Improved Sulfur Resistance of Noble Metal Catalyst for Lean-Burn Natural Gas Applications

Natural gas and biogas alone or in combination with conventional liquid fuels (dual-fuel applications) are advanced alternative solutions to diesel and gasoline in the future. Burning of natural- or biogas produces less CO₂ emissions per energy unit, and particulate matter emissions can also be reduced compared to more traditional liquefied fuels. This decrease in engine out emissions can be utilized as a tool to meet tightening emission limits and to improve the air quality locally in the areas with big challenges especially related nitrogen oxide and particulate emissions.

In the present study the focus was on the development of catalytic emission control technology for both mobile and stationary lean-burn natural gas applications. Main activities were related to the oxidation catalyst and its improvements towards sulfur poisoning and to enhance methane light-off performance. Combination between oxidation catalyst and selective catalytic reduction (SCR) to reduce NO_x emissions from especially dual-fuel engines is discussed as well.

The study showed that catalytic washcoat composition played an important role in methane oxidation. Methane combustion activity and sulfur resistance were improved by modifying chemical composition of the catalyst to optimize adsorption properties and support-active site interactions. Sulfur resistance of the catalyst was improved by modifying washcoat with acidic raw material, since it may change sulfur adsorption properties of the catalyst. Washcoat modification enabled also reduction in the noble metal loading which reduces significantly the cost of the catalyst.