Mobil Olefin Interconversion

MOI [Mobil olefin interconversion] A process for increasing the yield of propylene from steam crackers and fluid catalytic crackers, using a ZSM-type catalyst. Developed in 1998 by Mobil Technology. 

Three fluidized bed processes are available for license from Mobil Badger (now ExxonMobil-Badger). These are MBR (Mobil benzene reduction), MOG (Mobil olefins to gasoline), and MOI (Mobil olefin interconversion). All three use zeolite catalyst and a dual dense fluidized bed reactor-regenerator system. The MOI process is shown in Fig. 17. The other two processes are conceptually very similar. 

So, the ethylene production does correlate with coke presence, in particular with aromatics formation as far as the diffusion limitations are not significant. However, it seems that the majority of ethylene is not always formed directly from MeOH [115]. The aromatics and other coke species could be the products of the conversion of primary carbenium ions, which are mobile and could equilibrate each other [28]. This may explain the isotopic distribution in products and retained coke molecules and the coexistence of aromatics and carbenium ions [28], In addition to the coproduction of ethylene with aromatics in olefins interconversion cycle, formation of ethylene via alkylation-dealkylation of methyl aromatics with heavy olefins or with the equivalent carbenium ions like ethyP, propyP, and butyP could be an option. The alkyl aromatics with the side chain length of two carbons or longer are not stable in the pore and dealkylates on the acid sites due to too long residence time and steric hindrances. This may lead to formation of ethylene, other olefins, and alkylaromatics with different structure, namely PMBs [129]. In other words, the ethylene is formed via interaction of the carbenium ions like ethyP, propyP, and butyP formed from MeOH or heavy olefins with aromatics and other coke precursors followed by cracking and in a less extent by a direct alkylation of PMBs with methanol. The speculation is based properly on analysis of the prior arts and is not contradictory with the concept of the aromatic cycle for ethylene formation. 

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