Chapman, S., Brookes, C., Bowker, M., Gibson, E. K. and Wells, P. P. (2016) Design and stabilisation of a high area iron molybdate surface for the selective oxidation of methanol to formaldehyde. Faraday Discussions, 188, pp. 115-129. (doi: 10.1039/C5FD00153F) (PMID:27067956)
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Abstract
The performance of Mo-enriched, bulk ferric molybdate, employed commercially for the industrially important reaction of the selective oxidation of methanol to formaldehyde, is limited by a low surface area, typically 5–8 m2 g−1. Recent advances in the understanding of the iron molybdate catalyst have focused on the study of MoOx@Fe2O3 (MoOx shell, Fe2O3 core) systems, where only a few overlayers of Mo are present on the surface. This method of preparing MoOx@Fe2O3 catalysts was shown to support an iron molybdate surface of higher surface area than the industrially-favoured bulk phase. In this research, a MoOx@Fe2O3 catalyst of even higher surface area was stabilised by modifying a haematite support containing 5 wt% Al dopant. The addition of Al was an important factor for stabilising the haematite surface area and resulted in an iron molybdate surface area of ∼35 m2 g−1, around a 5 fold increase on the bulk catalyst. XPS confirmed Mo surface-enrichment, whilst Mo XANES resolved an amorphous MoOx surface monolayer supported on a sublayer of Fe2(MoO4)3 that became increasingly extensive with initial Mo surface loading. The high surface area MoOx@Fe2O3 catalyst proved amenable to bulk characterisation techniques; contributions from Fe2(MoO4)3 were detectable by Raman, XAFS, ATR-IR and XRD spectroscopies. The temperature-programmed pulsed flow reaction of methanol showed that this novel, high surface area catalyst (3ML-HSA) outperformed the undoped analogue (3ML-ISA), and a peak yield of 94% formaldehyde was obtained at ∼40 °C below that for the bulk Fe2(MoO4)3 phase. This work demonstrates how core–shell, multi-component oxides offer new routes for improving catalytic performance and understanding catalytic activity.
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Gibson, Dr Emma |
Authors: | Chapman, S., Brookes, C., Bowker, M., Gibson, E. K., and Wells, P. P. |
College/School: | College of Science and Engineering > School of Chemistry |
Journal Name: | Faraday Discussions |
Publisher: | Royal Society of Chemistry |
ISSN: | 1359-6640 |
ISSN (Online): | 1364-5498 |
Published Online: | 08 December 2015 |
Copyright Holders: | Copyright © 2016 The Authors |
First Published: | First published in Faraday Discussions 188:115-129 |
Publisher Policy: | Reproduced under a Creative Commons License |
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