Mechanisms of coke growth on mordenite zeolite

- Pressure of propene influences kinetic of coke formation and its growth mechanism.
- Nature of coke is function on the pressure of coking agent.
- At 1 bar coke grows by successive alkylation/cyclization/hydrogen transfer reactions.
- At 0.1 bar coke grows by condensation of coke molecules.

Mechanisms of coke formation and growth transformation on MOR zeolite were investigated using a microbalance at 623 K for two propene pressures: 0.1 and 1 bar. The low and high coking pressures correspond to laboratory and industrial conditions, respectively. Initial coke deposition is faster at high pressure, but the maximum uptake is higher at low pressure. The complete determination of chemical composition of coke has required the use of a lot of techniques (IRFT, GC-MS, MALDI-TOF). From the change of chemical composition of coke, it can be proposed by different mechanisms of growth of coke molecules trapped in the zeolite micropores. The coke grows under industrial conditions (high olefins pressure) by successive alkylation/cyclization/aromatization reactions, while under laboratory conditions (low olefins pressure) the growth proceeds preferentially by condensation of coke molecules.

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