Ethanol transformation into higher hydrocarbons over HZSM-5 zeolite: Direct detection of radical species by in situ EPR spectroscopy

HZSM-5 (Si/Al ratio = 40) zeolite is an efficient catalyst for ethanol transformation due to its capacity to maintain a high activity in C3 + hydrocarbons formation with time-on-stream (TOS) and this in spite of a great loss of acidity and microporosity and a high coke content deposited inside the pores of the zeolite. A study by in situ Electron Paramagnetic Resonance (EPR) spectroscopy in ethylene conversion to hydrocarbons showed that a fraction of radicals was active.

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► HZSM-5(Si/Al = 40) is found to be a stably and selective catalyst.
► Ethanol transformation is accompanied by a great loss of acidity and microporosity.
► 25% of radicals formed are consumed during the ethylene oligomerization.
► The Brønsted acid sites and radicals are active sites for ethylene oligomerization.
► This study highlights the reactivity of radicals in ethylene oligomerization.