aromatic reaction products the working fluid can be any condensible fluid having a substantially lower boiling point than that of the aromatic substrate preferably the working fluid comprises acyclic hydrocarbons having a boiling point difference of at least 60 u00b0 c with the aromatic substrate hydrocarbons for the working fluid are preferably light hydrocarbons composed of c 4 or lower carbon number paraffins and more preferably c 3 paraffins normally the addition rate of the working fluid is equal to 2 20 of the net effluent mass flow rate essentially all of the working fluid will be in a vapor phase before it is combined with the effluent stream the working fluid is vaporized by heat exchange with one or more process streams therefore a suitable working fluid must be able to extract heat from one or more process streams at temperature levels that will vaporize the working fluid or preferably super heat the working fluid in addition the working fluid must be easily separated from the aromatic substrate it is also desired to recycle the working fluid as a pumpable liquid therefore the working fluid is preferable condensable at ordinary process pressure levels without refrigeration the combined effluent and working fluid enter a flash separator at a temperature sufficient to maintain a majority of the working fluid and a portion of the effluent in the vapor phase this temperature is less than the boiling point of the aromatic substrate the combined effluent and working fluid may be brought.