In Friedel craft reaction benzene with ethylene in presence of HCl and anhydrous AlCl3 reacts to form ethyl benzene. 
Related Theory Anhydrous AlCl3 is used as a catalyst because it acts as a Lewis acid which can accept electron by forming intermediates and also by speeding up the reaction. It also leads in the creation of carbocation which is used in the electrophilic substitution reaction.