Magnetic and spectroscopic investigations on cobalt-alumina and cobalt-molybdenum-alumina. Electron spin resonance of the oxidized, sulfided, and reduced catalysts

M. Lo Jacono, J.L. Verbeek, G.C.A. Schuit

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Abstract

The ESR spectra of CoO-Al2O3, MoO3-Al2O3 and CoO-MoO3-Al2O3 were investigated in the oxidized state and after redn. with H2 + H2S (sometimes followed by a further treatment with H2) or by H2. All Co-contg. samples produce signals at 1200 Oe (for g-Al2O3) which shift to 1750 and 4300 Oe after treatment at 1300 Deg (formation of a-Al2O3). The signals are assigned to Co2+ in tetrahedral sites in the support; they are not affected by sulfiding or redn. If no Mo is present, redn. leads to the formation of an extremely broad and strong signal ascribed to Co metal; it is eliminated by the presence of Mo. In the absence of Co and in the oxidized state Mo-contg. samples develop a weak signal at g = 1.93, assigned to traces of Mo5+ in free MoO3; in the presence of Co this signal disappears. Pretreatment of Mo-contg. samples with H2 + H2S leads first to a hundredfold enhancement of the signal which, however, disappears after application of longer redn. times or higher temps. No signal connected with Mo3+ could be found. Finally, H2 after H2 + H2S treatments produced a signal at g = 2.16 if Co was present; it is assigned to either Co+ or Co2+ (low spin). A catalyst model is proposed containing 2 solid states. State I is the support with Co2+ and Mo6+ in its subsurface layers. Its fate after redn. is uncertain but Co2+ is not changed. State II is a separate system of compds. Co3O4, MoO3, or CoMoO4, depending on the compn. Treatments with H2 + H2S lead, resp., to Co + CoS, MoS2, or CoS + MoS2 (CoMo2S4).
Original languageEnglish
Pages (from-to)463-474
Number of pages12
JournalJournal of Catalysis
Volume29
Issue number3
DOIs
Publication statusPublished - 1973

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Molybdenum
Aluminum Oxide
Cobalt
molybdenum
Paramagnetic resonance
electron paramagnetic resonance
Alumina
cobalt
aluminum oxides
Lead
catalysts
Catalysts
Metals
molybdenum trioxide
pretreatment
solid state
augmentation
shift

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@article{3079b3bd982f4a8eb8bcc5f1563c3c16,
title = "Magnetic and spectroscopic investigations on cobalt-alumina and cobalt-molybdenum-alumina. Electron spin resonance of the oxidized, sulfided, and reduced catalysts",
abstract = "The ESR spectra of CoO-Al2O3, MoO3-Al2O3 and CoO-MoO3-Al2O3 were investigated in the oxidized state and after redn. with H2 + H2S (sometimes followed by a further treatment with H2) or by H2. All Co-contg. samples produce signals at 1200 Oe (for g-Al2O3) which shift to 1750 and 4300 Oe after treatment at 1300 Deg (formation of a-Al2O3). The signals are assigned to Co2+ in tetrahedral sites in the support; they are not affected by sulfiding or redn. If no Mo is present, redn. leads to the formation of an extremely broad and strong signal ascribed to Co metal; it is eliminated by the presence of Mo. In the absence of Co and in the oxidized state Mo-contg. samples develop a weak signal at g = 1.93, assigned to traces of Mo5+ in free MoO3; in the presence of Co this signal disappears. Pretreatment of Mo-contg. samples with H2 + H2S leads first to a hundredfold enhancement of the signal which, however, disappears after application of longer redn. times or higher temps. No signal connected with Mo3+ could be found. Finally, H2 after H2 + H2S treatments produced a signal at g = 2.16 if Co was present; it is assigned to either Co+ or Co2+ (low spin). A catalyst model is proposed containing 2 solid states. State I is the support with Co2+ and Mo6+ in its subsurface layers. Its fate after redn. is uncertain but Co2+ is not changed. State II is a separate system of compds. Co3O4, MoO3, or CoMoO4, depending on the compn. Treatments with H2 + H2S lead, resp., to Co + CoS, MoS2, or CoS + MoS2 (CoMo2S4).",
author = "{Lo Jacono}, M. and J.L. Verbeek and G.C.A. Schuit",
year = "1973",
doi = "10.1016/0021-9517(73)90253-4",
language = "English",
volume = "29",
pages = "463--474",
journal = "Journal of Catalysis",
issn = "0021-9517",
publisher = "Academic Press Inc.",
number = "3",

}

Magnetic and spectroscopic investigations on cobalt-alumina and cobalt-molybdenum-alumina. Electron spin resonance of the oxidized, sulfided, and reduced catalysts. / Lo Jacono, M.; Verbeek, J.L.; Schuit, G.C.A.

