Activity continuous catalyst regeneration

As practiced today, FCC is a fluidized-bed process with continuous catalyst regeneration which reUes on short contact in a riser reactor between the feed and catalyst, fluidized with an inert gas, followed by disengagement and catalyst regeneration to burn off coke deposits and return the catalyst to near-fresh activity. 

None of the above properties and characteristics act independently. When one among them is changed with a view to improvement, the others are also modified and not necessarily in the direction of an overall improvement. As a result, industrial catalysts are never ideal. Fortunately, however, the ideal is not altogether indispensable. Certain properties, such as activity and reproducibility, are always necessary, but selectivity, for example, has hardly any meaning in reactions such as ammonia synthesis, and the same holds true for thermal conductivity in an isothermal reaction. Stability is always of interest but becomes less important in processes that include continuous catalyst regeneration. Regenerability must be optimized in this case. 

Description The complex consists of a reactor section, continuous catalyst regeneration (OCR) section, product separation section and fractionation section. Four radial-flow reactors (1) are used to achieve optimum conversion and selectivity for the endothermic reaction. Catalyst activity is maintained hy continuously regenerating catalyst (2). Reactor effluent is compressed (3), dried (4) and sent to a cryogenic... 

This catalyst regeneration operation is performed using published processes, examples of which include the use of a fixed bed switching reactor system in the case of the Z-Forming process(l), and the use of a continuous catalyst regeneration system in the case of the Cyclar process(2). However, catalyst activity gradually decreases due to the repeated reaction and regeneration. Catalyst life, therefore, is considered terminated at the point where its activity falls below the point at which it is able to maintain a pre-set aromatic yield. 

Depending on tlie time. scale of deactivation, the catalytic activity can be restored in different ways. For example, in fluid catalytic cracking, where the deactivation is very fast, a recirculating leacTor is used for continuous catalyst regeneration. However, if the deactivation is slow and constant conversion is desired 10 meet certain environmental regulations as in VOCoxidation, the temperature level can be used to compensate fur the loss of intrinsic catalytic activity. Under such additions, the deactivation effects are measured by the temperature increase required to maintain constant conversion. 

The activity of catalyst degrades with time. The loss of activity is primarily due to impurities in the FCC feed, such as nickel, vanadium, and sodium, and to thermal and hydrothermal deactivation mechanisms. To maintain the desired activity, fresh catalyst is continually added to the unit. Fresh catalyst is stored in a fresh catalyst hopper and, in most units, is added automatically to the regenerator via a catalyst loader. 

Tire decline in catalyst activity seen in some continuous photocatalytic systems has prompted researchers to examine methods of restoring activity to used photocatalysts. Because the decline in catalyst activity is often attributed to the accumulation of recalcitrant intermediates or by-products on the catalyst surface, most catalyst regeneration techniques focus on the removal of these presumed species. Two such methods, thermal regeneration and photocatalytic regeneration, have been examined for use in association with the photocatalytic oxidation of aromatic contaminants. 

The CCR Meta-4 process features are a hard, highly active and robust catalyst, low catalyst inventory, low operating temperature and pressure, outstanding yields, liquid-phase operation, and continuous operation and catalyst regeneration. 

From the standpoint of daily capacity, the greatest application of fluidized bed catalysis is to the cracking of petroleum fractions into the gasoline range. In this process the catalyst deactivates in a few minutes, so that advantage is taken of the mobihty of fluidized catalyst to transport it continuously between reaction and regeneration zones in order to maintain its activity some catalyst also must be bled off continuously to maintain permanent poisons such as heavy metal deposits at an acceptable level. 

Periodic catalyst regeneration or carbon burn off is required to maintain the activity of the catalyst. Typical cycle time is reported to be at least 8 hr, with 7 hr of process time and 1 hr of regeneration time. For continuous operation, various furnace modules can be operated such that, for example, seven operate in the process mode while one is in the regeneration mode. Fig. 13 shows a schematic diagram of a STAR process unit. ... 

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