Microactivity Tester: This instrument is used for determining the microactivity of catalytic cracking catalysts. It can be used for industrial catalyst balancing, assessing the activity of aged and fresh catalysts, as well as for studying catalytic reaction mechanisms, exploring reaction conditions, and screening catalysts. Standard reaction operating conditions: Standard feed oil – straight-run light diesel in the 235–337°C fraction, used uniformly. Reaction bed temperature: 460±1°C. Feed rate: 1.56±0.02 grams. Feed time: 70 seconds. Catalyst load: 5 grams. Nitrogen purging time after reaction: 10 minutes. Flow rate of the purge gas: 20 ml/min. Standard method for determining microreactivity (MAT): 5 grams of catalyst are placed in a standard microreactor with a bed temperature of 460°C; 1.56 grams of standard feed oil is slowly injected into the reactor over 70 seconds to initiate the reaction. After that, the reactor is purged with nitrogen for 10 minutes. The reaction products are collected in a bottle, which is placed in an ice-water bath. The reaction products are analyzed using chromatography, and the microreactivity index of the catalyst is calculated based on the analysis results.

This post was last edited by kaminocmyhc on 2011-5-7 at 14:03. Different units of activity yield different results, but catalyst manufacturers often conduct such tests, so their results should be comparable. Qilu’s products have high activity

The standard method for measuring microreactivity (MAT) that I have seen is as follows: 5 grams of catalyst are placed in a standard microreactor with a bed temperature of 460 degrees. 1.56 grams of standard feed oil is evenly injected into the reactor within 70 seconds to initiate the reaction. After that, the reactor is purged with nitrogen for 10 minutes. The reaction products are collected in a bottle, which is then placed in a cold trap filled with ice water. The reaction products are analyzed using chromatography, and the microreactivity index of the catalyst is calculated based on the analysis results.

What we’re talking about here is the micro-reactivity of the catalyst alone; generally, a value around 65 is sufficient to meet the requirements of production.

How can we be different? Ours is only in the 30s

Microreactivity refers to the calculation of the mass conversion rate when standard feed oil is reacted through a catalyst bed