NMR and acidity studies of dealuminated metakaolin and their correlation with cumene cracking

Macedo, JoséCarlos D.; Mota, Cláudio J. A.; Menezes, Sônia Maria Cabral de; Camorim, Vera Lúcia L.

doi:10.1016/0169-1317(94)90022-1

Cited by 23 publications

(12 citation statements)

References 12 publications

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“…The high octahedral aluminum content makes kaolin resistant to acid leaching (28,29), but metakaolin (produced by heating kaolin in air at temperatures > 450 • C (29)) is much more susceptible to acid activation, producing a catalyst with the same activity as acid activated montmorillonite at about half the fresh surface area (29). Thus, acid-activated metakaolin (AAMK) is a material which offers both enhanced surface area and acidity compared with either kaolin or metakaolin (29)(30)(31). As with acid treated bentonites, the activity of AAMKs reaches a maximum and then declines as the severity of the activation process increases although Lussier has reported that AAMKs with high surface areas and activities can be prepared using very low acid concentrations if the metakaolin was produced in a narrow calcination window (29).…”

Section: Introductionmentioning

confidence: 98%

Preparation and Characterization of Dealuminated Metakaolin and Its Use in the Transformation of Waste Plastics to Aromatic Hydrocarbons

Breen

Taylor

Burguin

et al. 2002

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 98%

Preparation and Characterization of Dealuminated Metakaolin and Its Use in the Transformation of Waste Plastics to Aromatic Hydrocarbons

Breen

Taylor

Burguin

et al. 2002

Journal of Colloid and Interface Science

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“…The total number of sites, the ratio of Lewis to Bronsted sites, and their relative strengths depend on the calcination temperature . Partially dealuminated MK may act as superacids . This was attributed to synergizing between Bronsted and Lewis acidity, associated with 4‐and‐5 coordinated Al, respectively.…”

Section: Resultsmentioning

confidence: 99%

Characterization of LDH (phyllosilicate/carbonate) type compounds formed in the pozzolanic reaction of phyllosilicate‐rich industrial waste

et al. 2019

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Reutilization of industrial waste products as cement additives yields a number of secondary materials, yet their identification is not always trivial. Confirmation of the formation of a LDH-type (phyllosilicate/carbonate) material is the main purpose of this study. Mineralogically, organic and inorganic compounds form some industrial wastes, among which the phyllosilicates are prominent. Crystalline and amorphous hydrated phases appeared during the pozzolanic reaction in a dehydroxylated phyllosilicate/lime system, whose controlled activation yielded dehydroxylated products with high pozzolanic properties. The LDH-type (phyllosilicate/carbonate) material was one of the reaction products; this material could be considered as the superposition type 1:1 of tetrahedral layers of silicon and aluminum and octahedral layers of aluminum (dehydroxylated kaolinite), generating a positive charge in the interlaminar region compensated by carbonate anions with a basal spacing (001) measured by XRD at 7.57Å. Therefore, several techniques were used to determine whether they could be included in the structural group named Layered Double Hydroxides (LDHs), as they are, too, laminar layers of oxides and hydroxides with a positive laminar charge in the interlayer region compensated by the presence of anions with similar basal spacing. In this research, the effects of activation temperature and calcite proportion were analyzed on the hydrated phases formed after 28 days of pozzolanic reaction in a metakaolin (MK)/lime system. The MK was obtained from a mix of 1:1; 2:1 and 3:1 kaolinite:calcite mixture, thermally activated at 750°C for 2 hours, comparing it with kaolinite activated at 600°C for 2 hours. As the most LDH-rich sample, the 1:1 LDH-type (phyllosilicate/carbonate) phase was characterized using XRD, SEM-EDX, HRTEM-EDX, FTIR, NMR-MAS, and Raman spectroscopy. K E Y W O R D S calcium silicate hydrate, LDH type (phyllosilicate carbonate), metakaolin, Portland cement, SEM, transmission electron microscopy, X-ray diffraction | 4991 SÁNCHEZ Et al. How to cite this article: Sánchez I, Ramírez M, Casas Angulo M, et al. Characterization of LDH (phyllosilicate/carbonate) type compounds formed in the pozzolanic reaction of phyllosilicate-rich industrial waste. J Am Ceram Soc. 2019;102:4990-4998. https://

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“…3, but the heterogeneous mix of elements within the brick sample, combined with the range of angles between the elements in the presumably distorted tetrahedra and octahedra, precludes unequivocal identification of the vibrational bands associated with individual OH groups which contribute intensity to the spectral envelope. 28,29 The incoming water molecules will also hydrogen bond with any available structural hydroxyls at the surface and then with each other, leading to the generic OH stretching assignments at 3620, 3450, and 3260 cm À1 described above. For example, a peak at this position in an unfired clay is associated with a structural hydroxyl that resides in the octahedral sheet.…”

Section: Resultsmentioning

confidence: 99%

“…The pentavalent aluminum sites, identified using 27 Al MAS-NMR, arising in milled kaolin represent a pertinent example. 28,29 The incoming water molecules will also hydrogen bond with any available structural hydroxyls at the surface and then with each other, leading to the generic OH stretching assignments at 3620, 3450, and 3260 cm À1 described above. These band positions are not associated with a single, clearly defined hydrogen bond with a discrete energy, but represent the center of gravity of a broad range of hydrogen bonds that differ in strength (over a extended range) and O-O bond distances in this H-bonded water network.…”

Section: Resultsmentioning

confidence: 99%

Dehydroxylation and Rehydroxylation Mechanisms in Fired Clay Ceramic: A TG‐MS and DRIFTS Investigation

et al. 2011

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Selected instrumental techniques [dilatometry, thermogravimetry – mass spectrometry (TG‐MS), and variable temperature – diffuse reflectance infrared Fourier transform spectroscopy (VT‐DRIFTS)] have been used to investigate the role of moisture in the rehydroxylation reaction which causes expansion and mass gain in fired clay ceramics. The temperature range over which adsorbed water molecules and structural hydroxyl groups are desorbed from fired clay ceramic as it is reheated, and the nature of the structural hydroxyls that are formed as the ceramic is cooled and then held under controlled conditions have been explored. The mass chromatogram for m/z = 18, supported by VT‐DRIFTS, showed that physisorbed water molecules were removed from the ceramic at about 105°C, whereas strongly bound molecules of water and structural hydroxyls were held to ≤500°C. Dilatometry revealed a marked contraction of the ceramic between 200°C and 330°C which corresponded to loss of strongly bound molecules of water. The VT‐DRIFTS also showed that the interaction of water molecules with the ceramic body following reheating occurred in two stages and confirmed the kinetic law previously derived from mass gain and moisture expansion in fired clay ceramics.

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NMR and acidity studies of dealuminated metakaolin and their correlation with cumene cracking

Cited by 23 publications

References 12 publications

Preparation and Characterization of Dealuminated Metakaolin and Its Use in the Transformation of Waste Plastics to Aromatic Hydrocarbons

Preparation and Characterization of Dealuminated Metakaolin and Its Use in the Transformation of Waste Plastics to Aromatic Hydrocarbons

Characterization of LDH (phyllosilicate/carbonate) type compounds formed in the pozzolanic reaction of phyllosilicate‐rich industrial waste

Dehydroxylation and Rehydroxylation Mechanisms in Fired Clay Ceramic: A TG‐MS and DRIFTS Investigation

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