Synthesis of quinolines from glycerol over tungstic acid functionalized mesoporous KIT-6 catalyst in aqueous medium

Abstract

Mesoporous tungstic acid functionalized KIT-6 has been synthesized through a condensation of (3-chloropropyl) triethoxysilane and Si-KIT-6 followed by substitution of chloromethylation functionalized KIT-6 by sodium tungstate dihydrate. The synthesized tungstic acid functionalized KIT-6 (W-KIT-6) was characterized by low and wide angle X-ray diffraction analysis (XRD), N₂ adsorption-desorption isotherm, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), NH₃-temperature programmed desorption (NH₃-TPD), ¹³C CP/MAS NMR spectrum and FT-IR analysis. The functionalized KIT-6 posses surface area of 663 m²/g with corresponding pore size 6.3 nm and pore volume 0.65 cm³/g. The catalytic activity of W-KIT-6 nanoparticles evaluated in the Skraup synthesis of quinoline and its derivatives using water as solvent, the results show the target compound was obtained as 89% yield with complete conversion of glycerol (100%) under the reaction conditions of 200 ^oC for 3 h. The catalyst has been recycled for five times without significant loss in catalytic activity.