Investigate Why The Discovery Of Some Chemical Catalysts Could Be Worth Millions

Investigate why the discovery of some chemical catalysts could be worth millions

Catalysts are at the very heart of almost all industrial and biological reactions and they are greatly underappreciated for the role they play in fuelling the operation and development of our society. From food production to the synthesis of pharmaceuticals to the protection of the environment, the influence of catalysts can be found behind the scenes of countless facets of daily life. It was around two centuries ago in 1836 when the term ‘catalysis’ was first introduced by a Swedish chemist called Jöns Jacob Berzelius, and from this there became a real appreciation of catalysts within the science community and they began to become a staple within the chemical industry, driving the emergence of a plethora of large-scale industrial processes, the number of which has grown exponentially up to the present day. Despite modern day advances in the field of catalysis, catalysts have been an irreplaceable part of the world since it first began and in fact without their existence, not only would the 21st century-industrialised world be inconceivable, but the human body itself would fail to function to any level capable of sustaining life. Within this extended project I aim to probe into the fundamentals of catalysis, using scientific theory and reasoning to explain the value of certain catalysts found in the world. The world of catalysis is a broad one, spanning so far across that 75% of all chemicals are produced with the aid of catalysts and in newly developed processes, the figure is over 90% and so through the careful consideration of a select few catalyst examples I aim to provide a conclusive answer to the question of why some catalysts, when discovered, could be worth millions.

A chemical reaction is something which occurs when one or more substances undergo a chemical transformation to produce one or more new chemical products, this is done through a process of breaking the bonds in the reactant molecules so that they can rearrange themselves in order to form new bonds and make up product molecules with structures different to what they originally started with. It is possible to detect when a chemical reaction is happening as they are often accompanied by changes in colour, temperature, texture and smell. Some common chemical reactions that can be found in everyday life are rusting, which is when oxygen (O2) in the air reacts with iron (Fe) in a metal to form a new product called iron oxide (Fe3O4), this product is what we see when an orange or brown flaky layer forms on the surface of iron. Another is digestion, within our bodies each day the process of chemical digestion is actually the result of hundreds of microscopic chemical reactions which break down large molecules like carbohydrates and proteins into smaller molecules which can then be absorbed by the body. Photosynthesis is also a key process, this system constructed of thousands of inter-connected chemical reactions is so efficient and well-constructed that it is the basis on which all plant life is sustained, using sunlight to convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6).

Despite some chemical reactions, such as rusting, taking place spontaneously, many reactions such as digestion and photosynthesis do not as they are thermodynamically unfavourable, and this is where the necessity for catalysts begins to develop. For a reaction to take place, as mentioned earlier bonds in the reactant molecules need to be broken, however they do not do this on their own, this process is endothermic and requires the input of energy. In industry, this energy is often provided in the form of thermal energy, which can be seen in the high temperatures used in industrial processes such as fuel generation right through to small scale activities such as everyday cooking. Companies often use the high temperatures because not only do they allow a reaction to take place, in terms of providing the energy needed to break the bonds in the reactant molecules, but higher temperatures also increase the rate at which a reaction takes place, which means in a given amount of time they will produce a greater quantity of output, which will lead to higher revenues and larger potential profits for the company which they can use for a multitude of reasons, such as to grow, to keep shareholders happy or to be dynamically efficient and reinvest into the firm in the form of research and development pursuits. However, the issue with using higher temperatures, is that not only do they lead to higher costs for a firm which will subtract from a firm’s profits, but they also pose an increased safety risk, due to the natural dangers which come with intense heat, whilst also increasing the instability that many chemicals face at high temperatures which can lead to inefficiency and waste. Therefore, chemical catalysts are used as an alternative (or sometimes in addition to) high temperatures and pressures in industrial processes.

