Rational synthesis

Lead Research Organisation: University of Oxford
Department Name: OxICFM CDT

Abstract

This project falls within the EPSRC Hydrogen and Alternative Energy Vectors Research Area.
The Haber-Bosch process is used globally to produce ammonia from hydrogen and atmospheric nitrogen, mainly for use in fertilisers. Ammonia production is so important for our agricultural system that around 1.8percent of global energy production goes towards the Haber-Bosch process. The Haber-Bosch process in its current form requires very high temperatures and pressures (approximately 450C and 200 times atmospheric pressure) to operate effectively, partially explaining why it consumes so much of our energy output.
High temperatures are used to ensure the rate of the process is fast. High pressures are used to ensure the yield of ammonia is high, as this is an equilibrium process. Reducing the required temperature and pressure of operation of the Haber-Bosch process would not only represent a great reduction in energy use, but also increase the feasibility that this process could be powered by renewable energy sources, such as solar power, alone.
Ammonia is being widely researched as an alternative fuel with various applications, even examined for use in jet engines by Reaction Engines Ltd. and STFC (Science and Technology Facilities Council). The prospect of a carbon neutral fuel such as ammonia is an exciting step towards solving the climate crisis and reducing the energy requirements of the Haber-Bosch process is a key part of realising ammonia's potential.
A method of achieving this is the use of sorbents to shift the equilibrium of the reaction mixture. The removal of ammonia from the mixture by an absorption material promotes more reaction of nitrogen and hydrogen to form ammonia. Of course, absorbing the ammonia must be accompanied by desorbing the ammonia under less harsh conditions, so the ammonia can be in its useful, pure form. A balance of the strength of the interaction between the ammonia and the sorbent must therefore be found so the ammonia does not become 'stuck' in, or difficult to remove from, the sorbent.
Ammonia containing layered materials have been widely studied for the property of superconductivity. Due to the layered nature of these materials, it would be expected that ammonia sorption is fast in these materials. However, the understanding of the role of ammonia within many of these layered structures remains limited.
The aims of this project are to gain a greater understanding of the structural and electronic properties of ammonia containing materials. Once achieved, this knowledge can be used to develop sorbents beyond the magnesium chloride (MgCl2) and calcium chloride (CaCl2) already studied. This project intends to study layered materials and mixtures which involving absorbing and non-absorbing components. As such, the resulting mixture should be tuneable based on its composition, a very useful characteristic for optimising the ammonia absorption properties for the application.
It is hoped that an effective ammonia sorbent, composed of readily available materials, that can release its ammonia under a simple pressure change will be found.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023828/1 01/04/2019 30/09/2027
2265963 Studentship EP/S023828/1 01/10/2019 30/09/2023 Jonathan Betteridge Betteridge