Variations in the synthesis of barium hexaferrite doped with iridium and its effect in the catalytic combustion of hydro
- PDF / 228,787 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 6 Downloads / 199 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Variations in the synthesis of barium hexaferrite doped with iridium and its effect in the catalytic combustion of hydrocarbons A. C. Pierre,a) A. Favre, and N. Guilhaume Universit´e Claude Bernard-Lyon I, Lace, UMR-CNRS 5634, France (Received 3 September 1996; accepted 7 July 1997)
This paper discusses the influence of the synthesis technique on the porous structure, phase transformation, and catalytic properties of barium hexaferrite. Barium hexaferrite was synthesized by two different citrate gel methods. The first one involved metal salts, citric acid, and ammonia, while the second dispersed the same components in a polyacrylamide gel. X-ray diffraction analysis was used to determine the nature of the phase while the Brunauer, Emmett, and Teller (BET) analysis was used to study the porous structure of the material which were heat-treated at 700 ±C, 900 ±C, and 1200 ±C. The catalytic activity of all materials in the combustion of methane was also measured. I. INTRODUCTION
New and cheap catalyst materials are needed to replace expensive noble metals. Within this general purpose, it was reported that advanced ceramics derived from the aluminate BaMn2 Al10 O19 present interesting properties in the clean catalytic combustion of hydrocarbons.1–5 The interesting properties of this material are in part due to its layered atomic structure, as it is well known that powders with randomly oriented flat faces do not sinter well.6 This is the reason why u-alumina, for instance, can maintain a relatively high specific surface area above 1000 ±C, before transforming to a –alumina. Moreover, foreign additives can act either as sintering aids or as sintering retarding agents, and it appears that Mn retards sintering. Finally, Mn is a catalytically active transition element, which participates in the spinel related BaMnAl10 O19 phases, and hence is maintained homogeneously dispersed, on the free surface of the catalyst, as well as in the bulk. This paper is part of a project to study similar materials derived from the barium hexaferrite BaFe12 O19 , some of which are also doped with up to 5% iridium. The study reports on the nature of the material synthesized, either by a citrate gel or a mixed citrate-polyacrylamide gel technique, as well as on their phase transformation, on the evolution of the porous structure during heat treatment up to 1200 ±C, and on their effect in the catalytic combustion of methane. II. EXPERIMENTAL PROCEDURE
BaFe12 O19 is synthesized by two different citrate gel methods. The first one uses barium acetate [Ba(CH3 CO2 )2 ], hydrated ferric nitrate [Fe(NO3 )3 ? 9H2 O], and a)
Present address: IRC, UPR-CNRS 5401, 2 Ave. Albert Einstein, 69626 Villeurbanne Cedex, France. J. Mater. Res., Vol. 13, No. 6, Jun 1998
http://journals.cambridge.org
Downloaded: 16 Mar 2015
citric acid [HO2 CCH2 C(OH) (CO2 H)CH2 CO2 H ? H2 O] as chemical precursors. The technique involves dissolving those precursors in distilled water at about 70 ±C in molar proportions of 1y12y26 in
Data Loading...
