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Title: Factors affecting CO oxidation over nanosized Fe{sub 2}O{sub 3}

Abstract

Nanocrystallite iron oxide powders with different crystallite sizes were prepared by co-precipitation route. The prepared powders with crystallite size 75, 100 and 150 nm together with commercial iron oxide (250 nm) were tested for the catalytic oxidation of CO to CO{sub 2}. The influence of different factors as crystallite size, catalytic temperature and weight of catalyst on the rate of catalytic reaction was investigated using advanced quadrupole mass gas analyzer system. It can be reported that the rate of conversion of CO to CO{sub 2} increased by increasing catalytic temperature and decreasing crystallite size of the prepared powders. The experimental results show that nanocrystallite iron oxide powders with crystallite size 75 nm can be recommended as a promising catalyst for CO oxidation at 500 deg. C where 98% of CO is converted to CO{sub 2}. The mechanism of the catalytic oxidation reaction was investigated by comparing the CO catalytic oxidation data in the absence and presence of oxygen. The reaction which was found to be first order with respect to CO is probably proceeded by adsorption mechanism where the reactants are adsorbed on the surface of the catalyst with breaking O-O bonds, then CO pick up the dissociated O atommore » forming CO{sub 2}.« less

Authors:
 [1];  [2];  [3];  [2]
  1. Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan, Cairo (Egypt). E-mail: khaledsaad@cmrdi.sci.eg
  2. Materials Chemistry Department, Faculty of Science, Beni Suef University (Egypt)
  3. Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan, Cairo (Egypt)
Publication Date:
OSTI Identifier:
21000623
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 42; Journal Issue: 4; Other Information: DOI: 10.1016/j.materresbull.2006.07.009; PII: S0025-5408(06)00296-0; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ADSORPTION; CARBON DIOXIDE; CARBON MONOXIDE; CATALYSTS; CHEMICAL PREPARATION; COPRECIPITATION; FERRITES; IRON OXIDES; MICROSTRUCTURE; NANOSTRUCTURES; OXIDATION; POWDERS; QUADRUPOLES

