Scott M. Rogers

In situ spectroscopic investigations of MoOx/Fe2O3 catalysts for the selective oxidation of methanol

Multicomponent oxide shell@core catalysts have been prepared, affording overlayers of MoOx on Fe2O3. This design approach allows bulk characterization techniques, such as X-ray Absorption Fine Structure (XAFS), to provide surface sensitive information. Coupling this approach with in situ methodologies provides insights during crucial catalytic processes. Calcination studies were followed by a combination of XAFS and Raman, and demonstrate that amorphous multi-layers of MoOx are first converted to MoO3 before formation of Fe2(MoO4)3. However, a single overlayer of Oh Mo units remains at the surface at all times. In situ catalysis studies during formaldehyde production identified that Mo6+ was present throughout, confirming that gas phase oxygen transfer to molybdenum is rapid under reaction conditions. Reduction studies in the presence of MeOH resulted in the formation of reduced Mo–Mo clusters with a bonding distance of 2.6 A. It is proposed that the presence of the clusters indicates that the selective conversion of MeOH to formaldehyde requires multiple Mo sites.

The challenges of characterising nanoparticulate catalysts: general discussion

Rosa Arrigo, Kassim Badmus, Francesca Baletto, Maurits Boeije, Michael Bowker, Katharina Brinkert, Aram Bugaev, Valerii Bukhtiyarov, Michele Carosso, Richard Catlow, Revana Chanerika, Philip R. Davies, Wilke Dononelli, Hans-Joachim Freund, Cynthia Friend, Simone Gallarati, Bruce Gates, Alexander Genest, Emma K. Gibson, Justin Hargreaves, Stig Helveg, Haoliang Huang, Graham Hutchings, Nicola Irvine, Roy Johnston, Stanley Lai, Carlo Lamberti, Joseph Macginley, David Marchant, Toru Murayama, Rene Nome, Yaroslav Odarchenko, Jonathan Quinson, Scott Rogers, Andrea Russell, Said Said, Paul Sermon, Parag Shah, Sabrina Simoncelli, Katerina Soulantica, Federico Spolaore, Bob Tooze, Laura Torrente-Murciano, Annette Trunschke, David Willock and Jiaguang Zhang

Unraveling the H2 Promotional Effect on Palladium-Catalyzed CO Oxidation Using a Combination of Temporally and Spatially Resolved Investigations

The promotional effect of H2 on the oxidation of CO is of topical interest, and there is debate over whether this promotion is due to either thermal or chemical effects. As yet there is no definitive consensus in the literature. Combining spatially resolved mass spectrometry and X-ray absorption spectroscopy (XAS), we observe a specific environment of the active catalyst during CO oxidation, having the same specific local coordination of the Pd in both the absence and presence of H2. In combination with Temporal Analysis of Products (TAP), performed under isothermal conditions, a mechanistic insight into the promotional effect of H2 was found, providing clear evidence of nonthermal effects in the hydrogen-promoted oxidation of carbon monoxide. We have identified that H2 promotes the Langmuir–Hinshelwood mechanism, and we propose this is linked to the increased interaction of O with the Pd surface in the presence of H2. This combination of spatially resolved MS and XAS and TAP studies has provided previously unobserved insights into the nature of this promotional effect.