a process for separating dichlorotoluene isomers from a mixture containing at least two dichlorotoluene isomers comprising passing said mixture containing dichlorotoluene isomers through a mordenite having the following composition ; in molar ratios : a h 2 o : b m 2 / n o : al 2 o 3 : in which m is hydrogen or at least one cation selected from an alkali metal or an alkaline - earth metal with the exception of cesium and rubidium , n is the valence of m , 0 . 7 ≦ a + b ≦ 1 . 1 , and 0 ≦ b ≦ 0 . 2 , separating the non - adsorbed dichlorotoluenes from said mordenite , contacting said mordenite containing the adsorbed isomers with a desorbent capable of separating said isomers from said mordenite , and separating the desorbed isomers from the desorbent .