The reactions of formaldehyde over the surfaces of uranium oxides. A comparative study between polycrystalline and single crystal materials

S D Senanayake, S V Chong, Hicham Idriss

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The reaction of formaldehyde has been studied on the surfaces of UO2 (1 1 1) single crystal and polyerystalline UO2. Most of adsorbed formaldehyde on the single crystal at room temperature reacted to give ethylene during TPD. On the polycrystalline surface, IR analyses showed that the main species present in the 88-200 K temperature domain are poly- and dioxymethylene. These species are mainly converted to stable formates that decompose at high temperature (above 550 K). The apparent activation energy for the reaction of the oxymethylenic species to formates in the 250-450 K region (calculated from the intensity of the v(a) COO IR band of formates, at 1575 cm(-1)) is found equal to 12 kJ/mol. Overall, both surfaces (single crystal and polycrystalline) give qualitatively the same products, with the exception of formation of traces of methyl formate in the case of powder. However, the single crystal is far more active for the reductive coupling of formaldehyde to ethylene than the polycrystalline material. The difference in reaction selectivity between the single crystal and powder work is attributed to the method of preparation of the polycrystalline UO2 material (made by H-2-reduction of alpha-U3O8) rather than to an intrinsic difference between both materials. (C) 2003 Published by Elsevier B.V.

Original languageEnglish
Pages (from-to)311-320
Number of pages10
JournalCatalysis Today
Volume85
Issue number2-4
DOIs
Publication statusPublished - 15 Oct 2003

Keywords

  • polycrystalline UO2
  • H-2-reduction
  • stable formates
  • UO2(111) single crystals
  • formaldehyde-infrared
  • TEMPERATURE-PROGRAMMED DESORPTION
  • BENZENE FORMATION
  • ETHANOL REACTIONS
  • CARBOXYLIC-ACIDS
  • FT-IR
  • CATALYSTS
  • ADSORPTION
  • MECHANISM
  • OXIDATION
  • METHANOL

Cite this

The reactions of formaldehyde over the surfaces of uranium oxides. A comparative study between polycrystalline and single crystal materials. / Senanayake, S D ; Chong, S V ; Idriss, Hicham.

In: Catalysis Today, Vol. 85, No. 2-4, 15.10.2003, p. 311-320.

Research output: Contribution to journalArticle

@article{69e947a19a11410c94d41466f22543f4,
title = "The reactions of formaldehyde over the surfaces of uranium oxides. A comparative study between polycrystalline and single crystal materials",
abstract = "The reaction of formaldehyde has been studied on the surfaces of UO2 (1 1 1) single crystal and polyerystalline UO2. Most of adsorbed formaldehyde on the single crystal at room temperature reacted to give ethylene during TPD. On the polycrystalline surface, IR analyses showed that the main species present in the 88-200 K temperature domain are poly- and dioxymethylene. These species are mainly converted to stable formates that decompose at high temperature (above 550 K). The apparent activation energy for the reaction of the oxymethylenic species to formates in the 250-450 K region (calculated from the intensity of the v(a) COO IR band of formates, at 1575 cm(-1)) is found equal to 12 kJ/mol. Overall, both surfaces (single crystal and polycrystalline) give qualitatively the same products, with the exception of formation of traces of methyl formate in the case of powder. However, the single crystal is far more active for the reductive coupling of formaldehyde to ethylene than the polycrystalline material. The difference in reaction selectivity between the single crystal and powder work is attributed to the method of preparation of the polycrystalline UO2 material (made by H-2-reduction of alpha-U3O8) rather than to an intrinsic difference between both materials. (C) 2003 Published by Elsevier B.V.",
keywords = "polycrystalline UO2, H-2-reduction, stable formates, UO2(111) single crystals, formaldehyde-infrared, TEMPERATURE-PROGRAMMED DESORPTION, BENZENE FORMATION, ETHANOL REACTIONS, CARBOXYLIC-ACIDS, FT-IR, CATALYSTS, ADSORPTION, MECHANISM, OXIDATION, METHANOL",
author = "Senanayake, {S D} and Chong, {S V} and Hicham Idriss",
year = "2003",
month = "10",
day = "15",
doi = "10.1016/S0920-5861(03)00397-3",
language = "English",
volume = "85",
pages = "311--320",
journal = "Catalysis Today",
issn = "0920-5861",
publisher = "Elsevier",
number = "2-4",