In the words of Baltic German chemist Wilhelm Ostwald, ‘a catalyst accelerates a chemical reaction without affecting the position of the equilibrium’ despite being true, this statement was from 1895 and so a more modern definition of chemical catalysts is that they are ubiquitous compounds which speed up the rate of a chemical reaction without being used up themselves. Each catalyst is specific to a certain reaction and some examples are palladium (Pd) which can be found in catalytic converters, iron (Fe) which is used as a catalyst in the Haber process for the production of ammonia and nickel (Ni) which can be used to catalyse the hydrogenation of alkenes, a process which is vital to the food industry in the making of spreads and fats from liquid oils. (2) They work by lowering the activation energy (also known as Ea) of a reaction, which is the minimum energy that a reaction needs to take place, by providing an alternative pathway for the reaction to take place, meaning an alternative way of breaking and making bonds, such that less energy needs to be provided externally for an industrial reaction to take place. Furthermore they do this without being used up themselves in the reaction, such that in a theoretical situation a catalyst can be used over and over again without replacement and this boasts enormous benefits for sustainability. (3,4) The way in which catalysts function is known as the ‘catalytic cycle’, which can be seen in figure 1. Reactant molecules bind to the catalyst’s active site where the chemical transformation will take place and then products will be released, regenerating the catalyst for this cycle to continue again. These abilities of catalysts have led to them being an essential part of the majority of industries in the world, they can be seen enabling the production of chemicals on a very large scale, but there is also a need to make our society more sustainable and catalysts are critical for this too. This can be seen as right the way back in 1991 when inflation levels were lower, the market for catalysts was over $2.0 billion in the US this was partly made up of $750 million in chemical production and $600 million for petroleum refining and these values have sky-rocketed since to the point where the global catalyst market size is expected to reach $48.0 billion by 2027. Despite these price tags being audaciously high, they are nonetheless justified as the products made by the catalysts are even more valuable than the catalysts themselves, for example going back to 1991 again, the total value of fuels and chemical products produced by catalysts at the time was over $900 billion, which was about 18% of U.S. gross national product. Catalysts function in two major ways, the first and most conventional type is heterogeneous catalysis. This is where the catalyst is in a different phase to the reactants in the reaction it is catalysing, for example a solid heterogeneous catalyst will take part in a reaction between two liquids or more often two gases. Heterogeneous catalysts come in a range of different shapes and sizes and are often nano-sized metal clusters which come on sponge like porous supports which allow the reactant molecules to access the active site on the catalysts’ surface. They function by adsorbing one or more of the reactants to their surface, this interaction between the catalyst and the reactants begins with physisorption which is where the reactant molecules form weak intermolecular bonds with the catalyst, then this is followed by chemisorption which is when chemical bonds are then formed between the two this process means less external energy will need to be provided to fully break the bonds in the reactant as the catalyst does part of this already, making the reaction more feasible. Thus the activation energy for the reaction decreases and it will happen at a lower temperature and at a faster rate, and once the reaction has occurred the product molecules are desorbed from the catalyst which then gives space for new reactants to join, and the catalysis process begins again because of this in an ideal situation the catalyst itself should never be used up in the reaction. This process can be seen illustrated on figure 2, where the black line shows a reaction to form a product without the presence of a catalyst and this has a large energy barrier. However, when a catalyst is introduced there becomes an alternative way for the product to be formed such that many smaller energy barriers must be climbed and the reaction becomes more feasible, shown by the red line. For a heterogeneous catalyst to work at a maximum level of efficiency, it must firstly have as large a surface area as possible, the larger the surface, the more reactants that can be catalysed at one moment in time and the greater the increase in the rate of reaction will be. Another feature of a good heterogeneous catalyst should be an optimal level of strength of adsorption and desorption, a good catalyst will bind a reactant molecule strongly enough for the reaction to occur, but not so strongly that the product molecule then becomes permanently bound to its surface, as not only does this give less space for new reactants to join, but it also then means more energy has to be put in to remove the products from the catalyst’s surface. Because of this, the adsorption and desorption steps of the catalysis process are often the ones which limit the rate of reaction. Heterogeneous catalysts are also used a lot and are highly valued as they are able to be separated from their product very easily, which saves time, effort and money in industry these properties of warrant their use on a larger industrial scale compared to their homogeneous counterparts. Homogeneous catalysis is where the catalyst is in the same phase as the reactants in the reaction it is catalysing, and this will often be a liquid catalyst and multiple solutions of reactants. They function