Combustion synthesized WO3–ZrO2 nanocomposites as catalyst for the solvent-free synthesis of coumarins

Abstract

Abstract Nanosized ZrO 2 and WO 3 –ZrO 2 particles were prepared by solution combustion synthesis using urea as fuel. These materials were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. XRD study indicates the presence of a mixture of tetragonal and monoclinic phases in the synthesized ZrO 2 particles. The tetragonal phase content is enhanced in the WO 3 –ZrO 2 nanocomposite oxide. IR study indicates the presence of well-dispersed WO x species grafted on to the surface of the tetragonal ZrO 2 . TEM analysis of the sample shows the presence of uniform particles with size in the range of 10–25 nm. The catalytic activity of the WO 3 –ZrO 2 nanocomposite catalyst was evaluated for the synthesis of coumarins by Pechmann condensation of phenols with β-ketoesters. It was observed that the composite oxide catalyst was highly active for the reaction. Grafting of WO 3 species on the surface of ZrO 2 has a beneficial effect on the catalytic activity of the WO 3 –ZrO 2 nanocomposite catalyst.