Aluminum doped mesoporous silica SBA-15 for glycerol dehydration to value-added chemicals

A series of Al-grafted mesoporous SBA-15 silica was synthesized and tested as catalysts in the gas-phase dehydration of glycerol to acrolein. Different Si/Al molar ratios were employed to tune the structure, texture and acidity of catalysts in order to analyze their effect on the catalytic performance. Different characterization techniques, such as powder X-ray diffraction, X-ray photoelectron spectroscopy, Al-27 MAS NMR, N-2 adsorption-desorption at -196 A degrees C, ammonia temperature programmed desorption (NH3-TPD) and adsorption of pyridine coupled to Fourier transform infrared spectroscopy were employed. All materials were active in glycerol dehydration, being acrolein the main product in all cases. The catalyst with the highest Al content (AlSBA-2.5) showed the highest acrolein yield (27.6%) after 8 h of time-on-stream. A clear relationship between the effective production of acrolein and the acidity of catalysts could be established. Catalysts suffered from deactivation by coke deposition on the surface, but they can be reused, at least during three catalytic cycles, after regeneration at 550 A degrees C in air during 4 h after each cycle. [GRAPHICS]