De NOx catalysts at the exhaust of a spark ignition natural gas engine operating in lean conditions

In the present paper the catalytic properties of two different systems in the NOx reduction at the exhaust of a natural gas lean-burn engine are analysed. The proposed approach consists in using methane present in the exhaust as reducing agent. In particular, a sample of ferrierite zeolite modified with cobalt is compared with a platinum catalyst supported on gamma-Al2O3. Cobalt-ferrierite catalyst resulted much more active with respect to Pt-gamma-Al2O3 in dry exhaust conditions, but a strong inhibiting effect of water on NOx catalytic reduction was detected.