Catalyst device for exhaust gas purification and method for exhaust gas purification

A method for purifying an exhaust gas discharged from an engine, the method comprising:

• disposing a first catalytic layer containing Pt-loaded silica-alumina obtained by loading Pt on silica-alumina in which alumina is modified by silicon such that the exhaust gas contacts with the first catalytic layer first, and disposing a second catalytic layer containing Pd or Rh such that the exhaust gas that has contacted with the first catalytic layer contacts with the second catalytic layer next;
• oxidizing and purifying a saturated hydrocarbon having a carbon number of 5 or more in the exhaust gas using the first catalytic layer, and increasing a temperature of the exhaust gas entering the second catalytic layer by heat of reaction generated by the oxidation and purification;
• and
• oxidizing and purifying a hydrocarbon other than the saturated hydrocarbon having the carbon number of 5 or more using the second catalytic layer that has been activated by an increase in the temperature of the exhaust gas.