Energy and the Physical Sciences: Advanced materials for thermo-chemical oxygen storage and production

In this proposal we intend to take a novel approach to problems involving reaction and/or separation. We adopt the ideas of high temperature chemical looping and apply them at intermediate temperature by developing and investigating new, advanced materials capable of acting as solid state oxygen carriers. This approach would be applicable to a wide range of processes; here we intend to begin by demonstrating its validity through autothermal reforming of oxygenates and oxygen production. More advanced materials open up new areas of application owing to the ability to tailor their chemistry and structure to change both the thermodynamics and kinetics of oxygen transfer.

We will also work across many scales to link the fundamental chemistry of the materials to their oxygen transfer characteristics, facilitating a rational approach to materials design. This feedback between the fundamental chemistry and the process engineering is a unique feature of this proposal.

Simple metal oxides and mixtures, and mixed metal oxide anion conducting materials, e.g. LSCF (a perovskite) and lanthanum-nickelates/cobaltates (a Ruddlesdon Popper structure), will be examined to determine their usefulness in oxygen donor/chemical looping processes. The latter materials offer a starting point for material design since they are amenable to substitution with other cations allowing the chemical potential of their oxygen sources/sinks to be tuned.

In parallel we will also screen, making use of energetics available from publicly available data bases and via targeted first principles using DFT calculations, for novel materials suitable for reforming and oxygen production processes.

This project aims to open up near areas of application for chemical looping technologies, as well as providing fundamental insight into the behaviour of materials used for redox processes. Our focus on materials which allow chemical looping and oxygen transfer at temperatures not possible with standard chemical looping materials means that new applications are possible. Other redox processes that integrate better with other industrial or energy processes in terms of heat recovery and operability can also be conceived. This proposal also represents one of the few attempts to integrate the detailed structural chemistry with the process engineering, with significant interaction and feedback between these areas. Thus, we aim contribute significantly to the field by providing links between the atomic scale to the process scale, something which is currently lacking in the field of chemical looping. As such we expect this work to have more impact than simply reports on the behaviour of materials synthesised by trial and error (by in large the current state of the art), by moving to toward being able to tailor a material's characteristics a priori to suit the target process. To do this we are required to work at the interface between chemistry and process engineering, which is of benefit to both fields. The understanding and methodologies developed will have application to the chemical looping field in general, and other areas which rely on inorganic redox chemistry.
Oxygen production is central to many industrial processes, both current (e.g. Steel, gasification, partial oxidation), and proposed (e.g. oxyfuel combustion for carbon capture, underground coal gasification). Thus, the development of systems which can reduce the cost of oxygen production and lower the energy input is likely to become increasingly important. The cycles proposed here reject and accept heat at temperatures which are amenable to heat integration, potentially allowing efficiency gains. The same oxygen transfer materials also can be used for reforming, producing H2, an important industrial gas and energy vector. One barrier to implementation of redox schemes for oxygen production for carbon capture is the inherent risk in using a new technology on such a large scale, both from the point of view of capital cost and the powerplant availability if problems are encountered. A benefit, and important potential impact of this work, is production of materials which allow efficient oxygen production/reforming at a smaller scale for industrial processes or niche applications. Smaller scale application will build confidence in the technology and act as a stepping stone towards application at the kind of scale needed for oxy-fuel combustion power plants. This also provides opportunities for smaller enterprises to produce new technologies and applications which whilst not solving global warming, improve process efficiencies and generate economic activity in the UK.