Patent ID: 8540953

Claim:
An internal combustion engine exhaust gas control apparatus characterized by comprising: a selective reduction type NOx catalyst disposed in an exhaust passageway of an internal combustion engine, wherein a state of adsorption of NH 3 on the selective reduction type NOx catalyst includes a weakly adsorbed state in which NH 3 adsorbed on the NOx catalyst is useful for a reduction reaction of NOx, and a strongly adsorbed state in which NH 3 adsorbed on the NOx catalyst is not useful for the reduction reaction of the NOx unless the state of adsorption of NH 3 is changed into the weakly adsorbed state; a reductant dispensation portion that is disposed in the exhaust passageway upstream of the selective reduction type NOx catalyst and that dispenses a reductant for supplying NH 3 to the selective reduction type NOx catalyst; an actual weakly adsorbed amount calculation portion that calculates an actual weakly adsorbed amount of NH 3 that is adsorbed on the selective reduction type NOx catalyst in the weakly adsorbed state; and a dispensation control portion that performs a dispensation control of the reductant dispensed by the reductant dispensation portion, according to the actual weakly adsorbed amount calculated by the actual weakly adsorbed amount calculation portion.