Dry-gas selectivity

Generally speaking, resid FCC (RFCC) catalysts should be very effective in bottoms cracking, be metals tolerant, and coke and dry gas selective. Based on many years of fundamental research and industrial experiences, a series of RFCC catalysts, such as Orbit, DVR, and MLC, have been developed by the SINOPEC Research Institute of Petroleum Processing (RIPP) and successfully commercialized [1]. These catalysts are very effective in paraffinic residue cracking. However, in recent years more and more intermediate-based residue has been introduced into FCC units, and the performances of conventional RFCC catalysts are now unsatisfactory. Therefore, novel zeolites and matrices have been developed to formulate a new generation of RFCC catalysts with improved bottoms cracking activity and coke selectivity. 

For example, the gasoline, IPG and dry gas selectivities obtained with 4B do not differentiate between the REY (catalyst A) and the USY/REY (catalyst B) as well as the other methods. The reason for this is not fully understood but may be related to the relatively mild steaming (1400°F, 4 hours) which does not severely deactivate the catalysts. 

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