Investigation of the Catalytic Performance of an Activated Smectite on the Esterification Réaction of Acetic Acid by Butan-2-ol

Abstract

In this work, a solid-phase acid catalyst was prepared from a natural Cameroonian smectite and sulfuric acid. The natural clay was treated by refluxing it in sulfuric acid for 4 hours at 80°C under constant stirring. The catalyst obtained after washing and drying was used for the esterification reaction of acetic acid by a secondary alcohol (butan-2-ol). The natural clay and the catalyst obtained were characterized by Fourier Transform Infrared spectroscopy, which allowed us to confirm that the natural clay consists of OH groups, which constitute its framework, water molecules and cations in its interlayer spaces and Si-O bonds constituting its basic structure. The examination of the FTIR spectrum of the catalyst allowed us to note a remarkable decrease in the intensity of the absorption bands attributable to the water molecules of the interlayer space on the one hand and to the Al-Fe-OH and Al-Mg-OH bonds on the other hand; proof that our natural clay has indeed undergone a structural modification by exchanging its interlayer space cations for H+ protons. After optimising the parameters influencing the reaction kinetics and yield, the optimal temperature was found to be 80°C; the optimal reaction time 120 minutes; the optimal catalyst mass 200 mg; the best molar ratio 1:2 (1 eq of acetic acid and 2 eq of butan-2-ol, respectively); and the optimal stirring speed 400 rpm. Using equimolar proportions, we obtained an optimal yield of 78.41%. This yield is significantly higher than the 60% reported in the literature when the reaction is carried out after approximately 30 hours without considering kinetics.