Structural and chemical disorder of cryptomelane promoted by alkali doping: Influence on catalytic properties

• Type: Article in International Scientific Journal
• Date: 2012

Authors

V.P. Santos (Author) Other; O.S.G.P. Soares (Author) FEUP; J.J.W. Bakker (Author) Other; Manuel Fernando R Pereira (Author) FEUP; José Melo Orfão (Author) FEUP; J. Gascon (Author) Other; F. Kapteijn (Author) Other; José Luís Figueiredo (Author) FEUP

Journal

Title: Journal of Catalysis

Vol. 293

Pages: 165-174

ISSN: 0021-9517

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 75 Citations

ISI Web of Science

Scopus - 122 Citations

Scientific classification

FOS: Engineering and technology > Chemical engineering

Other information

Authenticus ID: P-002-61S

DOI: 10.1016/j.jcat.2012.06.020

Abstract (EN): Different amounts of cesium (0.8-1.3 at.%) and lithium (up to 0.5 at.%) were introduced in the tunnel structure of cryptomelane in order to tailor its physical and chemical properties. The mechanism by which cryptomelane accommodates these alkali cations is different; Li occupies mainly empty sites by a redox-type reaction, while Cs is ion-exchanged by H3O+ cations. The adsorption of these alkali metals into cryptomelane was highly selective and is dictated by the solvation energy and ionic radius. Extrinsic defects (e.g. positive holes and oxygen vacancies) are created upon doping, enhancing the redox-properties of cryptomelane. The basicity of the framework also increases when Cs and Li are incorporated. The catalytic properties of this material were tested in the oxidation of ethyl acetate, and greatly improved after doping. The observed activity increase is explained by the redox and basic properties of the modified materials. The amount of cesium loaded has no effect on the activity, as a result of pore mouth catalysis.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10