Elements are the atomic building blocks of the universe, creating the world as we know it. The majority of elements in the periodic table are metals and each element has a unique set of properties that make them appropriate for specific applications. In particular, platinum group metals (PGMs) are pivotal to various chemical syntheses and products. Platinum in the form of a complex is an essential part of certain anticancer drugs, including the life-changing drug cisplatin, and the metallic form is also used in many medical devices and implants. Platinum and its fellow PGMs palladium and rhodium are active components in many catalytic converters, ensuring the removal of toxic contaminants from vehicle exhausts. PGMs such as ruthenium and palladium are used in many reactions, catalysing the creation of a variety of industrially important chemicals. Beyond the PGMs, metallic elements such as lithium, nickel and cobalt play an important role in battery cathode materials which are being developed to power the vehicles of the future.
Understanding the chemical and physical properties of specific elements is important for industry, but leveraging and combining those properties successfully for industrial applications requires skill and expertise. Johnson Matthey (JM) has more than 200 years of experience in applying scientific research to develop solutions to the major challenges that society will face today and in the future. Over the years, JM has applied its experience and expertise in metallurgical research to develop materials to give us cleaner air, innovative catalysts for vital chemical industry processes and novel materials for cross-coupling and other industrially relevant reactions. JM has also developed technologies to recover and recycle PGMs, thereby ensuring these finite and valuable metals are available for reuse.
Elements that power our vehicles
Battery technologies are central to electric vehicles, which have an increasing role in transportation strategies. The UK government has pledged that half of all new car sales will be hybrid or electric by 2030.
One of the most pressing challenges facing the world today is the need for cleaner air. To achieve this, technologies are needed that reduce emissions in the transportation industry, and there is already a trend across the globe to reduce the proportion of solely petrol- or diesel-powered vehicles. With this comes the need for newer, cleaner power sources, such as batteries, to meet the demands of the transportation industry.
Recognising the future demand for new higher performance battery materials, JM developed the eLNOTM battery cathode material technology. This technology combines lithium, nickel and oxygen with minimal quantities of cobalt to make an ultra-high-energy-density lithium-ion battery material for the future.
Current lithium-ion battery materials typically include larger quantities of cobalt. This element is in limited supply and thus rising demand has caused the price to quadruple in recent years. However, cobalt is currently a critical component for ensuring lithium-ion battery stability and lifetime.
In eLNO materials, the amount of cobalt added to the formulation has been minimised and this is a key market differentiator for this battery material. The specific formulation of elements in eLNO materials ensures step-change improvements could be achieved in energy density and cycle life with lower cobalt and thus at lower cost. Lower cobalt is key to ensuring the sustainable commercialisation of high-energy-density cathode materials for lithium-ion batteries.
Removing pollutants through catalysis
PGMs and metallurgical research are also essential components for developing solutions for cleaner air by reducing harmful emissions from vehicles powered by internal combustion engines. These vehicles produce various chemical contaminants that are known to be hazardous to human health. Improving air quality is about understanding how to convert pollutants – such as carbon monoxide, unburnt hydrocarbons and nitrogen oxide compounds (NOx) – into innocuous emissions.
JM has widespread expertise in this field, with around one in every three vehicles globally containing a JM autocatalyst. JM’s catalytic converter innovations first began in the late 1960s with the two-way catalyst, which used platinum and rhodium. This was later improved in the three-way catalyst, which added palladium to the catalyst bed. Effectively, these catalysts combine oxidising and reducing capabilities. The platinum and palladium metals oxidise toxic carbon monoxide to less immediately harmful carbon dioxide and unburnt hydrocarbons into carbon dioxide and water, while the rhodium reduces NOx compounds into nitrogen.
Constant innovation is needed in this field. Consider diesel engines: reduction of NOx was previously only achieved once the catalyst technology had reached a certain temperature in the exhaust. This meant in the initial minutes following engine ignition, NOx emissions were still released into the atmosphere. To address these emissions, JM developed its cold start technology. This uses metal and zeolite chemistry to store the initial NOx emissions. Once the temperature conditions of the catalyst have then been met, reduction to nitrogen then occurs.
A new palladium catalyst can selectively perform classically challenging cross-coupling reactions at high yields, while in the presence of reactive side groups.
Providing new routes to products
Beyond clean air and transportation uses, one of the most widely known applications of metal complexes in chemistry is to catalyse various industrial processes. Catalysis is an integral component of many industrial reactions. For instance, the Haber–Bosch process produces ammonia from hydrogen and nitrogen, and this ammonia is then used for fertilisers. But it is only viable at a large scale using an iron catalyst.
Fundamentally, catalysis helps to make difficult reactions easier. Cross-coupling reactions, for instance, are one method of making new carbon–carbon bonds. These bonds are useful throughout chemical industries due to their universality and functionality. Palladium catalysts are continuously being developed that improve chemoselectivity, reactivity and activity throughout cross-coupling reactions.
What makes palladium useful for cross-coupling reactions is its ability to access multiple oxidation states and readily swap between them. Accessing these various states makes it possible for the catalyst to change from its precatalyst Pd(l) form into the active Pd(0) form. This allows the palladium catalyst to undergo the necessary oxidative addition, transmetalation, and reductive elimination processes. Novel metal complexes are continuously being developed at JM with the aim to make these processes more selective. For example, recent research has demonstrated how a new JM palladium catalyst can selectively perform classically challenging cross-coupling reactions at high yields, while in the presence of reactive side groups.
Sustainable supply of metals
All these industrial catalysts, autocatalysts and clean air technologies rely on several common PGM elements, typically platinum, palladium, ruthenium and rhodium, while the increasing use of automotive battery materials will place further demand on other metallic elements, including lithium, nickel and cobalt. However, all these elements are in finite supply in the Earth’s crust, so it is imperative that they are used as efficiently as possible, that reuse and recycling technologies are considered and that sustainable procurement frameworks are employed or developed to ensure a continued ethical supply.
Sustainability and longevity lie at the heart of JM’s business. As a result, the company also focuses on recycling the PGMs used in autocatalysts or other applications so that they can be reused. JM has concentrated on developing technologies and strategies that recover as much of the PGM as possible from any feedstock. Typical feedstocks include autocatalysts, industrial catalysts or other PGM-containing materials. These can then be processed at JM’s dedicated recycling and refining facilities. Within these facilities, specific hydro- and pyrometallurgical separation techniques and technologies are used to isolate the seven key platinum group metals: gold, silver, rhodium, platinum, palladium, ruthenium and iridium.
While it will be some time before significant volumes of automotive batteries are in operation or at the end of their useful life, JM is looking at all areas of battery activities across their life cycle.
Metallic elements are common in eLNO battery cathode technologies, autocatalysts, industrial catalysts, healthcare devices and pharmaceuticals. However, combining and applying these elements to the specific applications requires an in-depth understanding of metallurgy and specific reaction, manufacturing and development processes. In addition, sustainability must be a high priority; it is essential that raw elemental metals are acquired sustainably over the long term. Innovation in the chemical industry relies on combining the right elements with the right expertise to make a reaction or product successful.
Article originally published by Chemistry World on 11th January 2019.