Catalysis for Energy
With decreasing reserves of oil resources, there is a growing need to find a range of alternative energy sources over both short and longer timescales. Moreover, these new energy sources will need to be sustainable and have no or minimal impact on the environment. This field poses substantial scientific and technological challenges in the development of areas such as catalytic reduction of CO2, catalytic biodiesel production and catalytic water-spitting, which will require state of the art tools for catalysts preparation, characterisation, structure/activity/selectivity relations and mechanistic investigations, especially using the facilities at Diamond and ISIS.
The catalysis for energy theme aims to use fundamental science & engineering to develop innovative & practical solutions for current and future energy needs
there are currently five projects running as part of the energy theme including one project co funded with the design theme There is one Project still running from the initial projects
- A Multifunctional Flow Platform For Enhanced Biobutanol Production
This project aims to develop and understand an catalytic platform for performing the Guerbet reaction. This reaction is of considerable interest to upgrade bioethanol into butanol (BuOH) - Whilst EtOH is used as a fuel additive to gasoline for use in normal petrol cars it has many problems, including water solubility, corrosivity and poor energy content. BuOH is a superior fuel, has a higher energy content, better miscibility with petrol, lower water absorption and is compatible with current infrastructure. Crucially, current engines do not need modification to combust neat BuOH enabling rapid uptake of this biorenewable resource.
Our goal is to integrate macro, micro and nanoscale (by understanding complex synergistic interactions of multifunctional supported catalysts) to develop novel multifunctional catalysts to perform the conversion of EtOH to n-BuOH in an economical continuous process.
Dr Richard Bourne
- Chemical looping: the use of an oxidation state operating window for selectivity improvement
continuing form New approaches to Reforming and Integrated assessment
Chemical looping has been defined as occurring when “a given reaction (e.g., A + B →C + D) is divided into multiple sub-reactions with each typically being carried out in a separate reactor”. The definition need not be restricted to solid intermediates, or carriers, alone as what is critical is the requirement for the products and intermediates to be in different phases for ease of separation.
Chemical looping reforming of e.g. methane involves the reaction of methane with iron oxide (here haematite because of the nature of the cycle) in a multi-step process. Methane reacts step-wise with the solid phase, reducing the iron oxide progressively to iron and syngas (or complete combustion products depending upon contact time and mixing patterns)
Prof Ian Metcalfe
Prof Paola Lettieri
Prof John Dennis
- Non-Thermal Plasma Promotion of Low Temperature Water Gas Shift Catalysts
Water gas shift (WGS) catalysis is a key step in the purification of hydrogen following reforming processes both in refineries and for the use of hydrogen as a fuel in PEM fuel cell applications. In these processes, a successful low-temperature WGS catalyst will have to possess high activity and selectivity as well as good stability under a wide range of reaction conditions.
Existing catalysts do not meet these requirements due to the challenge associated with the thermodynamics of the reaction, which favours CO conversion at low temperature, and the need for high hydrogen purities. Therefore, it is important to operate the reaction as close to room temperature as possible and definitely below 150 oC. However, whilst there are catalysts active in this range, for example Au/CeZrO4, these catalysts deactivate rapidly with time on stream.
Catalysts which are more robust, for example based on copper are used industrially for the “low temperature” WGS reaction but generally operate above 250 oC and do not have sufficient activity at the much low temperatures that are required to maximise hydrogen purity. Recently, non-thermal plasmas has been utilised to enable catalysts to operate at low temperatures for a range of reactions by activating the gas phase molecules. This has proved to be very effective in reducing the temperature of operation for processes including reforming and deNOx reactions. For example, results from QUB have demonstrated that the selective catalytic reduction of NOx using toluene and n-octane can be achieved at ambient temperature over Ag/Al2O3 using a non-thermal plasma compared with needing temperatures of >300 oC under thermal activation.
This project aims to examine whether it is possible to decouple the thermodynamics of the WGS process from the kinetics using the hybrid non thermal plasma-heterogeneous catalyst technology thus allowing the reaction to occur as close to room temperature as possible.
Prof Chris Hardacre
- In-situ Probing Structure and Electronic Properties of Transition Metal Oxide Electrocatalysts
The project aims at unravelling the mechanism of the oxygen reduction (ORR) and evolution (OER) reactions catalysed by transmission metal oxides (TMOs) employing in-situ X-ray and surface techniques. The combination of different surface (X-ray photoelectron spectroscopy (XPS), low energy ion-scattering (LEIS) and secondary ion mass spectroscopy (SIMS)) and X-ray absorption/fluorescence techniques, as well as computer modelling, will elucidate the interplay between active surface sites and key intermediate species for the most active TMOs
Prof David Fermin
- Reaction Pathways in Alcohol to Hydrocarbon Conversion: a Multi-technique Approach.
