Preparation of novel mesoporous SO₄^2-/TiO₂ solid acid catalyst and its catalytic activity for esterification

A novel mesoporous S0₄^2-/TiO₂ solid acid catalyst with whisker morphology was prepared by incipient impregnation using amorphous titanic acid hydrate (H₂Ti₂O₅ · xH₂O) as the catalyst support. Its structural characteristics, surface acidity, and catalytic activity were characterized by X-ray diffraction, N₂ adsorption, scanning electron microscopy, infrared spectroscopy, thermogravimetry, and NH₃ temperature-programmed desorption. The catalytic performance was evaluated by the esterification reaction of butanol with acetic acid. The results indicated that the SO₄^2-/TiO solid acid catalyst has not only nano-scale particles, whisker morphology, high specific surface area, and mesostructure, but also pure anatase phase, strong acidity, and high thermal stability. SO₄^2- on the surface desorbed gradually, and the number of acid sites decreased when the calcination temperature was above 500°C. Under the optimal reaction conditions, i.e., m(catalyst) = 0.2 g, n(n-butanol)/n(acetic acid) = 1.5, and the reaction time of 3 h, the catalyst calcined at 500°C shows a n-butanol conversion of 94% with a high selectivity for butyl acetate of 100%. Furthermore, the SO₄^2-/TiO₂ solid acid catalyst has higher catalytic activity and separation-settling performance than the SO₄^2-/P25 catalyst.