ADSORPTION AND THERMAL-DECOMPOSITION OF N-AZOPROPANE ON PT(111)

The adsorption and thermal decomposition of n-azopropane on Pt(111) we re studied by using temperature-programmed desorption (TPD) and reflec tion-absorption infra-red spectroscopy (RAIRS). At low temperatures, n -azopropane chemisorbs molecularly on Pt(111), but it isomerizes into a cis configuration upon bonding to the surface and changes its adsorp tion orientation as a function coverage. Multilayer and monolayer mole cular desorption occur about 130 and 170 K respectively, and a new sur face species probably probably dipropyl hydrazine - forms upon anneali ng the remaining chemisorbed molecules above 175 K. Further heating of the sample leads to the desorption of small amounts of propylene and ethylene. at 240 and 275 K. respectively. Another surface transformati on is identified by RAIRS around 275 It. possibly the conversion to an inline-type species. and propionitrile and small amounts of propyl an d methyl amines are produced soon after that: they desorb at 320 and 3 30 K respectively. Finally, a more extensive dehydrogenation of the re maining surface species takes place and HCN desorbs in two stages arou nd 525 and 600 K. The chemistry of propionitrile and propyl amine was also explored briefly by RAIRS and TPD for reference. (C) 1998 Elsevie r Science B.V. All rights reserved.