The conversion of alcohols to hydrocarbons was first introduced in the Mobil MTG process using an HZSM-5 catalyst. Lurgi’s MTO (also ZSM-5) and UOP-Statoil’s MTO (SAPO-34) processes followed. The driver for these technologies was the availability of cheap methanol from natural gas as a feedstock for gasoline or olefins production.
Plants have now been built in China for generating gasoline and olefins from coal derived methanol, while the possibility of converting bioethanol to hydrocarbons via similar technology is attracting attention.
There have been numerous investigations of reaction mechanisms of methanol-to-hydrocarbons (MTH) over acid zeolite catalysts (1). Three different components of the reaction pathway can be distinguished:
(i) the initial reaction steps in which methanol reacts with acid sites in the zeolite or SAPO catalysts;
(ii) the mechanisms by which different hydrocarbon products are produced during steady-state working conditions; and
(iii) the causes of catalyst deactivation through coke formation. Understanding how the reaction pathways work is essential if optimum product selectivities and catalyst performance are to be achieved.
CoFunded with Design and Energy
Dr Stewart Parker
Prof Russell Howe
- Fuel Cells beyond methanol and ethanol – 3rd generation direct fuel cells using oxygenates as fuels.
The project brings together groups spanning materials synthesis, electrocatalysis, photocatalysis, engineering with the aim to develop new fuel cell technology to use of oxygenates (>C2) as fuels. It will combine the design of the new anode catalysts with the investigation of alternative oxidants and finally the production of a demonstrator unit based on the best technology developed within the project. It spans both the catalysis by design theme (DFT modeling and synchrotron/neutron source usage) and the energy theme. It requires a multidisciplinary approach and encompasses theory/experiment and science/engineering.
Dr Wen-Feng Lin
Prof Dan Brett
Prof Andrea Russell
- Understanding the components required for low temperature methane oxidation catalysts
As methane is 20 times more damaging a greenhouse gas than CO2, development of low temperature methane combustion catalysts is of vital importance to UK and global industry whether for after treatment in automotive applications or abatement of methane released from natural or bio-gas sources.
Recently Dr Thompson’s research group at QUB reported easily prepared 4-component catalysts for total methane oxidation where it is proposed that the acidic zeolite support plays a key role in increasing the electrophilicity of the Pd(0) species assisting in its reoxidation, whereas TiO2 improves oxygen supply and assists in the reduction of the PdO. The presence of platinum is proposed to maintain a high distribution of palladium [Osman, Applied Catalysis B, 187, 2016, 408]. Preliminary optimisation of the ratio of each component gave a catalyst with a T10% of 200°C and T97% of 300 °C using a realistic space velocity of 100,000 mLhr-1. This facile synthesis method gave one of the lowest temperature catalysts reported to-date and no decrease in conversion was observed over 50 hours time on stream. Decreased metal loading lowered activity, demonstrating the importance of close interaction of all four components. The aim of this proposal is to better characterise such catalysts, quantify the extent of interaction of the four components required for high activity and use this information to design more active catalysts with lower metal loadings for use in compressed natural gas automotive or stationary applications.
- Nature-Inspired Hybrid “Heterogeneous Catalytic, Photocatalytic and Biocatalytic” Approach for CO2 Utilisation
Biocatalysis is widely employed in the manufacture of chemicals and pharmaceuticals. Over a quarter of the known enzymes are oxidoreductases which require the action of a cofactor, typically nicotinamide adenine dinucleotide (NADH) or its phosphorylated form (NADPH). In the biocatalytic cycle, NADH serves as hydrogen donor oxidised to NAD+). Inspired by nature, efficient enzymatic (and photocatalytic) CO2 (Greenhouse Gas) conversion to useful chemicals (e.g. methanol) is attractive with low energy demand. But given the high cost of NADH (bulk price: $3,000/mol3), stoichiometric supply in biotransformations is not economically feasible and efficient regeneration (NAD+ → NADH) is required.
We have recently demonstrated for the first time a novel and clean strategy for NADH regeneration (by selective hydrogenation of NAD+) that draws on heterogeneous catalysis using Pt/Al2O3 and H2 as reducing agent. A move from other sacrificial hydrogen sources to H2 gas and use of solid catalysts simplify downstream separation, eliminating toxic waste byproducts as protons are the sole released species. However, when coupled in situ with bioconversion the overall efficiency was limited by the low regeneration rate, suggesting further enhancement is critical.
