Trimethyl Acetate on TiO₂(110): Preparation and Anaerobic Photolysis
The preparation and anaerobic ultraviolet photolysis of trimethyl acetate (TMA) on rutile TiO?(110) have been examined with an emphasis on reaction paths. Substrates for photolysis were prepared by dosing trimethyl acetic acid at 100, 300 and 550 K. The chemistry was characterized by mass spectrometry during dosing, and by H?O adsorption and temperature programmed desorption after dosing. Using temperature programmed desorption after photolysis and mass spectrometry during photolysis, the products ejected and retained during photolysis were sought. The photolysis results are interpreted using the following mechanistic model. Photons with energies exceeding 3 eV create electronhole pairs in the substrate. With probabilities of 10-? or lower, the holes initiate TMA chemistry by extracting an electron from the ? orbital of the carboxylate moiety. The accompanying electrons are trapped at the surface and inhibit this chemistry. The electron deficient intermediate, TMA*, decarboxylates to form CO? and either chemisorbed t-butyl, (-C(CH?)?), or physisorbed i-butene. For photolysis at 100 or 200 K, the (-C(CH?)?) accumulates and there is a slow photon-driven secondary reaction that, with a source of H, hydrogenates adsorbed t-butyl to physisorbed i-butane. For photolysis at 300 K, (-C(CH?)?) thermally reacts to form and desorb i-butene and ibutane during photolysis.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15020634
- Report Number(s):
- PNNL-SA-44359; 11105; KC0302010; TRN: US0504680
- Journal Information:
- Journal of Physical Chemistry B, Vol. 109, Issue 25
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACETATES
ACETIC ACID
ADSORPTION
CHEMISTRY
DESORPTION
ELECTRONS
MASS SPECTROSCOPY
PHOTOLYSIS
PHOTONS
RUTILE
SECONDARY REACTIONS
SUBSTRATES
environmental molecular sciences laboratory
photocatalysis
TiO2(110)
trimethyl acetic acid
surface science