RedNOx - Rational design of Pt and Pd catalysts for NOx reduction using H2 at low temperatures in lean exhaust gases (Duration: 11/2019 - 10/2021)







A new research project concerning the knowledge-based development of precious metal catalysts for the reduction of nitrogen oxides using hydrogen as reducing agent (H2-DeNOx) was started in November 2019. The research project is funded by grants from the Sächsische AufbauBank (SAB) and the European Regional Development Fund (ERDF).

Combustion engines based on liquid and gaseous fuels play an important role in ensuring mobility and in the generation of heat and electricity, e.g. in decentralized combined heat and power plants (CHP). In particular, CHPs play an important role with regard to the German government's climate plan, as they are able to provide energy flexibly if the fluctuating renewable energy sources wind and sun are not available in sufficient quantities.

However, combustion engines achieve high efficiencies and thus lower CO2 emissions, especially under lean, i.e. oxygen-rich combustion conditions. The high efficiencies are contrasted by the emission of pollutants, especially nitrogen oxides (NOx).  With the established processes for nitrogen oxide reduction, selective catalytic reduction using ammonia (SCR) and NOx storage catalysts (NSK), a significant reduction in NOx emissions can only be achieved above about 200°C. In real operation, however, the exhaust gas temperatures of diesel engines are often below 200°C, and in CHP applications, temperatures of only 120°C are reached after the heat exchanger. The only method for NOx reduction at low exhaust temperatures in oxygen-rich exhaust gases is the use of hydrogen as a reducing agent (H2-DeNOx). Platinum and palladium catalysts are effective for this reaction but have the disadvantage that the nitrogen oxides on these catalysts are not completely converted to N2, but partly also to N2O. However, N2O has a greenhouse effect that is 310 times greater than that of CO2, so that its emission must be avoided.

The scientific-technical objective of the RedNOx project is therefore the knowledge-based development of a novel catalyst for efficient NOx reduction using H2 in lean exhaust gases. The catalyst should provide the following properties: 

      • High H2-DeNOx activity between approx. 120 and 250°C
      • Selective NOx reduction to N2 (no N2O formation)
      • High selectivity of H2 for NOx reduction over the reaction with O2