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High-surface area γ-alumina is industrially used as a catalyst support. Catalytically active elements are doped onto the support, where they can bind to AlO4, AlO5 or AlO6 sites on the surface. Pretreating the surface with alkaline earth oxides can alter the availability of these surface sites, hence affecting the catalytic activity. The surface binding sites of strontium oxide (SrO) on γ-alumina were previously unknown. Direct 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) could not detect AlO5 sites at 9.4 T, so 1H–27Al cross-polarisation (CP) MAS NMR was used to preferentially select the surface environment signals. We directly observed the three surface environments on dehydrated γ-alumina as a function of SrO impregnation up to 4 wt% SrO. We found that Sr2+ preferentially binds to AlO5 and AlO6 surface sites. 1H MAS NMR revealed SrO impregnation causes a reduction in the terminal (−0.3 ppm) and bridging (2.2 ppm) hydroxyl environments, as well as the promotion of a new peak in between these sites, at 0.5 ppm. By using 1H–27Al CP/MAS NMR the relative proportions of surface sites on γ-alumina can be determined, allowing an optimal level of SrO doping that can saturate all the AlO5 sites. Importantly, this provides a method of subsequently depositing catalytically active elements on just the AlO4 or AlO6 sites, which can provide a different catalytic activity or stability compared to the AlO5 binding site.
Heterogeneous catalysis often involves the use of metal nanoparticles, often between 1–10 nm in size. These particles are usually finely dispersed onto high surface area supports and act as an active centre during a catalytic reaction. The performance of a supported catalyst can be directly related to the size and spatial distribution of the metal nanoparticles. Therefore, it is of...
This book represents the latest magnum opus in a line of multi-author books on process tomography, with the first dating from 20 years ago. Following in the tradition of Beck and Williams (1) this book presents a comprehensive overview of process relevant tomographic modalities, reconstruction techniques and industrial applications. The editor Professor Mi Wang has done an excellent job...
In Part I of this Final Analysis series (1), the identification and quantification of elements by X-ray (excited) photoelectron spectroscopy (XPS) was discussed. A statement was made that the core energy levels do not vary a great deal – but there is usually some variation for a given element in different chemical forms. This can be thought of as being caused by variations in the oxidation...
The water solubility of 22 platinum group metal (pgm) containing substances was evaluated to provide useful data for regulatory compliance and to aid assessment of their environmental impact. The flask method from OECD Guideline 105 (1) for the testing of chemicals (water solubility) was used to test each material. For substances that could not be isolated as pure solids, a simplified water solubility test was carried out. The results provide reliable data on solubility previously unavailable in the literature.
Small metallic nanoparticles used for polymer exchange membrane fuel cells (PEMFC) represent a characterisation challenge. Electron microscopy would seem the ideal technique to analyse their structure at high resolution. However, their minute size and sensitivity to irradiation damage makes this difficult. In this review, the latest techniques for overcoming these limitations in order to provide quantitative structural and compositional information are presented, focusing specifically on quantitative annular dark-field (ADF) scanning transmission electron microscopy (STEM) and quantitative energy dispersive X-ray (EDX) analysis. The implications for the study of bimetallic fuel cell catalyst materials are also discussed.
Neutron scattering is a severely underused technique for studies of catalysts. In this review we describe how and why neutrons are useful to catalysis. We illustrate the range of systems that have been studied by both elastic and inelastic neutron scattering. These range from structural studies of adsorbates in zeolites to determination of the structure of surface adsorbates, characterisation of nanoparticles, the measurement and mechanism of diffusion and spectroscopic characterisation of adsorbed species. We conclude with how to access neutron facilities and some future prospects for the application of these techniques to industrially useful materials.
An invitation-only event was held from 5th–6th September 2016 to launch the new state-of-the-art imaging facility, opened on 5th September 2016, which will see the University of Oxford, UK, Johnson Matthey Plc, UK, and Diamond Light Source, UK, in close collaboration on the study of nanoscale materials. The ePSIC is located at the Harwell Science and Innovation Campus in Oxfordshire, UK,...