}

TY - JOUR

T1 - The reactions of formaldehyde over the surfaces of uranium oxides. A comparative study between polycrystalline and single crystal materials

AU - Senanayake, S D

AU - Chong, S V

AU - Idriss, Hicham

PY - 2003/10/15

Y1 - 2003/10/15

N2 - The reaction of formaldehyde has been studied on the surfaces of UO2 (1 1 1) single crystal and polyerystalline UO2. Most of adsorbed formaldehyde on the single crystal at room temperature reacted to give ethylene during TPD. On the polycrystalline surface, IR analyses showed that the main species present in the 88-200 K temperature domain are poly- and dioxymethylene. These species are mainly converted to stable formates that decompose at high temperature (above 550 K). The apparent activation energy for the reaction of the oxymethylenic species to formates in the 250-450 K region (calculated from the intensity of the v(a) COO IR band of formates, at 1575 cm(-1)) is found equal to 12 kJ/mol. Overall, both surfaces (single crystal and polycrystalline) give qualitatively the same products, with the exception of formation of traces of methyl formate in the case of powder. However, the single crystal is far more active for the reductive coupling of formaldehyde to ethylene than the polycrystalline material. The difference in reaction selectivity between the single crystal and powder work is attributed to the method of preparation of the polycrystalline UO2 material (made by H-2-reduction of alpha-U3O8) rather than to an intrinsic difference between both materials. (C) 2003 Published by Elsevier B.V.

AB - The reaction of formaldehyde has been studied on the surfaces of UO2 (1 1 1) single crystal and polyerystalline UO2. Most of adsorbed formaldehyde on the single crystal at room temperature reacted to give ethylene during TPD. On the polycrystalline surface, IR analyses showed that the main species present in the 88-200 K temperature domain are poly- and dioxymethylene. These species are mainly converted to stable formates that decompose at high temperature (above 550 K). The apparent activation energy for the reaction of the oxymethylenic species to formates in the 250-450 K region (calculated from the intensity of the v(a) COO IR band of formates, at 1575 cm(-1)) is found equal to 12 kJ/mol. Overall, both surfaces (single crystal and polycrystalline) give qualitatively the same products, with the exception of formation of traces of methyl formate in the case of powder. However, the single crystal is far more active for the reductive coupling of formaldehyde to ethylene than the polycrystalline material. The difference in reaction selectivity between the single crystal and powder work is attributed to the method of preparation of the polycrystalline UO2 material (made by H-2-reduction of alpha-U3O8) rather than to an intrinsic difference between both materials. (C) 2003 Published by Elsevier B.V.

KW - polycrystalline UO2

KW - H-2-reduction

KW - stable formates

KW - UO2(111) single crystals

KW - formaldehyde-infrared

KW - TEMPERATURE-PROGRAMMED DESORPTION

KW - BENZENE FORMATION

KW - ETHANOL REACTIONS

KW - CARBOXYLIC-ACIDS

KW - FT-IR

KW - CATALYSTS

KW - ADSORPTION

KW - MECHANISM

KW - OXIDATION

KW - METHANOL

U2 - 10.1016/S0920-5861(03)00397-3

DO - 10.1016/S0920-5861(03)00397-3

M3 - Article

VL - 85

SP - 311

EP - 320

JO - Catalysis Today

JF - Catalysis Today

SN - 0920-5861

IS - 2-4

ER -