A method of modifying a ZSM-5-type zeolite catalyst to increase selectivity of the catalyst for para-isomers in aromatic alkylation reactions is provided. The method includes contacting a ZSM-5-type zeolite catalyst with a fluoride-containing compound. The fluoride-containing zeolite catalyst can be used in aromatic alkylation to provide di-alkyl aromatic products. A method of preparing a xylene product is also accomplished by providing a fluoride-treated ZSM-5-type zeolite catalyst within a reactor. The fluoride-treated ZSM-5 zeolite catalyst is contacted with a toluene/methanol feed under reaction conditions conditions suitable for toluene methylation to form a xylene product containing at least 50% para-xylene by total mixed xylenes.