The application of three-dimensional electrical capacitance tomography (3D-ECT) for the in situ monitoring of a hard boundary or interface has been investigated using imaged phantoms that simulate real-life processes. A cylinder-in-tube phantom manufactured from polyethylene (PE), a low di-electric and non-conductive material, was imaged using the linear back projection (LBP) algorithm with the larger tube immersed at varying intervals to test the ability of the technique to image interfaces axially through the sensor. The interface between PE and air is clearly imaged and correlates to the known tube penetration within the sensor. The cylinder phantom is imaged in the centre of the sensor; however, the reduction in measurement density towards the centre of the ECT sensor results in reduced accuracy. A thresholding method, previously applied to binary systems to improve the imaged accuracy of a hard boundary between two separate phases, has been applied to the 3D-ECT tomograms that represent the PE phantom. This approach has been shown to improve the accuracy of the acquired image of a cylinder of air within a non-conductive PE tube.
We have previously described some of Johnson Matthey’s core competencies in modelling (1) and the control of advanced materials at the atomic scale (2). The third of these competencies, and a vital component of the company’s strategy to develop high performance solutions to its customers’ problems, is characterisation of materials. Materials characterisation is a huge and diverse field....
The improvement of catalytic processes is strongly related to the better performance of catalysts (higher conversion, selectivity, yield and stability). Additionally, the desired catalysts should meet the requirements of being low cost as well as environmentally and user-friendly. All these requirements can only be met by catalyst development and optimisation following new approaches in design and synthesis. This article discusses three major approaches in the design and development of catalysts: (a) high-throughput synthesis; (b) reaction kinetic studies; (c) in situ and operando spectroscopy for studying catalysts under process conditions. In contrast to approaches based on high-throughput synthesis and reaction kinetic studies, an emerging approach of studying catalysts under process conditions using in situ and operando spectroscopy and transferring the gained knowledge to design of new catalysts or the optimisation of existing catalysts is not yet widely employed in the chemical industry. In this article, examples of using in situ or operando spectroscopy for studying the surface and bulk of catalysts under process conditions are discussed, with an overview of applying in situ X-ray absorption spectroscopy (XAS), in situ infrared (IR) spectroscopy and in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) for monitoring the bulk and surface composition of PdZn/ZnO and Pd2Ga/Ga2O3 methanol steam reforming catalysts.
The understanding of location and accessibility of zeolite acid sites is a key issue in heterogeneous catalysis. This paper provides a brief overview of Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) characterisation of acidity in zeolites based on the application of test molecules with a diverse range of basicity and kinetic diameters. Many zeolites,...
Johnson Matthey has a long history and track record of designing and supplying specialist coatings into a wide range of application areas and substrate types. A common theme is the requirement to deposit precise amounts of materials. This is key for expensive platinum group metals and for the resulting coating to provide a function such as catalytic, conductive, protective or optical....
As it is the surface of a heterogeneous catalyst where the catalysed chemical processes take place, understanding the nature of the outer atomic layers of such surfaces is of great interest to those involved in the creation and improvement of such materials. The surface scientist has various tools to acquire information about a surface but one of the few that directly provides chemical...
Low-energy ion scattering (LEIS) can be used to selectively analyse the atomic composition of the outer atomic layer of a catalyst, i.e., precisely the atoms that largely determine its activity and selectivity. It is shown how a new development in LEIS significantly improves its mass resolution. Using this advanced separation and quantification of signals from platinum and gold, the atomic composition of the outer surface of a realistic supported platinum-gold bimetallic system can be determined for the first time.
Tim Hyde is a Principal Scientist in the Advanced Characterisation Department at the Johnson Matthey Technology Centre, Sonning Common, UK. His research interests focus on the development of synchrotron radiation-based characterisation using in particular X-ray absorption spectroscopy (XAS) on a range of applications in environmental catalysis, process technologies and battery research. He...
It has come to our attention that the author attribution on the article published in the previous issue of Johnson Matthey Technology Review was incorrect (1). The corrected author list for the original article appears in this erratum.
Introduction Johnson Matthey has over 200 years of history, creating sustainable technologies, shaped around customers’ needs. Our ambition is to research, develop and innovate solutions to make the world cleaner and healthier, today and for future generations. Much of the underpinning science behind these technologies relies on a knowledge of chemistry and its application. Like most...
Dynamic nuclear polarisation (DNP) gives large (>100-fold) signal enhancements in solid-state nuclear magnetic resonance (solid-state NMR) spectra via the transfer of spin polarisation from unpaired electrons from radicals implanted in the sample. This means that the detailed information about local molecular environment available for bulk samples from solid-state NMR spectroscopy can now...
