Identification of superactive centers in thermally treated formamide-intercalated kaolinite

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33 Citations (Scopus)

Abstract

The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350°C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.

Original languageEnglish
Pages (from-to)132-138
Number of pages7
JournalJournal of Colloid and Interface Science
Volume289
Issue number1
DOIs
Publication statusPublished - Sep 1 2005

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Kaolin
kaolinite
Kaolinite
grinding
Alkalinity
Fourier transform infrared spectroscopy
Mass spectrometry
Thermogravimetric analysis
Carbonates
carbonates
Minerals
Chemical activation
Heat treatment
Spectroscopy
Carbon Monoxide
Bicarbonates
Decomposition
Temperature
thermogravimetry
carboxylates

Keywords

  • Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT)
  • Intercalation
  • Kaolinite
  • Mechanochemical activation
  • Thermogravimetry-mass spectrometry (TG-MS)

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces

Cite this

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title = "Identification of superactive centers in thermally treated formamide-intercalated kaolinite",
abstract = "The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350°C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.",
keywords = "Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), Intercalation, Kaolinite, Mechanochemical activation, Thermogravimetry-mass spectrometry (TG-MS)",
author = "E. Horv{\'a}th and J. Krist{\'o}f and Frost, {Ray L.} and E. Jakab and E. Mak{\'o} and V. V{\'a}gv{\"o}lgyi",
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T1 - Identification of superactive centers in thermally treated formamide-intercalated kaolinite

AU - Horváth, E.

AU - Kristóf, J.

AU - Frost, Ray L.

AU - Jakab, E.

AU - Makó, E.

AU - Vágvölgyi, V.

PY - 2005/9/1

Y1 - 2005/9/1

N2 - The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350°C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.

AB - The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350°C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.

KW - Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT)

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KW - Kaolinite

KW - Mechanochemical activation

KW - Thermogravimetry-mass spectrometry (TG-MS)

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