Cyclization of aliphatic butane 1,4-diol in presence of hydrogen sulphide gas was carried out in the vapour phase. The catalysts used for this reaction are modified and unmodified ZSM-5 and HY molecular sieves. The effect of variation of catalyst and reaction temperature are studied for this reaction. A probable reaction mechanism for the formation of butane dithiol, which is used as protecting agent in the organic synthesis was proposed.