in a slightly different way to their heterogeneous equivalents, these catalysts work when the two liquids on their own have a reluctance to react with each other, which could be due to electrostatic repulsion, which would occur if the reacting molecules have the same electrical charge, or it could be because the reactant molecules are highly unreactive species. Therefore, a homogeneous catalyst will actually take part in the reaction, as it will have an affinity to one of the reacting species and so will react with one of the reactant molecules to form an intermediate, and this intermediate will then react with the second reactant molecule in order to produce the desired product and release the catalyst to be used again. These two separate reactions involving the homogeneous catalyst are more thermodynamically favourable and so will require less intense conditions compared to if the single reaction without a catalyst took place. Despite this, homogeneous catalysts are less commonly found in industry due to the nature of their catalysis process as the catalyst is in the same phase as the reactants, the catalyst is more difficult to retrieve after the reaction has reached completion thus making any processes involving them less economically viable as their ‘re-use’ ability is limited in this regard. Homogeneous catalysts are however more selective in terms of the reactions they catalyse and so can be used when dealing with highly complex structures. In addition to this given the fact that there are no phase boundaries between a homogeneous catalyst and the reactant molecules, it means that the catalyst molecules have a higher degree of dispersion compared to heterogeneous catalysts and so each atom can be catalytically active whilst with heterogeneous catalysts only atoms on the surface are useful, and therefore homogeneous catalysts are capable of producing higher rates of reaction than heterogeneous ones. Because of their properties, homogeneous catalysts are often found being used on a smaller scale for more specialised reactions instead of industrial reactions which are less specific and are carried out in bulk. Other minor types of catalysis do exist, however are much less industrially significant as these first two. One of these is a rare type of catalysis called ‘autocatalysis’, and this is where a product of the reaction actually happens to be a catalyst for that very reaction, such that as the reaction progresses, the greater the quantity of product/catalyst is present and so the greater the rate of reaction will be An even rarer type are bifunctional catalysts which are able to catalyse the conversion of one compound to another, using two substances on the catalyst surface rather than one. There are also some emerging forms of catalysis being developed, one being electrocatalysis for the synthesis of platform chemicals, which is good as long as the electricity used is sustainable, being generated using wind, solar etc another is photocatalysis and this is an extension of electrocatalysis since it will involve a direct conversion of reactants into products. Both of these methods need a lot of work to improve their efficiency but there is a lot of research work going into this area.

Using this knowledge of exactly how catalysts work, I would like to consider a real world application of a catalyst which is worth millions, the heterogeneous catalyst found within a catalytic converter. Catalytic converters were invented around 1950 by Eugène Houdry to convert toxic waste gases and pollutants from exhaust gases in vehicles into less toxic gases through the catalysis of redox reactions because of this toxicity-reducing ability, from 1975, most gasoline-powered vehicles have been equipped with catalytic converters, and so they can be found in almost all methods of transport including cars, buses and planes and now the likes of electrical generators, forklifts and mining equipment. There are two main types of catalytic converters which are distinguishable in terms of the way that they function. A two-way catalytic converter has two primary roles, one is that it oxidises carbon monoxide to carbon dioxide and the other being to oxidise unburnt hydrocarbons to carbon dioxide and water. Whereas a three-way catalytic converter is not only able to do the two tasks that two-way converters can do, but on top of this it can also control the emissions of nitrous oxides. Regardless of the type of converter, inside they all consist of porous channels where noxious gas molecules come in through exhaust and are catalysed such that less harmful gases are released. The mechanism for the conversion of carbon monoxide to carbon dioxide begins with the chemisorption of both carbon monoxide molecules and oxygen molecules onto the surface of the metals. The adsorbed oxygen molecules split up into separate atoms of oxygen. Each of these oxygen atoms can combine with a chemisorbed carbon monoxide molecule to form a carbon dioxide molecule. The carbon dioxide molecules are then desorbed from the surface of the catalyst, in order to leave space for more reactants to be adsorbed. All of these smaller steps, have lower activation energies than the direct reaction between oxygen and carbon monoxide with no catalyst, leading to the reaction occurring at a faster rate. The reactions behind this process can be seen depicted in figure 3. This process is so important because the effects of unburned hydrocarbons, carbon monoxide and nitrogen oxide escaping into the atmosphere are that they can lead to acid rain which damages buildings and infrastructure, and furthermore carbon monoxide can bind to the haemoglobin in our blood, reducing its ability to carry oxygen, making it harder to breathe, not to mention the role these greenhouse gases play in contributing to climate change, so catalytic converters play a vital role in the protection of both the environment and the health of society.

