Reaction-induced transformations in Pt-Sn/SiO2 catalysts

In situ 119Sn Mössbauer study

K. Lázár, W. D. Rhodes, I. Borbáth, M. Hegedűs, J. L. Margitfalvi

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Reaction-induced separation of tin-rich surface layers and tin-depleted inner region was observed in metallic particles of Pt-Sn/SiO2 catalysts in two reactions: (i) dechlorination of 1,2-dichloroethane at 473 K (modeling catalytic removal of chlorine from hazardous chlorocarbons) and (ii) oxidation of carbon monoxide at room temperature. In the former, a Pt: Sn catalyst (1:2 atomic ratio, 1 wt% metal content), prepared via co-impregnation, showed high selectivity (>80%) toward ethylene (at the expense of ethane), but only after a prolonged (ca. 24 h) period. In situ Mössbauer studies revealed stabilization of a homogeneous Pt-Sn alloy and SnCl2 after activation in hydrogen; whereas tin-depleted and tin-rich components were separated after a 24-h period. Hence, inhibition of the hydrogenation activity of Pt, by surface tin enrichment and Cl deposition favors high ethylene selectivity. For the oxidation of CO at room temperature, a catalyst with a Pt: Sn atomic ratio of 3:2 (3 wt% Pt) was prepared by an organometallic (CSR) method using 119Sn(CH3)4. Platinum-rich PtSn(1) and tin-rich PtSn(2) components were separated in the Mössbauer spectra of catalyst activated at 570 K. The PtSn(2) component is primarily involved in surface reactions. Both in CO oxidation and the subsequent re-activation in hydrogen at room temperature a reversible PtSn(2) ↔ Sn4+ interconversion occurred. d 1n(A77/A300)/dT data indicate the surface location of the involved components.

Original languageEnglish
Pages (from-to)87-96
Number of pages10
JournalHyperfine Interactions
Volume139-140
Issue number1-4
DOIs
Publication statusPublished - 2002

Fingerprint

Tin
tin
catalysts
Catalysts
Carbon Monoxide
Oxidation
oxidation
Hydrogen
Ethylene
room temperature
ethylene
chlorocarbons
selectivity
Chemical activation
activation
Dechlorination
Ethane
Chlorine
Surface reactions
Organometallics

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials
  • Nuclear and High Energy Physics

Cite this

Reaction-induced transformations in Pt-Sn/SiO2 catalysts : In situ 119Sn Mössbauer study. / Lázár, K.; Rhodes, W. D.; Borbáth, I.; Hegedűs, M.; Margitfalvi, J. L.

In: Hyperfine Interactions, Vol. 139-140, No. 1-4, 2002, p. 87-96.

Research output: Contribution to journalArticle

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N2 - Reaction-induced separation of tin-rich surface layers and tin-depleted inner region was observed in metallic particles of Pt-Sn/SiO2 catalysts in two reactions: (i) dechlorination of 1,2-dichloroethane at 473 K (modeling catalytic removal of chlorine from hazardous chlorocarbons) and (ii) oxidation of carbon monoxide at room temperature. In the former, a Pt: Sn catalyst (1:2 atomic ratio, 1 wt% metal content), prepared via co-impregnation, showed high selectivity (>80%) toward ethylene (at the expense of ethane), but only after a prolonged (ca. 24 h) period. In situ Mössbauer studies revealed stabilization of a homogeneous Pt-Sn alloy and SnCl2 after activation in hydrogen; whereas tin-depleted and tin-rich components were separated after a 24-h period. Hence, inhibition of the hydrogenation activity of Pt, by surface tin enrichment and Cl deposition favors high ethylene selectivity. For the oxidation of CO at room temperature, a catalyst with a Pt: Sn atomic ratio of 3:2 (3 wt% Pt) was prepared by an organometallic (CSR) method using 119Sn(CH3)4. Platinum-rich PtSn(1) and tin-rich PtSn(2) components were separated in the Mössbauer spectra of catalyst activated at 570 K. The PtSn(2) component is primarily involved in surface reactions. Both in CO oxidation and the subsequent re-activation in hydrogen at room temperature a reversible PtSn(2) ↔ Sn4+ interconversion occurred. d 1n(A77/A300)/dT data indicate the surface location of the involved components.

AB - Reaction-induced separation of tin-rich surface layers and tin-depleted inner region was observed in metallic particles of Pt-Sn/SiO2 catalysts in two reactions: (i) dechlorination of 1,2-dichloroethane at 473 K (modeling catalytic removal of chlorine from hazardous chlorocarbons) and (ii) oxidation of carbon monoxide at room temperature. In the former, a Pt: Sn catalyst (1:2 atomic ratio, 1 wt% metal content), prepared via co-impregnation, showed high selectivity (>80%) toward ethylene (at the expense of ethane), but only after a prolonged (ca. 24 h) period. In situ Mössbauer studies revealed stabilization of a homogeneous Pt-Sn alloy and SnCl2 after activation in hydrogen; whereas tin-depleted and tin-rich components were separated after a 24-h period. Hence, inhibition of the hydrogenation activity of Pt, by surface tin enrichment and Cl deposition favors high ethylene selectivity. For the oxidation of CO at room temperature, a catalyst with a Pt: Sn atomic ratio of 3:2 (3 wt% Pt) was prepared by an organometallic (CSR) method using 119Sn(CH3)4. Platinum-rich PtSn(1) and tin-rich PtSn(2) components were separated in the Mössbauer spectra of catalyst activated at 570 K. The PtSn(2) component is primarily involved in surface reactions. Both in CO oxidation and the subsequent re-activation in hydrogen at room temperature a reversible PtSn(2) ↔ Sn4+ interconversion occurred. d 1n(A77/A300)/dT data indicate the surface location of the involved components.

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