Particular properties of the coke formed on nano-sponge *BEA zeolite during ethanol-to-hydrocarbons transformation

• *BEA morphology impacts coking and decoking in the ethanol dehydration.
• Micron-, nanometer-sized and nano-sponge *BEA zeolites were synthesized.
• Extreme crystal downsizing favors products mass transfer that limits coke growth.
• A low amount of light coke in nano-sponge is enough to blocks micropores access.

The impact of crystal size and textural properties of *BEA-type zeolites in the conversion of ethanol-to-hydrocarbons at 350 °C and under 3.0 MPa pressure is investigated. Three *BEA zeolites (molar ratio Si/Al of ca. 23) with important differences concerning their textural properties are synthesized: a material constituted of micron-sized crystals and two hierarchical porous zeolites with a mesoporous network created either by the aggregation of nanometer-sized crystals or by the use of a gemini-type quaternary ammonium surfactant given a nano-sponge zeolite. The micrometric zeolite favors the formation of polyaromatic molecules in same proportion than the concentration of Brønsted acid sites. The deactivation mode of acid sites is poisoning rather than pore blocking. The short thickness of crystal in the nano-sponge zeolite combined with its low acidity, limit the growth of coke molecules as well as their accumulation inside micropores. Coke precursors (alkylbenzenes) are adsorbed on many silanol group located in the ordered mesopores, but the extreme downsizing of the zeolite crystal leads to an unexpected pore blocking by these light molecules.

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