Coupling Electrochemical NO Reduction with Selective Catalytic Reduction for Off-Gas Treatment Without External Reducing Agents

The removal of nitrogen oxides (NOx), specifically NO and NO2, is crucial in the treatment of industrial off-gases. It is typically done using reducing agents like ammonia through selective noncatalytic or selective catalytic reduction (SCR). A promising alternative independent of external reducing agents is electrochemical nitrogen oxide reduction (NORR) to NH3, but challenges arise at lower NO concentrations typical of industrial off-gases, affecting Faradaic efficiency. We propose a novel process that combines NORR and SCR: half of the NOx is converted to NH3 via NORR, and the remaining NOx is reduced via SCR using the NH3 produced before. This approach overcomes NORR limitations, reduces NORR electricity consumption by approximately 50%, and eliminates SCR’s need for external NH3. Our techno-economic analysis indicates that this NORR-SCR configuration has slightly higher costs than traditional SCR, while offering the potential for lower costs through optimized catalyst performance and enhanced sustainability via electrification and renewable energy integration.