Sulfated TiO2/SnO2 nanocomposite as a green heterogeneous catalyst for direct amide formation reaction

Abstract Heterogeneous binary TiO2/SnO2 nanocomposite (with 4:1 wt% of TiO2 and SnO2, respectively) catalyst was prepared by a sol–gel method, and further sulfated by chlorosulfonic acid. X-ray diffraction technique revealed the structure of the nanocrystalline catalyst to be tetragonal. Fourier transformed infrared technique elucidated the presence of surface-anchored sulfonic (–SO3H) groups on the catalyst. Morphological details of the catalyst were obtained by transmission electron microscopy. Elemental analysis of the catalyst was carried out by X-ray photoelectron spectroscopy. NH3-TPD technique was used to elucidate the surface acidity of the catalyst. The active surface area and mesoporosity of catalyst were studied by the BET method. Thereafter, this sulfated catalyst was utilized for the direct amidation reaction between a series of amine derivatives and acetic acid. The reaction gives excellent product yield within 120 min, and at a relatively moderate temperature of ~115 °C.