Catalyst improves methane combustion performance

Researchers from Penn – University of Pennsylvania, along with collaborators from Italy and Spain, have created a material that catalyses the burning of methane 30 times better than currently available catalysts.

According to a statement, the discovery offers a way to more completely exploit energy from methane, potentially reducing emissions of this powerful greenhouse gas from vehicles that run on natural gas. The catalyst may also offer a cleaner and cheaper way of generating energy from catalytic combustion in gas turbines.

‘It’s hard to come up with materials that are active enough and stable enough to withstand the harsh conditions of methane combustion,’ said Raymond J Gorte, the Russell Pearce and Elizabeth Crimian Heuer professor in the University’s department of chemical and biomolecular engineering. ‘Our materials look promising for some important applications.’

A representation of the newly developed catalyst on an aluminium oxide surface depicts the core-shell structure
A representation of the newly developed catalyst on an aluminium oxide surface depicts the core-shell structure

Catalysts that are currently available to burn methane do not do so completely, leaving unburned methane to escape into the atmosphere.

‘Particularly if you have a natural-gas engine, methane is going to be a major part of that tailpipe exhaust,’ Gorte said.

In addition, these conventional catalysts can require high temperatures of 600°C to 700°C to encourage reactions. Yet the catalysts themselves often lose their efficiency or deactivate when exposed to the high temperatures generated by methane combustion.

Additional environmental harm can result when methane is used to produce energy in a gas turbine. In this process, methane is typically burned in excess of 800°C. When those temperatures rise to around 1,300°C or higher, the reaction can produce harmful byproducts, including nitrogen oxides, sulphur oxides and carbon monoxide.

Conventional catalysts for methane combustion are composed of metal nanoparticles, and in particular palladium (Pd), deposited on oxides such as cerium oxide (CeO2).

Adjusting that approach, the researchers instead used a method that relies on the self-assembly of nanoparticles.

They first built the palladium particles and then surrounded them with a protective porous shell made of CeO2, creating a collection of spherical structures with metallic cores.

Because small particles such as these tend to clump together when heated, and because these clumps can reduce a catalyst’s activity, the team deposited them on a hydrophobic surface composed of aluminium oxide to ensure they were evenly distributed.

Testing the material’s activity, the researchers reportedly found that their core-shell nanostructure performed 30 times better than the best methane combustion catalysts currently available, using the same amount of metal. It completely burned methane at 400°C.

The researchers plan to further study the structure of the new catalyst to better understand why it works so well and they will use similar methods to create new materials to test.

The study, published in the journal Science, involved input from Matteo Cargnello, a postdoctoral fellow in Penn’s department of chemistry; Paolo Fornasiero and Tiziano Montini of Italy’s University of Trieste and National Research Council; and José J Calvino, Juan José Delgado and Juan Carlos Hernández Garrido of the Universidad de Cádiz.