Nano TiCl4/γ-Al2O3: An efficient heterogeneous solid acid catalyst for rapid and solvent-less synthesis of azo dyes based on 2-naphthol at room temperature

Abstract

A green heterogeneous solid acid was prepared as an extremely efficient catalyst, through the reaction of γ-alumina with titanium tetrachloride. Nano TiCl4/γ-Al2O3 was characterized by fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Brunner–Emmet–Teller (BET) surface area analysis, X-ray fluorescence (XRF) and thermal gravimetric analysis (TGA). Nano TiCl4/γ-Al2O3 was used for the synthesis of aryl diazonium salts as the starting reactant and then, diazo coupling with 2-naphthol produced the azo dyes in a solvent-free medium at room temperature (25 ◦C). The work-up of the reaction is easy, and the catalyst is removed from the products by simple filtration.