What allows catalytic converters to perform their function is the chemical properties of the noble metals within them which act as catalysts. One of these metals is palladium which acts as a heterogeneous catalyst, it has become a precious metal that is more valuable than gold, the price has shot up in the last couple years. In 2018 it was worth nearly $35 per gram, now a single gram is worth around $100, contributing heavily to the cost of a new catalytic converter which can cost $1,000 or more, making it amongst one of the most expensive individual parts on any car. This value can not only be demonstrated in its worth to the automobile industry, but it can also be seen illustrated by the high theft rates of catalytic converters. Thieves recognise the value, and it has gotten to the point where 108 catalytic converters were stolen per month across America in 2018 and by 2020 this value has now risen to 1,203. Furthermore, manufactures are trying to reduce their environmental impact and governments are enforcing stricter emissions regulations, so demand for palladium is increasing whilst the supply is relatively fixed there are only two major global suppliers of palladium, Russia and South Africa yet the demand lies elsewhere, for example the US only mines around 14,000kg of palladium each year, but uses around 90,000kg in this same time period resulting in the price skyrocketing. These complications are worsened by the fact that in theory catalysts can be used over and over, indefinitely, but in practice the performance of catalysts degrades over time. To compensate, manufacturers are forced to use more of these expensive metals up front, adding to the unsustainable demand. Not only is the supply of palladium and other metals used in catalytic converters, such as platinum and rhodium, becoming an issue, but also their effectiveness is another area of heavy development and large quantities of investment are being carried out to maximise the efficiency of these catalysts. One reason why catalysts lose their effectiveness is known as deactivation and this is due to issues with the surface area manufacturers typically spread many small particles over the surface of a new catalytic converter, this is done by producing the catalyst as a metal casing made from palladium along with rhodium or platinum, with a ceramic honeycomb structure acting as a support system in order to maximise the surface area as can be seen in figure 4. Metal atoms in the catalyst begin to move over time, and at high temperatures used in exhaust pipes, the particles of a finely divided catalyst tend to fuse together forming larger particles which offer less surface area, becoming less effective. This clumping process is known as sintering. To counteract sintering, manufacturers use excessive amounts of metal so that the converter meets emissions standards for the 10-to-15-year lifespan of the car and they also add other substances, known as promoters which act as a barrier to the clumping together of catalyst particles and also allow chemisorption to happen more readily. Another cause of deactivation is the opposite of sintering, where particles actually decompose into smaller particles and eventually become single particles which are catalytically inactive. Research suggests the by controlling the size and spacing of the metal particles, palladium particles won’t sinter into larger clumps, nor will they decompose into single atoms and so nanotechnology is being researched for these catalysts to increase their surface area to volume ratio which will lead to them becoming even more efficient. Catalysts can also be subject to poisoning, this is when products or contaminants collect on the surface of the catalyst, reducing the surface area available for reactants to be adsorbed onto. This is an issue for almost all heterogeneous catalysts, and therefore it affects catalytic converters as sulfur dioxide and lead poisons platinum and palladium catalysts. Therefore, all lead must be removed from fuels before being used in cars and this has also encouraged the rise of unleaded petrol which is not as harmful as its leaded alternative, in the sake of protecting the catalytic converter, as just a trace of a poisonous impurity can heavily disrupt the catalysis process. This has allowed catalytic converters to have a twofold positive impact on society, not only reducing the volume of harmful gases emitted, but they also reduced the volume of harmful fuel used.

A polymerisation reaction is one where a compound called a monomer, joins together with other monomers in order to form a long-chain molecule called a polymer. For polymerisation reactions the traditionally used catalyst was the Ziegler-Natta catalyst, which could be used to catalyse the polymerisation of alkenes such as ethene and propene, which is the basis of the production of plastics and other organic chemicals. These catalysts were prepared from titanium compounds, with an aluminium trialkyl compound which acts as a promoter. They function by the alkene molecule inserting itself onto a vacant site on the titanium atom, and after this the alkene molecule then moves around the titanium atom to join onto the alkyl chain and form the polymer as can be seen on figure 5. When polymers form, they can have atoms in the same positional order, however the atoms can have different arrangements in space, and this is known as stereoisomerism. As differently shaped molecules have different properties, only one particular orientation of the polymer may be desired, and so Ziegler-Natta catalysts are highly important as they provide stereochemical control such that only the isotactic polymer is produced.

