Highly selective and stable CsPW/Nb2O5 catalysts for dehydration of glycerol to acrolein

Acrolein production by gas-phase dehydration of glycerol at 300 degrees C, catalyzed by a Cs+-substituted Keggin-type phosphotungstate, Cs-2 H-5(0) 5PW12O40 (CsPW), supported on Nb2O5 was investigated. The catalysts were characterized using N-2 adsorption-desorption, X-ray diffraction, Fourier-transform infrared and Raman spectroscopies, and NH3 temperature-programmed desorption. It was demonstrated that Lewis acid sites were responsible for byproduct formation, and that Bronsted acid sites of medium strength were the active sites for acrolein production by glycerol dehydration. The acidity of the supported CsPW was affected by the calcination temperature and CsPW loading. The CsPW was well dispersed on Nb2O5 at loadings 20 wt%, and the strong acid sites of bulk CsPW were converted to selective medium acid sites. The CsPW catalyst with 20% of CsPW loading calcined at 500 degrees C gave 96% of glycerol conversion and 80% of acrolein selectivity, and there was no significant deactivation in 10 h. The catalyst with a 20% decrease in activity was regenerated by simple coke burning with air at 500 degrees C. (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.