Sustainable production of acrolein: Catalytic gas-phase dehydration of glycerol over dispersed tungsten oxides on alumina, zirconia and silica

Tungsten oxides dispersed on Al2O3, ZrO2, and SiO2 supports were investigated for catalytic dehydration of glycerol (GL) to form acrolein (AC) in the gas phase at 315 degrees C with aqueous GL (GL concentration: 36.2 wt% or 10 mol%, molar GL/H2O = 1/9) as the feed (GHSVGL= 400 h(-1)). The WO3 /Al-2 03 and WO3/ZrO2 catalysts are found much more effective than WO3/SiO2 in catalyzing the reaction in terms of the selectivity (ca. 70 mol% vs. 60 mol%) and yield (49-58% vs. 11-32%) for AC production. Optimization of the WO3 loading (5-40 wt%) and calcination temperature (550-900 degrees C) of the WO3/Al2O3 and WO3/ZrO2 catalysts identifies that the calcination at 800 degrees C of a 30 wt%WO3/Al2O3 sample would generate the most efficient catalyst that offers an AC yield as high as 61% AC for longer than 10 h (AC selectivity: 69 mol%). Correlating the catalytic performance with the density of W atoms at the surfaces of WO3/Al2O3 and WO3/ZrO2 samples discloses that those catalysts having the intermediate numbers for the surface density of W atoms (3.5-7.6 W nm(-2) or 0.5-1.0 monolayer), either on Al2O3 or on ZrO2, would offer the highest AC selectivity (69-72 mol%). The catalytic results obtained in the temperature range of 280-400 degrees C uncover 315 degrees C as the optimum reaction temperature; significant derivation from this temperature would lead to faster catalyst deactivation and lower AC selectivity. (C) 2014 Elsevier B.V. All rights reserved.