The present invention relates to a process for the selective production of para-diethyl benzene from a mixed aromatic feedstock containing ethyl benzene and at least one other aromatic compound selected from benzene, alkylated benzene having alkyl group with carbon number 1 to 6, mono-alkyl aromatics, dialkyl aromatics, trialkyl aromatics, tetraalkyl aromatics, pentaalkyl aromatics, hexaalkyl aromatics, containing side chains having 1 to 6 carbon atoms, and any mixtures thereof, the process comprising of (a) alkylating the feedstock under alkylating conditions, over a selectivated metallosilicate composite catalyst; and (b) recovering a product stream containing at least 95 wt % para-diethyl benzene, the product stream being substantially free from other isomers of diethylbenzene, C.sub.8 aromatics, C.sub.9 aromatics, C.sub.10+ heavy aromatics other than diethyl benzene isomers, sulphur, halogen, olefinic compound and carbonyl compounds.