However, an example of when new catalysts are discovered is when metallocenes were first discovered to provide even greater stereochemical control in polymerisation than the Ziegler-Natta substitutes. Metallocene catalysts, which were based on metal complexes with two cyclopentadienyl (Cp) or substituted Cp groups, (examples are shown in figure 6) displayed a new level of precision which allowed polymers to have unprecedented strength and clarity to the point where other polymers at the time were thought obsolete compared to it and because of this almost all major polymer producers invested heavily into the development of metallocenes and other single-site catalysts for polyolefins, these are a type of polymer with multiple uses in consumer goods, manufacturing materials and industrial products. The value that a catalyst breakthrough can have is shown by the response from the chemical industry to the emergence of new metallocene catalysts as at the turn of the millennium when first discovered dozens of chemical companies raced to develop an ever-increasing number of these catalyst structures, giving rise to an enormous stable of new materials. According to Science IP, the patent search arm of Chemical Abstracts Service, the number of patents published for metallocene catalysts peaked in 2002 at 387 globally and they were valued so highly that one firm was willing to embark on a $500 million 15-year effort to produce a metallocene catalyst based on titanium and zirconium. (11) Despite this, these catalysts could not take over immediately due to the fact that resins produced by metallocene catalysts such as linear low-density polyethylene (LLDPE) for film were harder to process than traditional Ziegler-Natta catalyst-based LLDPE, thus limiting their use in wider industry. This was because the narrow molecular-weight distribution of the metallocene-based resins affected the rheology, or flow properties, of the resin during processing, and so it did not work very well with existing converter process equipment. (11) However, metallocene products have continued to grow over time just because of the value they bring and the increased strength and the ability to down-gauge, so they are growing much faster than the polyethylene market is growing, demonstrating once again that catalysts can grow faster than the product that they are helping to make. (11)

The search for a new catalyst is always one of the highest priorities for the chemical industry due to the advantages for sustainability they provide by facilitating the running of industrial processes at less intense conditions (lower temperatures and pressures) whilst maintaining an appreciable rate of reaction. Improving catalyst performance for specific reactions has both financial and environmental benefits, in terms of lowering fuel costs and reducing the production of harmful waste gases as well as the fact that they can be re-used, preventing the use and subsequent waste of reactants. Considering what the previously discussed high-value catalyst examples all have in common, it is possible to explore a trend that links certain features of a catalyst to its immense worth. These links and connections form one of the main determinants of the value of a catalyst, which is the notion of criticality. Criticality has three main aspects, the first is importance in use, which relates to the ease or difficulty of substituting another material that can provide the desired properties of a scarce material. (8) Putting this in the context of metallocenes, it is clear that the next best alternative which were Ziegler-Natta catalyst offered nowhere near the advantages in polymerisation as they did, and so this established a notable level of importance of metallocenes in their respective industry. The second aspect is supply risks, concerning whether supply chains will be able to keep up with demand, this directly relates to how costly and abundant the substance is, some elements are only found as by-products of another substance or may only be found in certain geographical locations. In the perspective of palladium used in catalytic converters, they have been so important to society that it is rare to find an automobile that is fitted without one, and the palladium, rhodium and platinum materials used in the process are not very substitutable, and they are clearly in short supply, platinum used in catalytic converters has been shown to have very complicated supply chains whilst also not being very naturally abundant, to the point where producers are actively searching for alternatives as consumption of palladium at the current rate is unsustainable. The third aspect is time, criticality changes with time, what is critical today may not be critical tomorrow and so it is heavily dependent on what is important in society at any given moment. Despite these three aspects feeding into how critical something is, there is no value for criticality, instead something falls into a range between high and low criticality, and it is ‘in the eye of the beholder’. The noble metals used in catalytic converters