Aerogel and Xerogel Catalysts Based on θ‐Alumina Doped with Silicon for High Temperature Reactions

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

doi:10.1002/ejic.200400657

“…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: 95%

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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“…The crystalline phases were identified by comparison with powder diffraction files (PDF) standards from ICDD (PDF number: TiO 2 anatase: 21-1272; TiO 2 rutile: 21-1276). The crystallite sizes were determined from the Scherrer equation (Popa et al 2005) using the integrated width corrected from apparatus using LaB 6 as a standard.…”

Section: Samples Characterizationmentioning

confidence: 99%

Study of effect of chromium on titanium dioxide phase transformation

Bellifa

¹

,

Piraúlt-Roy

²

,

Kappenstein

³

et al. 2014

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MTiX samples with different atomic chromium percentages were synthesized by sol-gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 °C. Without Cr content, the anatase-rutile transition takes place at 600 °C and the rutile fraction increases with increase of temperature. In the presence of Cr content, rutile phase appeared at 700 °C. Cr 2 O 3 phase was shown only in the case of CrTi20 content at 800 °C which indicates that the segregation remains modest. We have also studied the anatase-rutile transition kinetics by using in situ X-ray measurements. It was found that the anatase phase stability increases as the chromium content increases. Results confirm that the transformation of anatase-rutile is of first order.

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“…The effect of drying technique (subcritical drying xerogel; CO 2 supercritical drying aerogel) was studied when silicon was selected as a dopant to be inserted in γ -alumina. The introduction method of 5 wt.% Pt was also discussed [189]. 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.…”

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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Aerogel and Xerogel Catalysts Based on θ‐Alumina Doped with Silicon for High Temperature Reactions

Cited by 17 publications

References 29 publications

Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Study of effect of chromium on titanium dioxide phase transformation

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

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