Catalytic aluminas I. Surface chemistry of eta and gamma alumina

MacIver, D. S.

doi:10.1016/0021-9517(63)90004-6

Cited by 174 publications

(56 citation statements)

References 17 publications

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“…For the given experimental design, the temperature range where the metakaolinite and spinel phase are developed is also consistent with the time-temperature-transformation diagrams for kaolinite presented by Onike et al (1986). Maciver et al (1963) indicated that γ-alumina strongly adsorbs molecular water on its surface. Moreover, Liu (2008) attributes the presence of a broad 2.84 µm absorption band to adsorbed water in hydrated γ-alumina.…”

Section: Kaolin Calcination Reaction In the Mwir And Lwir Rangessupporting

confidence: 54%

“…In particular, amorphous γ-alumina is highly reactive, and crystalline γ-alumina has a high water adsorption capacity, as Maciver et al (1963) and Peri (1965) verified. In the IR spectrum (Figure 1), the amorphous phases typically have broad absorption bands that shift toward lower wavelengths, near 8.33 µm for the Si-spinel and toward 11.90 µm for the γ-alumina.…”

Section: Metakaolinite-mullite Transitionmentioning

confidence: 99%

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Toward an on-line characterization of kaolin calcination process using short-wave infrared spectroscopy

Guatame-Garcia

Buxton

Deon

et al. 2018

Mineral Processing and Extractive Metallurgy Review

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In the production of calcined kaolin, the on-line monitoring of the calcination reaction is becoming more relevant for the generation of optimal products. In this context, this study aimed to assess the suitability of using infrared (IR) spectroscopy as a potential technique for the on-line characterization of the calcination of kaolin. The transformation of kaolin samples calcined at different temperatures were characterized in the short-wave (SWIR) spectra using the kaolinite crystallinity (Kx) index and the depth of the water spectral feature (1900D). A high correlation between the standard operational procedure for the quality control of calcined kaolin and the Kx index was observed (r = -0.89), as well as with the 1900D parameter (r = -0.96). This study offers a new conceptual approach to the use of SWIR spectroscopy for the characterization the calcination of kaolin, withdrawing the need of using extensive laboratory techniques.

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Section: Kaolin Calcination Reaction In the Mwir And Lwir Rangessupporting

confidence: 54%

Section: Metakaolinite-mullite Transitionmentioning

confidence: 99%

Toward an on-line characterization of kaolin calcination process using short-wave infrared spectroscopy

Guatame-Garcia

Buxton

Deon

et al. 2018

Mineral Processing and Extractive Metallurgy Review

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“…19 The removal of adjacent hydroxyl groups by the elimination of molecular water is accompanied by an increase in both the catalytic activity and surface acidity ; 2 1~ 229 8 the removal of molecular water also increases surface acidity. 8 The spectroscopic investigation of adsorbed indicators has shown that, prior to outgassing, both the a-Al203 and y-Al203 used in the present calorimetric study were neutral in the Brsnsted sense, but possessed slight Lewis acidity3 For the y-Al2O3, outgassing was observed to increase the Lewis acidity, without changing the Bronsted neutrality. Various structures have been suggested for the dehydrated centres responsible for the acidity and catalytic activity 21,249 25 which include the following ionic and stable free radical structures : View Article Online HEATS OF IMMERSION OF a-Al203 A N D y-AI203 Irrespective of the exact structure of the centres, they will affect immersional behaviour by providing sites at which the chemisorption of reactive molecules can occur.…”

Section: Heats Of Immersion Of A-al203 a N D Y-ala03mentioning

confidence: 92%

Heats of immersion of alpha and gamma alumina

Cochrane¹,

Rudham²

1965

Trans. Faraday Soc.

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The heats of immersion of a-AI203 and y-Al2O3 in water, benzene, five n-butyl derivatives, and an epoxy resin in benzene, have been determined at 25°C. Values for the heats of immersion of alumina on substrate aluminium in the same liquids have been recalculated, and they show that the immersional properties of this solid approximate to those of y-Al2O3. Immersion of all three solids in water, a-Al2O3 in n-butyraldehyde and y-Al2O3 in n-butyl alcohol, give rise to high heats, which are indicative of a contribution from chemisorptive processes. The catalytic activities of the solids for parahydrogen conversion at 77°K have also been determined. The results are discussed in relation to current ideas on imersional processes and the surface properties of alumina.The measurement of heats of immersion of solids in liquids permit the investigation of a number of the properties of the solid surface. The thermodynamics of the immersion process, developed by Harkins,l has been reviewed by Eley 2 from the viewpoint of adhesion. Both the integral and differential heats of adsorption of vapours on solids can be determined from heats of immersion. The results of Hollabaugh and Chessick,3 on the adsorption of vapours on rutile, illustrate the close agreement that can be obtained between isosteric heats and those from immersion data. Zettlemoyer and coworkers 4 9 5 have shown that the variation in the heat of immersion of a solid in a series on n-butyl derivatives of differing dipole moment can be used to estimate an average value for the electrostatic field strength at the solid surface.The present contribution reports an investigation of the surface properties of welldefined alpha and gamma alumina by the heat of immersion technique. To permit a direct comparison between the present results and those for aluminium oxide on substrate aluminium,6 the aluminas were given the same outgassing treatment. It is doubtful whether evacuation for 72 h at 300°C and < 10-6 mm Hg removed all surface water,7* 8 but reproducible surfaces were obtained. The majority of the heats of immersion were determined using pure liquids, but benzene solutions (5 % by weight) were used with n-butyl alcohol, n-butyraldehyde and the epoxy resin, Araldite 6100. EXPERIMENTAL A P P A R A T U S

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“…The fuel is vaporized in a vaporizer heated at 453 K and mixed with Ar before entering the flow tube. The flow tube with an inner diameter of 7.0 mm and a heating length of 150 mm is made of a-Al 2 O 3 to reduce wall catalytic effects [18][19][20]. Three pressures in the pyrolysis chamber are investigated, i.e.…”

Section: Flow Reactor Pyrolysismentioning

confidence: 99%