DOI: 10.1595/147106709X474307 The Taylor Conference 2009 CONVERGENCE BETWEEN RESEARCH AND INNOVATION IN

Reviewed by S. E. Golunski§ and A. P. E. York*‡ Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; and ‡Department of Chemical Engineering and Biotechnology, , New Museums Site, Pembroke Street, Cambridge CB2 3RA, U.K.; *E-mail: [email protected]

The Taylor Conferences are organised by the Professor Gabor Somorjai (University of Surface Reactivity and Catalysis (SURCAT) Group California, Berkeley, U.S.A.) developed the theme of the Royal Society of in the U.K. (1). that progress in catalysis is stimulated by revolu- The series began in 1996, to provide a forum for tionary changes in thinking. He predicted that, discussion of the current issues in heterogeneous whereas in previous eras new catalysts were identi- catalysis and, equally importantly, to promote fied through an Edisonian approach (based on trial interest in this field among recent graduates. The and error) or discovered on the basis of empirical fourth in the series was held at understanding, future catalyst design will be based in the U.K. from 22nd to 25th June 2009, attract- on the principles of nanoscience. He highlighted his ing 120 delegates, mainly from U.K. academic idea of ‘hot electrons’ that are ejected from a metal centres specialising in catalysis. Abstracts of all lec- by the heat of reaction produced at active sites, but tures given at the conference are available on the which could become a potential energy source if conference website (2). The first half of the confer- they were generated by the absorption of light. ence consisted of presentations by established As described by Professor researchers from the U.K., Japan and the U.S.A., (University College London, U.K.) and Stephen with each presentation afforded ample time for Jenkins (University of Cambridge, U.K.), quantum debate and discussion. The format of the second mechanical techniques for modelling many- half was similar, but with a key difference: the pre- electron systems lend themselves to the study of senters were some of the postgraduate students catalytic materials and catalytic reaction pathways. and postdoctoral researchers who, it is hoped, will Professor Catlow’s particular expertise lies in the become the future generation of catalysis experts. study of defective metal oxides, and the way in which they interact with metal particles. In the case Concepts, Theories and Methodology of palladium deposited on ceria, his models predict Professor Sir Hugh Taylor, after whom the an increase in the concentration of Ce3+ species Taylor conferences are named, was a pioneer in resulting from electron transfer from the metal to the study of chemisorption and catalysis on metals the metal oxide. Jenkins has been examining the and metal oxides (3). As Professor Frank Stone likelihood of specific reaction steps taking place on (Emeritus Professor of Chemistry, University of the surface of supported metal catalysts. For both Bath, U.K.) reminded us in his opening address, alkane synthesis and combustion, his calculations H. S. Taylor (as he was known in his time) was implicate a common formyl intermediate, which is responsible for introducing the concepts of acti- not readily detected by spectroscopic techniques. vated adsorption and of the active site, both of However, Professor Charles Campbell (University which were highly controversial when he first of Washington, U.S.A.) cautioned against an over- proposed them around 1930 (4), but which have reliance on surface modelling. Based on classical become fundamental to our understanding of microcalorimetric measurements, he has shown many catalytic phenomena. that density functional theory (DFT) underpredicts

§Present address: Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, U.K.

Platinum Metals Rev., 2009, 53, (4), 221–225 221 the heat of adsorption for a variety of molecules Mellon University, U.S.A.) separately described (for example, carbon monoxide, cyclohexene and the complex dependence of enantioselective reac- aromatics) on a range of surfaces (such as carbon, tions on surface composition and structure. precious metals or metal oxides). As explained by Professor James Anderson (University of Aberdeen, U.K.), in the context of Taking a View alkyne hydrogenation, poor selectivity is often the Professor (University of result of heterogeneity in the exposed sites, even Cambridge) described how macroscopic and on apparently clean and compositionally homoge- microscopic events can be tracked in an optically neous surfaces. Through targeted use of additives, opaque system, such as a catalytic reactor. Using such as bismuth in the case of palladium-based magnetic resonance imaging (MRI) – essentially the hydrogenation catalysts, specific non-selective same technique as used diagnostically in medicine – sites can be deliberately blocked. she has been able to observe the liquid flow fields During the direct synthesis of hydrogen perox- that develop in packed bed reactors. By combining ide from hydrogen and oxygen, the combustion of the images with measurements from temperature hydrogen and the over-hydrogenation of hydrogen sensors, detailed reaction profiles can be produced peroxide to water need to be suppressed. for steady-state and dynamic operating conditions. Professor Graham Hutchings (Cardiff University, On a different scale, Professor Chris Kiely U.K.) has shown that gold-palladium catalysts are (Lehigh University, U.S.A.) has used dark-field among the most effective, but their performance imaging techniques to detect the smallest metallic, can be sensitive to the support material used. In bimetallic and metal oxide particles (less than 1 nm collaboration with Professor Kiely, he has found in diameter) by electron microscopy. In what may that the nature of the dispersed gold-palladium can become a seminal study, he has correlated the high vary, with core-shell particles (on titania and

