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Compressed natural gas (CNG) has been regarded as an alternative fuel for current fossil fuels such as gasoline and diesel. Recently the increasing interest in shale gas is drawing more attention to CNG vehicles of which number is expected to increase. Exhaust gas from CNG engines with lean combustion contains relatively low nitrogen oxides and particulate matters compared to conventional fossil fuel based engines. However, high amount of unburned methane, which has much higher greenhouse warming potential than CO2, limits the wide use of CNG for many applications. Even though Pd-based catalysts have been popularly studied in order to convert methane, their activity and durability have not been sufficient for practical applications to aftertreatment of lean burn CNG engines and the formation of a new Pd containing.

Urea-SCR systems have become one effective method for meeting the ever tightening NOx emission control regulations for diesel engines. Higher activity of SCR catalysts in the low temperature region is crucial for meeting emission regulations and improving fuel economy. Some of the new catalytic components in the literature have shown good low temperature SCR activity, but they have not been fully confirmed to be durable enough for mobile applications. Fe-zeolite has been widely used in mobile applications due to its wide operating temperature window, but after exposure to large amounts of HCs at low temperatures, it is easily deactivated. We developed new SCR catalysts with improved low temperature activity and improved durability against HC fouling and thermal sintering by combining OSC (oxygen storage component) with Fe-zeolite.

Improved Lean NOx Trap (LNT) catalysts with enhanced NH3 generation feature were developed for the small diesel engine. The next generation LNT system needs to perform good NOx conversions over the wide temperature range including below 200°C for urban driving and above 400°C for motorway of real road driving. However, the extended use of BaO, a component of LNT known to be very effective for high temperature NOx storage, results in the decrease of low temperature NOx conversion due to the degradation of NO oxidation associating with sulfur over time. The improvement of the low-temperature LNT performance is a key requirement for the real driving emission control as the best operation temperature for urea-SCR is above ~250°C. In this study, our next generation LNT with new washcoat architecture has demonstrated improved NOx removal efficiencies under the wider operation temperature window than the current production technology.