Effect of doping elements on the thermal stability of transition alumina

Abstract The thermal stability of porous transition alumina at high temperature is a crucial challenge for several applications. To delay the θ to α-alumina transition temperature (1180°C), the synthesis by sol–gel method and the introduction of doping element as nitrate salt M(NO 3 ) x (M=Ba, Mg, Pr, La and Ce) have been investigated. Over three preparation procedures, the introduction of the doping element through the sol–gel process gave the higher BET surface area. Additional thermal analysis and powder X-ray diffraction studies have shown that only a few amount (1 mol percent) of doping element is sufficient to increase the θ→α-Al 2 O 3 phase transition temperature up to 1315°C. The most promising samples are (Al 2 O 3 ) 0.98 Ba 0.02 and (Al 2 O 3 ) 0.99 Pr 0.01 . Even after 5 h at 1200°C, they maintain a rather good specific area (32 m 2 /g) in relation with the incomplete and very slow transformation of θ into α-alumina.

[1]  R. M. Levy,et al.  The effect of foreign ions on the stability of activated alumina , 1967 .

[2]  Z. Ismagilov,et al.  New technology for production of spherical alumina supports for fluidized bed combustion , 1999 .

[3]  M. Menéndez,et al.  Thermal stability of γ-Al2O3/α-Al2O3 mesoporous membranes , 1998 .

[4]  M. Ozawa,et al.  Structural phase transformations of rare-earth modified transition alumina to corundum1Work supported by US Department of Energy, BES, contract No. W-31-109-ENG-38.1 , 1997 .

[5]  L. Allard,et al.  Sol-gel processed fluorite-structured PrOy-ZrO2 mixed oxides deposited on alumina , 1999 .

[6]  M. Ozawa,et al.  Thermal stability and characterization of γ-Al2O3 modified with lanthanum or cerium , 1990 .

[7]  M. Ozawa,et al.  Thermal stability and characterization of γ-Al2O3 modified with rare earths , 1990 .

[8]  M. Pijolat,et al.  Influence of surface area and additives on the thermal stability of transition alumina catalyst supports. I: Kinetic data , 1987 .

[9]  J. Geus,et al.  Sintering of pseudo-boehmite and γ-Al2O3 , 1991 .

[10]  J. Church,et al.  Stabilisation of aluminas by rare earth and alkaline earth ions , 1993 .

[11]  J. Livage.  Sol-gel synthesis of heterogeneous catalysts from aqueous solutions , 1998 .

[12]  Marvin F. L. Johnson.  Surface area stability of aluminas , 1990 .

[13]  M. Ozawa,et al.  Effect of cerium addition on the thermal stability of gamma alumina support , 1990 .

[14]  A. Pierre,et al.  Comparison of the Structure and Porous Texture of Alumina Gels Synthesized by Different Methods , 1998 .

[15]  A. J. Burggraaf,et al.  Thermal stability and its improvement of the alumina membrane top-layers prepared by sol-gel methods , 1991 .

[16]  T. Ishikawa.  Thermally stabilized transitional alumina prepared by fume pyrolysis of boehmite sols , 1992 .

[17]  F. Mizukami,et al.  Preparation and Catalytic Effects of CeoX-MOy-Al2O3 (M=Ba,La,Zr and Pr) by an improved sol gel method for automotive catalysts , 1991 .

[18]  D. Trimm.  Materials selection and design of high temperature catalytic combustion units , 1995 .

[19]  M. Pijolat,et al.  Influence of surface area and additives on the thermal stability of transition alumina catalyst supports. II: Kinetic model and interpretation , 1987 .

[20]  Bulent E. Yoldas,et al.  Alumina gels that form porous transparent Al2O3 , 1975 .

[21]  H. Arai,et al.  Research and development on high temperature catalytic combustion , 1995 .

[22]  K. Eguchi,et al.  Preparation and Characterization of Large Surface Area BaO·6Al2O3 , 1988 .