Cost-effective ‘supercatalyst’ recycles CO2 and CH4

CHEMICAL engineers at the University of Surrey, UK have developed a cost-effective ‘supercatalyst’ that can convert CO₂ and methane, two major greenhouse gases, into syngas.

Syngas can be converted into a range of useful fuels and chemicals. The researchers, led by chemical engineering lecturer Tomas Reina, say that recycling CO₂ in this way could provide a practical alternative to simply burying it, while still having a meaningful impact on emissions.

Syngas is usually made by the steam reforming of methane. However, the researchers at Surrey instead looked at the bi-reforming of methane and the dry reforming of methane, both of which processes also require CO₂. One of the major problems with the processes is deactivation of the nickel-based catalysts due to carbon deposition and sintering. Reina and the team found that this could be mitigated through the use of tin and ceria.

The catalyst was created sequentially. The researchers first impregnated an alumina catalyst support with Ce(NO₃)₂.H₂O and calcined it at 800^oC. This was then impregnated with Ni(NO₃).6H₂O and calcined again, before being impregnated in the same way with SnCl. They synthesised a range of catalysts and tested them in the dry reforming and bi-reforming reactions. The most effective catalyst was found to have an Sn/Ni molar ratio of 0.2. Higher quantities of tin cover the active sites of the nickel, thus reducing the catalyst activity.

The catalyst remained active for at least 92 hours, and when tested in a bi-reforming reaction, Reina and the team found that it was very stable and effective with a range of CO₂-containing feedstocks, producing high-quality syngas at high conversion levels.

"This is an extremely exciting project and we believe we have achieved something here that can make a real impact on CO₂ emissions,” said Reina. “The goal we're all chasing as climate scientists is a way of reversing the impacts of harmful gases on our atmosphere – this technology, which could see those harmful gases not only removed but converted into renewable fuels for use in poorer countries is the Holy Grail of climate science.”

Applied Catalysis B: Environmental doi.org/cgfs