VORRICHTUNG ZUR ABGASREINIGUNG IN EINEM VERBRENNUNGSMOTOR

In an internal combustion engine, an NO X selective reducing catalyst (15) is arranged in an engine exhaust passage. Urea is fed in the NO X selective reducing catalyst (15), ammonia generated from this urea is adsorbed at the NO X selective reducing catalyst (15), and the NO X contained in the exhaust gas is selectively reduced mainly by the adsorbed ammonia. An NO X sensor (29) able to detect NO X and ammonia contained in the exhaust gas is arranged in the engine exhaust passage downstream of the NO X selective reducing catalyst (15). It is judged that the amount of adsorption of ammonia at the NO X selective reducing catalyst (15) is saturated based on the detection value of the NO X sensor (29) when the feed of fuel to the engine is stopped during the deceleration operation.