Abstract: Disclosed herein is a method and apparatus for reducing exhaust gases in an initial cold start period, in which a main catalyst unit is connected to an engine through an exhaust pipe, including the steps of receiving signals for stopping engine operation from an engine, and removing engine exhaust gases remaining in an exhaust pipe located at an inlet of a main catalyst unit.

Abstract: Disclosed herein is a transition metal-substituted hydrotalcite catalyst for removing nitrogen oxides using a storage-reduction method, in which a molar ratio of transition metal to magnesium is 0.2 or less, and a method of manufacturing a transition metal-substituted hydrotalcite catalyst for removing nitrogen oxides using a storage-reduction method, including the steps of preparing a hydrotalcite synthesis solution including transition metal precursors such that the molar ratio of transition metal to magnesium is 0.2 or less, and preferably 0.001 to 0.2; aging the synthesis solution; and hydrothermally treating the synthesis solution.