An integrated process to generate energy from methane combustion without producing waste carbon dioxide has been proposed by UK scientists.

With climate change an ever-present threat, reducing CO₂ emissions is critical. But increasing energy demands mean the solution isn't as simple as cutting fossil fuel combustion. Michael North and his team at the University of Newcastle say that it could be possible to maintain the energy production and immediately convert the waste CO₂ into useful chemicals avoiding the costs associated with carbon capture and storage.

North's system uses a membrane to separate and feed pure oxygen to the fuel allowing clean combustion, eliminating any NOx production. The waste CO₂ is then fed into a reaction mixture with an epoxide and a catalyst producing cyclic carbonates. Cyclic carbonates have many applications including degreasing agents, electrolytes and solvents.

Although reusing waste CO₂ is to make cyclic carbonates is not a new idea, previous proposals involve using a catalyst that needs temperatures above 150 °C and high pressures which requires more energy to be put in. North previously developed an aluminium complex with a tetrabutylammonium bromide as a cocatalyst that catalyses the reaction at temperatures in the range of 20-100 °C, compatible with waste heat from the power plant.

'The beauty of this system is that you're not making a new C-H or C-C bond, so the reaction is exothermic,' says North.

Nilay Shah, a chemical engineering expert at Imperial College London, UK, is impressed by the system. 'It's about the creativity of looking for the best molecules to make from CO₂ is , so that you can start to make really high volume molecules,' he says.

North demonstrated the process on a laboratory scale but says he is confident it could be made into a continuous flow process for a commercial system. He also plans to further investigate the catalyst's tolerance towards water and other impurities.

Yuandi Li 

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