I.FLUID CATALYTIC CRACKING: www.wissenschaftler-avh.in
B.CATALYST/ADDITIVES:
Q-47:
What is the impact of the FCC Catalyst Matrix on Bottoms Upgradaing when processing
Heavy Feedstocks?
A-47:
The Impact of the FCC Catalyst Matrix on Bottoms Upgrading when Processing Heavy Feedstocks
When processing relatively heavy FCC feedstocks, a primary objective is to maximize the conversion of the heavy oil to lighter, more valuable products. The FCC catalyst characteristics can play a key role in the ultimate results obtained from each unit. Modern FCC catalysts are primarily composed of crystalline silica alumina zeolites in an inorganic oxide type matrix. The zeolite controls gas oil cracking, while the matrix provides a mechanically stable particle and can contain active sites for cracking heavier hydrocarbons. This Catalyst Report will examine the importance of the catalyst matrix on the bottoms upgrading and conversion obtained from the FCC.
Deactivation Differences Between the Zeolite and the Matrix
A catalyst deactivation curve (Figure 1) is used to help assess FCC catalyst stability. In this figure, two distinct rates of deactivation are evident. The first four hours show a significant loss of catalyst conversion for both the Rare Earth Exchanged Y Zeolites (REY) and Ultrastable Y Zeolites (USY) type catalysts. This is mainly because of rapid zeolite deactivation that accompanies equilibration of the unit cell size. After this initial deactivation, the rate of conversion loss decreases. Both types of catalysts continue to lose activity and surface area during this period of slower deactivation.
In a commercial FCC unit, catalyst is replaced at a typical rate of 1-5 % per day. This means that the equilibrium catalyst possesses an age distribution. For example, at a 2 % make up rate, about half of the catalyst inventory is younger than 40 days old. There is also a significant catalyst fraction that is over 100 days old. Because of its faster initial deactivation rate, the zeolite activity comes mostly from the young catalyst fraction. Because of the higher activity per unit of surface area for the zeolite compared to the matrix, most of the catalyst conversion also comes from the youngest catalyst fraction.
This principle is illustrated in Figure 2, which shows a catalyst activity distribution for an FCCU. As can be seen from the figure, over 50 % of the total activity in the unit is supplied by catalyst that is 20 days old or less. The 20-40 days old catalyst contributes only
16 % of the unit activity.
Therefore we can think of two different catalyst types within the unit at a given time. The younger particles supply mostly gas oil conversion activity from their zeolite component. But the majority of the catalyst inventory, because of its age distribution, has little zeolite activity. However, it does possess a significant amount of matrix activity (which deactivates more slowly). This older part of the inventory is responsible for providing the activity to upgrade the heavy portion of the feedstock.
To the refiner that processes heavier FCC feedstocks and wants to maximize conversion of this material, catalysts with an in-situ type matrix provide a greater potential to upgrade heavy oil and minimize slurry production. In addition, these catalysts can provide a higher overall activity to the unit, which can result in a higher conversion level and/or a lower required operating severity for the same conversion.
B.CATALYST/ADDITIVES:
Q-47:
What is the impact of the FCC Catalyst Matrix on Bottoms Upgradaing when processing
Heavy Feedstocks?
A-47:
The Impact of the FCC Catalyst Matrix on Bottoms Upgrading when Processing Heavy Feedstocks
When processing relatively heavy FCC feedstocks, a primary objective is to maximize the conversion of the heavy oil to lighter, more valuable products. The FCC catalyst characteristics can play a key role in the ultimate results obtained from each unit. Modern FCC catalysts are primarily composed of crystalline silica alumina zeolites in an inorganic oxide type matrix. The zeolite controls gas oil cracking, while the matrix provides a mechanically stable particle and can contain active sites for cracking heavier hydrocarbons. This Catalyst Report will examine the importance of the catalyst matrix on the bottoms upgrading and conversion obtained from the FCC.
Deactivation Differences Between the Zeolite and the Matrix
A catalyst deactivation curve (Figure 1) is used to help assess FCC catalyst stability. In this figure, two distinct rates of deactivation are evident. The first four hours show a significant loss of catalyst conversion for both the Rare Earth Exchanged Y Zeolites (REY) and Ultrastable Y Zeolites (USY) type catalysts. This is mainly because of rapid zeolite deactivation that accompanies equilibration of the unit cell size. After this initial deactivation, the rate of conversion loss decreases. Both types of catalysts continue to lose activity and surface area during this period of slower deactivation.
In a commercial FCC unit, catalyst is replaced at a typical rate of 1-5 % per day. This means that the equilibrium catalyst possesses an age distribution. For example, at a 2 % make up rate, about half of the catalyst inventory is younger than 40 days old. There is also a significant catalyst fraction that is over 100 days old. Because of its faster initial deactivation rate, the zeolite activity comes mostly from the young catalyst fraction. Because of the higher activity per unit of surface area for the zeolite compared to the matrix, most of the catalyst conversion also comes from the youngest catalyst fraction.
This principle is illustrated in Figure 2, which shows a catalyst activity distribution for an FCCU. As can be seen from the figure, over 50 % of the total activity in the unit is supplied by catalyst that is 20 days old or less. The 20-40 days old catalyst contributes only
16 % of the unit activity.
Therefore we can think of two different catalyst types within the unit at a given time. The younger particles supply mostly gas oil conversion activity from their zeolite component. But the majority of the catalyst inventory, because of its age distribution, has little zeolite activity. However, it does possess a significant amount of matrix activity (which deactivates more slowly). This older part of the inventory is responsible for providing the activity to upgrade the heavy portion of the feedstock.
To the refiner that processes heavier FCC feedstocks and wants to maximize conversion of this material, catalysts with an in-situ type matrix provide a greater potential to upgrade heavy oil and minimize slurry production. In addition, these catalysts can provide a higher overall activity to the unit, which can result in a higher conversion level and/or a lower required operating severity for the same conversion.
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