The adsorption and reaction of 2-butanol on clean and oxygen-covered Pd(100)

The surface chemistry of 2-butanol is explored on clean Pd(100), c(2 x 2)-O/Pd(100) and p(2 x 2)-O/Pd(100) surfaces by means of temperature-programmed desorption, reflection-absorption infrared and X-ray photoelectron spectroscopies. 2-Butanol adsorbs molecularly on clean and oxygen-covered Pd(100) below similar to 190K, but then appears to react to form 2-butoxide species at similar to 200 K. Both 2-butanone and 2-butanol desorb from the clean surface at similar to 226 K, by beta-hydride elimination from the 2-butoxide species and rehydrogenation of the 2-butoxide, respectively. In contrast, almost exclusively 2-butanone is formed on oxygen-covered surfaces. Butanone desorbs at similar to 195K and similar to 260K from c(2 x 2)-O/Pd(100) with the 195 K peak being the most intense. However, on p(2 x 2)-O/Pd(100), 2-butanone desorbs at similar to 195K and similar to 295K, and the latter peak is the most intense. The similar to 195 K, 2-butanone state is proposed to occur due to abstraction by adsorbed atomic oxygen and the change in relative intensity of these features is ascribed to the lower ability of surface hydroxyl groups to facilitate beta-hydride elimination on oxygen-covered surfaces. Further heating results in the formation of hydrogen and carbon monoxide and leaves a small amount of carbon deposited on the surface. (C) 2010 Elsevier B.V. All rights reserved.