The lean catalytic reduction of nitric oxide by solid carbonaceous materials

The reactions of Oz, NO, and soot from diesel exhaust over Cu containing ca talysts can significantly reduce soot and NOx emissions while producing N-2 and CO2. We have evaluated the performance of Cu ion exchanged ZSM-5 and C u 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 O-2, 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 N-2 at 500 degreesC at the representative gas hourly space vel ocity of 50,000. Both catalysts art: poisoned by H2O and SO2. A mechanism i s presented that is consistent with the experimental results. (C) 2001 Else vier Science B.V. All rights reserved.