CataRaman: Watching Catalysts in situ using Total Internal Reflection Raman Spectroscopy
Lead Research Organisation:
Durham University
Department Name: Chemistry
Abstract
Research Challenge:
Until recently, most methods for studying solid catalysts have been under low pressure / low temperature conditions - very different from those required for the chemistry to occur. Thus, new techniques that allow insight under typical catalyst operating conditions are very valuable in understanding how these important processes work at a molecular level. In the area of optical spectroscopy very few truly surface-sensitive techniques exist, despite in principal being very well suited to studying materials under operational conditions (many materials and reactants such as gases are more transparent to light than electrons or soft X-rays). Since the catalytic chemistry of interest typically only occurs at the catalyst surface, surface-sensitivity is very important for studying these materials. To understand the chemistry occurring on a solid catalyst's surfaces it is easier to study materials of a well defined uniform size, structure and composition. This eliminates the problem of having many competing processes on different parts of the material's surface. Methods for making these uniform materials in a scalable way (to allow enough material for realistic high pressure catalyst testing) are generally limited to using colloidal synthesis of nanoparticles and subsequent deposition onto an oxide such as silica. This is a problem for spectroscopic studies, because the synthesis necessarily involves additives to stop particle agglomeration - these are hard to remove, remain on the surface of the metal particles and are likely to give rise to spectroscopic signals obscuring those of the molecules reacting at the catalyst surface.
Timeliness / UK Importance:
Solid catalysts are used in 90% of all petrochemical-based industrial processes; heterogeneous catalyst manufacture is worth $250bn annually. Commodity chemicals in the UK alone turnover £18.4bn annually. Currently, 99% of carbon-based feedstocks used by the chemicals industry (and indirectly by many others) are derived from petroleum and natural gas. The pressure to switch existing chemical processes to more sustainable feedstocks requires the development of new catalysts with significantly different properties. To do this requires a greater understanding of the way these materials actually work, allowing rational design of catalytic materials and processes, and thus enabling more efficient and sustainable manufacturing of commodity chemicals. This is important to the UK specifically not only in securing the future of the manufacturing sector but also addressing the energy challenge by both 'greening' current technologies and providing new more sustainable, alternative processes.
Project Aims: This project aims to use a new advanced spectroscopic technique to studying solid catalysts both during their preparation and under realistic operating conditions. The project will focus on epoxidation chemistry of higher olefins - an important reaction for producing strategic intermediates that are used in products such as surfactants, hydraulic fluids, de-icers, plastics and fibres. This reaction is an important current target for new catalytic technology as it currently uses non-green oxidants that are environmentally harmful and atom inefficient.
Innovative Solution:
This project will take TIR (Total Internal Reflection) Raman spectroscopy, a recently developed spectroscopic tool, and apply it to study solid catalysts in situ for the first time. This provides a new tool that allows intrinsically surface sensitive Raman spectra to be acquired from a catalyst surface under reaction conditions. To facilitate this, well defined materials in terms of uniform size, structure and composition will be obtained by using organometallic chemistry to prepare nanoparticles directly on a silica surface. This avoids the use of synthetic agents often used in this kind of synthesis allowing spectroscopy of adsorbates on clean nanoparticles.
Until recently, most methods for studying solid catalysts have been under low pressure / low temperature conditions - very different from those required for the chemistry to occur. Thus, new techniques that allow insight under typical catalyst operating conditions are very valuable in understanding how these important processes work at a molecular level. In the area of optical spectroscopy very few truly surface-sensitive techniques exist, despite in principal being very well suited to studying materials under operational conditions (many materials and reactants such as gases are more transparent to light than electrons or soft X-rays). Since the catalytic chemistry of interest typically only occurs at the catalyst surface, surface-sensitivity is very important for studying these materials. To understand the chemistry occurring on a solid catalyst's surfaces it is easier to study materials of a well defined uniform size, structure and composition. This eliminates the problem of having many competing processes on different parts of the material's surface. Methods for making these uniform materials in a scalable way (to allow enough material for realistic high pressure catalyst testing) are generally limited to using colloidal synthesis of nanoparticles and subsequent deposition onto an oxide such as silica. This is a problem for spectroscopic studies, because the synthesis necessarily involves additives to stop particle agglomeration - these are hard to remove, remain on the surface of the metal particles and are likely to give rise to spectroscopic signals obscuring those of the molecules reacting at the catalyst surface.
