IMOKAT: Precious metal-free catalyst for methane oxidation

Aim of the project "IMOKAT – Development of an innovative methane oxidation catalyst to reduce exhaust emissions from ships operating on gas" was to develop a catalyst for the oxidation of methane that is reduced in precious metals or at best free of precious metals. With the addition of nitrogen dioxide as oxidant and at pressures of up to 5 bar, the catalyst should achieve a methane conversion of at least 60 percent at a temperature of less than 550 °C. The methane should be oxidized as completely as possible to minimize the formation of by-products such as carbon monoxide or formaldehyde. Another focus was the identification of the best production method for a corresponding honeycomb catalyst: extrusion, impregnation or dip coating.

The IMO Tier III emissions standard of the International Maritime Organization limits nitrogen oxide emissions from ships in order to protect the environment and climate. One option to reduce NOx emissions is to switch from conventional diesel to gas engines. However, the use of gas-based fuels leads to another challenge: incompletely burned methane ends up in the exhaust gas and contributes to global warming. The solution: the use of catalysts for methane oxidation.

Up to now, methane oxidation has mainly been carried out by using catalysts containing precious metals. They have two disadvantages: Firstly, they react with the sulfur contained in fuel and engine oil and are therefore limited in their effectiveness. Secondly, the costs of precious metals are difficult to calculate and have risen sharply in recent years. Within the framework of IMOKAT, Fraunhofer UMSICHT was therefore been asked to develop a catalyst with reduced or no precious metals, which would have a high mechanical and chemical stability.

The project at Fraunhofer UMSICHT focused on the development of an exhaust gas catalyst based on cerium and manganese. Tests of promising catalyst samples on a laboratory scale showed that the cerium-manganese catalyst is suitable for methane oxidation under ship-specific process conditions. Based on these results, the cerium-manganese catalyst will be further optimized.

In addition, the researchers concluded that extrusion is the best synthesis method for non-precious metal honeycomb catalysts. Both impregnation and dip coating, in which a thin catalyst film is applied to a carrier material in each case, were unable to achieve the required methane conversions. Only during extrusion can a large amount of catalyst material be introduced without cavities being blocked by applied layers. Further optimizations are also planned in this area.

• MAN Energy Solutions SE
• Ruhr-University Bochum, Chair of Technical Chemistry
• Technical University Munich, Chair of Technical Chemistry I