Cookies Policy
X

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies.

I accept this policy

Find out more here

Promotion Effect of Metal Oxides On C-o bOnd Dissociation in Co Hydrogenation Over Rh/Sio2 Catalyst - Possible Role of Partially Reduced State Cations

No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
The full text of this article is not currently available.

Brill’s MyBook program is exclusively available on BrillOnline Books and Journals. Students and scholars affiliated with an institution that has purchased a Brill E-Book on the BrillOnline platform automatically have access to the MyBook option for the title(s) acquired by the Library. Brill MyBook is a print-on-demand paperback copy which is sold at a favorably uniform low price.

Access this article

+ Tax (if applicable)
Add to Favorites
You must be logged in to use this functionality

image of Research on Chemical Intermediates

In CO hydrogenation over Rh/SiO catalysts, the effect of additive metal oxides on C-O bond dissociation was studied by using pulse surface reaction rate analysis (PSRA). The addition of oxides of Al, Ti, Cr, V, and Mn resulted in an increase in the rate constant for the dissociation according to this sequence, while the oxides of Cu, Zn, and Ag added decreased the rate constant to almost the same extent. In contrast to these metal oxides, MoO3 and WO3 did not change the dissociation activity. CO adsorption measurement indicated that all of the added metal oxides covered a considerable portion of the Rh metal surface, although the efficiency of covering was different from one metal oxide to another. Covering the Rh metal surface with an added metal oxide should decrease the rate constant of C-O bond dissociation, because ensemble sites, consisting of a group of surface Rh atoms and considered necessary for the dissociation, were destroyed. The suppression effect resulted from the destruction of the ensemble sites by adding the oxides of Cu, Zn, and Ag. For other metal oxides, temperature-programmed reduction (TPR) or O2 uptake measurement revealed that the added oxides, especially those existing on the Rh metal surface, were in a partially reduced state under reaction conditions. Owing to its high affinity for an oxygen atom, the cation in a partially reduced state participated in the reaction in such a way that the oxygen end of adsorbed CO species was bound to the cation so as to dissociate the C-O bond, which resulted in promotion of the dissociation. The observed promotion was explained in terms of the enhancement owing to the high affinity sufficient to overcome the suppression caused by destroying ensemble sites. Lack of the promotion effect of MoO3 and WO3 might result from a balance between promotion due to the high affinity of the partially reduced Mo or W and suppression caused by destroying ensemble sites. Excellent correlation was observed between the intrinsic activity increase, from which the suppression effect was excluded, and the heat of formation of metal oxide including MoO3 and WO3. Since the heat of formation of metal oxide is considered to be a measure of the affinity, this correlation supports the idea that the high affinity of additive cations for an oxygen atom is of primary importance in the promotion of C-O bond dissociation in CO hydrogenation.

Affiliations: 1: Department of Applied Chemistry, School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464, Japan; 2: National Industrial Research Institute of Nagoya, Hirate-cho, Kita-ku, Nagoya 462, Japan

10.1163/156856795X00116
/content/journals/10.1163/156856795x00116
dcterms_title,pub_keyword,dcterms_description,pub_author
6
3
Loading
Loading

Full text loading...

/content/journals/10.1163/156856795x00116
Loading

Data & Media loading...

http://brill.metastore.ingenta.com/content/journals/10.1163/156856795x00116
Loading

Article metrics loading...

/content/journals/10.1163/156856795x00116
1995-01-01
2016-12-06

Sign-in

Can't access your account?
  • Tools

  • Add to Favorites
  • Printable version
  • Email this page
  • Subscribe to ToC alert
  • Get permissions
  • Recommend to your library

    You must fill out fields marked with: *

    Librarian details
    Your details
    Why are you recommending this title?
    Select reason:
     
    Research on Chemical Intermediates — Recommend this title to your library
  • Export citations
  • Key

  • Full access
  • Open Access
  • Partial/No accessInformation