Ethanol Steam Reforming: Higher Dehydrogenation Selectivities Observed by Tuning Oxygen-Mobility and Acid/Base Properties with Mn in CeO2•MnOx•SiO2 Catalysts

Doping CeO2-SiO2 catalysts with Mn was found to increase H-2 selectivity and decrease ethylene selectivity. In the presence of SiO2, relatively high surface areas (similar to 150-190 m(2) g(-1) range) were stabilized with these coprecipitated catalysts after calcining at 500 A degrees C for 5 h. By means of a combination of ex-situ (XRD, TPR, CO2-TPD, OSC measurements) along with in situ (Ce L-III edge XANES, DRIFTS) techniques Mn was proposed to act to improve the ability of ceria to deliver active oxygen surface species essential to the stepwise oxidative dehydrogenation of adsorbed species from ethoxides to acetates. Doping ceria with Mn at low levels improved the carbonate decomposition rate by weakening surface basicity. At high Mn content, acetates become too stable and poison catalytically active sites.