In this project, we propose to introduce light energy to our innovative H2-driven (use as reducing agent throughout the project) NADH regeneration system employing photoactive TiO2 supported Pt nanoparticles as a multifunctional catalyst (Pt promotes hydrogenation of NAD+ and TiO2 promotes photocatalytic NAD+ reduction). We will also investigate the feasibility of integrating such regeneration technology in tandem with “one-pot” CO2 bioconversion, where again Pt/TiO2 exhibits multifunction for both NADH regeneration and direct photocatalytic CO2 conversion.
(i): to establish the feasibility of H2-driven Pt/TiO2 catalysing both selective hydrogenation of NAD+ to NADH and photocatalytic NAD+ reduction with associated optimal process parameters and catalyst characteristics;
(ii): to understand the surface reaction mechanism (e.g. active sites and reaction intermediates/steps, etc.) by advanced infrared spectroscopy and other surface sensitive measurements for further catalyst design;
(iii): to examine the feasibility of “one-pot” reaction coupling CO2 biotransformation in tandem with NADH regeneration by Pt/TiO2, with and without light energy.
James A. Anderson
- Scaleable Production of High Purity Hydrogen using a Hybrid Non-Thermal Plasma-Catalytic Process
The water gas shift (WGS) reaction is an important process in the production of clean hydrogen both for refinery processes as well as for hydrogen fuel cells. The main objective is to remove the CO impurities which are formed during the reforming reactions. The WGS reaction is exothermic (ΔHo = -41.2 kJ mol-1) and is equilibrium limited at high temperature which limits the CO conversion, therefore, low temperature operation is desirable. The main objective for the current project is to establish if the gas phase reactants can be activated using non-thermal plasma (NTP) in order to allow the reaction to proceed at the lowest temperature possible.
The remainder of the present project will: 1) examine the mechanism of the process via modelling (University of Aberdeen and University of Liverpool) as well as in Belfast/Manchester via the spectroscopic measurements and 2) obtain an understanding of the reaction parameters affecting the activity and, particularly, the stability of the catalyst with time on stream (gas phase composition, temperature of the feed, voltage-frequency characteristics).
The aims of this proposal are:
(i) to develop reactor designs that enable NTP-catalytic WGS reaction to be scaled up;
(ii) to stabilise the gold based catalysts by plasma treatments/preparation prior use;
(iii) to investigate the use of a hybrid NTP-catalyst process for oxygen activated WGS and PROX reactions
- Photoelectrocatalytic direct alcohol fuel cells
Low molecular weight alcohols, such as methanol and ethanol, have been proposed as promising alternative fuels to H2 in low-temperature PEM fuel cells due to their liquid nature, high energy density, low toxicity, availability and ease of handling. Methanol and ethanol are widely studied as fuels for direct alcohol fuel cells. Methanol is toxic, whereas ethanol is non-toxic and can be produced by fermentation of sugar. However, there is an on-going public debate on the ethics of utilizing food stocks for fuel production instead of nutrition. Thus, second generation bio-fuels, such as methanol and ethanol, are proposed to be produced from non-food based biomass feedstock such as lignocellulose biomass. As well as ethanol, n-butanol is considered as a 2nd generation bio-fuel and it has some advantages such as better infrastructure compatibility than ethanol, higher energy density, lower water adsorption, and better blending ability with gasoline.
The current UK Catalysis Hub project has been examining new electrocatalysts for the electrooxidation of the range of butanol isomers in both acidic and alkaline media. In particular, significantly higher activity of a PtSn bimetallic catalyst for n-butanol electro-oxidation in acidic media compared to pure Pt has been clearly demonstrated. On addition of Sn, a distinguishable oxidation pre-peak was observed at a much lower onset potential for PtSn compared to those for Pt. This has been attributed to facile formation of OHads at lower potentials on Sn. These results have been extended to examine the selectivity of the electrocatalyst and at least some CO2 is formed from the butanol oxidation as noted by IR spectroscopic measurements. Furthermore, utilising a rotating disk electrode, the deactivation of the electrocatalyst on repeated potential cycles is eliminated. This has been the major problem with Pt-Sn based direct ethanol fuel cells and was attributed to the loss of the Pt-Sn interaction through, for example, dissolution of the Sn off the surface of the catalyst. These new exciting results show that this is not the case and we speculate that it is a diffusion issue with the alcohol forming a “hydrophobic” layer above the electrode which prevents efficient diffusion of the oxidant (water in this case) to its surface and decreases the low overpotential activity.
The aim of this proposal is to develop a photoelectrocatalytic system to generate the oxidant at a lower over potential at the electrode surface. A number of studies have used this approach for methanol fuel cell applications, predominantly in alkaline media. In addition, porous α-Fe2O3 supported Pt has been used as a photoactive anode for the oxidation of ethanol under alkaline conditions, showing an enhancement of the current obtained under illumination. Within this project, acidic conditions will be employed to build on the most promising results obtained within the current project, as well as the practical issues associated with finding a suitable commercial membrane material for alkaline fuel cells.
