Exhaust gas purification method and apparatus therefor

An exhaust gas purification method, comprising the steps of:

• providing an exhaust gas purification system including a catalyst-adsorbent structure containing an adsorbent element for adsorbing hydrocarbon compounds in an exhaust gas and a first catalyst element for lowering said hydrocarbon compounds in said exhaust gas, said catalyst-adsorbent structure being disposed in an exhaust gas pipe of an internal combustion engine;
• and
• regulating amounts of combustion air and fuel which are supplied to said internal combustion engine (i) substantially at the same time as the start of said internal combustion engine or prior to the desorption of said hydrocarbon compounds from said adsorbent element and (ii) during desorption of said hydrocarbon compounds from the adsorbent element to provide an oxygen rich exhaust gas with respect to a stoichiometric point, wherein during cold start-up said hydrocarbon compounds in said exhaust gas are adsorbed by said catalyst-adsorbent structure and desorbed from said catalyst-adsorbent structure as a temperature of said catalyst-adsorbent structure is increased by said exhaust gas, said oxygen rich exhaust gas being present during at least desorption of the hydrocarbon compounds whereby the desorbed hydrocarbon compounds are oxidized on said catalyst-adsorbent structure.

An exhaust gas purification apparatus comprising:

• an exhaust gas pipe through which is flowed an exhaust gas stream from an internal combustion engine;
• a catalyst-adsorbent containing an adsorbent element for adsorbing hydrocarbon compounds in the exhaust gas stream and a catalyst element for lowering said hydrocarbon compounds in said exhaust gas stream, said catalyst-adsorbent being disposed in said exhaust gas pipe;
• and a means for regulating amounts of combustion air and fuel which are supplied to the internal combustion engine (i) substantially at the same time as the start of said internal combustion engine or prior to the desorption of said hydrocarbon compounds from said adsorbent element and (ii) during desorption of said hydrocarbon compounds from the adsorbent element to provide an oxygen rich exhaust gas with respect to a stoichiometric point.