Atomic force microscopy (AFM), an analytical technique based on probing a surface or interface with a microcantilever, has become widely used in formulation engineering applications such as consumer goods, food and pharmaceutical products. Its application is not limited to imaging surface topography with nanometre spatial resolution, but is also useful for analysing material properties such as adhesion, hardness and surface chemistry. AFM offers unparalleled advantages over other microscopy techniques when studying colloidal systems. The minimum sample preparation requirements, in situ observation and flexible operational conditions enable it to act as a versatile platform for surface analysis. In this review we will present some applications of AFM, and discuss how it has developed into a repertoire of techniques for analysing formulated products at the nanoscale under native conditions.
This study was a small part of the EURARE project concerned with the processing of eudialyte concentrates from Greenland and Norra Kärr, Sweden. Eudialyte is a potential rare earth elements (REE) primary resource due to its good solubility in acid, low radioactivity and relatively high REE content. The main challenge is avoiding the formation of silica gel, which is non-filterable when using acid to extract REE. Some methods have been studied to address this issue and, based on previous research, this paper examined a complete hydrometallurgical treatment of eudialyte concentrate to the production of REE carbonate as a preliminary product. Dry digestion with concentrated hydrochloric acid (10 M) and subsequent water leaching of the treated eudialyte concentrate resulted in high REE extraction while avoiding gel formation. Experiments were performed at a small scale to obtain the optimal parameters. After the first two stages, 88.8% REE was leached under the optimal conditions (HCl:concentrate ratio 1.25:1, digestion time 40 min, water:concentrate ratio 2:1, leaching temperature 20–25°C and leaching time 30 min). After obtaining the pregnant leach solution, preliminary removal of impurities by a precipitation method was examined as well. When adjusting the pH to ~4.0 using calcium carbonate, zirconium, aluminium and iron were removed at 99.1%, 90.0% and 53.1%, respectively, with a REE loss of 2.1%. Finally, a pilot plant test was performed to demonstrate the feasibility and recovery performance under optimal parameters. The material balance in the upscaling test was also calculated to offer some references for future industrial application. A REE carbonate containing 30.0% total REE was finally produced, with an overall REE recovery yield of 85.5%.
The adsorption and diffusion of species in activated carbons is fundamental to many processes in catalysis and energy storage. Nuclear magnetic resonance (NMR) gives an insight into the molecular-level mechanisms of these phenomena thanks to the unique magnetic shielding properties of the porous carbon structure, which allows adsorbed (in-pore) species to be distinguished from those in the bulk (ex-pore). In this work we investigate exchange dynamics between ex-pore and in-pore solvent species in microporous carbons using a combination of one-dimensional (1D) and two-dimensional (2D) NMR experiments. We systematically compare the effects of four variables: particle size, porosity, solvent polarity and solvent viscosity to build up a picture of how these factors influence the exchange kinetics. We show that exchange rates are greater in smaller and more highly activated carbon particles, which is expected due to the shorter in-pore–ex-pore path length and faster diffusion in large pores. Our results also show that in-pore–ex-pore exchange of apolar solvents is slower than water, suggesting that the hydrophobic chemistry of the carbon surface plays a role in the diffusion kinetics, and that increased viscosity also reduces the exchange kinetics. Our results also suggest the importance of other parameters, such as molecular diameter and solvent packing in micropores.
Introduction “Solid-State NMR in Zeolite Catalysis” was written by four professors from the Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, who have tremendous expertise in the fields of solid-state nuclear magnetic resonance (solid-state NMR) and heterogeneous catalysis. This book is Volume 103 in the series ‘Lecture Notes in Chemistry’ published by Springer. It...
We review developments in the study of the stability of platinum-iridium standard weights, in particular the kilogram prototypes manufactured from alloy supplied by Johnson Matthey in the 1880s that still stand at the heart of the International System of Units (abbreviated SI from the French: Système international d’unités). The SI has long since moved on from length standards based on physical artefacts fabricated from this alloy, but the SI unit of mass is still defined in this way, as the mass of a real physical object. The stability of these reference masses has been a concern since the 1930s, with mass loss or gain at the surface being the principal concern. In recent years X-ray photoelectron spectroscopy (XPS) has been particularly valuable in elucidating the types of contamination present and the mechanism by which contamination takes place. While direct studies on the International Prototype Kilogram are understandably difficult, at Newcastle University we have examined the surfaces of six Pt mass standards also manufactured in the mid-19th century, using XPS to identify contamination chemically. XPS shows a significant quantity of mercury on the surfaces of all six. The most likely source of Hg vapour is the accidental breakage of thermometers and barometers, and the mechanism of contamination may be similar to the poisoning of platinum group metal (pgm) catalysts by Hg, an effect known for almost a century.