and metallocenes used in polymerisation, due to their natural qualities, could therefore be regarded as a catalyst with a high level of criticality. The more critical an element in a catalyst is found to be, the greater the demand will be and the lower the supply will be, this combination of market forces will lead to there being pressure put on the prices of the catalyst which may not always be instant as markets respond to demand and supply signals with time lags, and so changes in criticality of certain elements may not be immediately noticeable, however there is a definite connection. Metallocenes were limited in the past by how well they were able to catalyse pre-existing processes and by how willing producers in those industries were to change their processes to suit the catalyst, this is an example of how the success of a catalyst in industry is dependent on the product that the catalyst is helping to make in this case companies in the U.S., Europe, South Korea, and Japan worried about the wave of commodity polyolefin capacity in the Middle East and China and wanted to use metallocene catalysts to differentiate their product lines which was further boosted their value. (11) As metallocenes were in direct competition with the Ziegler-Natta catalyst, it is evident that price is heavily dependent on how good a catalyst is relative to what is already available on the market, furthermore changes in the availability of a critical element or sudden changes in cost can heavily disrupt the activity that the catalyst is used in. Despite this critical elements are not always the most costly component of catalysts, this can be seen with the ferrocynal iridium phosphine catalyst, where 5kg of iridium is able to produce 10 million kilograms of product per year, with 2 million molecules being able to be catalysed by one catalyst molecule at a rate of 600,000 per hour. This 5kg of iridium would cost $100,000, but this only accounts for 30% of the cost of the catalyst, the main cost comes from other parts of the catalyst that work with the metal called ligands, and these cannot be recycled leading to the weighty cost. In addition to this, despite being used widely around the world, catalysts are made in very small quantities, and small-scale production tends to be expensive and taking into account the fact that catalysts often require multistep syntheses, this all leads large sums of money being involved which can very easily rise into the millions. This is apparent with rhodium when it is used as a catalyst, where prices increased 20-fold during a four-and-a-half-year period starting in early 2004, jumping from $16,000 to $314,000 per kilogram, these large price fluctuations are often as a result of derived demand, as for emerging industries these catalysts may be regarded as critical and so large values are attached. (8) High prices are also the result of complicated supply chains the metals used in catalysis often have global supply chains which involve multiple parties, for example if a certain quantity of platinum was required for an industrial process, this platinum would have to be obtained from a platinum broker for sale or rent, then the platinum would have to be sent to a catalyst manufacturer, and then the catalyst would have to be sent to a refiner to retrieve the platinum again at the end of the process as all parties would look to make a profit, by the end of the supply chain the net price of the catalyst will be ridiculously inflated.

Current catalysts touch every aspect of life, consider the Haber Bosch Process which fuels ammonia production via catalysis. The importance of ammonia comes from the fact that it is a nitrogen fertiliser which can then be used to increase production in agricultural industry shown in figure 7,500 million tons of artificial fertiliser are produced per year, a process which takes up around 2% of the world’s energy supply and accounts for 5% of the world’s annual gas production. It is classed as the most important discovery of the 20th century and as can be seen in figure 7, is vital for sustaining growth in human life. (12) This is an example of a catalyst that was established a long time ago and has been running for many decades, however the catalysts that will be the most important in today’s society are those that increase sustainability. The 20th century has witnessed a revolution in science which has led to us having the lives which we do today however it has also led to climate change from increased greenhouse gas emissions, this means that new catalysts are needed that don’t facilitate the production of chemicals and fuels through the use of fossil feedstocks, biomass feedstocks should be used instead. For us to stay below an increase in climate temperature of 2 °C it will actually mean having a net negative carbon emission meaning we would capture more carbon than we emit. (12) This is achievable as energy from renewable sources is becoming cheaper over time, solar and wind energy are actually cheaper than natural gas. The biggest issue is with energy storage, as these methods only