NMR study of the chemisorption and surface chemistry of methylamine on Pd/SiO2
2008 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 8, 3042-3048 p.Article in journal (Refereed) Published
Results of an investigation of the interaction of methylamine with a Pd/SiO2 catalyst utilizing nuclear magnetic resonance (NMR) spectroscopy are presented. Two sets of experiments were conducted. In one set, a sample of catalyst was initially exposed to (CH3NH2)-C-13-N-15 at 77 K and then subjected to a lengthy equilibration period at 190 K. A C-13 spectrum at 77 K obtained on the sample at this point exhibited a single symmetric line at a frequency very close to the resonance frequency for methylamine in the absence of the catalyst. The line is attributed to methylamine adsorbed without dissociation. In C-13 spectra obtained at 77 K on the sample after each of a series of subsequent annealing periods at successively higher temperatures in the range 253-298 K, the line exhibited a gradual broadening on the downfield side. Deconvolution of the spectra resolved the original symmetric line from a very broad downfield line attributed to partially dehydrogenated surface species designated by the formula (CN)H-x. In the second set of experiments, (CH3NH2)-C-13-N-15 was adsorbed on a sample of catalyst at 298 K. The sample was then annealed at successively higher temperatures in the range 325-450 K. Deconvolution of the C-13 spectra obtained at 298 K after the various annealing periods revealed extensive formation of dimethylamine, reaching a maximum after the annealing period at 400 K. Ammonia and methane were first detected in the N-15 and C-13 spectra, respectively, after the annealing period at 375 K. During the annealing periods at 425 and 450 K, the dimethylamine decomposed almost completely, leaving only methane, ammonia, and residual surface species.
Place, publisher, year, edition, pages
2008. Vol. 112, no 8, 3042-3048 p.
EVAPORATED METAL FILMS, CARBON-NITROGEN BOND, CATALYTIC FISSION, RHODIUM CATALYST, SIMPLE MOLECULES, DECOMPOSITION, HYDROGEN, CLUSTERS, KINETICS, CH3NH2
IdentifiersURN: urn:nbn:se:kth:diva-34307DOI: 10.1021/jp076637nISI: 000253355700035ScopusID: 2-s2.0-40549137130OAI: oai:DiVA.org:kth-34307DiVA: diva2:420379
QC 201106012011-06-012011-06-012012-03-22Bibliographically approved