The lean catalytic reduction of nitric oxide by solid carbonaceous materials

The reactions of O2, NOx and soot from diesel exhaust over Cu containing catalysts can significantly reduce soot and NOx emissions while producing N2 and CO2. We have evaluated the performance of Cu ion exchanged ZSM-5 and Cu adsorbed on granulated activated carbon (Cu-GAC) using GAC as a surrogate for soot in a packed bed reactor. CO, formed primarily by the oxidation of GAC with O2, appears to be a stable intermediate in the reduction of NO. With experimental parameters chosen to simulate diesel exhaust conditions, Cu-GAC is more effective than GAC mixed with Cu-ZSM-5, converting six times more NOx to N2 at 500°C at the representative gas hourly space velocity of 50,000. Both catalysts are poisoned by H2O and SO2. A mechanism is presented that is consistent with the experimental results.