generate electricity when the wind blows or when the sun shines. To solve this issue batteries can be used, lithium-ion batteries are a good option, but these have a low energy density despite their high efficiency, on the other hand synthetic fuels can be used which have a high energy density and the infrastructure is in place and would be the basis for a sustainable chemical industry. To make these feedstocks are required, these can be produced using ‘e’-refineries, (12) current catalysts used in these processes are very expensive catalysts e.g. platinum which are scarce and so there is a search for better catalysts, and therefore new catalysts need to be discovered for such processes. This is why vast amounts of fundamental and applied research is done by industry giants and university research laboratories to find out how catalysts work and to improve their effectiveness, this can be done my improving catalysts that are already in use or by finding a brand-new catalyst. In the search for new and better catalysts there is a lot of focus on experiments in real life to test theoretical models. When developing these new catalysts the properties of the best catalysts in terms of performance are determined by its composition and the physical and electronic structure on the atomic scale, by measuring and understanding these properties in relation to the catalyst activity it allows certain catalysts to be designed with the best properties for performance in terms of reactivity and selectivity. When the chemical industry was less technologically advanced in the 1900’s Alwin Mittasch, a German chemist known for his work in the pioneering of catalysts for the Haber-Bosch process, spent two years with 30 reactors on this process each testing for the ability of different materials as a catalyst for this process, this resulted in a low level of efficiency which really limited the overall progress which could be made. (5) Nowadays researchers have access to software theory and computational modelling which can be used to obtain information about processes and calculations can be done to give reliable results and this is much faster than experiment by hand, scientists can get a lot of information from calculation which cannot be easily gotten from real experiments as we have much more control over parameters and conditions that in real life would be difficult to obtain, helping to drive forward the discovery process. The procedure taken when considering properties for reactivity and selectivity, revolves around studying the structure of the active site and any intermediates involved in the catalysis process and this is known as characterisation and it is vital in the rational design of new catalysts. This process is done using the Stanford Synchrotron Radiation Lightsource (SSRL) which uses very intense x-rays to probe the structure of different potential catalysts, x-ray absorption spectroscopy using the SSRL allows catalyst analysis to be conducted much more efficiently than in a lab. (5) This is all done ‘in-situ’ whilst the catalyst is actually working such that the active site is being probed during testing, this is done by recreating the industrial catalyst reactors on a miniature scale for research purposes it is acknowledged that this information gained from working on the small scale can easily be transferred to the large industrial scale and chemical engineers help this transition. The catalysts will be probed by heating it to a very high temperature, watching how it changes its structure, and then reactant molecules will be introduced to see how it performs. Looking at the structure-activity relationship of a catalyst during this testing process makes it possible to see which structure of the catalysts in the course of the reaction is the most impactful one. This is key in the development and discovery of new catalysts, and it is only getting better over time, figure 8 shows mean sin or absolute errors (MSE and MAE) in successive computational models over time and they have decreased such that reliable results can be obtained. Graphing data is also helpful when it comes to comparing different catalyst options. For example platinum group metals have been shown to be some of the optimum metals in hydrogen gas synthesis, figure 9 illustrates this as the platinum metals are found at the top of the peak, now with computational analysis you can find alternative molecules that are close to the peak which may be more abundant and you can alter those structurally, for example increasing surface area by nano-structuring these materials, so that they become valid alternatives. (12) Oher factors come into the process of finding the right catalyst, such as when there may be multiple intermediates involved the catalysts needs to be capable of catalysing both reactions and then it needs to remain stable in working conditions. This whole process of catalyst discovery involves theory, synthesis, characterisation and then real-life testing, a procedure which can take decades, but at the end of it can change the landscape of entire industries.