Timeliness / UK Importance:
Solid catalysts are used in 90% of all petrochemical-based industrial processes; heterogeneous catalyst manufacture is worth $250bn annually. Commodity chemicals in the UK alone turnover £18.4bn annually. Currently, 99% of carbon-based feedstocks used by the chemicals industry (and indirectly by many others) are derived from petroleum and natural gas. The pressure to switch existing chemical processes to more sustainable feedstocks requires the development of new catalysts with significantly different properties. To do this requires a greater understanding of the way these materials actually work, allowing rational design of catalytic materials and processes, and thus enabling more efficient and sustainable manufacturing of commodity chemicals. This is important to the UK specifically not only in securing the future of the manufacturing sector but also addressing the energy challenge by both 'greening' current technologies and providing new more sustainable, alternative processes.
Project Aims: This project aims to use a new advanced spectroscopic technique to studying solid catalysts both during their preparation and under realistic operating conditions. The project will focus on epoxidation chemistry of higher olefins - an important reaction for producing strategic intermediates that are used in products such as surfactants, hydraulic fluids, de-icers, plastics and fibres. This reaction is an important current target for new catalytic technology as it currently uses non-green oxidants that are environmentally harmful and atom inefficient.
Innovative Solution:
This project will take TIR (Total Internal Reflection) Raman spectroscopy, a recently developed spectroscopic tool, and apply it to study solid catalysts in situ for the first time. This provides a new tool that allows intrinsically surface sensitive Raman spectra to be acquired from a catalyst surface under reaction conditions. To facilitate this, well defined materials in terms of uniform size, structure and composition will be obtained by using organometallic chemistry to prepare nanoparticles directly on a silica surface. This avoids the use of synthetic agents often used in this kind of synthesis allowing spectroscopy of adsorbates on clean nanoparticles.
Planned Impact
This project will take a new spectroscopic technique and use it to provide direct in situ insight into heterogeneous catalytic processes, a key underpinning technology at the heart of almost all industrial chemical processes. Accordingly, the project has clear potential for impacting Society and the Economy via the catalysis and process industries. New knowledge about heterogeneous epoxidation will help develop better, more selective / greener catalysts. More importantly, the future availability of this novel technique for surface sensitive in situ Raman studies of heterogeneous catalysts will have wider impact by offering a highly advantageous in situ technique for tackling challenges in this field. Additionally, a number of broader impacts in terms of People and Knowledge (including outreach) have been identified. Overall, the outcomes of the project have a broad range of beneficiaries:
a) Catalysis and Process Industries: The UK commodity chemicals industry contributes significantly (annual turnover £18.4bn) to the UK's economy. This project will impact this sector of the economy by providing a new way to get underpinning and fundamental insights into the catalytic processes at the heart of the chemical transformation processes involved. In turn this will allow the rational design of new heterogeneous catalysts with enhanced performance (selectivity, energy-/resource-efficiency). This project will directly investigate heterogeneous direct higher olefin epoxidation with the aim of understanding the key selectivity problem and how greater selectivity could be achieved. This process currently lacks commercially viable catalysts unless non-green oxidants (peroxides, PhIO, NaOCl), which are environmentally very harmful are used. The resulting new technique will also offer a valuable means to investigate other specific questions about exisiting catalytic processes or those under development.
b) Academic Community: The above importance of heterogeneous catalysis in societal and economic terms necessitates a substantial community of researchers providing underpinning expertise in this field. This project will both springboard SKBs early research career in this area and impact PhD and project students working with / in collaboration with SKB in the next 1-5 years (including the PhD participating directly). Making available the knowledge and understanding required to apply this technique to heterogeneous catalysis (the goal of this project) will also enable other academic researchers to draw on this approach to get otherwise unobtainable information using this surface sensitive, in situ Raman technique.
c) General Public: The impact of improved heterogenous catalysts in terms of efficiency gains, mitigation of environmental damage and the financial benefits to UK economy means improvements to this technology benefit us all. The provision of techniques and expertise delivered by this project for making such improvements will help allow us to continue to enjoy the many manufactured goods and energy resources we take for granted while addressing the need to mitigate environmental damage and find more sustainable approaches to the production of consumer goods. This project specifically targets greener catalysts for higher alkene epoxidation - a reaction that is currently carried out using environmentally harmful processes, but produces many important consumer goods such as surfactants, hydraulic fluids, de-icers, plastics and fibres.
d) Schools: Outreach specifically related to this project will be targeted through DU Institute of Advanced Study and a student project offered through the North East Schools Industry Partnership event held annually at DU.
a) Catalysis and Process Industries: The UK commodity chemicals industry contributes significantly (annual turnover £18.4bn) to the UK's economy. This project will impact this sector of the economy by providing a new way to get underpinning and fundamental insights into the catalytic processes at the heart of the chemical transformation processes involved. In turn this will allow the rational design of new heterogeneous catalysts with enhanced performance (selectivity, energy-/resource-efficiency). This project will directly investigate heterogeneous direct higher olefin epoxidation with the aim of understanding the key selectivity problem and how greater selectivity could be achieved. This process currently lacks commercially viable catalysts unless non-green oxidants (peroxides, PhIO, NaOCl), which are environmentally very harmful are used. The resulting new technique will also offer a valuable means to investigate other specific questions about exisiting catalytic processes or those under development.
