Coke formation from propene was investigated at 623 K and P propene 100 kPa on a pure 5A zeolite and an industrial adsorbent (5A zeolite 80 wt.%±binder 20 wt.%). The composition and location of coke molecules were determined as a function of time on stream. Coking on the pure zeolite was faster than on the industrial adsorbent. This result is mainly due to the trapping of coke precursors by the binder, and consequently a signi®cant decrease in the amount of coke on the zeolite present in the adsorbent. While the coke deposited on the binder is very polyaromatic, the carbonaceous compounds formed on the zeolite and on the adsorbent are constituted at low coke content by mono-, bi-, tri-and tetra-alkyl aromatic components, and these compounds are sterically blocked in the a-cages of the 5A zeolite. At high coke content, very heavy polyaromatic compounds appear and are certainly located on the external surface of the zeolite crystallites. Adsorption measurements of both samples show that coke is heterogeneously distributed in the zeolite pores. Whatever be the adsorbent, the partial oxidation of coke on highly coked samples caused an increase in the adsorption capacity. The ®rst few steps of regeneration of coked samples remove the heavy polyaromatic molecules responsible for the pore blockage and thus liberate the pores which are not occupied by coke molecules.