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

The removal of nitrogen oxides (NO x ), 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 NO x is converted to NH3 via NORR, and the remaining NO x 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.