Raman Spectroscopy of the Kaolinite Hydroxyls at 77 K

1998 ◽  
Vol 52 (10) ◽  
pp. 1277-1282 ◽  
Author(s):  
Ursula Johansson ◽  
Ray L. Frost ◽  
Willis Forsling ◽  
J. Theo Kloprogge
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Low Temperature ◽  
Liquid Nitrogen Temperature ◽  
Hydroxyl Groups ◽  
Frequency Shifts ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Inner Surface ◽  
Raman Microprobe

Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the inner hydroxyl and the inner surface hydroxyl groups. The inner hydroxyl frequency is reduced, and the outer hydroxyl frequencies move to higher frequencies upon cooling to 77 K. The inner hydroxyl frequency shifts from 3620 cm−1 at 298 K to 3615 cm−1 at 77 K. The two in-phase inner surface hydroxyl frequencies move from 3684 and 3689 cm−1 at 298 K to 3690 and 3699 cm−1 at 77 K. The two out-of-phase vibrations shift from 3650 and 3668 cm−1 to 3656 and 3675 cm−1. The bandwidth of the inner hydroxyl frequency decreases from 3.7 to 2.1 cm−1 at 77 K. The bandwidth of the inner surface hydroxyl frequency ( v1) increases upon cooling from 17.4 to 19.2 cm−1. It is proposed that the increased resolution at low temperature enabled an additional inner surface hydroxyl frequency to be observed.

Kaolinite hydroxyls in dimethylsulphoxide-intercalated kaolinites at 77 K – a Raman spectroscopic study

Clay Minerals ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 443-454 ◽  
Author(s):  
R. L. Frost ◽  
J. Kristof ◽  
E. Horvath ◽  
J. T. Kloprogge
Keyword(s):  
Raman Spectroscopy ◽  
Spectroscopic Study ◽  
Dmso Molecule ◽  
Molecular Forms ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Raman Spectroscopic ◽  
Raman Spectroscopic Study ◽  
Surface Hydroxyl Groups ◽  
Inner Surface

AbstractKaolinite hydroxyls in dimethylsulphoxide-intercalated (DMSO-intercalated) kaolinites have been determined using Raman spectroscopy at 298 and 77 K. The inner surface hydroxyl frequencies at 3650, 3670, 3684 and 3693 cm-1 move to higher wavenumbers upon cooling to 77 K and are observed at 3659, 3676, 3692 and 3702 cm-1. The inner hydroxyl frequency is at 3620 cm-1 at 298 K and is at 3615 cm-1 at 77 K. Upon intercalation with DMSO, additional bands are found at 3660, 3536 and 3501 cm-1 for the low-defect kaolinite and at 3664, 3543 and 3509 cm-1 for the high-defect kaolinite at 298 K. The 3660 cm-1 band at 298 K is resolved into two bands at 3658 and 3663 cm-1 at 77 K for the low-defect kaolinite and these bands are assigned to the inner surface hydroxyl groups, hydrogen-bonded to the DMSO molecule. It is proposed that the DMSO molecule exists with two different orientations in the intercalate and these two molecular forms are differentiated by the OH-stretching bands of the inner surface hydroxyl groups. This band for the high-defect kaolinite is found at 3664 cm-1 at 298 K and resolves into two bands at 3664 and 3673 cm-1 at 77 K.

Kaolinite hydroxyls – a Raman microscopy study

Clay Minerals ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 471-484 ◽  
Author(s):  
R. L. Frost ◽  
S. J. van der Gaast
Keyword(s):  
Hydrogen Bonding ◽  
Domain Size ◽  
Microscopy Study ◽  
Raman Microscopy ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Inner Surface ◽  
Relationship Of ◽  
Spectral Intensities

AbstractRaman microscopy of the kaolinite polymorphs was used to study single crystals and bundles of aligned crystals of kaolinite. The spectra of the hydroxyl stretching region were both sample and orientation dependent. Kaolinites can be classified into two groups according to the ratio of the intensities of the 3685 and 3695 cm−1 bands. No relationship was found between the d-spacing and the crystal domain size measurement from the 001 reflection and the Raman spectral intensities indicating the Raman spectra are independent of d-spacing and crystallinity. However, a relationship of the crystallinity in the a-b direction and intensities of the 3685 and 3695 cm−1 bands indicate that the relative position of one layer to the other determines the position of the inner surface hydroxyl groups and the hydrogen bonding with the oxygen of the opposite layer. A new hypothesis based on symmetric and non-symmetric hydrogen bonding of the inner surface hydroxyl groups is proposed to explain the two inner surface hydroxyl bands centred at 3685 and 3695 cm−1. The bands at 3670 and 3650 cm−1 are described in terms of the out-of-phase vibrations of the in-phase vibrations at 3695 and 3685 cm−1.

Mg–Al hydrotalcite-supported Pd catalyst for low-temperature CO oxidation: effect of Pdn+ species and surface hydroxyl groups

2018 ◽  
Vol 47 (42) ◽  
pp. 14938-14944 ◽  
Author(s):  
Xingyi Lin ◽  
Jianke Zhou ◽  
Yanyu Fan ◽  
Yingying Zhan ◽  
Chongqi Chen ◽  
...  
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Hydroxyl Groups ◽  
Pd Catalyst ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Low Temperature Co Oxidation ◽  
Oxidation Effect ◽  
Supported Pd

HTlcs is demonstrated as an alternative support for Pd-based catalyst in low temperature CO oxidation due to its unique characteristics.

The synthesis and structure of silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complexes

1986 ◽  
Vol 51 (7) ◽  
pp. 1430-1438 ◽  
Author(s):  
Alena Reissová ◽  
Zdeněk Bastl ◽  
Martin Čapka
Keyword(s):  
Free Surface ◽  
Hydroxyl Groups ◽  
Titanium Complex ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Cyclopentadienyl Anion

The title complexes have been obtained by functionalization of silica with cyclopentadienylsilanes of the type Rx(CH3)3 - xSi(CH2)nC5H5 (x = 1-3, n = 0, 1, 3), trimethylsilylation of free surface hydroxyl groups, transformation of the bonded cyclopentadienyl group to the cyclopentadienyl anion, followed by coordination of (h5-cyclopentadienyl)trichlorotitanium. The effects of single steps of the above immobilization on texture of the support, the number of free hydroxyl groups, the coverage of the surface by cyclopentadienyl groups and the degree of their utilization in anchoring the titanium complex have been investigated. ESCA study has shown that the above anchoring leads to formation of the silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complex.

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