Esterification of Acetic Acid with n-Butanol Using Molybdenum Oxides Supported on γ-Alumina

Two γ-alumina-supported molybdenum oxide catalysts with different Mo loadings were prepared by the impregnation of a precipitated alumina. The alumina support and the supported catalysts were characterized using X-ray diffraction, N₂ adsorption and NH₃-TPD techniques and tested in the liquid-phase esterification of acetic acid with n-butanol. The effects of the reaction time, of the molar ratio of the reactants, of the speed of agitation and of the mass fraction of the catalyst on the catalytic properties were studied. After only 120 min of reaction at 100 °C with an n-butanol to acetic acid mole ratio equal to 3 the conversion reached 81% in the presence of the supported catalyst containing 10 wt% MoO₃ (10Mo-Al₂O₃ sample). The conversion as well as the total NH₃-TPD acidity increased in the following order: Al₂O₃ < 5Mo−Al₂O₃ (5 wt% MoO₃/Al₂O₃) < 10Mo-Al₂O₃. The selectivity of n-butyl acetate was, in all cases, 100%. No loss in catalytic activity and product selectivity after three cycles with 10Mo-Al₂O₃ catalyst was observed. Graphical Abstract [graphic removed]