CO-oxidation activity of a specific gold/iron oxide alumina) producing lower yields of H2O2 than

(Au/Fe2O3) catalyst with the presence of two- palladium-rich alloy particles (on carbon). Both layer, 0.5 nm-diameter gold clusters. types of core-shell particle, those with a gold core The importance of studying catalysis over a and palladium shell and those with a palladium core range of scales was emphasised by Professor and gold shell, were less active than the palladium- Trevor Rayment (Diamond Light Source Ltd, gold alloy. U.K.). The new U.K. synchrotron light source is Professor Masatake Haruta (Tokyo Metropoli- intended to provide understanding of ‘real tan University, Japan) has found that small gold catalysts, under real conditions, in real time’ (5). clusters can selectively catalyse some particularly One of the ambitions is to increase the through- challenging reactions. The outstanding example is put for techniques such as X-ray absorption the selective insertion of oxygen into propylene to spectroscopy, by reducing the amount of non- form propylene oxide, which is currently produced productive beam time. Although the Diamond by indirect processes that produce large quantities facilities are not expected to provide the tools for of waste byproducts. By reactively grinding a non- catalyst discovery, it is hoped that they can accel- chloride Au(III) precursor with titanium silicalite erate the development process by identifying the (TS-1), Professor Haruta has dispersed the gold as critical relationships between catalyst structure 1.6 nm particles, which can activate propylene to and performance. react with O–O–H species formed from oxygen and water at the metal-support interface. Controlling Selectivity Stressing a point made by Professor Somorjai Promoting and Maintaining Activity that catalysis in the 21st century is all about selec- Vanadia supported on θ-alumina is one of the tivity, Chris Baddeley (University of St Andrews, best catalysts for butane dehydrogenation, but the U.K.) and Professor Andrew Gellman (Carnegie rate of reaction is very sensitive to the vanadia

