AEROGEL CATALYST Conversion of Alcohols to Amines

Kearby, K.K.; Kistler, S. S.; Swann, Sherlock

doi:10.1021/ie50345a033

“…Indeed, interpenetrating PBO-FeOx networks were obtained recently by catalyzing polymerization of a benzoxazine (BO) monomer by the Bronsted acidity of a [Fe(H 2 O) 6 ]Cl 3 sol in DMF (p K a,1 = 1.19, p K a,2 = 2.49) . Gelation of the [Fe(H 2 O) 6 ]Cl 3 sol was carried out by irreversible deprotonation with an epoxide (epichlorohydrin – Scheme A). − Ring-fusion aromatization of the PBO network (at 200 °C/air – Scheme B) ensured a high carbonization yield . Pyrolysis of aromatized PBO-FeOx networks at 800 °C/Ar triggered carbothermal reduction of the FeOx network to monolithic metallic Fe(0).…”

Section: Introductionmentioning

confidence: 99%

Explosive versus Thermite Behavior in Iron(0) Aerogels Infiltrated with Perchlorates

Leventis

¹

,

Donthula

²

,

Mandal

³

et al. 2015

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Monolithic nanoporous iron was prepared via carbothermal reduction of interpenetrating networks of polybenzoxazine and iron oxide nanoparticles. Excess carbon was burned off at 600 °C in air, and oxides produced from partial oxidation of the Fe(0) network were reduced back to Fe(0) with H2 at different temperatures (temp) ranging from 300 to 1300 °C. Samples were carbon-free, for temp > 400 °C also oxide-free, and are referred to according to the final H2-reduction temperature as Fe-temp. Fe-temp monoliths were infiltrated with perchlorates, dried exhaustively and were ignited with a flame in open air. Most experimentation was conducted with LiClO4. Depending on temp, monoliths fizzled out (≤400 °C), exploded violently (500–900 °C) or behaved as thermites (≥950 °C). Samples sealed in evacuated tubes did not explode, while if sealed under N2 the explosive effect was intensified. Thus, explosive behavior was attributed to rapid heating and expansion of gas filling nanoporous space. However, although that condition was necessary for explosive behavior, it was not sufficient. Based on SEM, particle sizes via N2 sorption, electrical conductivity measurements and mechanical strength data under quasi-static compression, it was concluded that the boundaries between the three types of behavior after ignition were associated with (a) mild sintering (fizzling/explosive boundary at around 500 °C); and, (b) melting-like fusion of skeletal nanoparticles (explosive/thermite boundary at around 950 °C). Overall, mechanically weaker networks fizzled out; too strong behaved as thermites; networks of intermediate strength exploded. For thermite behavior in particular, other factors may be also at play, such as a combination of reduced porosity, a substoichiometric amount of LiClO4 and a slower heat release rate. The latter was supported by TGA data in O2 and was attributed to a slower rate of oxidation of progressively thicker nanostructures as the H2-reduction temperature increased.

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“…5. Kearby, Kistler, and Swann (9) showed that an aluminachromic oxide aerogel was a less active amination catalyst for alcohols than the xerogel, but had a higher selectivity for the formation of monobutylamine.…”

Section: Discussionmentioning

confidence: 99%

“…Catalysts 4 and 5. The details of preparing these catalysts were given previously (9). They contain 90.6 per cent alumina and 9.36 per cent chromic oxide.…”

Section: Catalyst Preparationmentioning

confidence: 99%

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AEROGEL CATALYSTS Dehydrations and Decarboxylations

Kearby¹,

Swann²

1940

Self Cite

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A comparison is made of the activities of aerogels, xerogels, and precipitates as catalysts for the dehydration of alcohols, the esterification of acetic acid with ethanol and the dehydration and decarboxylation of aliphatic acids. The aerogels were often, but not always, the most active catalysts. The advantages of the aerogel form are found to be of smaller magnitude than was predicted from earlier work. THIS communication is an extension of the general problem of evaluating aerogels as catalysts, which is being carried out in this laboratory. Kistler, Swann, and Appel (11) showed that thoria aerogel was a more active catalyst than the xerogel (ordinary dried gel) or precipitate for decarboxylating aliphatic acids and esters to ketones. In a study of the vapor-phase oxidation of acetaldehyde to acetic acid over silica and platinized silica, Foster and Keyes (7) showed that the best aerogels and xerogels have about the same activity. These gels appear to be the best vapor-phase

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“…Table 6 gives some examples of metal-doped aerogels and their application in catalytic reactions. [94], [95] epoxidation of olefins Al 2 O 3 -SiO 2 [96] [AlCl 3 þ ethylene oxide] þ Si(OEt) 4 [73] catalyst support Al(OAc) 3 , Al(acac) 3 3 4 [97] preparation of high-purity ceramics Fe 2 O 3 -SiO 2 [98] Fe(acac) 3 þ Si(OMe) 4 Fischer -Tropsch syntheses…”

Section: Metal Oxide Aerogelsmentioning

confidence: 99%

Aerogels

Hüsing

¹

,

Schubert

²

2006

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Synthesis 2.1. Network Formation and Structure 2.1.1. Inorganic Aerogels 2.1.1.1. SiO 2 Aerogels 2.1.1.2. Metal Oxide Aerogels 2.1.2. Inorganic/Organic Hybrid Aerogels 2.1.3. Organic Aerogels 2.2. Drying Methods 2.2.1. Supercritical Drying 2.2.1.1. Drying in Organic Solvents 2.2.1.2. Supercritical Drying with CO 2 2.2.2. Freeze Drying 2.2.3. Ambient Pressure Drying 2.3. Modification of Aerogels after Drying 3. Properties 3.1. Structural Properties 3.2. Physical and Chemical Properties 3.2.1. Optical Properties 3.2.2. Mechanical and Acoustic Properties 3.2.3. Thermal Conductivity 3.2.4. Hydrophobicity 4. Applications 4.1. Çerenkov Detectors 4.2. Thermal Insulation 4.3. Catalysis 4.4. Application as Storage Media 4.5. Electrical and Electronic Applications 4.6. Acoustic and Mechanical Applications 4.7. Optical Applications 4.8. Other Applications 5. Future Perspectives Aerogels are unique among solid materials. They have extremely low densities (up to 95 % of their volume is air), large open pores, and a high inner surface area. This combination of properties results in interesting physical properties, e.g., for silica aerogels extremely low thermal conductivities and low sound velocities are combined with optical transparency. Aerogels are typically prepared via wet chemical processes, such as sol – gel processing, and thus their pore system is initially filled with liquid. Only special drying techniques allow for exchange of the pore liquid against air while maintaining the filigrane solid framework. The most common drying technique is supercritical extraction, and sometimes chemical modification of the inner surface can be used to facilitate drying. The structure of the gel network, and thus the physical properties of aerogels, decisively depends on the choice of the precursors and the chemical reaction parameters for preparing the gels. Therefore, the later materials properties can be deliberately designed in the starting reaction solution.

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AEROGEL CATALYST Conversion of Alcohols to Amines

Cited by 27 publications

References 4 publications

Explosive versus Thermite Behavior in Iron(0) Aerogels Infiltrated with Perchlorates

Explosive versus Thermite Behavior in Iron(0) Aerogels Infiltrated with Perchlorates

AEROGEL CATALYSTS Dehydrations and Decarboxylations

Aerogels

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