Heterogeneous CO Oxidation and Homogeneous Anthracene Hydrogenation Catalyzed by Gold, Silver and Alloys Nanoparticles
Date Issued
2007
Date
2007
Author(s)
Shih, Wen-Cheng
DOI
en-US
Abstract
The heterogeneously catalytic CO Oxidation with Au-Ag alloy deposited on inert and acidic mesoporous aliminosilicate MCM-41 support, prepared by either one-pot or two-step procedure, has been investigated in terms of the experimental kinetics, in-situ DRIFTS, O2 pulse adsorption, O2-TPD and theoretical reaction modeling.
For one-pot/3:1 Au-Ag/MCM-41 alloy catalyst, the unexpectedly high catalytic activity at 80oC may be associated with the non-dissociative and non-competitive adsorption Langmuir-Hinshelwood model between CO and O2 species in intimate proximity on the alloy surface. The small activation energy, negligible surface coverage and desorption with raising temperature for both CO and O2 may give rise to the unusual behavior in reaction rate above 80oC. At higher temperature, the different reaction behavior and/or active site for CO oxidation could be altered, which may behave like supported monometallic metal catalyst.
For two-step/5:1 Au-Ag/MCM-41 catalyst, the high catalytic activity at 80oC could be due to non-dissociative and non-competitive or competitive Langmuir-Hinshelwood model between adsorbed CO on Au and O2 on Ag in close proximity of Au-Ag alloy surface as the RDS. The decrease in CO conversion with the increasing temperature could be caused by either desorption of both CO and O2 or dissociative adsorption for O2 on the Au-Ag alloy surface.
Anthracene hydrogenation in aqueous micellar solutions at room temperature is homogeneously catalyzed by ionic-surfactant-protected Au and Ag nanoparticles with well-controlled particle sizes. A remarkable size-dependence of catalytic activity is derived. The difference in the optical property of meal nanoparticles could be related to the charging of their surfaces, indicating that both the metal nanoparticles play a role as the nanoelectrode storing electrons from hydrides. The behavior about the electron transfer-relaying effects of metal nanoparticles is proposed for the hydrogenation reaction.
Subjects
異相催化
一氧化碳氧化反應
金銀合金觸媒
反應動力學
反應模型計算
均相催化
氫化反應
Heterogeneous Catalysis
CO Oxidation
Au-Ag Alloy Catalyst
Reaction Kinetics
Reaction Modeling
Homogeneous Catalysis
Hydrogenation
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-D90223026-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):a9ab8a02849f99e3db325eeb6a731902