Closing the carbon cycle
Chemical strategies to provide a sustainable environmental and economic global transformation
The theme of global transformations is contributing to rethinking social adaptation in the context of our changing environment and global economy.
The uranium methoxide complex
Peak oil and climate change are two major resource constraint-driven adaptations that will transform the global economy over the next 50 years. Chemists at Sussex are developing potentially transformative solutions to address these two issues, that have arisen from modern society's absolute reliance on the finite resources of extracted oil and other fossil fuels.
Currently, over 80 per cent of the world's energy is generated from extracted oil and other fossil fuels, while many of our major industrial processes rely on this same source. This includes the production of chemicals, pharmaceuticals, plastics and petroleum, as well as the fertilizers (using the Haber-Bosch process) that support the agriculture needed to sustain an estimated 1.5 billion people worldwide. With an ever-increasing global population, demands on energy and food production will continue to increase. The problem of 'peak oil', the point at which hydrocarbon production will fall due to a decline in available resources, is now inevitable, although the timelines remain a matter for debate. Regardless, even a limitless oil resource would not negate the production of the greenhouse gases such as carbon dioxide (CO2) that results from the combustion of hydrocarbons and is contributing to potentially catastrophic global warming. Technical solutions to climate change must, therefore, include an attempt to 'close the carbon cycle', converting industrially produced CO2 and carbon monoxide (CO) back into hydrocarbons; a process that necessitates the formation of new carbon-carbon (C-C) and carbon-hydrogen (C-H) bonds.
Dr Alistair Frey preparing a uranium compound, which will then be reacted with carbon dioxide
Changing carbon into gasoline
Recent research by the Clean Fuels and Energy Group in the Department of Chemistry, headed by Professor Geoff Cloke FRS, has succeeded in using a uranium complex to generate methanol from CO and hydrogen at low temperature and pressure. Producing methanol from CO presents a potentially sustainable fuel source, as processes that convert methanol to gasoline - such as the Mobil MTG process - have existed since the 1970s.
This technology follows the breakthrough discovery of the uranium-based coupling of CO to form deltic acid - in the form of the so-called diuranium-deltate complex - using similar uranium complexes. This 'proof-of-principle' experiment demonstrated that C-C bonds could be formed to give complex molecular architectures from CO.
A non-fossil fuel source of hydrogen is essential for this process. The preferred alternative solution is to use solar energy to photo-catalytically 'crack' water to produce oxygen and hydrogen. A solar source of hydrogen secures the benefits of the Haber- Bosch process and, therefore, the supply of ammonia for fertilizers. Competing with groups from CalTech and MIT, other members of the Clean Fuels and Energy Group at Sussex are working on the use of mixed semi-conductor systems to capture solar energy to generate hydrogen from water and sunlight. The ultimate goal is to link the uranium-based C-C and CH bond forming reactions with photoproduction of hydrogen to photocatalytically produce hydrocarbons, closing the carbon cycle and powering the planet directly from the sun.
Professor Cloke's research group has recently been awarded a £1.5-million Advanced Investigator award from the European Research Council to further this research, with the goals of developing new methods of generating more complex carbon-derived organic molecules from CO and CO2 and to use a combined electrochemical and chemical approach to develop systems that will catalytically drive these processes.
Jess's perspective
After undertaking a research year in the laboratory of Professor Cloke as part of my MChem degree, I realised how much I enjoyed being involved in cutting-edge scientific exploration. I have always felt that Chemistry is like an ever-expanding jigsaw puzzle with many pieces yet to be filled in, and starting a DPhil feels like a natural extension of this pursuit for knowledge. Being a part of the Cloke group, and working to investigate potential new f-block catalysts for the functionalisation of small molecules such as carbon monoxide is thrilling, as I feel I can actively contribute to finding a solution for pressing global issues such as carbon-capture and waste gas recycling. I look forward to the challenges of participating in a research group, particularly one in such an inspiring and enthusiastic Chemistry department as the one here at Sussex. After falling in love with Brighton during my undergraduate degree I am very much looking forward to spending the next four years here and cannot wait to start in October.
Jess Higgins
DPhil student
