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Rapid Microwave Assisted Sol-Gel Synthesis of CeO2 and CexSm1-xO2 Nanoparticle Catalysts for CO Oxidation

Polychronopoulou, K, Zedan, AF, Katsiotis, MS, Baker, Mark, AlKhoori, AA, AlQaradawi, SY, Hinder, Steven and AlHassan, S (2017) Rapid Microwave Assisted Sol-Gel Synthesis of CeO2 and CexSm1-xO2 Nanoparticle Catalysts for CO Oxidation Journal of Molecular Catalysis A: Chemical, 428. pp. 41-55.

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Abstract

CeO2 and CexSm1-xO2 nanoparticle mixed oxides have been synthesized by microwave assisted sol-gel (MW sol-gel) and conventional sol-gel (C sol-gel) synthesis carried out at 60oC (typical sol-gel) and 100oC (approaching the MW temperature). Different characterization techniques, namely, XRD, BET, Raman, SEM, FTIR, TEM, XPS, H2-TPR, CO2-TPD, and XPS have been employed to understand the process-structure-properties relationship of the catalysts. The CO oxidation performance has been determined both in the absence and in the presence of H2 in the feed gas stream. Microwave heating yields a more thermally stable precursor material, which preserves 75% of its mass up to 600oC, attributable to the different chemical nature of the precursor, compared to the typical sol-gel material with the same composition. Varying the synthesis method has no profound effect on the surface area of the materials, which is in the range 4-35m2/g. Conventional sol-gel synthesis performed at 60 and 100oC yields CeO2 particles with a crystallite size of 29 nm and 24 nm compared to 21-27 nm for MW sol-gel synthesis (at different power values). The MW sol-gel CexSm1-xO2 catalysts exhibit a smaller crystallite size (12-18 nm). The pure ceria nanoparticles were shown to have a stoichiometry of approximately CeO1.95. The presence of Ce3+ and Sm3+ in the mixed oxide particles facilitates the presence of oxygen vacant sites, confirmed by Raman. Oxygen mobile species have been traced using H2-TPR studies and a compressive lattice strain in the 0.45-1.9% range of the cubic CexSm1-xO2 lattice were found to be strongly correlated with the CO oxidation performance in the presence and absence of H2 in the oxidation feed stream. MW sol-gel synthesis led to more active CeO2 and Ce0.5Sm0.5O2 catalysts, demonstrated by T50 (temperature where 50% CO conversion is achieved), being reduced by 131 oC and 47 oC, respectively, compared to typical sol-gel catalysts. Conventional synthesis performed at 100oC leads to a CeO2 catalyst of initially higher activity at a certain temperature window (220-420oC), though with a slower increase of XCO with temperature compared to the MW one. MW sol-gel synthesized Ce0.8Sm0.2O2 exhibited a high performance (~90%) for CO oxidation over a period of more than 20 h in stream. In addition the effect of reaction temperature and contact time (W/F) on the activity of the CeO2-based materials for CO oxidation kinetics were investigated. The activation energy of the reaction was found to be in the 36-43 kJ/mole range depending on the catalyst composition.

Item Type: Article
Subjects : Mechanical Engineering Science
Divisions : Faculty of Engineering and Physical Sciences > Mechanical Engineering Sciences
Authors :
NameEmailORCID
Polychronopoulou, KUNSPECIFIEDUNSPECIFIED
Zedan, AFUNSPECIFIEDUNSPECIFIED
Katsiotis, MSUNSPECIFIEDUNSPECIFIED
Baker, MarkM.Baker@surrey.ac.ukUNSPECIFIED
AlKhoori, AAUNSPECIFIEDUNSPECIFIED
AlQaradawi, SYUNSPECIFIEDUNSPECIFIED
Hinder, StevenS.Hinder@surrey.ac.ukUNSPECIFIED
AlHassan, SUNSPECIFIEDUNSPECIFIED
Date : 31 March 2017
Identification Number : 10.1016/j.molcata.2016.11.039
Copyright Disclaimer : © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Uncontrolled Keywords : microwave; sol-gel; CeO2; CexSm1-xO2; Sm-doped ceria; CO oxidation; XPS; XRD; H2-TPR; Redox properties; kinetc studies
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 14 Dec 2016 18:29
Last Modified : 07 Jul 2017 11:34
URI: http://epubs.surrey.ac.uk/id/eprint/813116

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