b) Academic Community: The above importance of heterogeneous catalysis in societal and economic terms necessitates a substantial community of researchers providing underpinning expertise in this field. This project will both springboard SKBs early research career in this area and impact PhD and project students working with / in collaboration with SKB in the next 1-5 years (including the PhD participating directly). Making available the knowledge and understanding required to apply this technique to heterogeneous catalysis (the goal of this project) will also enable other academic researchers to draw on this approach to get otherwise unobtainable information using this surface sensitive, in situ Raman technique.
c) General Public: The impact of improved heterogenous catalysts in terms of efficiency gains, mitigation of environmental damage and the financial benefits to UK economy means improvements to this technology benefit us all. The provision of techniques and expertise delivered by this project for making such improvements will help allow us to continue to enjoy the many manufactured goods and energy resources we take for granted while addressing the need to mitigate environmental damage and find more sustainable approaches to the production of consumer goods. This project specifically targets greener catalysts for higher alkene epoxidation - a reaction that is currently carried out using environmentally harmful processes, but produces many important consumer goods such as surfactants, hydraulic fluids, de-icers, plastics and fibres.
d) Schools: Outreach specifically related to this project will be targeted through DU Institute of Advanced Study and a student project offered through the North East Schools Industry Partnership event held annually at DU.
Organisations
People |
ORCID iD |
| Simon Beaumont (Principal Investigator) |
| Description | We have been able to achieve our primary original objective of demonstrating that "total internal reflection Raman spectroscopy" can be used as a tool to look at adsorbates (reactants, intermediates) on small metal nanoparticles, typical of those found in heterogeneous (solid) catalysts, such as are found ubiquitously in chemical plants or in the catalytic converters of cars. Specifically, we have developed a spectrometer using a CCD and spectrograph able to monitor further into the infrared and a cylindrical lens setup allowing distribution of incident laser light to limit sample damage while maintaining high optical throughput - modifications necessary to obtain good spectra of heterogeneous catalysts. We have looked at a number of different types of nanoparticles outlined in the proposal or being developed for other applications using the TIR Raman setup and been able to see the removal of trace species from the surface as a result of plasma cleaning and then the adsorption of catalytic reactants and intermediates - e.g. when ethylene gas is adsorbed we observe di-sigma bonded and pi bonded ethylene - the latter is difficult to see using alternative techniques such as SFG or various forms of IR spectroscopy and is important as a substrate/reactant in both prototypical reduction and oxidation reactions (in particular ethylene epoxidation, the goal of our study). A significant challenge or negative result was the use of the ubiquitous nanoparticle capping agent PVP (used widely to prepare nanoparticles) - we identified this fluoresced with all incident wavelength lasers tested and had to be removed thoroughly to acquire Raman spectra. We were successful using the surface organometallic routes proposed or other capping agents such as oleylamine. |
| Exploitation Route | The first demonstration of using TIR Raman to study catalysts is likely to find application in accessing complimentary spectroscopic information for many studies of solid catalysts and discussions are very positive as a result of conference presentations, both with leading UK groups (e.g. Prof. Chris Hardacre), and companies (e.g. Johnson Matthey) about possible use of this technique in future studies (we have begun to use the technique to support a iCASE award student with Johnson Matthey very recently). In order to take this work forward with a view to practical / industrial applications a key next step is to demonstrate how it will work for more complex systems, such as supported catalysts, as well as for single layers of catalyst nanoparticles, as well as investigating the applicability of the technique to a wider range of systems. A PhD student to take this forward is in place for October 2020 start after a student regrettably pulled out at the last minute in September 2019. |
| Sectors | Chemicals |
| Description | While our initial development of the instrument and methods to use TIR Raman is something which stalled for some time after the EPSRC CataRaman project, we have recently been able to apply this past learning to both a JM Case student and a European ITN project (both in collaboration with a catalyst manufacturer) Johnson Matthey, providing evidence that this approach can be used on important catalytic systems for greener or more efficient chemical processes (societal benefit of more sustainable chemical productin) or to tune catalysts on the basis of improved structural insight (mainly economic in feeding into the iCASE partners understand of efficient catalyst synthesis). We do anticipate public facing outputs such as papers from these projects drawing on the progress since CataRaman in the near future. |
| First Year Of Impact | 2020 |
| Sector | Chemicals |
| Impact Types | Societal,Economic |
| Description | EPSRC - JM iCASE |
| Amount | £58,000 (GBP) |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 10/2017 |
| End | 10/2021 |