Fluorine-doped tin oxide as efficient solid acid catalyst: acidity and the catalytic activity relationship

Abstract

Herein we report an easy and facile method for preparation of Tin oxide-doped fluorine. SnO2 nanoparticles were synthesized using the sol–gel method. The obtained Sn(OH)4 is calcined at 450 °C then impregnated with different loading 10–55 wt.% of HF as a source of fluoride, followed by calcination at 200, 300, and 400 °C. The particle size of SnO2 was found to be between 5 and 8 nm. The SBET values and pore size distribution of the F–Sn data were discussed. Examining the surface acidity, confirm that the addition of fluoride ions increases both of the total surface acidity and the ratio of Bronsted to Lewis acid sites. The catalytic activity of the fluoride-tin oxide nanoparticles solid catalysts was investigated through the synthesis of 3,4-dihydropyrimidin-2(1H)-one. 45 F–Sn catalyst calcined at 200 °C has the highest and strongest acid sites (Ea = 450.0 mV) that enhance the catalytic activity reaching the maximum yield of (96.5%). The F–Sn catalysts were reused several times with no activity loss.