Synthesis and characterization of a (Zn, Ti)-substituted layered silicate

V LUCA, D J MACLACHLAN, Russell Francis Howe, R BRAMLEY

Research output: Contribution to journalArticle

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Abstract

The incorporation of Ti-IV into the framework of zinc-substituted fluorohectorite is reported. Various spectroscopic techniques point to the substitution of Ti-IV into predominantly the octahedral rather than tetrahedral sublattice of the smectite framework, For clay particles prepared from a reactant composition with Ti/Ti+Si=0.063 (ZTFH), energy-dispersive X-ray analysis of the particles observed by transmission electron microscopy indicates that Ti accounts for ca. 6% of the Ti+Si. X-Ray absorption near-edge spectra indicate that the Ti-IV in these clay particles is predominantly in an octahedral coordination. This is supported by electron paramagnetic resonance (EPR) spectra of an oriented film sample in which Ti-IV is reduced to Ti-III by heating the sample to 450 degrees C in 30 Torr of CO. The observed single-ion Ti-III EPR spectrum shows dramatic dependence of the orientation of the clay film in the magnetic field. This orientation dependence is consistent with the principal g-tensor axis of the Ti-III site being perpendicular to the clay layers. The EPR parameters of this Ti-III species are consistent with Ti-III occupying an octahedral site. Three-pulse electron spin-echo modulation data taken at the Ti-III EPR line position shows modulation at the Li-7 nuclear frequency and simulation indicates that Ti-III ions are at a distance of 0.30-0.35 nm from Li-I ions, a distance that is consistent with these two ions occupying adjacent sites in the octahedral sheet. The MAS NMR spectrum of the zinc/titanium-substituted fluorhectorite consists of an intense Q(3) resonance at -96.4 ppm and a weak shoulder at ca. -92.5 ppm. These two resonances are interpreted as due to variations in the octahedral sheet composition. Therefore Ti-IV appears to have a strong preference for occupation of the octahedral sites in the zinc-substituted fluorohectorite framework.

Original languageEnglish
Pages (from-to)557-564
Number of pages8
JournalJournal of Materials Chemistry
Volume5
Issue number4
DOIs
Publication statusPublished - Apr 1995

Keywords

  • spin echo envelope
  • titanium silicalite
  • NMR-spectroscopy
  • chemical-shifts
  • MAS-NMR
  • modulation
  • resonance
  • zeolites
  • XANES
  • EXAFS

Cite this

Synthesis and characterization of a (Zn, Ti)-substituted layered silicate. / LUCA, V ; MACLACHLAN, D J ; Howe, Russell Francis; BRAMLEY, R .

In: Journal of Materials Chemistry, Vol. 5, No. 4, 04.1995, p. 557-564.

Research output: Contribution to journalArticle

LUCA, V ; MACLACHLAN, D J ; Howe, Russell Francis ; BRAMLEY, R . / Synthesis and characterization of a (Zn, Ti)-substituted layered silicate. In: Journal of Materials Chemistry. 1995 ; Vol. 5, No. 4. pp. 557-564.
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abstract = "The incorporation of Ti-IV into the framework of zinc-substituted fluorohectorite is reported. Various spectroscopic techniques point to the substitution of Ti-IV into predominantly the octahedral rather than tetrahedral sublattice of the smectite framework, For clay particles prepared from a reactant composition with Ti/Ti+Si=0.063 (ZTFH), energy-dispersive X-ray analysis of the particles observed by transmission electron microscopy indicates that Ti accounts for ca. 6{\%} of the Ti+Si. X-Ray absorption near-edge spectra indicate that the Ti-IV in these clay particles is predominantly in an octahedral coordination. This is supported by electron paramagnetic resonance (EPR) spectra of an oriented film sample in which Ti-IV is reduced to Ti-III by heating the sample to 450 degrees C in 30 Torr of CO. The observed single-ion Ti-III EPR spectrum shows dramatic dependence of the orientation of the clay film in the magnetic field. This orientation dependence is consistent with the principal g-tensor axis of the Ti-III site being perpendicular to the clay layers. The EPR parameters of this Ti-III species are consistent with Ti-III occupying an octahedral site. Three-pulse electron spin-echo modulation data taken at the Ti-III EPR line position shows modulation at the Li-7 nuclear frequency and simulation indicates that Ti-III ions are at a distance of 0.30-0.35 nm from Li-I ions, a distance that is consistent with these two ions occupying adjacent sites in the octahedral sheet. The MAS NMR spectrum of the zinc/titanium-substituted fluorhectorite consists of an intense Q(3) resonance at -96.4 ppm and a weak shoulder at ca. -92.5 ppm. These two resonances are interpreted as due to variations in the octahedral sheet composition. Therefore Ti-IV appears to have a strong preference for occupation of the octahedral sites in the zinc-substituted fluorohectorite framework.",
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AU - LUCA, V