Before joining Johnson Matthey, Tuğçe Eralp Erden was a Marie Curie PhD student at the University of Reading, UK, studying model chiral adsorption systems using synchrotron-based structural and spectroscopic techniques (1–5). After completing her PhD, she joined the advanced characterisation department at Johnson Matthey, Sonning Common, UK, where she is currently leading the surface...
The accurate and precise characterisation of disordered, mesoporous solids continues to be an ongoing challenge due to the high level of complexity of such materials. Common, indirect methods, such as gas sorption and mercury porosimetry, still offer relatively cheap, and, most importantly, statistically representative characterisations of macroscopic samples. This work reviews and expands upon recent developments aimed at increasing, and cross-validating, the information obtained from such methods. This involves developing a better understanding of the pore-pore co-operative effects that emerge only in extensive, disordered pore networks to better interpret raw characterisation data, and to use these effects to deliver more information on the void space. This work also describes novel hybrid methods that also greatly increase the information that indirect methods can deliver on complex mesoporous solids.
It is known that platinum-rhodium thermocouples exhibit mass loss when in the presence of oxygen at high temperatures due to the formation of volatile oxides of platinum and rhodium. The mass losses of platinum, Pt-6%Rh and Pt-30%Rh wires, commonly used for thermocouples, were considered in this paper to characterise the mass loss of wires of the three compositions due to formation and evaporation of the oxides PtO2 and RhO2 under the conditions that would be seen by thermocouples used at high temperature. For the tests, the wires were placed in thin alumina tubes to emulate the thermocouple format, and the measurements were performed in air at a temperature of 1324°C, i.e. with oxygen partial pressure of 21.3 kPa. It was found that the mass loss of the three wires increases linearly with elapsed time, consistent with other investigations, up to an elapsed time of about 150 h, but after that, a marked acceleration of the mass loss is observed. Remarkably, previous high precision studies have shown that a crossover after about 150 h at 1324°C is also observed in the thermoelectric drift of a wide range of platinum-rhodium thermocouples, and the current results are compared with those studies. The mass loss was greatest for Pt-30%Rh, followed by Pt6%Rh, then platinum.
Sensors are vital to process and product control across a large number of industries. A network of sensors is used for monitoring and controlling machinery, systems and processes in chemicals, pharmaceuticals, biotechnology, energy, water, wastewater, oil, gas, plastic, paper, food and beverages among others. Technologies for Sensing The technologies are as varied as the applications....
1. Introduction There are few mathematical breakthroughs that have had as dramatic impact on the scientific process as the Fourier transform. Defined in 1807 in a paper by Jean Baptiste Joseph Fourier (1) to solve a problem in heat conduction, the integral transform, Equation (i): (i) and its inverse, Equation (ii): (ii) provide the framework to determine the spectral make up of a time...
In Part I (1), the failure response of a 1 Ah layered pouch cell with a commercially available nickel manganese cobalt (NMC) cathode and graphite anode at 100% state of charge (SOC) (4.2 V) was investigated for two failure mechanisms: thermal and mechanical. The architectural changes to the whole-cell and deformations of the electrode layers are analysed after failure for both mechanisms. A methodology for post-mortem cell disassembly and sample preparation is proposed and demonstrated to effectively analyse the changes to the electrode surfaces, bulk microstructures and particle morphologies. Furthermore, insights into critical architectural weak points in LIB pouch cells, electrode behaviours and particle cracking are provided using invasive and non-invasive X-ray computed tomography techniques. The findings in this work demonstrate methods by which LIB failure can be investigated and assessed.
The assessment of lithium-ion battery (LIB) safety is a multiscale challenge: from the whole-cell architecture to its composite internal three-dimensional (3D) microstructures. Substantial research is required to standardise failure assessments and optimise cell designs to reduce the risks of LIB failure. In this two-part work, the failure response of a 1 Ah layered pouch cell with a commercially available nickel manganese cobalt (NMC) cathode and graphite anode at 100% state of charge (SOC) (4.2 V) is investigated. The mechanisms of two abuse methods: mechanical (by nail penetration) and thermal (by accelerating rate calorimetry) are compared by using a suite of post-mortem analysis methods.