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Title: Characterization of V{sub 2}O{sub 5}-TiO{sub 2} catalysts prepared by milling by ESR and solid state {sup 1}H and {sup 51}V NMR

Abstract

The interaction between V{sub 2}O{sub 5} and TiO{sub 2} under milling in a ball mill (an alternative procedure of catalyst preparation) was characterized by {sup 1}H, {sup 51}V MAS, and {sup 51}V static (wide line) NMR spectroscopy supplemented by simulations of {sup 51}V NMR spectra. Additionally, ESR and magnetic susceptibility measurements were carried out for the characterization of the paramagnetic V{sup 4+} and V{sup 3+} sites. It has been shown that after milling, two different types of octahedrally coordinated vanadium (V{sup 5+}) species (V{sup 5+}(I) and V{sup 5+}(II)) strongly bonded to TiO{sub 2} are formed. At the same time, the appearance of V{sup 3+} ions and an increase of their concentration is observed during milling-calcination processes, along with the formation of at least three different types of paramagnetic V{sup 4+} species corresponding to (1) V{sup 4+} centers in O-deficient V{sub 2}O{sub 5{minus}x}; (2) VO{sup 2+} vanadyl species (V{sup 4+}(I)) with the vanadium centers in octahedral symmetry with axial distortion; (3) V{sup 4+}(II) species with vanadium centers also in octahedral symmetry, but with different bond lengths and strengths as compared to V{sup 4+}(I). Relative amounts of different V{sup 4+} and V{sup 5+} species depend on the milling time, the presence ofmore » H{sub 2}O in the system, and the subsequent calcination procedure (temperature and calcination time). Thus, V{sup 5+}(I) species formed predominantly during milling, whereas V{sup 5+}(II) species formed after thermal treatment. For the structural characterization of these species, complete sets of the quadrupole and chemical shielding tensor parameters, including relative tensor orientations, have been estimated. This allowed the conclusion that the octahedral environment of vanadium in V{sup 5+}(II) species is less distorted than in V{sup 5+}(I) and in both cases the distortion is less axial than in V{sub 2}O{sub 5}. Combined NMR, ESR, and magnetic susceptibility measurements indicate that all vanadium species (V{sup 3+}, V{sup 4+}, and V{sup 5+}) are isolated from each other on the TiO{sub 2} support.« less

Authors:
; ;  [1]; ; ;  [2]
  1. Boreskov Inst. of Catalysis, Novosibirsk (Russian Federation)
  2. Univ. Muenchen, Munich (Germany). Inst. for Physikalische Chemie
Publication Date:
OSTI Identifier:
691297
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 103; Journal Issue: 36; Other Information: PBD: 9 Sep 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CATALYSTS; VANADIUM OXIDES; TITANIUM OXIDES; ELECTRON SPIN RESONANCE; VANADIUM 51; NUCLEAR MAGNETIC RESONANCE; MILLING; HYDROGEN 1

Citation Formats

Lapina, O.B., Shubin, A.A., Nosov, A.V., Bosch, E., Spengler, J., and Knoezinger, H. Characterization of V{sub 2}O{sub 5}-TiO{sub 2} catalysts prepared by milling by ESR and solid state {sup 1}H and {sup 51}V NMR. United States: N. p., 1999. Web. doi:10.1021/jp991405c.
Lapina, O.B., Shubin, A.A., Nosov, A.V., Bosch, E., Spengler, J., & Knoezinger, H. Characterization of V{sub 2}O{sub 5}-TiO{sub 2} catalysts prepared by milling by ESR and solid state {sup 1}H and {sup 51}V NMR. United States. doi:10.1021/jp991405c.
Lapina, O.B., Shubin, A.A., Nosov, A.V., Bosch, E., Spengler, J., and Knoezinger, H. Thu . "Characterization of V{sub 2}O{sub 5}-TiO{sub 2} catalysts prepared by milling by ESR and solid state {sup 1}H and {sup 51}V NMR". United States. doi:10.1021/jp991405c.
@article{osti_691297,
title = {Characterization of V{sub 2}O{sub 5}-TiO{sub 2} catalysts prepared by milling by ESR and solid state {sup 1}H and {sup 51}V NMR},
author = {Lapina, O.B. and Shubin, A.A. and Nosov, A.V. and Bosch, E. and Spengler, J. and Knoezinger, H.},
abstractNote = {The interaction between V{sub 2}O{sub 5} and TiO{sub 2} under milling in a ball mill (an alternative procedure of catalyst preparation) was characterized by {sup 1}H, {sup 51}V MAS, and {sup 51}V static (wide line) NMR spectroscopy supplemented by simulations of {sup 51}V NMR spectra. Additionally, ESR and magnetic susceptibility measurements were carried out for the characterization of the paramagnetic V{sup 4+} and V{sup 3+} sites. It has been shown that after milling, two different types of octahedrally coordinated vanadium (V{sup 5+}) species (V{sup 5+}(I) and V{sup 5+}(II)) strongly bonded to TiO{sub 2} are formed. At the same time, the appearance of V{sup 3+} ions and an increase of their concentration is observed during milling-calcination processes, along with the formation of at least three different types of paramagnetic V{sup 4+} species corresponding to (1) V{sup 4+} centers in O-deficient V{sub 2}O{sub 5{minus}x}; (2) VO{sup 2+} vanadyl species (V{sup 4+}(I)) with the vanadium centers in octahedral symmetry with axial distortion; (3) V{sup 4+}(II) species with vanadium centers also in octahedral symmetry, but with different bond lengths and strengths as compared to V{sup 4+}(I). Relative amounts of different V{sup 4+} and V{sup 5+} species depend on the milling time, the presence of H{sub 2}O in the system, and the subsequent calcination procedure (temperature and calcination time). Thus, V{sup 5+}(I) species formed predominantly during milling, whereas V{sup 5+}(II) species formed after thermal treatment. For the structural characterization of these species, complete sets of the quadrupole and chemical shielding tensor parameters, including relative tensor orientations, have been estimated. This allowed the conclusion that the octahedral environment of vanadium in V{sup 5+}(II) species is less distorted than in V{sup 5+}(I) and in both cases the distortion is less axial than in V{sub 2}O{sub 5}. Combined NMR, ESR, and magnetic susceptibility measurements indicate that all vanadium species (V{sup 3+}, V{sup 4+}, and V{sup 5+}) are isolated from each other on the TiO{sub 2} support.},
doi = {10.1021/jp991405c},
journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
number = 36,
volume = 103,
place = {United States},
year = {1999},
month = {9}
}