Mobil Olefin Interconversion MOI

MOI was developed by the Mobil Oil Corporation and converts light hydrocarbons containing C4-C7 olefins to more valuable light olefins by contacting the feed with a catalyst containing ZSM-5 and/or ZSM-11. 

The feedstocks will t3 ically be low value refinery or petrochemical streams, such as steam cracker by-products rich in C4 s, which have poor propylene selectivity when recycled to the steam cracker. The feedstock can include raffinates, catalytic cracked naphtha, coker naphtha, steam cracker pyrolysis gasoline, as well as synthetic chemical streams containing sufficient amounts of C4-C7 olefins. Dienes, sulfur, nitrogen and oxygenates in the feeds are preferably selectively hydrotreated prior to the conversion process. However, feeds with low levels of dienes, sulfur, nitrogen, metal compounds and oxygenates can be processed directly from FCC units, cokers or steam crackers without any pretreatment. 

The process uses a dense fluidized bed and the hydrocarbon feed containing the C4-C7 olefins is continuously passed through the bed under conversion conditions in the presence of the catalyst. The catalyst is continuously circulated between the fluidized bed and a regenerator. The fluidizable catalyst can transfer heat from the latter to the former thereby helping to supply some of the thermal needs of the conversion reaction, which is endothermic. The operation of the process is similar to that of conventional FCC. 

The dense fluidized bed conversion conditions include temperature in the range 540 C to 650 C and pressure from 0.10 to 0.45 MPa, catalyst/oil weight ratio of 0.1 to 10, and a weight hourly space velocity (WHSV) of 1 to 10 h. Because the catalyst used in the process has lower cracking activity relative to conventional FCC catalysts, a higher temperature compared with that for conventional FCC may be used in order to achieve a higher conversion to the desired light olefins. 

The catalyst in MOI contains only ZSM-5 and/or ZSM-11 without any large pore zeolites. The ZSM-5 and/or ZSM- 11 preferably have a high initial silica/aliunina molar ratio and are modified by phosphorus and metals such as gallium. 

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