Johnson Matthey Highlights: July 2015
Johnson Matthey Highlights: July 2015
A selection of recent publications by Johnson Matthey R&D staff and collaborators
EMISSION CONTROL TECHNOLOGIES
Increased NO2 Concentration in the Diesel Engine Exhaust for Improved Ag/Al2O3 Catalyst NH3-SCR Activity
W. Wang, J. M. Herreros, A. Tsolakis and A. P. E. York, Chem. Eng. J., 2015, 270, 582 LINK http://dx.doi.org/10.1016/j.cej.2015.02.067
Fast-SCR was investigated for NOx reduction in internal combustion engines. H2 addition was found to increase NO2 formation over a Ag/Al2O3 catalyst. This led to an improved NH3-SCR activity at low temperature. It is concluded that NO2 formation before the Ag/Al2O3 catalyst either in the engine or a Pt/Al2O3 based DOC will improve SCR performance. This NO2 promotion effect was less at higher temperatures.
Thermochemical Recovery Technology for Improved Modern Engine Fuel Economy – Part 1: Analysis of a Prototype Exhaust Gas Fuel Reformer
D. Fennell, J. Herreros, A. Tsolakis, K. Cockle, J. Pignon and P. Millington, RSC Adv., 2015, 5, (44), 35252 LINK http://dx.doi.org/10.1039/C5RA03111G
Reformed exhaust gas recirculation (REGR) provides H2 to the combustion process to recover heat from exhaust and improve fuel conversion efficiency. A full scale prototype reformer for gasoline direct injection engines is presented and its performance is assessed. The performance is better at higher temperatures with a decline in performance at lower exhaust temperature. The reformate quality is also dependent on process temperature and reactant composition.
Palladium-Catalyzed ɑ-Arylation Reactions in Total Synthesis
S. T. Sivanandan, A. Shaji, I. Ibnusaud, C. C. C. Johansson Seechurn and T. J. Colacot, Eur. J. Org. Chem., 2015, (1), 38 LINK http://dx.doi.org/10.1002/ejoc.201403301
New methods for synthesising natural products and active pharmaceutical ingredients have been explored using palladium-catalysed ɑ-arylation of carbonyl compounds. The advantages of this particular method are an increase in the overall yield, an improved synthesis scope and a reduction in the number of steps. The significance of palladium-catalysed ɑ-arylation methods are discussed and a number of case studies have been included.
The Effects of 1-pentyne Hydrogenation on the Atomic Structures of Size-selected AuN and PdN (N = 923 and 2057) Nanoclusters
K.-J. Hu, S. R. Plant, P. R. Ellis, C. M. Brown, P. T. Bishop and R. E. Palmer, Phys. Chem. Chem. Phys., 2014, 16, (48), 26631 LINK http://dx.doi.org/10.1039/c4cp02686a
The variation in atomic structures of size-selected Au and Pd nanoclusters (containing 923 and 2057 atoms) supported on amorphous carbon films before and after being exposed to the vapour-phase hydrogenation of 1-pentyne was studied. The populations of the nanoclusters were studied at atomic resolution before and after the reaction using an aberration-corrected high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). The atomic structures of the observed nanoclusters were determined by comparing the multi-slice HAADF-STEM and experimental images for a full range of cluster orientations. The results show that Au nanoclusters consisting of 923 ± 20 and 2057 ± 45 atoms are robust and exhibit high structural stability. A big proportion of Pd923 ± 26 nanoclusters, on the other hand, appear to be amorphous before the treatment and after the reaction were found to exhibit high symmetry structures which suggests the reduction of oxidised Pd nanoclusters in reaction conditions.
FINE CHEMICALS: CATALYSIS AND CHIRAL TECHNOLOGIES
Stereoselective Synthesis of the Halaven C14-C26 Fragment from D-Quinic Acid: Crystallization-Induced Diastereoselective Transformation of an α-Methyl Nitrile
F. Belanger, C. E. Chase, A. Endo, F. G. Fang, J. Li, S. R. Mathieu, A. Z. Wilcoxen and H. Zhang, Angew. Chem. Int. Ed., 2015, 54, (17), 5108 LINK http://dx.doi.org/10.1002/anie.201501143
A series of substrate controlled stereoselective reactions with crystalline intermediates was carried out via an α-methyl nitrile to produce a C14–C26 fragment of halichondrin B/Halaven. The synthesis does not require chromatography and relies entirely on crystallisation for quality control. D-quinic acid is the starting material, providing all four chiral centres, and is readily available. Raw material cost and waste are both reduced by the present synthesis.
A Halogen- and Hydrogen-Bonding Catenane for Anion Recognition and Sensing
J. M. Mercurio, A. Caballero, J. Cookson and P. D. Beer, RSC Adv., 2015, 5, (12), 9298 LINK http://dx.doi.org/10.1039/C4RA15380D
Halogen bonding has been little explored outside the areas of solid state crystal engineering. A novel halogen bonding rotaxane structure was prepared for use in anion recognition and exhibits good anion recognition and sensing properties. An ion templated Grubbs’ II-catalysed RCM clipping mechanical bond forming was used to synthesise the structure which contains both halogen- and hydrogen-bonding macrocyclic components. 1H NMR spectroscopy and fluorescence titration experiments were carried out and showed that the new structure can strongly associate with acetate and dihydrogen phosphate.
