Abstract: Production of unsaturated hydrocarbons of 2-5 carbon atoms from methanol in the presence of zeolitic catalysts is effected by introducing gaseous methanol into a carrier gas, the concentration of the methanol in the entering mixture being between 5 and 60% by volume, and passing the mixture through a catalytic bed based on synthetic mordenite of the so-called de-aluminized type whose Si/Al ratio (atomic) is higher than 80, the flow rate of the methanol being between 1 and 5 liters of liquid methanol per liter of catalyst and per hour. The reaction is carried out at a temperature between 350.degree. and 550.degree. C., under a pressure which can reach 20 bars. The de-aluminized synthetic mordenite is prepared by subjecting the mordenite to a series of alternate acid and hydrothermic treatments, the said series commencing with an acid treatment and terminating with an acid treatment.