A high-surface-area mesoporous sulfated nano-titania solid superacid catalyst with exposed (101) facets for esterification: facile preparation and catalytic performance

In this paper, a high-surface-area mesoporous sulfated nano-titania exposed with (101) facets was prepared by a simple hydrothermat method without any template followed by surface sulfate modification. The physicochemical properties of the as-prepared catalyst were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), N-2 adsorption-desorption isotherms, temperature programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and pyridine adsorption infrared spectroscopy. The BET surface area of sulfated nano-titania with exposed (101) facets was 121 m(2) g(-1). Well dispersed bidentate sulfate groups were linked to the exposed (101) facets of anatase nano-titania. Acid sites with moderate- and superacidic strength formed in the sulfated titania catalyst. Also, the as-prepared sulfated sample possessed both Lewis and Bronsted acid sites. The catalytic activity of sulfated nano-titania with exposed (101) facets was evaluated using the esterification reaction between acetic acid and n-butanot. It was found that the yield of butyl acetate increased to about 92.2% in the presence of the catalyst. Compared with the exposed (001) facets, the exposed (101) facets showed better catalytic activity of sulfated TiO2 in esterification. The effects of different reaction conditions were discussed in detail. Additionally, the as-prepared sulfated sample could be efficiently recycled and regenerated by simple soaking in sulfuric acid followed by calcination.