DECOMPOSITION OF ACETATE GROUPS ON AN ALUMINA-SUPPORTED RHODIUM CATALYST

The decomposition of adsorbed acetate groups on a 1% Rh/Al2O3 catalyst has been investigated by means of temperature-programmed desorption ( TPD) at atmospheric pressure, in a microreactor fitted with an on-line mass spectrometer. Under certain conditions of catalyst pretreatment, the adsorbed acetate groups decompose autocatalytically in a process that has been described in the past as a ''surface explosion.'' The ph enomenon of surface explosions has been investigated by various groups and was generally considered to be confined to ultrahigh vacuum regim es using single crystals. It is found, however, that the explosive ace tate decomposition reaction actually translates directly to real suppo rted metal catalysts at atmospheric pressure. A description is given i nvolving the influence of adsorbed oxygen and differentiated acetate a dsorption sites on the metal, the support, and at the interface betwee n the two. Surface migration of the acetate groups is also involved in determining the intensities of the various TPD peaks. (C) Press Acade mic Press.