Platinum Metals Rev., 2009, 53, (4) 222 loading. Professor David Jackson (University of air quality led to the development of technology Glasgow, U.K.) reported that maximum activity for catalytic aftertreatment using pgm catalysts (7). coincides with the presence of a mainly polymeric This highly effective technology does not, howev- form of vanadate species which covers most of the er, address the global problem of greenhouse gas alumina surface. However, another key perfor- emissions, which is now the prime motivator for mance criterion is durability. During butane the introduction of fuel cells. dehydrogenation, two forms of deactivation can Appropriately, there was an environmental be discerned: a short-term but reversible effect theme running through many of the presentations caused by deposition of carbon-rich species on in this section of the conference. For example, CO the catalyst surface, and a longer-term effect asso- oxidation was covered by Sankaranarayanan ciated with an irreversible phase change in the Nagarajan (National Chemical Laboratory, Pune, alumina. India), who looked at oxygen mobility and the role In the Francois Gault Lecture, Professor of subsurface oxygen on palladium surfaces (8, 9), Robbie Burch (Queen’s University Belfast, U.K.) Figure 1. The subject was also covered by Kevin explained the challenges faced in developing and Morgan (Queen’s University Belfast), who present- studying catalyst technology for removing nitro- ed a temporal analysis of products (TAP) study gen oxides (NOx) from diesel exhaust. Focusing showing that the addition of gold to CuMnOx on the use of silver for NOx reduction by direct results in the availability of more surface oxygen reaction with some of the diesel fuel, he showed and promotion of the Mars-van Krevelen oxygen that its performance can be dramatically improved transfer mechanism. by the addition of hydrogen. As described in a A number of researchers from Cardiff presentation by Stan Golunski (Johnson Matthey University presented work on selective oxidation Technology Centre, Sonning Common, U.K.) the reactions. For example, Jonathan Counsell has been hydrogen can be generated in situ through a studying the effect of adding gold to a supported process of exhaust gas reforming using a rhodium palladium acetoxylation catalyst. He has found catalyst. Professor Burch explained how X-ray that the gold suppresses carbon formation on the absorption fine structure (EXAFS) studies of palladium surface by preventing dehydrogenation. silver have been used to refute one of the pro- Kara Howard described her work on modelling posed roles of hydrogen, as a structural modifier, oxygen dissociation on gold clusters supported implying instead that it is directly involved in the on iron oxide, and showed that the iron oxide NOx-reduction mechanism. Although several stabilises dissociated oxygen atoms. Dyfan spectroscopic studies have been published (6) Edwards presented a surface science study of the showing the presence of cyanide and isocyanate synergy between the individual metal oxides in on the silver surface when hydrogen is present, iron molybdate catalysts, which are used for oxi- kinetic measurements at Queen’s University Belfast dising methanol to formaldehyde. The selectivity have ruled these out as reactive intermediates, of iron oxide changes with the level of coverage suggesting that more transitory species (such as by molybdenum, from total combustion when no hydroxamic acid or ammonia) are involved. molybdenum is present, to partial oxidation (to CO) at low coverage, and finally selective oxida- Future Prospects tion (via a methoxy intermediate) at high coverage. During his introduction to the postgraduate Dr Jennifer Edwards has been examining the student and postdoctoral researcher presentations, effect of preparation and pretreatment variables Jack Frost (Johnson Matthey Fuel Cells, U.K.) on the performance of gold-palladium catalysts compared and contrasted the academic process of for the direct synthesis of hydrogen peroxide. research with the industrial activity of innovation. Acid pretreatment of the support material has He used the example of vehicle emission control resulted in catalysts with lower activity for the to show how the pressing need for improved local unwanted consecutive hydrogen peroxide-hydro-

Platinum Metals Rev., 2009, 53, (4) 223 1 2 O2

CO Pd(111) Pd(111)

3 4

δ + δ Pd (111) Pd +(111)

5 6 CO2

δ+ δ Pd (111) Pd +(111)

δ+ Fig. 1 Schematic model for oxygen diffusion followed by CO + O2 reaction on Pd(111) > 550 K. Pd = mildly oxidised Pd (Courtesy of Chinnakonda S. Gopinath, National Chemical Laboratory, Pune, India) genation reaction, leading to very impressive Finally, there were several very topical presenta- hydrogen peroxide yields. tions concerned with clean synthesis of chemicals The influence of the iron:cobalt ratio in an and fuels. Lee Dingwall (University of York, U.K.)

Fe2O3-Co3O4 catalyst, for converting ethanol to has been synthesising and working with a bifunc- hydrogen, has been studied by Abel Abdelkader tional heterogeneous catalyst that combines an

(Queen’s University Belfast). Fe2O3 catalyses active ruthenium organometallic centre with a ethanol steam reforming, and Co3O4 the water-gas polyoxometallate cage, Figure 2. This provides acid shift reaction, so that a 1:1 ratio produces the opti- sites and also confers great stability, and the cata- mum yield. In the field of syngas and hydrogen lyst structure displays high activity for C–C bond utilisation, Poobalasuntharam Iyngaran (University formation. Ceri Hammond (Cardiff University) of Cambridge) presented a study of the effect of described the reaction of glycerol with urea over potassium promoters on ammonia synthesis over zinc, gallium or gold supported on zeolite. iron, which showed that stepwise hydrogenation Glycerol carbonate can be obtained with high of nitrogen surface adatoms is unaffected by the selectivity in a one-step solvent-free process over presence of potassium. Sharon Booyens (Cardiff these catalysts, though there is some question over University) is interested in DFT modelling of CO their stability. adsorption on iron surfaces, in the context of The prize for the best student presentation was Fischer-Tropsch catalysis. The models predict awarded to Janine Montero (University of York) that surface carbon causes a weakening of the who is researching the use of heterogeneous Fe–CO interaction, and therefore CO dissociation catalysts for biodiesel synthesis by transesterifica- becomes less favourable. Andrew McFarlane tion, as a replacement for the liquid catalysts (University of Glasgow) presented his work on currently in use. She has shown, by Auger electron