NEW BUSINESSES: FUEL CELLS
Platinum-carbide Interactions: Core-shells for Catalytic Use
J. L. R. Yates, G. H. Spikes and G. Jones, Phys. Chem. Chem. Phys., 2015, 17, (6), 4250 LINK http://dx.doi.org/10.1039/C4CP04974H
Five carbides (TiC, NbC, TaC, WC and SiC) were investigated using density functional theory with the aim of determining their suitability as core-shell components in fuel cell applications. The fcc forms of the carbides were compared with hexagonal close-packed (hcp) WC and zinc blende SiC and the latter was found to support Pt overlayers on surfaces, therefore, showing potential for full Pt encapsulation. The transition metal surface resonances (TMSRs) play a vital role during the adsorption of Pt on fcc (111) carbide surfaces and fcc (100) was found to be adverse towards Pt adsorption. Reduced oxygen adsorption energies was displayed by several Pt-WC surfaces during the oxygen adsorption study; the authors conclude that ORR activity should be promoted or maintained with respect to nanoparticulate Pt catalysts.
Dual Doping Effects (Site Blockage and Electronic Promotion) Imposed by Adatoms on Pd Nanocrystals for Catalytic Hydrogen Production
S. Jones, S. M. Fairclough, M. Gordon-Brown, W. Zheng, A. Kolpin, B. Pang, W. C. H. Kuo, J. M. Smith and S. C. E. Tsang, Chem. Commun., 2015, 51, (1), 46 LINK http://dx.doi.org/10.1039/C4CC06195K
Additives based on polymer or metal adatoms can modify the electronic structure of metal nanoparticles but greater understanding of atomic level effects is needed to rationally design better catalysts by surface tailoring. Electronic and geometric effects of various metals on unsupported Pd nanocrystals were investigated using the decomposition of HCOOH to H2 and CO2 as a probe reaction. Bi was found to occupy high index sites causing a decrease in HCOOH dehydration, Te occupies terrace sites which reduces the dehydrogenation rate while Ag induced strong electronic effects and increased the activity of the Pd surface sites. Ag and Bi were concluded to be the most effective additives for a surface reaction, while Te should be added at corner sites to promote the desired reaction route.
Surfactant Mediated CO2 Adsorption: The Role of the Coimpregnation Species
C. M. Starkie, A. Amieiro-Fonseca, S. P. Rigby, T. C. Drage and E. H. Lester, Energy Procedia, 2014, 63, 2323 LINK http://dx.doi.org/10.1016/j.egypro.2014.11.252
Carbon capture and storage requires novel, second generation adsorbent systems to potentially reduce costs associated with this technology. Solid supported amines have been investigated. These consist of basic amines either tethered or impregnated on silica or alumina and co-impregnated with surfactant additives. The mechanisms of adsorption of these systems were studied and they were shown to have 55% improved working capacity relative to single component systems. Triethanolamine and sodium dodecylsulfate produced the best adsorbent properties.
The Synergistic Effect in the Fe-Co Bimetallic Catalyst System for the Growth of Carbon Nanotube Forests
D. Hardeman, S. Esconjauregui, R. Cartwright, S. Bhardwaj, L. D’Arsié, D. Oakes, J. Clark, C. Cepek, C. Ducati and J. Robertson, J. Appl. Phys., 2015, 117, (4), 044308 LINK http://dx.doi.org/10.1063/1.4906846
The growth of multi-walled carbon nanotube forests using an active bimetallic Fe-Co catalyst was investigated. When this bimetallic catalyst system was compared to pure Fe or Co a synergistic effect is observed. The height of the forests was considerably increased and an improvement of the homogeneity in the as-grown nanotubes was found. The catalyst system was characterised using energy dispersive spectroscopy and in situ X-ray photoelectron spectroscopy. The authors conclude that the growth rate of the nanotubes is greatly improved in the presence of Fe and Co.
TEM Characterization of Simultaneous Triple Ion Implanted ODS Fe12Cr
V. de Castro, M. Briceno, S. Lozano-Perez, P. Trocellier, S. G. Roberts and R. Pareja, J. Nucl. Mater., 2014, 455, (1–3), 157 LINK http://dx.doi.org/10.1016/j.jnucmat.2014.05.064
The performance of oxide dispersion strengthened (ODS) ferritic/martensitic steels under irradiation is studied. This is essential in the design of advanced fusion reactors. Transmission electron microscopy was used to characterise a simultaneous triple ion implanted ODS Fe12Cr steel with the aim of investigating the impact of irradiation on the grain and dislocation structures, oxide nanoparticles and other secondary phases present in steel. The ODS steel was irradiated simultaneously with Fe8+, He+ and H+ at room temperature to a damage of 4.4 dpa at the Joint Accelerators for Nanosciences and NUclear Simulation (JANNUS) Saclay facility. The authors concluded that ODS nanoparticles are very stable under these irradiation conditions.
An Experimental Investigation of Biodiesel Steam Reforming
S. Martin, G. Kraaij, T. Ascher, D. Wails and A. Wörner, Intl. J. Hydrogen Energy, 2015, 40, (1), 95 LINK http://dx.doi.org/10.1016/j.ijhydene.2014.10.143
The optimum operating conditions of a proprietary precious metal based catalyst for biodiesel steam reforming was investigated with the aim of preventing catalyst deactivation. Different operating conditions include varying the temperature from 600ºC to 800ºC, applying different pressure from 1 bar to 5 bar and altering the molar steam-to-carbon ratio from 3 to 5. Coke formation and sintering have been determined as the main deactivation mechanisms. The authors conclude that coking can be reduced by using low feed flow rates (31 g h–1 cm–2) and a relatively high catalyst inlet temperature (>750ºC).