T-Butyl Nitrite (TBN) and t-Butyl Alcohol (TBA) Reactions on Clean and O-Covered Rh

Abstract

The reactions of t-butyl nitrite (TBN) and t-butyl alcohol (TBA) on clean and O-covered Rh foils were investigated using time-of-flight mass spectrometry temperature-programmed desorption and Auger electron spectroscopy. Although t-butoxy groups are formed when TBN and TBA dissociate on clean Rh and when TBA dissociates on O-covered Rh, there are significant differences in the thermal behaviors of these systems. For TBN on clean Rh, there is evidence that a monolayer decomposes to form NO and two oxygen-containing fragments, t-butoxy and a stabilized oxametallacycle. The proposed oxametallacycle decomposes at 350 K to acetone, whereas t-butoxy, relatively stable in the presence of N and NO, decomposes to isobutene at 500 K. For TBA dosed onto an O-covered surface, the OH bond breaks between 200 and 300 K to form t-butoxy. This occurs in competition with TBA desorption. The t-butoxy is stable only up to 380 K where, assisted by O, it decomposes to acetone and butene via a transient form of the oxametallacycle involved in TBN decomposition. Combustion reactions to form water, carbon monoxide, and carbon dioxide compete. For a monolayer of TBA dosed onto a clean Rh surface, H2, H2O, and CO, but no acetone or butene, are observed TPD, and carbon remains after TPD.