Silica-doped alumina cryogels with high thermal stability

Osaki, Toshihiko; Nagashima, Kiho; Watari, Koji; Tajiri, Koji

doi:10.1016/j.jnoncrysol.2007.04.016

Cited by 62 publications

(38 citation statements)

References 17 publications

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“…In our previous studies, the sol-gel processing and subsequent freeze drying, bringing about cryogel, successfully improved the stability of platinum (0.5 mass) on alumina at elevated temperatures. 6), 7) In the present studies, platinum-alumina cryogel with high platinum concentration (5 mass) was prepared, and the thermal stability and catalytic combustion activity were examined in comparison to those of the corresponding xerogel and two impregnation catalysts using alumina cryogel and commercial alumina as the supports.…”

Section: Introductionmentioning

confidence: 99%

Thermally stable Pt-Al2O3 cryogel with high platinum concentration for catalytic combustion

Osaki

Yamada

Tajiri

2008

J. Ceram. Soc. Japan

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The alumina cryogel with 5 mass platinum was prepared from aluminum sec-butoxide and H 2 PtCl 6 through the sol-gel processing and subsequent freeze drying. The cryogel showed higher thermal stability of platinum than the corresponding xerogel and impregnation catalysts at elevated temperatures. Also for the catalytic VOC combustion the cryogel exhibited higher activity than other catalysts. It was revealed that about half of the platinum surface was inside the alumina cryogel, and such encapsulation was considered the principal cause for the higher stability. 2008 The Ceramic Society of Japan. All rights reserved.Key-words : Cryogel, Sol-gel, Freeze drying, Platinum, Alumina, Catalytic combustion, Thermal stability, Dispersion, VOC [Received November 2, 2007; Accepted January 17, 2008] 1. Introduction As growing the demands for global environmental protection, much attention has been paid to the performance of a catalyst for exhaust emission control.1) Platinum is one of the important elements used for purifying the harmful emissions.2),3) However it is known that a precious metal agglomerates and sinters easily at high temperatures, decreasing the surface area of the metal, which results in catalyst deactivation. 4),5) It is also known that such agglomeration and sintering of a metal become pronounced with an increase in the concentration of the metal. In order to provide against such catalyst deactivation, excess precious metals have to be loaded despite the high cost. In our previous studies, the sol-gel processing and subsequent freeze drying, bringing about cryogel, successfully improved the stability of platinum (0.5 mass) on alumina at elevated temperatures. 6),7) In the present studies, platinum-alumina cryogel with high platinum concentration (5 mass) was prepared, and the thermal stability and catalytic combustion activity were examined in comparison to those of the corresponding xerogel and two impregnation catalysts using alumina cryogel and commercial alumina as the supports.

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Section: Introductionmentioning

confidence: 99%

Thermally stable Pt-Al2O3 cryogel with high platinum concentration for catalytic combustion

Osaki

Yamada

Tajiri

2008

J. Ceram. Soc. Japan

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“…The drying at high pressures is hazardous and furthermore, there is possibility of not only effluence of platinum ions from wet gels but also uncontrolled reduction to metallic platinum during the drying and/or solvent exchange. Cryogels, the highly porous solid materials derived from wet gels through freeze drying, are fascinating and useful in that they possess the bulk density as very low as that of aerogels [11,12]. The drying is safer, more economical, and there is very little fear of the effluence of platinum ions and uncontrolled reduction during the drying.…”

Section: Introductionmentioning

confidence: 99%

Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Osaki¹,

Nagashima²,

Tajiri³

2007

Catal Lett

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The cryogel catalyst of platinum on alumina was prepared from aluminum sec-butoxide and H 2 PtCl 6 through the sol-gel technique and subsequent freeze drying. The cryogel catalyst showed higher thermal stability of platinum than the corresponding xerogel or impregnation catalysts, which was ascribed to the more intimately developed platinum-alumina interaction accompanied by the encapsulation of the metal into the alumina cryogel. It was also shown that platinum accessibility was higher on the cryogel than on the xerogel despite the higher thermal stability of the metal on the formed than on the latter. For the VOC combustion, the cryogel exhibited higher activity than the xerogel and impregnation catalysts. Also for the methane combustion the cryogel showed higher activity, although it showed lower activity than the impregnation catalysts above 600°C. By the addition of ceria as an additive to the cryogel catalyst, the CH 4 combustion activity was improved especially in the temperature region above 600°C.

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“…One such system is the aqueous silica sols forming dense cryogels. When SiO 2 .nH 2 O is introduced into the composition of raw ceramic slurry, the amount of polymeric additives can be reduced significantly or even neglected [50,89,[136][137][138][139]. Modification of the porous structure of SiO 2 cryogels allows the formation of porous materials with a density as low as 0.05 g cm À3 and with excellent thermal insulation properties at cryogenic temperatures [15].…”

Section: Cryogel-derived Bulk Materialsmentioning

confidence: 99%

Inorganic Cryogels

Shlyakhtin¹

2014

Polymeric Cryogels

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Silica-doped alumina cryogels with high thermal stability

Cited by 62 publications

References 17 publications

Thermally stable Pt-Al2O3 cryogel with high platinum concentration for catalytic combustion

Thermally stable Pt-Al2O3 cryogel with high platinum concentration for catalytic combustion

Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Inorganic Cryogels

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