Adsorbed species on Pd catalyst during nitrite hydrogenation approaching complete conversion

Yingnan Zhao, K.R. Nidadavolu, Leonardus Lefferts

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)

Abstract

Pd catalysts are well known for their ability to hydrogenate nitrite to form molecular nitrogen as well as ammonium. Removal of nitrite and nitrate form drinking water requires extreme high selectivity to molecular nitrogen. This work shows that selectivity to ammonium can suddenly rise when complete conversion of nitrite is achieved in semi-batch operation. Surprisingly, formation of ammonium is continuing after exhaustion of nitrite. These observations were confirmed for unsupported colloidal Pd particles stabilized with PVA, colloid Pd NPs supported on Al2O3, as well as conventional Pd/alumina catalysts prepared via impregnation. The amount of ammonium formed after exhaustion of nitrite was quite similar to the number of accessible Pd surface sites, indicating that N-containing species adsorbed on the Pd surface are responsible for the effect. ATR-IR experiments prove that the responsible adsorbed species is not IR active and we propose that the surface of the catalyst is importantly covered with rather unreactive atomic nitrogen. These N atoms are almost unreactive, and neither the formation of ammonium via hydrogenation, nor the formation of N2 via dimerization contribute significantly during steady-state operation.
Original languageEnglish
Pages (from-to)102-110
Number of pages9
JournalJournal of catalysis
Volume337
DOIs
Publication statusPublished - 23 Feb 2016

Fingerprint

nitrites
Nitrites
Ammonium Compounds
Hydrogenation
hydrogenation
Nitrogen
catalysts
Catalysts
exhaustion
Dimerization
nitrogen
Colloids
Impregnation
Potable water
Particles (particulate matter)
selectivity
Nitrates
Alumina
drinking
Aluminum Oxide

Keywords

  • IR-99488
  • METIS-315945

Cite this

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title = "Adsorbed species on Pd catalyst during nitrite hydrogenation approaching complete conversion",
abstract = "Pd catalysts are well known for their ability to hydrogenate nitrite to form molecular nitrogen as well as ammonium. Removal of nitrite and nitrate form drinking water requires extreme high selectivity to molecular nitrogen. This work shows that selectivity to ammonium can suddenly rise when complete conversion of nitrite is achieved in semi-batch operation. Surprisingly, formation of ammonium is continuing after exhaustion of nitrite. These observations were confirmed for unsupported colloidal Pd particles stabilized with PVA, colloid Pd NPs supported on Al2O3, as well as conventional Pd/alumina catalysts prepared via impregnation. The amount of ammonium formed after exhaustion of nitrite was quite similar to the number of accessible Pd surface sites, indicating that N-containing species adsorbed on the Pd surface are responsible for the effect. ATR-IR experiments prove that the responsible adsorbed species is not IR active and we propose that the surface of the catalyst is importantly covered with rather unreactive atomic nitrogen. These N atoms are almost unreactive, and neither the formation of ammonium via hydrogenation, nor the formation of N2 via dimerization contribute significantly during steady-state operation.",
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Adsorbed species on Pd catalyst during nitrite hydrogenation approaching complete conversion. / Zhao, Yingnan; Nidadavolu, K.R.; Lefferts, Leonardus.

In: Journal of catalysis, Vol. 337, 23.02.2016, p. 102-110.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Adsorbed species on Pd catalyst during nitrite hydrogenation approaching complete conversion

AU - Zhao, Yingnan

AU - Nidadavolu, K.R.

AU - Lefferts, Leonardus

PY - 2016/2/23

Y1 - 2016/2/23

N2 - Pd catalysts are well known for their ability to hydrogenate nitrite to form molecular nitrogen as well as ammonium. Removal of nitrite and nitrate form drinking water requires extreme high selectivity to molecular nitrogen. This work shows that selectivity to ammonium can suddenly rise when complete conversion of nitrite is achieved in semi-batch operation. Surprisingly, formation of ammonium is continuing after exhaustion of nitrite. These observations were confirmed for unsupported colloidal Pd particles stabilized with PVA, colloid Pd NPs supported on Al2O3, as well as conventional Pd/alumina catalysts prepared via impregnation. The amount of ammonium formed after exhaustion of nitrite was quite similar to the number of accessible Pd surface sites, indicating that N-containing species adsorbed on the Pd surface are responsible for the effect. ATR-IR experiments prove that the responsible adsorbed species is not IR active and we propose that the surface of the catalyst is importantly covered with rather unreactive atomic nitrogen. These N atoms are almost unreactive, and neither the formation of ammonium via hydrogenation, nor the formation of N2 via dimerization contribute significantly during steady-state operation.

AB - Pd catalysts are well known for their ability to hydrogenate nitrite to form molecular nitrogen as well as ammonium. Removal of nitrite and nitrate form drinking water requires extreme high selectivity to molecular nitrogen. This work shows that selectivity to ammonium can suddenly rise when complete conversion of nitrite is achieved in semi-batch operation. Surprisingly, formation of ammonium is continuing after exhaustion of nitrite. These observations were confirmed for unsupported colloidal Pd particles stabilized with PVA, colloid Pd NPs supported on Al2O3, as well as conventional Pd/alumina catalysts prepared via impregnation. The amount of ammonium formed after exhaustion of nitrite was quite similar to the number of accessible Pd surface sites, indicating that N-containing species adsorbed on the Pd surface are responsible for the effect. ATR-IR experiments prove that the responsible adsorbed species is not IR active and we propose that the surface of the catalyst is importantly covered with rather unreactive atomic nitrogen. These N atoms are almost unreactive, and neither the formation of ammonium via hydrogenation, nor the formation of N2 via dimerization contribute significantly during steady-state operation.

KW - IR-99488

KW - METIS-315945

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DO - 10.1016/j.jcat.2016.02.007

M3 - Article

VL - 337

SP - 102

EP - 110

JO - Journal of catalysis

JF - Journal of catalysis

SN - 0021-9517

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