Liquid-phase dehydration of glycerol to acrolein was investigated with solid acid catalysts, including H-ZSM-5, H3PO4-modified H-ZSM-5, H3PW12O40·14H2O and Cs2.5H0.5PW12O40, in the presence of sulfolane ((CH2)4SO2) as a dispersing agent under atmospheric pressure N2 in a batch reactor. High weak-acidity H-ZSM-5, high temperatures and high-boiling-point sulfolane improved the activity and selectivity for the production of acrolein through suppressing the formation of polymers and coke and promoting the diffusion of glycerol and products. Brønsted acid sites were soundly demonstrated to be responsible for dehydration of glycerol to acrolein by infrared spectroscopy of pyridine adsorption. Brønsted weak acid sites favored the selectivity to acrolein. Combined catalytic and temperature-programmed desorption of ammonia studies revealed that the selectivity to acrolein increased as the weak-acidity increased over the ZSM-5-based catalysts. The ZSM-5-based catalysts produced a higher selectivity to acrolein, while the heteropolyacids resulted in a higher selectivity to polymers and coke.
Keywords: Brønsted acid sites; H3PO4-modified; ZSM-5; acrolein; dehydration of glycerol; heteropolyacid; liquid-phase; sulfolane.