In: Journal of Catalysis, Vol. 29, No. 3, 1973, p. 463-474.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Magnetic and spectroscopic investigations on cobalt-alumina and cobalt-molybdenum-alumina. Electron spin resonance of the oxidized, sulfided, and reduced catalysts

AU - Lo Jacono, M.

AU - Verbeek, J.L.

AU - Schuit, G.C.A.

PY - 1973

Y1 - 1973

N2 - The ESR spectra of CoO-Al2O3, MoO3-Al2O3 and CoO-MoO3-Al2O3 were investigated in the oxidized state and after redn. with H2 + H2S (sometimes followed by a further treatment with H2) or by H2. All Co-contg. samples produce signals at 1200 Oe (for g-Al2O3) which shift to 1750 and 4300 Oe after treatment at 1300 Deg (formation of a-Al2O3). The signals are assigned to Co2+ in tetrahedral sites in the support; they are not affected by sulfiding or redn. If no Mo is present, redn. leads to the formation of an extremely broad and strong signal ascribed to Co metal; it is eliminated by the presence of Mo. In the absence of Co and in the oxidized state Mo-contg. samples develop a weak signal at g = 1.93, assigned to traces of Mo5+ in free MoO3; in the presence of Co this signal disappears. Pretreatment of Mo-contg. samples with H2 + H2S leads first to a hundredfold enhancement of the signal which, however, disappears after application of longer redn. times or higher temps. No signal connected with Mo3+ could be found. Finally, H2 after H2 + H2S treatments produced a signal at g = 2.16 if Co was present; it is assigned to either Co+ or Co2+ (low spin). A catalyst model is proposed containing 2 solid states. State I is the support with Co2+ and Mo6+ in its subsurface layers. Its fate after redn. is uncertain but Co2+ is not changed. State II is a separate system of compds. Co3O4, MoO3, or CoMoO4, depending on the compn. Treatments with H2 + H2S lead, resp., to Co + CoS, MoS2, or CoS + MoS2 (CoMo2S4).

AB - The ESR spectra of CoO-Al2O3, MoO3-Al2O3 and CoO-MoO3-Al2O3 were investigated in the oxidized state and after redn. with H2 + H2S (sometimes followed by a further treatment with H2) or by H2. All Co-contg. samples produce signals at 1200 Oe (for g-Al2O3) which shift to 1750 and 4300 Oe after treatment at 1300 Deg (formation of a-Al2O3). The signals are assigned to Co2+ in tetrahedral sites in the support; they are not affected by sulfiding or redn. If no Mo is present, redn. leads to the formation of an extremely broad and strong signal ascribed to Co metal; it is eliminated by the presence of Mo. In the absence of Co and in the oxidized state Mo-contg. samples develop a weak signal at g = 1.93, assigned to traces of Mo5+ in free MoO3; in the presence of Co this signal disappears. Pretreatment of Mo-contg. samples with H2 + H2S leads first to a hundredfold enhancement of the signal which, however, disappears after application of longer redn. times or higher temps. No signal connected with Mo3+ could be found. Finally, H2 after H2 + H2S treatments produced a signal at g = 2.16 if Co was present; it is assigned to either Co+ or Co2+ (low spin). A catalyst model is proposed containing 2 solid states. State I is the support with Co2+ and Mo6+ in its subsurface layers. Its fate after redn. is uncertain but Co2+ is not changed. State II is a separate system of compds. Co3O4, MoO3, or CoMoO4, depending on the compn. Treatments with H2 + H2S lead, resp., to Co + CoS, MoS2, or CoS + MoS2 (CoMo2S4).

U2 - 10.1016/0021-9517(73)90253-4

DO - 10.1016/0021-9517(73)90253-4

M3 - Article

VL - 29

SP - 463

EP - 474

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 3

ER -