Gold supported on ceria and ceria-alumina promoted by molibdena for complete hydrocarbons oxidation

Donka Andreeva 1Petya Petrova 1Janusz W. Sobczak 2Lyuba Ilieva 1

1. Institute of Catalysis BAS (IC), Acad.G. Bonchev bld.11, Sofia 1113, Bulgaria
2. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland

Abstract

The detoxification of the hydrocarbons pollutants is one of the global environmental problems. Considerable efforts have been made to design the highly efficient catalysts for complete oxidation of hydrocarbons. Nanosized gold supported catalysts are widely used as active catalysts at low temperatures in a lot of important reactions. The interesting properties of ceria as a support for the noble metals catalysts are well known to concern mainly its function as oxygen buffer. Efforts to increase the oxygen storage capacity by introducing of different cation dopants with valence lower than 4+ have been put forward. Most of these materials have shown promotion of both: oxygen vacancy concentration and oxygen storage capacity as well as redox activities, compared to undoped ceria. An accent was put also on the synthesis of nanosized ceria as an important factor for the preparation of highly active gold supported catalysts.The object of this study is to synthesize new gold catalysts supported on ceria and ceria-alumina non-promoted and promoted by molybdena for complete benzene oxidation. The catalysts were characterized by means of XRD, TPR, XPS and Raman spectroscopy. High and stable catalytic activity was established in the temperature region 200-2400C. The presence of gold causes a modification in ceria structure leading to an increase of Ce3+ and oxygen vacancies formation. The differences in the activities within the temperature range 150-1800C and in the region of 100 % conversion (200-2400C) could be explained by supposing that in the LT region the electron transfer between nanosized gold and ceria particles via oxygen vacancies has a crucial role. In the HT region the oxygen mobility, provoked by the defective structure of ceria due to the presence of Al3+, becomes of prevailing importance.. It was also concluded that alumina prevents the gold and ceria agglomeration, which is the main factor to avoid deactivation under extreme reaction conditions.

 

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium B, by Janusz W. Sobczak
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 14:53
Revised:   2009-06-07 00:44