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Selective oxidation of cyclohexane: Ce promotion of nanostructured manganese tungstate

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Title: Selective oxidation of cyclohexane: Ce promotion of nanostructured manganese tungstate
Authors: Graça, I
Al-Shihri, S
Chadwick, D
Item Type: Journal Article
Abstract: Cyclohexane selective oxidation over nanostructured MnWO4promoted with increasing amounts of Ce (1–5 wt%) has been investigated at mild conditions using molecular oxygen as oxidant. MnWO4nanorods were found to be an active catalyst for cyclohexane selective oxidation with selectivity to KA oil (cyclohexanol + cyclohexanone) of approximately 85%. The catalytic performance was improved by impregnation with 1 wt% Ce while the textural properties and crystallinity were preserved and Ce was well-dispersed on the surface. XPS analysis of 1%Ce-MnWO4showed Ce to be present mainly as Ce3+, which is known to promote oxygen adsorption, activation, and mobility. At higher Ce content, the proportion of Ce4+increased to be the main Ce species and large, heterogeneously-dispersed Ce oxide particles are formed on the catalyst surface. The lower Ce3+content reduces the promoting effect while the large Ce oxide particles block access to the active sites on the surface of the MnWO4nanorod. MnWO4and 1%Ce-MnWO4nanorods were shown to retain their selective oxidation performance in consecutive reaction runs. Surprisingly, physical mixtures of nanostructured MnWO4and a CeO2nanopowder showed enhanced selective oxidation activity compared to MnWO4alone reaching a plateau at 25–50 wt% CeO2, whereas CeO2nanopowder itself was found to be inactive at the reaction conditions. Ce promoted MnWO4shows promise as a catalyst for selective oxidation of cyclohexane and performs at least as well as the most active non-metallic heterogeneous catalysts reported in the literature.
Issue Date: 25-Nov-2018
Date of Acceptance: 26-Sep-2018
URI: http://hdl.handle.net/10044/1/63758
DOI: 10.1016/j.apcata.2018.09.025
ISSN: 0926-860X
Publisher: Elsevier
Start Page: 95
End Page: 104
Journal / Book Title: Applied Catalysis A: General
Volume: 568
Issue: 1
Copyright Statement: © 2018 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: King Abdulaziz City for Science and Technology (KA
Funder's Grant Number: DHRZEJ0
Keywords: Science & Technology
Physical Sciences
Life Sciences & Biomedicine
Chemistry, Physical
Environmental Sciences
Environmental Sciences & Ecology
Selective oxidation
KA oil
0306 Physical Chemistry (incl. Structural)
0904 Chemical Engineering
Physical Chemistry
Publication Status: Published
Online Publication Date: 2018-09-29
Appears in Collections:Chemical Engineering
Faculty of Engineering