Abstract: 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 % paradiethyl benzene, the product stream being substantially free from other isomers of diethylbenzene, Ca aromatics, C9 aromatics, C10+ heavy aromatics other than diethyl beizene isomers, sulphur, halogen, olefinc compound and carbonyl compounds.