C5 olefin hydrogenation over 1% Pd/Al2O3. He spectroscopy, that high-temperature calcination suggested that reaction of the cis-pentene isomer of nanoparticulate magnesium oxide results in must proceed via formation of the trans isomer increased surface polarisability, and therefore higher before hydrogenation can occur. Lewis basicity. Her results show that there is a

Platinum Metals Rev., 2009, 53, (4) 224 Fig. 2 Proposed structure of the + O - polyoxometallate-tethered ruthenium Ru C W complex + η5 – P [HNEt3] [(Ru{ -C5H5}{PPh3}2)2(PW12O40)] (Courtesy of Karen Wilson, University of HNEt33 York, U.K.)

P

linear relationship between polarisability and trans- vacuum, and those from real catalyst materials at esterification activity over these MgO catalysts. ambient or high pressures (10), having gradually narrowed. Frost had earlier commented on a sim- Summary ilar convergence, between research and In summing up the conference, Professor innovation. As he pointed out, though, these Wyn Roberts (Emeritus Professor, Cardiff activities need to remain distinct, because they University) recalled that when he began his Ph.D. fulfil quite different functions. However, with he had to make the choice between studying their shared values of insight, integrity, creativity clean surfaces (i.e. single crystals) or real catalysts. and professionalism, they will be increasingly As many of the presentations highlighted, this directed in parallel at our most urgent challenges distinction is no longer useful, with the so-called in catalysis and in society: sustainability and envi- ‘material’ and ‘pressure’ gaps in catalysis, between ronmental protection. results obtained from surface science studies, The fifth Taylor Conference is scheduled to usually using idealised surfaces under high take place in Aberdeen in 2013 (11).

References 1 Royal Society of Chemistry, Surface Reactivity and 6 F. Thibault-Starzyk, E. Seguin, S. Thomas, M. Daturi, Catalysis (SURCAT) Group: http://www.rsc.org/ H. Arnolds and D. A. King, Science, 2009, 324, (5930), Membership/Networking/InterestGroups/Surface 1048 Reactivity/index.asp (Accessed on 5th August 2009) 7 M. V. Twigg, Appl. Catal. B: Environ., 2007, 70, (1–4), 2 The Taylor Conference 2009: http://www.taylor. 2 cf.ac.uk/ (Accessed on 5th August 2009) 8 C. S. Gopinath, K. Thirunavukkarasu and S. Nagarajan, Chem. Asian J., 2009, 4, (1), 74 3 E. R. Rideal and H. S. Taylor, “Catalysis in Theory and 9 S. Nagarajan, K. Thirunavukkarasu and C. S. Gopinath, Practice”, Macmillan and Co Ltd, London, U.K., 1919 J. Phys. Chem. C, 2009, 113, (17), 7385 4 P. B. Weisz, Microporous Mesoporous Mater., 2000, 35–36, 10 J. M. Thomas, J. Chem. Phys., 2008, 128, (18), 182502 1 11 Royal Society of Chemistry, Publishing, Journals, 5 Diamond Light Source, Publications, Case Studies: PCCP, News, 2009: http://www.rsc.org/Publishing/ http://www.diamond.ac.uk/Home/Publications/case Journals/CP/News/2009/TaylorPCCPPrizes.asp _studies.html (Accessed on 27th August 2009) (Accessed on 5th August 2009)

The Reviewers Stan Golunski has recently been appointed Andy York is a Johnson Matthey Research Deputy Director of the Cardiff Catalysis in the Department of Chemical Institute; he was formerly Technology Engineering and Biotechnology at the Manager of Gas Phase Catalysis at the University of Cambridge, U.K. His Johnson Matthey Technology Centre at research interests lie at the interface Sonning Common in the U.K. His research between catalyst chemistry and reaction interests include catalytic aftertreatment engineering. and reforming.

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