New MOF turns CO₂ into methane

A NEW metal-organic framework developed at the University of Adelaide, Australia, can convert CO₂ and hydrogen into synthetic natural gas.

Christian Doonan, director of the university's Centre for Advanced Nanomaterials, and his team developed the catalyst, a ruthenium-impregnated zirconium-based MOF, in collaboration with CSIRO. Doonan says the catalyst could pave the way to making carbon neutral fuels. The methane could also be used in industrial processes, where methane is an important feedstock.

Carbon capture and utilisation (CCU) is a promising way to reduce net carbon emissions. The Sabatier reaction can reduce CO₂ to methane over a catalyst, but so far, finding efficient, resilient catalysts with good selectivity has proven difficult. Doonan and the team used CSIRO’s rapid catalyst testing facility to screen more than 100 catalysts, which greatly shortened the discovery process.

One of the major advantages of the catalyst is that it does not require a high-temperature calcination step or any caustic chemical processing. The catalyst is based on a commercially available zirconium terephthalate MOF called UiO-66. Using a wet impregnation method, RuCl₃was introduced into the pores of the activated MOF. 20 mg of the catalyst was used in each experiment in a fixed bed microreactor. The catalyst was dried and activated in the reactor under the reaction conditions. Hydrogen and CO₂ is flowed over the top of the catalyst at a ratio of 4:1. The best results were obtained at temperatures of 330–350˚C and 500 kPa of pressure. In these conditions, the catalyst converts 96% of CO₂ into methane, with 99% selectivity. The only observed byproduct was CO.

After more than 160 hours of testing, the catalyst remained stable and active and retained its selectivity for methane.

There is still some work to be done on the catalyst.

“The research priorities for us are a techno-economic assessment and development of scale-up methods. From a fundamental point of view we are also looking to fully determine the structure of the Ru species,” Doonan told The Chemical Engineer.

Journal of Materials Chemistry A doi.org/b82j