The vapor phase reaction of tert-butylbenzene (TBB) with isopropyl acetate (IPA) has been studied over mesoporous Al-MCM-41 (Si/Al=30, 51, 72, and 97) from 200 to 350^◦C. Catalysts were synthesized hydrothermally and characterized by XRD, FT-IR, BET (surface area), and ²⁹Si,²⁷Al MAS-NMR techniques. Conversion of TBB decreases with the increase in temperature. The activity of these cata-lysts followed the order Al-MCM-41 (30) > Al-MCM-41 (51) > Al-MCM-41 (72) > Al-MCM-41 (97). The catalysts with less Si/Al ratios (Si/Al=30 and 51) showed higher activity than the other catalysts. The reaction was observed to yield alkylated and acylated products namely 3-acetyl-4-isopropyl-tert-butylbenzene (3A-4ITBB), 4-acetyl-tert-butylbenzene (4-ATBB), 4-isopropyl-tert-butylbenzene (4-ITBB) ,Isopropylbenzene (IPB), and 2-acetyl-isopropyl benzene (2A-IPB). Both the alkylation and acylation reaction can be accounted by the nature of acid sites in the catalyst. The selectivity to 3A-4ITBB, 4-ATBB, and IPB increased with increase in temperature, whereas, the selectivity to other products decreased. Increase in the feed ratio increased the conversion, indicating the preferential adsorption of IPA on the catalyst surface. The time-on-stream studies with Al-MCM-41 (30) showed gradual decrease in conversion with the increase in stream was observed after 5 h.