Microactivity increase

The ultimate measurement of trap performance is if microactivity increases at constant fresh catalyst additions and metals levels or if the improved stability provides the flexibility to reduce additions or process higher vanadium containing feed. From an evaluation standpoint, it helps to have additional methods of determining success. 

A higher catalyst microactivity implies a reduced amount of unconverted material recycled to the catalytic cracker, thus increasing not only first pass feed conversion to desirable products but also permitting higher throughput of fresh feedstocks due to the reduction in recycle material. Consequently, the development of zeolite catalysts proved a major boon to the refining industry. 

Figure 4. Yearly increase in microactivity (MA) and decrease in recycle caused...

FIXED-BED AND FLUIDIZED-BED TESTS In the fixed-bed test, a sample of cracking catalyst was contacted with an FCC feed in a manner similar to the standard microactivity test (MAT) prescribed by ASTM (10). One major difference was that the reactor temperature was increased from 900°F to 960°F to better simulate current commercial operations. 

The decrease in the activity of the catalyst is reflected in the lowering of the conversion and impurities removal of the reactant feed to the desired products during time-onstream. It is generally practiced in the refineries that the catalyst is allowed to deactivate to a certain level and, to maintain the production rates within the desired product quality, the reactor temperature is steadily increased to compensate for catalyst deactivation. The level of catalyst deactivation can be measured by comparing the activity of the deactivated catalyst to that of the fresh one. This is, for instance, the approach used in FCC process, in which a microactivity test (MAT) is used to monitor catalyst deactivation by measuring catalyst activity at standard conditions with a standard feedstock. 

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