Citation Formats

Abdel Halim, K.S., Khedr, M.H., Nasr, M.I., and El-Mansy, A.M.. Factors affecting CO oxidation over nanosized Fe{sub 2}O{sub 3}. United States: N. p., 2007. Web. doi:10.1016/j.materresbull.2006.07.009.
Abdel Halim, K.S., Khedr, M.H., Nasr, M.I., & El-Mansy, A.M.. Factors affecting CO oxidation over nanosized Fe{sub 2}O{sub 3}. United States. doi:10.1016/j.materresbull.2006.07.009.
Abdel Halim, K.S., Khedr, M.H., Nasr, M.I., and El-Mansy, A.M.. Thu . "Factors affecting CO oxidation over nanosized Fe{sub 2}O{sub 3}". United States. doi:10.1016/j.materresbull.2006.07.009.
@article{osti_21000623,
title = {Factors affecting CO oxidation over nanosized Fe{sub 2}O{sub 3}},
author = {Abdel Halim, K.S. and Khedr, M.H. and Nasr, M.I. and El-Mansy, A.M.},
abstractNote = {Nanocrystallite iron oxide powders with different crystallite sizes were prepared by co-precipitation route. The prepared powders with crystallite size 75, 100 and 150 nm together with commercial iron oxide (250 nm) were tested for the catalytic oxidation of CO to CO{sub 2}. The influence of different factors as crystallite size, catalytic temperature and weight of catalyst on the rate of catalytic reaction was investigated using advanced quadrupole mass gas analyzer system. It can be reported that the rate of conversion of CO to CO{sub 2} increased by increasing catalytic temperature and decreasing crystallite size of the prepared powders. The experimental results show that nanocrystallite iron oxide powders with crystallite size 75 nm can be recommended as a promising catalyst for CO oxidation at 500 deg. C where 98% of CO is converted to CO{sub 2}. The mechanism of the catalytic oxidation reaction was investigated by comparing the CO catalytic oxidation data in the absence and presence of oxygen. The reaction which was found to be first order with respect to CO is probably proceeded by adsorption mechanism where the reactants are adsorbed on the surface of the catalyst with breaking O-O bonds, then CO pick up the dissociated O atom forming CO{sub 2}.},
doi = {10.1016/j.materresbull.2006.07.009},
journal = {Materials Research Bulletin},
number = 4,
volume = 42,
place = {United States},
year = {Thu Apr 12 00:00:00 EDT 2007},
month = {Thu Apr 12 00:00:00 EDT 2007}
}
  • Gold can be highly dispersed on a variety of metal oxides by coprecipitation and deposition-precipitation followed by calcination in air. The small gold particles are hemispherical in shape and stabilized by epitaxial contact, dislocations, or contact with an amorphous oxide layer. Such supported gold differs in catalytic nature from unsupported gold particles and exhibits high catalytic activities for low-temperature oxidation of CO. Especially, gold supported on TiO[sub 2], [alpha]-Fe[sub 2]O[sub 3], Co[sub 3]O[sub 4], NiO, Be(OH)[sub 2], and Mg(OH)[sub 2] is very active even at temperatures below 0[degrees]C. Among the gold catalysts supported on TiO[sub 2], [alpha]-Fe[sub 2]O[sub 3], andmore » Co[sub 3]O[sub 4] the turnover frequencies for CO oxidation per surface gold atom are almost independent of the kind of support oxides used and increase sharply with a decrease in diameter of gold particles below 4 nm. Small gold particles not only provide the sites for the reversible adsorption of CO but also appreciably increase the amount of oxygen adsorbed on the support oxides. In the temperature range -10 to 65[degrees]C, the activation energies for CO oxidation were 8.2 kcal/mol (Au/TiO[sub 2]), 8.4 kcal/mol (Au-[alpha]-Fe[sub 2]O[sub 3]), and 3.9 kcal/mol (Au/Co[sub 3]O[sub 4]). The rate of CO oxidation is zero order with respect to CO for the three catalysts, and 0.2-0.3 for Au/TiO[sub 2] and Au/Co[sub 3]O[sub 4] and zero order for Au/[alpha]-Fe[sub 2]O[sub 3] with respect to O[sub 2]. By taking into consideration TPD and FT-IR data, a mechanism is proposed in which CO adsorbed on gold particles migrates toward the perimeter on support oxides and there it reacts with adsorbed oxygen to form bidentate carbonate species. The decomposition of the carbonate intermediate is considered to be rate-determining. 57 refs., 13 figs., 1 tab.« less
  • The effects of nano-sized Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} addition on the superconducting and transport properties of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Bi-2223) in bulk form has been investigated. Bi-2223 superconductor was fabricated using co-precipitation method and 0.01 – 0.05 wt% of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles with average size of 20 nm were added into the samples. The critical temperature (T{sub c}) and critical current density (J{sub c}) of the samples were measured by using the four-point probe method, while the phase formation and microstructure of the samples were examined using x-ray diffraction and SEM respectively.more » It was found that J{sub c} of all samples added with Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} were higher than non-added sample, with x = 0.01 wt. % sample showing the highest J{sub c}. This study showed that small addition of nano-Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} can effectively enhance the transport critical current density in Bi-2223 superconductor.« less
  • To understand the effect of catalytic activity of Au/Fe{sub 2}O{sub 3} at low temperatures on a CO oxidation reaction, adsorption and changes in enthalpy were determined for the interaction of CO, O{sub 2}, or CO + O{sub 2} (2:1) pulses over Au (5 at.%)/Fe{sub 2}O{sub 3},FE{sub 2}O{sub 3}, and polycrystalline gold catalysts between 300 and 470 K. The results demonstrate that the oxidation of CO on both Fe{sub 2}O{sub 3} and Au/Fe{sub 2}O{sub 3} occur by means of similar redox mechanisms involving the removal and replenishment of lattice oxygen, where the presence of gold promotes these processes. The FTIR datamore » reveal that gold facilities the chemisorption of CO on Au/Fe{sub 2}O{sub 3}, leading predominantly to the formation of Au{sup 0}-CO species. The carbonate-like species, formed on both FE{sub 2}O{sub 3} and Au/Fe{sub 2}O{sub 3} during the adsorption of CO or CO + O{sub 2}, are stable below 375 K and are regarded to be mere by-products that do not play a major role in the CO oxidation process, particularly at low reaction temperatures ({gt}400 K). The larger gold particles inhibited the formation of CO{sub ad} species during exposure of Au/Fe{sub 2}O{sub 3} to CO + O{sub 2}; this was accompanied by a decrease in the adsorption of both CO and O{sub 2} and a decrease in the formation of CO{sub 2}. The promotional effect of gold is attributed to the presence of small (nanosize) Au crystallites that facilitate the chemisorption of CO molecules because of their inherent defective structural sites. It is suggested that the energy that evolves during the chemisorption of CO molecules is responsible for the surge in temperature at the Au-Fe{sub 2}O{sub 3} interfaces; these eventually serve as sites for the accelerated reaction between CO and the support.« less
  • Thermochemical and volumetric measurements were made for the adsorption and reaction of CO, O{sub 2}, and CO + O{sub 2} on catalysts from 300 to 470 K, as a function of H{sub 2} pretreatment. The transformation of Au/Fe{sub 2}O{sub 3} to Au/Fe{sub 3}O{sub 4} led to inhibited adsorption and oxidation of CO. The exposure of a reduced Au/Fe{sub 2}O{sub 3} to CO + O{sub 2} resulted in an O{sub 2(ad)}/CO{sub (ad)} ratio {gt} 1 as well as the reoxidation of the support and the progressive restoration of its catalytic activity. The reaction routes involved in the oxidation of CO overmore » polycrystalline gold were different from those over the Au/FE{sub 2}O{sub 3} catalyst. Thus, while the simultaneous adsorption of the reactant molecules was responsible for this reaction on Au metal, the redox mechanism involving the removal and subsequent replenishment of lattice oxygen played a role in both the Au/Fe{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} catalysts, where the presence of gold promoted these steps.« less