Catalytic activity of mesoporous Al-MCM-41 (Si/Al = 30, 51, 72 and 97) molecular sieves, which were synthesised and characterised by XRD, BET (surface area) and FT-IR was tested towards esterification of acetic acid with propanol isomers such as isopropanol and n-propanol under autogeneous pressure condition. The effect of Si/Al ratios of Al-MCM-41, reaction temperature, time, mole ratio (alcohol:acid) and catalyst loading on propanol conversion was studied. Al-MCM-41 (Si/Al = 30) was found to be more active than other Si/Al ratios owing to its high density of Bronsted acid sites and the reaction was also influenced by hydrophobic properties of the catalyst. The reaction was also studied over HY zeolite and H mordenite under same condition as Al-MCM-41 and their results are compared. The requirement of Br6nsted acid sites for the reaction was clearly established by running the reaction in the absence of catalyst. Occurrence of the reaction mainly within the pores was confirmed by running the reaction over the uncalcined catalyst that provides less conversion than the calcined material. (c) 2006 Elsevier B.V. All rights reserved.