Investigation on site-specific tolerance to water for solid acid catalysts employed for a model reaction of solketal formation

The glycerol value addition by ketalization with acetone leads to solketal. Herein, we demonstrate the comparative efficiency of Bronsted and Lewis acid sites, using H ss-zeolite & sulfated zirconia (SO42-ZrO2) as Bronsted and Lewis acid catalysts, respectively, for ketalization of glycerol to solketal. The catalysts were characterized using conventional techniques. Total acidity of both catalysts was ascertained with NH3-TPD. The sulfur content of SO42-ZrO2 was determined by CHNS analysis. The Bronsted/Lewis character of total acid sites for both catalysts was determined using FTIR of pyridine-Chemisorbed catalysts. Studies revealed that 5% (w/w) catalyst, 25 degrees C temperature and 2-hour reaction time were optimum parameters for H ss-zeolite while, SO42-ZrO2 required 50 degrees C to match the performance. H ss-zeolite exhibited higher selectivity at lower temperatures towards ketal and reusability without any performance drop upto 10 cycles. The performance-edge vis-`a-vis reusability of catalysts indicated tolerance of Lewis acid sites towards hydration, where H ss-zeolite outperforms SO42-ZrO2.