Method for the catalytic conversion of nitrogen oxides contained in the exhaust gas of an internal combustion engine

In a method for the catalytic conversion of nitrogen oxides contained in the exhaust gas of an internal combustion engine, by adding a reducing agent to the exhaust gas upstream of a denitrification catalytic converter, as seen in exhaust gas flow direction, and metering the reducing agent as a function of a nitrogen oxide concentration, the improvement which comprises:

• a) measuring an operating parameter of the internal combustion engine influencing the metering;
• assigning a limit value to the operating parameter;
• establishing an operating state of the internal combustion engine being unfavorable for metering, upon falling below or exceeding the limit value;
• b) increasing a metered quantity of reducing agent in a preset manner at least one of before and during falling below or exceeding the limit value;
• and
• c) terminating the increase in the metered quantity during the unfavorable operating state.