A detailed study of the deactivation and attempts of regeneration of Ni/AlMCM-41 was performed in the ETP-reaction. Ni/AlMCM-41 could be regenerated by an oxygen treatment at temperatures lower than 350 °C. Severe deactivation of Ni/AlMCM-41 was observed at conditions where propene was the major reaction product. Deactivation of Ni/AlMCM-41 is explained by a conjunct polymerization process as precursor of the reaction products.