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Titolo:
Competition between acetaldehyde and crotonaldehyde during adsorption and reaction on anatase and rutile titanium dioxide
Autore:
Rekoske, JE; Barteau, MA;
Indirizzi:
UnivUSAlaware, Ctr Catalyt Sci & Technol, Dept Chem Engn, Newark, DE 19716Univ Delaware Newark DE USA 19716 chnol, Dept Chem Engn, Newark, DE 19716
Titolo Testata:
LANGMUIR
fascicolo: 6, volume: 15, anno: 1999,
pagine: 2061 - 2070
SICI:
0743-7463(19990316)15:6<2061:CBAACD>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHASE ALDOL CONDENSATION; SINGLE-CRYSTAL SURFACES; CARBON BOND FORMATION; SOLID BASE CATALYSTS; ALIPHATIC-ALCOHOLS; TIO2 SURFACES; METAL-OXIDES; FORMIC-ACID; METHANOL; DECOMPOSITION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
65
Recensione:
Indirizzi per estratti:
Indirizzo: Barteau, MA UnivUSAlaware, Ctr Catalyt Sci & Technol, Dept Chem Engn, Newark, DE 19716 Univ Delaware Newark DE USA 19716 Chem Engn, Newark, DE 19716
Citazione:
J.E. Rekoske e M.A. Barteau, "Competition between acetaldehyde and crotonaldehyde during adsorption and reaction on anatase and rutile titanium dioxide", LANGMUIR, 15(6), 1999, pp. 2061-2070

Abstract

The adsorption of acetaldehyde and crotonaldehyde on the anatase and rutile polymorphs of TiO2 has been investigated with Fourier transform. infraredspectroscopy (FTIR). Chemisorption of acetaldehyde on TiO2 involves a strong interaction between the surface and the carbonyl oxygen, causing a significant shift in the location of the nu(C=O) vibrational mode to lower frequencies; no interaction with surface hydroxyl groups was observed. Capacities for acetaldehyde and crotonaldehyde adsorption under conditions relevant to aldolization reactions were determined in a novel reactor system providing simultaneous mass measurements and mass spectral analysis of gas-phase products. The coverage of acetaldehyde irreversibly adsorbed on TiO2 was similar to values previously reported for the adsorption of alcohols; coverages of crotonaldehyde were approximately 60% of those for acetaldehyde. Both gas-phase and surface analyses indicate that formation of crotonaldehyde byaldol condensation of acetaldehyde occurs on rutile TiO2 at temperatures as low as 313 K. This reaction was not observed on anatase at these conditions; higher temperatures were required. The production of crotonaldehyde on rutile at 313 K diminished with increasing exposure of acetaldehyde. Acetaldehyde and crotonaldehyde adsorbed in a similar fashion on both anatase andrutile, and either aldehyde could displace the other from the surface layer. Accordingly, the surface concentrations of adsorbed acetaldehyde and crotonaldehyde mirror those in the gas phase. Upon heating an adsorbed layer of acetaldehyde, small amounts of ethoxide and acetate species were formed, possibly from a Cannizzaro-type disproportionation reaction. The similarityof these results to those of studies on TiO2 single crystals illustrates the applicability of properly chosen metal oxide single-crystal surfaces as models for polycrystalline powders. Both demonstrate that the chemistry of aldehydes on TiO2 can be successfully explained in terms of the reactions of a few key surface species.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/03/20 alle ore 10:15:38