I.FLUID CATALYTIC CRACKING: www.wissensenschaftler-avh.in
B.CATALYST/ADDITIVES(Contd.)
Q-62:
It is well known that oxygen enrichment necessitates increased catalyst additions. Are some catalysts more tolerant of oxygen enrichment than others? Has anyone developed a good test to determine which catalysts can better withstand the oxygen enrichment environment?
A-62:
The use of oxygen enrichment will accelerate the catalyst deactivation rate due to a number of related effects. Bulk regenerator temperatures will increase due to the smaller nitrogen dilution effect. Catalyst particle temperatures will probably increase by even more than what is indicated by the bulk bed temperature, due to accelerated burning kinetics, although there is not any good way to directly measure this.
Since hydrothermal catalyst deactivation is caused by the presence of steam at high temperatures, the effect of concentrating the steam partial pressure formed from hydrocarbon burning with lower nitrogen dilution will also be present. The higher temperature and higher localized oxygen concentration will also accentuate vanadium mobility and, therefore, vanadium destruction of the zeolite.
All of these things occurring simultaneously will increase the catalyst deactivation rate. Commercial experience from one unit has shown deactivation rate increases by 40% with the use of oxygen enrichment. This increases the importance of activity and hydrothermal stability in catalyst selection.
High levels of both zeolite and active, stable matrix are employed to withstand these effects, without needing to go to excessive catalyst addition rates. If the base case catalyst is high zeolite-to-matrix ratio, it will probably be prudent to consider lowering it, since there is a limit to how much zeolite you can add, and higher matrix catalysts will hold up to the severe environment with more stability.
Certainly, for the case with oxygen enrichment, a more severe steaming treatment will be required to simulate what the regenerator operation will do, with some combination of higher temperature, time, and/or steam partial pressure.It is always a good practice to make sure the deactivation severity used in testing matches reasonably well in terms of microactivity test activity, zeolite and matrix properties and surface area retentions, with the known base catalyst in the commercial unit.
B.CATALYST/ADDITIVES(Contd.)
Q-62:
It is well known that oxygen enrichment necessitates increased catalyst additions. Are some catalysts more tolerant of oxygen enrichment than others? Has anyone developed a good test to determine which catalysts can better withstand the oxygen enrichment environment?
A-62:
The use of oxygen enrichment will accelerate the catalyst deactivation rate due to a number of related effects. Bulk regenerator temperatures will increase due to the smaller nitrogen dilution effect. Catalyst particle temperatures will probably increase by even more than what is indicated by the bulk bed temperature, due to accelerated burning kinetics, although there is not any good way to directly measure this.
Since hydrothermal catalyst deactivation is caused by the presence of steam at high temperatures, the effect of concentrating the steam partial pressure formed from hydrocarbon burning with lower nitrogen dilution will also be present. The higher temperature and higher localized oxygen concentration will also accentuate vanadium mobility and, therefore, vanadium destruction of the zeolite.
All of these things occurring simultaneously will increase the catalyst deactivation rate. Commercial experience from one unit has shown deactivation rate increases by 40% with the use of oxygen enrichment. This increases the importance of activity and hydrothermal stability in catalyst selection.
High levels of both zeolite and active, stable matrix are employed to withstand these effects, without needing to go to excessive catalyst addition rates. If the base case catalyst is high zeolite-to-matrix ratio, it will probably be prudent to consider lowering it, since there is a limit to how much zeolite you can add, and higher matrix catalysts will hold up to the severe environment with more stability.
Certainly, for the case with oxygen enrichment, a more severe steaming treatment will be required to simulate what the regenerator operation will do, with some combination of higher temperature, time, and/or steam partial pressure.It is always a good practice to make sure the deactivation severity used in testing matches reasonably well in terms of microactivity test activity, zeolite and matrix properties and surface area retentions, with the known base catalyst in the commercial unit.
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