Abstract: Catalytic process for producing alkylene epoxide, selected between ethylene oxide or propylene oxide, from the corresponding alkylene carbonate, selected between ethylene carbonate or propylene carbonate, comprising the decomposition reaction of alkylene carbonate, in the presence of sodium bromide as catalyst, in which: the reaction temperature is between 207 and 245° C., and the catalyst is in amounts comprised between 5×10?4 and 8×10?3 moles per mole of alkylene carbonate. This process can be carried out continuously. A further object of the invention is the modular plant which allows carrying out such a process.