Aims and objectives
The aims of this proposal are:
(i) to study the activity and selectivity of a range of photoelectrocatalysts for the oxidation of ethanol and butanol under acidic conditions;
(ii) to develop an understanding of the reaction mechanism on illumination of light;
(iii) to develop a photoelectrocatalytic fuel cell design to test the best photoelectrocatalysts.
Co-PIs: Wen Feng Lin, Daniel J Brett, Andrea E Russell
PDRA: V. Puthiyapura
- Solar-driven Water-splitting (reverse) gas Fuel Cell (SWFC)
The dwindling supplies of fossil fuels are not only the prime source of the world’s energy but also a valuable chemical feedstock. In addition, the burning of fossil fuels to create electricity is the major contributor to global warming, releasing ca. 8.0 Gt of carbon dioxide pa into the atmosphere, i.e. ca. 10% of the current level. Of the renewable energy resources that might substitute for the fossil fuels, only sunlight, or solar energy, has the capability to satisfy current and future global energy demands, since the amount of solar energy falling on the Earth is > 5000 times humankind’s present energy requirements.
There is a real need for an efficient (> 10%), inexpensive (< £5 m-2) solar energy conversion device that generates a readily utilisable chemical fuel. A current popular approach is to try to develop an efficient, solar-driven, water-splitting system, since it uses the sun’s energy to produce hydrogen, which can be readily stored and used for
transport. Hydrogen is also non-polluting when used as a fuel, since only water is produced when it is burned in air. The distribution of any fuel throughout the world also comes at a cost and there is increasing interest in efficient 'distributed energy', i.e. low-cost, simple to use energy-producing systems, such as a solar driven water splitting system, that can be used locally to create the fuel needed to power the home and transport.
In 2011, Lewis and his co-workers established that it was possible to use a proton exchange membrane, PEM, in a reverse fuel cell, to carry out the sustained electrolysis of water vapour and, in 2013, Martens et al. demonstrated that it could be driven photocatalytically, using a TiO2 photocatalyst. The basic features of such a 'Solar-driven Water-splitting (reverse) gas Fuel Cell' (SWFC) are illustrated in Figure 1 below:
Figure 1: Schematic illustration of a SWFC, comprising: (1) black flow plate, (2) cathode, (3) PEM, (4) photocatalyst anode and (5) clear, front flow plate.
Such a cell has significant benefits over that of a conventional photoelectrolysis cell in that: (i) efficiency-lowering bubble formation is avoided, (2) the source of the water vapour does not have to be pure and (3) no pumping is required as natural convection will provide the necessary supply of water vapour. Interestingly, this work has, so far, attracted only a small amount of attention (only 6 citations), possibly because a UV-absorbing photocatalyst (TiO2) was used and so the solar conversion efficiency of the cell was low.
The limited capability of a SWFC can be improved markedly through: (1) the incorporation of a visible light photocatalyst, (2) the use of a highly effective water oxidation catalyst, such as RuO2, and (3) the employment of a light-distributing PEM (Enocell), so as to render the cells stackable. Thus, a research programme based on these initiatives is proposed with the overall objective of producing an efficient, visible-solar light-driven, stackable, SWFC for commercialisation.
- Reaction-Separation Engineering for the Production of Bio-based Chemicals
As the security of supply of oil becomes increasingly uncertain, an increase in the use of renewable resources is expected. 5-hydroxymethylfurfural (HMF) is a key renewable compound, which can be readily obtained from hexose sugars. HMF can be oxidized to 2,5-furandicarboxylic acid (FDCA), a potential renewable replacement for the monomers used to manufacture polyamides, polyesters and polyurethanes e.g. renewable packaging. It can also undergo reductive deoxygenation to 2,5-dimethylfuran (DMF) or reduction to 2,5-dimethyltetrahydrofuran (DMTHF). Both have high energy density and low volatility and so are potential renewable fuel replacements.
This project seeks a world leading novel process for the production of HMF and its derivatives, with 4 key innovations: A: improved homogeneous catalysts for the production of HMF; B: a novel membrane reactor technology for HMF production/separation; C: develop heterogeneous catalysts and processes for downstream conversion of HMF to its derivatives; D: kinetic modeling.
Prof. Joe Wood
Dr Matthew Jones
the initial Projects focused on
i) Gas to liquid transformation,
ii)Synthesis and utilisation of biofuels,
iii) Process integration and intensification for efficient energy usage and storage, and
iv) Photocatalytic water splitting.
more information in the initial energy projects can be found here