Formation Of Gas-Phase Allyl Radicals From Glycerol On Rutile Tio2(110)

The reaction pathways of glycerol on TiO2(110) have been studied by molecular beam dosing and temperature-programmed desorption. The majority of adsorbed glycerol undergoes reactions to yield water, hydrogen, and carbon-containing products. For both water and hydrogen, we identify two distinct reaction channels resulting from the cleavage of O-H and C-H bonds. Quantification of the desorption yields reveals that the C-H bond scission channel, observed at temperatures higher than for the O-H bond scission, is a dominant reaction channel for hydrogen evolution. For the carbon-containing products, we identify gaseous allyl radical as the major product. Various minor carbon-containing products, including propylene, acrolein, allyl alcohol, acetone, formaldehyde, and ethylene, are also observed and quantified. The different surface chemistries observed between glycerol and simpler alcohols and glycols on TiO2(110), suggest that smaller oxygenates cannot serve as models for larger oxygenates in probing their reaction pathways on oxide surfaces.