A method for separating a mixture of hydrocarbons into fractions enriched in linear, mono-branched, or multi-branched hydrocarbons is disclosed. In particular, mono-branched alkanes are separated from a mixture of alkanes containing multi-branched, mono-branched and linear alkanes, by selectively adsorbing the mono-branched alkanes on a zeolitic adsorbent. The zeolitic adsorbent MCM-22 is particularly suitable for carrying out the method.