Environmentally Benign Approach for the Synthesis of Azo Dyes in the Presence of Mesoporous Sulfated Core-Shell Zirconia-Copper(I) Oxide Solid Acid Catalyst

Sulfated solid acid catalyst finds application mainly in the reactions which requires acid sites. Synthesis of azo dyes by diazo coupling in presence of sulfated core shell zirconia-copper oxide solid acid catalyst (Cu(I)@ZrO ₂ -SO ₄ ²⁻ ) has been discussed hereunder. A detailed investigation on, the effect of sulfate loading, surface area and surface acidity for the synthesis of azo dyes has been demonstrated. As sulfate loading increased on the catalyst, it decreased its surface area and this was evident from the Brunauer Emmett Teller surface area analysis. The robust catalytic activity of Cu(I)@ZrO ₂ -SO ₄ ²⁻ catalyst was due to its super acidity, which arises due to the presence of both Bronsted and Lewis acid sites, this was experimentally confirmed by Pyridine-Fourier transform infrared spectroscopy and ammonia-temperature programmed desorption studies. X-ray diffraction, transmission electron microscopy and selected area electron diffraction techniques provided detailed information about the effect of sulfate loading on phase and crystal structure of the catalyst. In the present work we describe a simple, efficient and environmentally benign catalytic process for the synthesis of azo dyes.