AU - MACLACHLAN, D J

AU - Howe, Russell Francis

AU - BRAMLEY, R

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N2 - The incorporation of Ti-IV into the framework of zinc-substituted fluorohectorite is reported. Various spectroscopic techniques point to the substitution of Ti-IV into predominantly the octahedral rather than tetrahedral sublattice of the smectite framework, For clay particles prepared from a reactant composition with Ti/Ti+Si=0.063 (ZTFH), energy-dispersive X-ray analysis of the particles observed by transmission electron microscopy indicates that Ti accounts for ca. 6% of the Ti+Si. X-Ray absorption near-edge spectra indicate that the Ti-IV in these clay particles is predominantly in an octahedral coordination. This is supported by electron paramagnetic resonance (EPR) spectra of an oriented film sample in which Ti-IV is reduced to Ti-III by heating the sample to 450 degrees C in 30 Torr of CO. The observed single-ion Ti-III EPR spectrum shows dramatic dependence of the orientation of the clay film in the magnetic field. This orientation dependence is consistent with the principal g-tensor axis of the Ti-III site being perpendicular to the clay layers. The EPR parameters of this Ti-III species are consistent with Ti-III occupying an octahedral site. Three-pulse electron spin-echo modulation data taken at the Ti-III EPR line position shows modulation at the Li-7 nuclear frequency and simulation indicates that Ti-III ions are at a distance of 0.30-0.35 nm from Li-I ions, a distance that is consistent with these two ions occupying adjacent sites in the octahedral sheet. The MAS NMR spectrum of the zinc/titanium-substituted fluorhectorite consists of an intense Q(3) resonance at -96.4 ppm and a weak shoulder at ca. -92.5 ppm. These two resonances are interpreted as due to variations in the octahedral sheet composition. Therefore Ti-IV appears to have a strong preference for occupation of the octahedral sites in the zinc-substituted fluorohectorite framework.

AB - The incorporation of Ti-IV into the framework of zinc-substituted fluorohectorite is reported. Various spectroscopic techniques point to the substitution of Ti-IV into predominantly the octahedral rather than tetrahedral sublattice of the smectite framework, For clay particles prepared from a reactant composition with Ti/Ti+Si=0.063 (ZTFH), energy-dispersive X-ray analysis of the particles observed by transmission electron microscopy indicates that Ti accounts for ca. 6% of the Ti+Si. X-Ray absorption near-edge spectra indicate that the Ti-IV in these clay particles is predominantly in an octahedral coordination. This is supported by electron paramagnetic resonance (EPR) spectra of an oriented film sample in which Ti-IV is reduced to Ti-III by heating the sample to 450 degrees C in 30 Torr of CO. The observed single-ion Ti-III EPR spectrum shows dramatic dependence of the orientation of the clay film in the magnetic field. This orientation dependence is consistent with the principal g-tensor axis of the Ti-III site being perpendicular to the clay layers. The EPR parameters of this Ti-III species are consistent with Ti-III occupying an octahedral site. Three-pulse electron spin-echo modulation data taken at the Ti-III EPR line position shows modulation at the Li-7 nuclear frequency and simulation indicates that Ti-III ions are at a distance of 0.30-0.35 nm from Li-I ions, a distance that is consistent with these two ions occupying adjacent sites in the octahedral sheet. The MAS NMR spectrum of the zinc/titanium-substituted fluorhectorite consists of an intense Q(3) resonance at -96.4 ppm and a weak shoulder at ca. -92.5 ppm. These two resonances are interpreted as due to variations in the octahedral sheet composition. Therefore Ti-IV appears to have a strong preference for occupation of the octahedral sites in the zinc-substituted fluorohectorite framework.

KW - spin echo envelope

KW - titanium silicalite

KW - NMR-spectroscopy

KW - chemical-shifts

KW - MAS-NMR

KW - modulation

KW - resonance

KW - zeolites

KW - XANES

KW - EXAFS

U2 - 10.1039/JM9950500557, Paper

DO - 10.1039/JM9950500557, Paper

M3 - Article

VL - 5

SP - 557

EP - 564

JO - Journal of Materials Chemistry

JF - Journal of Materials Chemistry

SN - 0959-9428

IS - 4

ER -