DRIFTS study of the chemical state of modifying gallium ions in reduced Ga/ZSM-5 prepared by impregnation I. Observation of gallium hydrides and application of CO adsorption as a molecular probe for reduced gallium ions

V.B. Kazansky, I.R. Subbotina, R.A. Santen, van, E.J.M. Hensen

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Abstract

Reduction in hydrogen at 773 K of gallium-modified HZSM-5 zeolite prepared by incipient wetness impregnation results in complete substitution of acidic hydroxyl groups. The modification of the zeolite with gallium suppresses dealumination of the hydrogen form due to substitution of protons by gallium species. When the reduction at 773 K is followed by evacuation, coordinatively unsaturated Ga+ ions are formed. These species can be reversibly oxidized by nitrous oxide at 673 K. Alternatively, these Ga+ ions adsorb molecular hydrogen at lower temperatures resulting in several types of hydride species. The latter species are completely decomposed only in vacuum at relatively high temperatures (773 K). We propose that the oxidation of gallium upon cooling of reduced samples to room temperature in hydrogen can be attributed to an oxidative addition of H2 resulting in the formation of gallium dihydrides.
Original languageEnglish
Pages (from-to)263-269
Number of pages7
JournalJournal of Catalysis
Volume227
Issue number2
DOIs
Publication statusPublished - 2004

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Molecular Probes
Gallium
Carbon Monoxide
Hydrides
Impregnation
hydrides
gallium
Ions
Hydrogen
Adsorption
adsorption
probes
Zeolites
hydrogen
ions
Substitution reactions
substitutes
dihydrides
nitrous oxides
Nitrous Oxide

Cite this

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title = "DRIFTS study of the chemical state of modifying gallium ions in reduced Ga/ZSM-5 prepared by impregnation I. Observation of gallium hydrides and application of CO adsorption as a molecular probe for reduced gallium ions",
abstract = "Reduction in hydrogen at 773 K of gallium-modified HZSM-5 zeolite prepared by incipient wetness impregnation results in complete substitution of acidic hydroxyl groups. The modification of the zeolite with gallium suppresses dealumination of the hydrogen form due to substitution of protons by gallium species. When the reduction at 773 K is followed by evacuation, coordinatively unsaturated Ga+ ions are formed. These species can be reversibly oxidized by nitrous oxide at 673 K. Alternatively, these Ga+ ions adsorb molecular hydrogen at lower temperatures resulting in several types of hydride species. The latter species are completely decomposed only in vacuum at relatively high temperatures (773 K). We propose that the oxidation of gallium upon cooling of reduced samples to room temperature in hydrogen can be attributed to an oxidative addition of H2 resulting in the formation of gallium dihydrides.",
author = "V.B. Kazansky and I.R. Subbotina and {Santen, van}, R.A. and E.J.M. Hensen",
year = "2004",
doi = "10.1016/j.jcat.2004.07.021",
language = "English",
volume = "227",
pages = "263--269",
journal = "Journal of Catalysis",
issn = "0021-9517",
publisher = "Academic Press Inc.",
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TY - JOUR

T1 - DRIFTS study of the chemical state of modifying gallium ions in reduced Ga/ZSM-5 prepared by impregnation I. Observation of gallium hydrides and application of CO adsorption as a molecular probe for reduced gallium ions

AU - Kazansky, V.B.

AU - Subbotina, I.R.

AU - Santen, van, R.A.

AU - Hensen, E.J.M.

PY - 2004

Y1 - 2004

N2 - Reduction in hydrogen at 773 K of gallium-modified HZSM-5 zeolite prepared by incipient wetness impregnation results in complete substitution of acidic hydroxyl groups. The modification of the zeolite with gallium suppresses dealumination of the hydrogen form due to substitution of protons by gallium species. When the reduction at 773 K is followed by evacuation, coordinatively unsaturated Ga+ ions are formed. These species can be reversibly oxidized by nitrous oxide at 673 K. Alternatively, these Ga+ ions adsorb molecular hydrogen at lower temperatures resulting in several types of hydride species. The latter species are completely decomposed only in vacuum at relatively high temperatures (773 K). We propose that the oxidation of gallium upon cooling of reduced samples to room temperature in hydrogen can be attributed to an oxidative addition of H2 resulting in the formation of gallium dihydrides.

AB - Reduction in hydrogen at 773 K of gallium-modified HZSM-5 zeolite prepared by incipient wetness impregnation results in complete substitution of acidic hydroxyl groups. The modification of the zeolite with gallium suppresses dealumination of the hydrogen form due to substitution of protons by gallium species. When the reduction at 773 K is followed by evacuation, coordinatively unsaturated Ga+ ions are formed. These species can be reversibly oxidized by nitrous oxide at 673 K. Alternatively, these Ga+ ions adsorb molecular hydrogen at lower temperatures resulting in several types of hydride species. The latter species are completely decomposed only in vacuum at relatively high temperatures (773 K). We propose that the oxidation of gallium upon cooling of reduced samples to room temperature in hydrogen can be attributed to an oxidative addition of H2 resulting in the formation of gallium dihydrides.

U2 - 10.1016/j.jcat.2004.07.021

DO - 10.1016/j.jcat.2004.07.021

M3 - Article

VL - 227

SP - 263

EP - 269

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 2

ER -