Alcohol chemistry as a probe of mixed-metal phases: Reactions of 2-propanol on cobalt-covered Mo(110)

The reactions of 2-propanol on cobalt-covered Mo(110) have been investigated in an effort to test for special reactivity associated with mixed Go-Mo phases. 2-Propanol reacts via 2-propoxide on a continuous Co overlayer supported on Mo(110), as shown by X-ray photoelectron and infrared spectroscopies. Carbon monoxide, acetone, propene, and hydrogen are the only gaseous products, while carbon and oxygen remain on the surface after temperature-programmed reaction up to 760 K. The acetone and CC) production increase whereas propene and propane production decrease as the Co coverage is increased from 0 to 1.5 monolayers (ML). This is consistent with independent reactions occurring on both Co and Mo, since 2-propanol is known to produce propene and propane on Mo(110). The C-O bond retention products (acetone and CO) are attributed to reaction on the Co overlayer. Infrared and temperature-programmed reaction studies confirm that the evolution of CO is desorption limited and that decomposition to CO competes with acetone formation at 330 K. Acetone is produced via selective cleavage of the beta C-H bond (adjacent to the oxygen), as shown by selective isotopic labeling experiments. The observed C-O bond retention on Co is consistent with the intermediate strength of the Co-O bond compared to other M-O bonds for transition metals. There is no evidence for aggregation of the Co overlayer induced by 2-propoxide, and therefore the observed reactivity is that of the dispersed Co overlayer.