期刊
FARADAY DISCUSSIONS
卷 188, 期 -, 页码 115-129出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5fd00153f
关键词
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资金
- UK Catalysis Hub Consortium
- EPSRC [EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1, EP/I019693/1]
- Diamond Light Source
- Cardiff Catalysis Institute (CCI)
- EPSRC [EP/K005030/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/K014714/1, EP/K014706/1, EP/K005030/1, EP/K014854/1, EP/K014668/1, EP/I019693/1] Funding Source: researchfish
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 m(2) 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 similar to 35 m(2) 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 Fe-2(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 Fe-2(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 similar to 40 degrees C below that for the bulk Fe-2(MoO4)(3) phase. This work demonstrates how core-shell, multi-component oxides offer new routes for improving catalytic performance and understanding catalytic activity.
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