Product yield in methanol conversion over ZSM-5 is predominantly independent of coke content

The conversion of methanol to hydrocarbons (MTH) over ZSM-5 with time on stream and resulting product distribution were monitored at 350 °C in a series of experiments in which catalyst mass was varied while other conditions were held constant. This method enabled product analysis with respect to degree of deactivation: product distributions at low conversions due to small catalyst loadings could be compared to product distributions at the same conversion due to deactivation. It was found that product selectivity during methanol conversion over ZSM-5 is predominantly independent of coke content. A few products showed a slight sensitivity to deposited coke, and their individual changes suggested that 1,2,4-trimethylbenzene and 1,2,4,5-tetramethylbenzene are intermediates for ethene formation. Yield versus conversion plots further suggested that ethene is converted to higher alkenes by oligomerisation.

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► A ZSM-5 catalyst was tested at contact times spanning one order of magnitude.
► Thereby, a mathematical model for deactivation description was validated, and.
► A test strategy for ZSM-5 catalysts was proposed.
► A complex correlation between Si/Al ratio and product yield was observed.
► Mechanistic details on ethene formation were elucidated.