Alkylation of aromatics, e.g. ethylbenzene preparation, with minimized o-xylene make by contacting with olefin alkylating agent in the presence of ZSM-5 crystals having a diffusion rate constant of at least about 100 sec.sup.-1 .times.10.sup.-6 and an alpha value of less than about 100 prepared from a non-organic forming mixture comprising a silica source of precipitated silica having a particle size of 1 to 500 microns.