The catalytic dehydration of glycerol to acrolein is a very attractive alternative to the propylene-based process, due to the future exhaustion of fossil feedstocks and the increasing production of biomass-based glycerol. This work aimed to study the selectivity control over Cs2.5H0.5PW12O40/Nb2O5 (CsPW-Nb). The Bronsted and Lewis acid sites were characterized by FTIR to understand the catalytic mechanism. The effects of reaction temperature (260-360 degrees C), oxygen co-feed ratio (0-0.175), and glycerol concentration (0.2-0.5 g/g) were studied to determine the optimum conditions for the production of acrolein. The loading of CsPW on Nb2O5 increased the Bronsted acidity and enhanced the acrolein dehydration route. Co-feeding oxygen at an appropriate ratio significantly enhanced the selectivity of the acrolein dehydration route and slightly enhanced the selectivity of the acetol dehydration route by suppressing the glycerol oligomerization reaction. The selectivity to acrolein significantly decreased when the glycerol concentration increased from 0.2 to 0.5 g/g due to increased glycerol oligomerization reactions. The acrolein selectivity in dehydration of glycerol was affected by reaction temperature, oxygen co-feeding, and glycerol concentration. The highest acrolein selectivity (76.5%) was obtained at 320 degrees C, O-2/N-2/glycerol molar ratio of 1/5/0.16 (mol/mol), and glycerol concentration of 0.2 g/g.