Structure and thermal decomposition of para- and ortho-xylene on Pt(111): a HREELS, LEED and TPD study

Abstract

High resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy and low energy electron diffraction (LEED) were used to investigate the low temperature adsorption structure and subsequent thermal decomposition of p- and o-xylene on Pt(111). Both xylenes adsorb intact on Pt(111) at 245 K with the aromatic ring oriented parallel to the surface. At about 350 K, both p- and o-xylene begin thermal decomposition by partial dehydrogenation of the methyl groups. Further decomposition pathways are markedly different for the two xylenes. For p-xylene, the remaining aliphatic and aromatic CH bonds break at about 550 K, leaving CH and C 2H species on the surface. In contrast, the aliphatic groups of o-xylene completely dehydrogenate at about 440 K, leaving a fragment with the aromatic ring oriented nearly perpendicular to the surface.