To obtain, without noxious byproduct in high yield, an aromatic ketone useful as an intermediate for an algesic demulcent, an antiinflammatory agent or the like by reacting an alkylbenzene with an organic acid anhydride or an acyl chloride in the presence of a specified catalyst at a specified temperature.

This compound of the formula [Ar is phenyl or naphthyl; R is a 1-14C (branched)alkyl; R1 is a 1-6C (branched)alkyl] such as p- isobutylacetophenone is obtained by reacting (A) in the presence of a catalyst consisting of an acidic high silica zeolite (e.g. a catalyst based on a β-zeolite treated so as to replace some metal cations with protons) having ≥0.5 nm in pore diameter and 5-200 in the ratio Si/M (M is Al, B, Ga, In, Fe, Cr, V, As or Sb) (B) an alkylbenzene such as isobutylbenzene with (C) an organic acid anhydride such as acetic anhydride or an acyl chloride at 50-250°C.