CO Oxidation Catalyzed by Gold Supported on MgO: Spectroscopic Identification of Carbonate-Like Species Bonded to Gold During Catalyst Deactivation

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Journal of Catalysis

DOI:https://doi.org/10.1016/j.jcat.2008.11.005· OSTI ID:980066

Hao, Y; Mihaylov, M; Ivanova, E; Hadjiivanov, K; Knozinger, H; Gates, B

MgO-supported gold prepared by adsorption of Au(CH{sub 3}){sub 2}(acac) (acac is acetylacetonate) on partially dehydroxylated MgO was activated for CO oxidation catalysis by treatment in flowing helium at 473 K. X-ray absorption spectra showed that the activation involved reduction of the gold and formation of clusters (with an average diameter <10 {angstrom}) in which the gold was essentially zerovalent. During CO oxidation catalysis in a batch reactor, at least some of the gold was oxidized, as evidenced by the appearance of an Au{sigma}{sup +}-CO band at 2151 cm{sup -1} in the infrared (IR) spectrum. During operation in a flow reactor, the catalyst underwent deactivation, accumulating species such as carbonate and bicarbonate on its surface, as indicated by IR spectra. The accumulation of such species on the MgO support took place only during the initial period of operation of the catalyst, whereas the accumulation of such species on the gold continued throughout the operation, consistent with the inference that these species blocked catalytically active sites on the gold. The catalyst was reactivated by decomposition of these species by treatment in helium at 473 K. After three activation-deactivation cycles, the average diameter of the supported gold clusters had increased to about 30 {angstrom}, and the catalytic activity increased. Thus, the results provide a resolution of the separate effects on the catalytic activity of gold aggregation and accumulation of species such as carbonates and bicarbonates.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 980066
• Report Number(s): BNL--92984-2010-JA
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 261; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
ACID CARBONATES
ADSORPTION
AGGLOMERATION
BUILDUP
CARBONATES
CATALYSIS
CATALYSTS
DEACTIVATION
DECOMPOSITION
GOLD
HELIUM
OPERATION
OXIDATION
REDUCTION
RESOLUTION
SPECTRA
SUPPORTS
national synchrotron light source