Platinum supported on doped alumina catalysts for propulsion applications. Xerogels versus aerogels

Courthéoux, Laurence; Popa, Florin; Gautron, Éric; Rossignol, Sylvie; Kappenstein, Charles

doi:10.1016/j.jnoncrysol.2004.06.051

“…Balakrishnan and Gonzalez prepared aerogel and xerogel catalysts of platinum-alumina systems, and concluded that the aerogels were inferior in comparison to the corresponding xerogels as far as the surface area and metallic dispersion were concerned [7]. The comparison of aerogel and xerogel catalysts were also done by Courtheoux et al [8] and Popa et al [9]; for the catalytic propellant decomposition the aerogels showed lower activities, although they had superior properties compared with xerogels. Sault et al developed a platinum-alumina aerogel catalyst via a combination of inverse micelle technology with sol-gel processing [10]; although the aerogel exhibited higher turnover frequency for propane dehydrogenation than the xerogel, the Pt diameter and the BET surface area were much larger and smaller, respectively, for the aerogels.…”

Section: Introductionmentioning

confidence: 96%

Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Osaki¹,

Nagashima²,

Tajiri³

2007

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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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“…Alumina preparation through a sol-gel process was performed [185], and the addition of doping elements and its consequences on the thermal stability of transition alumina were discussed [186]. The impact on thermal stability and 79 wt.% HAN-21 wt.% H 2 O decomposition catalytic activity of both drying procedures and active phase introduction (impregnation against one-step addition before sol formation) [188], xerogels and aerogels of alumina were compared. The consequences on homogeneity and thermal stability of the support were followed once heated up to 1200 • C for 5 h, leading to an alumina phase transition from γ -to θ-alumina [187].…”

Section: Catalytic Decomposition Of Han and And Hnfmentioning

confidence: 99%

Catalytic Decomposition of Energetic Compounds: Gas Generators and Propulsion1A list of abbreviations/acronyms used in the text is provided at the end of the chpater

Batonneau

¹

,

Kappenstein

²

,

Keim

³

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Energetic Compounds Propellants Gas generators Explosive Materials Ignition systems Scope of the Chapter, and Literature Data Units Some Propulsion Elements A Short Introduction to Propulsion Theory Comparison of Propulsion Types and Propellants Propulsion System Types Propellants Advantages of Catalytic Propulsion A Brief History of Rocketry and Catalytic Propulsion The Current Supremacy of Hydrazine Introduction Catalysts Heterogeneous Catalysis: General Studies Mechanistic Considerations A Literature Overview B Thermodynamic Data C Isotope‐Related Studies D Single‐Crystal Studies E Catalytic Cycle Proposals Iridium‐Based Industrial Catalysts A Shell 405 Catalyst ( USA ) B K ali C hemie KC 12 GA Catalyst ( G ermany) C C nesro Catalyst ( F rance) D GIPKh Catalysts (former USSR ) New Hydrazine Decomposition Catalysts Homogeneous Catalysis and Coordination Chemistry of Hydrazine Applications of Hydrazine Catalytic Decomposition Gas Generators Use in Fuel Cells Corrosion Protection Drawbacks of Hydrazine “Green” Propellants as Hydrazine Replacements Introduction Energetic Aqueous Ionic Liquids Thermal Decomposition Catalytic Decomposition of HAN , ADN , and HNF A Hydroxyl Ammonium Nitrate ( HAN ) B Hydrazinium NitroFormate ( HNF ) C Ammonium DiNitramide ( ADN ) Development of Tools for Catalyst Evaluation The Comeback of Hydrogen Peroxide Introduction Thermal and Catalytic Decomposition Catalysts for Monopropellant Engines Kinetic Rate of Decomposition Hybrid Engine Hypergolic Bipropellant Engine Effect of Stabilizers on Catalytic Decomposition Nitrous Oxide (N 2 O) for Monopropellant Engines or Hybrid Engines Introduction Catalysts Use of N 2 O as a Monopropellant Use of N 2 O for Hybrid Engine Future Prospective Applications of Catalytic Propulsion New Energetic Liquids Catalysts for Air‐Breathing Supersonic or Hypersonic Jets Catalysts for Pulse Detonating Engine Ignition of Gaseous Hydrogen–Oxygen Mixtures Gas Generator to Power Micropumps through Small Turbines Conclusion: A Biological System using H 2 O 2 Decomposition for Tactical Defense Acknowledgement

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“…Therefore, it is of vital importance to improve the thermal stability of alumina support for the catalytic decomposition of N 2 O propellant. Addition of promoters to alumina is an effective method for suppressing the surface area loss and avoiding transition to a-Al 2 O 3 induced by high-temperature reactions [5][6][7][8][9][10][11][12][13]. Beguin et al [9] reported that numerous cations, such as La 3?…”

Section: Introductionmentioning

confidence: 99%

“…, were extremely effective for retarding the sintering and phase transformation of alumina at high temperatures. Courthéoux et al [10] prepared silica-doped alumina aerogels by a sol-gel method and demonstrated a marked increase in the thermal stability after calcination at 1200°C, owing to silicon atoms stabilizing the alumina defect structure. Osaki et al [13] also found that silicadoped alumina cryogels exhibited a high thermal stability by virtue of the synergetic effects of the very low bulk density and the dopant.…”

Section: Introductionmentioning

confidence: 99%