Esterification of acetic acid with propanol isomers under autogeneous pressure: A catalytic activity study of Al-MCM-41 molecular sieves

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 Brönsted 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 Brönsted 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.

Graphical abstractThe catalytic activity of the Al-MCM-41 material was tested in the esterification of acetic acid using propanol isomers under autogeneous pressure. Al-MCM-41 (Si/Al = 30) was found to be more active than other Si/Al ratios owing to its high density of Brönsted acid sites and the reaction was also influenced by hydrophobic properties of the catalyst. Further, the reaction is proposed to occur mainly within the pores of the catalyst. Figure optionsDownload full-size imageDownload as PowerPoint slide