Removal of nitrogen monoxide from exhaust gases through novel catalytic processes

Abstract

The exhaust gas from vehicle engines and industrial boilers contains considerable amount of harmful nitrogen monoxide (NO) which causes air pollution and acid rain. To remove NO, at present, catalytic reduction processes using NH 3 or CO have been applied, but several problems remain to be solved. It is widely accepted that catalytic decomposition is the best method for the removal of NO; however, the catalyst with consistently high activity for the reaction has never been found. In this paper the present position of decomposition catalysts is mentioned and the catalytic performance of copper ion-exchanged zeolites and Ag-Co 3O 4 oxides etc. is summarized based on the respective authors' results. A reaction mechanism of the decomposition is also proposed on the Cu-zeolites. In the last section the catalytic reduction of NO by hydrocarbons in the presence of oxygen, the newly developed catalytic process for removal of NO, has been introduced. The observations reported here suggest that the catalytic decomposition and/or reduction may be used in practice instead of the present reduction processes.