From this discovery process some emerging catalyst fields have come to light, such as Fischer-Tropsch catalysts used in the conversion of waste to aviation fuels, although the process itself is not new, the catalysts involved in it are becoming increasingly important as they can be considered circular. This process involves the reaction between hydrogen and carbon monoxide, together known as syngas, using a catalyst and appropriate conditions can be used to produce hydrocarbon fuels and chemicals. Syngas can come from coal which is not very environmentally sustainable, therefore alternatives such as producing it from waste biomass are being developed by companies such as Fulcrum, who have developed and demonstrated a thermochemical process that converts municipal solid waste (MSW) feedstock into low-carbon renewable transportation fuels including jet fuel and diesel. The process combines gasification technology (conversion of biomass into gas) with the Fischer-Tropsch fuel process for the efficient, low-cost production of renewable transportation fuels. Applications of newly discovered catalysts can also be seen in reactions to convert CO2 into methanol on an industrial scale. Carbon dioxide is a notorious greenhouse gas and is widely recognised for its key contribution to global warming, and so there are efforts to reduce its emission worldwide by developing new technologies which don’t emit CO2 and also remove it. In the European Union, the current target is to reduce the greenhouse gas emission for 2030 to at least 55% compared with the level it was at in 1990. One of these ways is to convert it into something useful, methanol is an important platform molecule acting as chemical feedstock, which has the potential for manufacturing of nearly all chemical products. It is highly valuable not just because of this but also due to the fact that it is used for synthesis and reformulation of fuels and has high capacities for both energy and hydrogen storages. The global methanol demand has been increasing sharply in recent years, reaching the current annual methanol production capacity of over 100 million tons per year. Methanol is currently produced from the hydrogenation of carbon monoxide (CO), from syngas, using copper-zinc catalysts. The methanol synthesis technology from CO2 using heterogeneous catalysts has reached relatively high level of maturity. However this process is far from perfect as methanol synthesis from CO2 using heterogeneous catalysts suffers from several shortcomings such as harsh operating conditions in the form of high pressure and temperatures. Major amounts of sustainable and often expensive hydrogen are needed for the CO2 hydrogenation. Several new heterogeneous catalysts have been proposed for methanol synthesis and this has given rise to several new strategies for CO2 reduction to methanol which act as alternatives to thermocatalytic heterogeneous catalysis, for example homogeneous, enzymatic catalysis, photocatalysis and electrocatalysis. The advantages of the processes are that they use temperatures lower than in heterogeneous catalysis, they use of alternative sources of energy like light or electricity and they potentially higher methanol selectivity. In some of them, water is used for CO2 reduction instead of costly green hydrogen. Research is currently being done to compare different strategies for methanol synthesis from CO2 using quantitative criteria such as selectivity, productivity, stability, temperature, pressure, technological maturity and cost of the produced methanol evaluating the potential of these different ways to make methanol from CO2 in the most efficient ways and providing perspectives of their advancement over the coming years. A whole other area of catalysts research is in the field of biocatalysis which uses enzymes which work in the body, and so centuries ago being able to understand let alone use these to our advantage would have been unthinkable but with modern technology these could open up the pathway to whole new industries.

In conclusion, I believe that on a surface level a look into why the discovery of some chemical catalysts can be worth millions can be simply explained away by the fundamental principles of supply and demand. However, under a more careful consideration of the complexities of the different chemical structures and reaction mechanisms which fuel the reactions behind our day to day lives, I find that an alternative route can be taken to arrive at the answer, one which illustrates why catalysis will remain one of the most important areas of research in academia and technology for decades to come. Catalysis is the primary technology in the chemical industry, combining economic and ecological values more than any other technical principle, it is clear to see that the development of chemical products in advanced and industrialised societies will only be technically, economically, and ecologically possible by means of specific catalysts, shown by the fact that 95% of all products (in terms of volume) worldwide are synthesised by means of catalysis. (1) In 1948 Alwin Mittasch, described chemistry without catalysis as ‘a sword without a handle, a light without brilliance, a bell without sound’, catalysts are vital for allowing us to have the standard of living that we currently have. However, this does not explain why only some catalysts are worth millions and others such as the nickel used in the heterogeneous catalysis of synthesis gas production are not, despite performing at a high level compared to other noble metals. The catalyst market can be divided into four main areas: Chemistry catalysts (those used in the chemical industry), Environmental catalysts, Petroleum refining catalysts and Polymerisation catalysts, out of these four environmental and the polymerisation catalysts are seen as the key growth market for catalysts, while petroleum refining and chemistry catalysts are expected to have quite a stagnant trajectory. (1) As shown by my findings in this dissertation, the market does convey the value of important catalysts, however it does not truly reflect the economic importance of a catalyst in a process. I believe the true value of a catalyst should not be perceived in terms of what they bring to the market in terms of revenue and output, but rather I believe that their true worth should be looked at from the lens of what a world would look like without them, one filled with pollution, where the thought of efficiently carrying out chemical reactions would be unfathomable and where manufacturing industries would be seen as primitive compared to what they are today. This world is ever approaching as the criticality of elements used as catalysts increases, reserves depleting faster than they are being regenerated this is why current research is aiming to get new catalysts for new processes and better catalysts for existing processes to prevent this world from becoming a reality, new catalyst replacements must be discovered, and when they are discovered I truly now understand why they, not could, but will be worth millions.