초록 ▼

There is provided a multizone catalytic process for the treatment of exhaust gas comprising nitrogen oxides, hydrocarbons, and carbon monoxide. In the multizone catalytic process, the exhaust gas is directed through a first zone, a second zone, and a third zone. The first zone comprises a catalyst t

There is provided a multizone catalytic process for the treatment of exhaust gas comprising nitrogen oxides, hydrocarbons, and carbon monoxide. In the multizone catalytic process, the exhaust gas is directed through a first zone, a second zone, and a third zone. The first zone comprises a catalyst that is effective for the three-way conversion of nitrogen oxides, hydrocarbons, and carbon monoxide. The second zone comprises materials effective to sorb hydrocarbons, e.g., zeolites ZSM-5 and Beta, particularly iron modified zeolites ZSM-5 and Beta. The second zone is effective for the adsorption of hydrocarbons from the exhaust gas during the cold-start period of operation of an internal combustion engine. The third zone comprises a catalyst that is effective for the oxidation of hydrocarbons and carbon monoxide.

대표청구항 ▼

A process for continuously removing one or more nitrogen oxides, carbon monoxide, and hydrocarbons from the exhaust gas from an internal combustion engine, the process comprising a cold-start stage and a warm-running stage, wherein the cold-start stage comprises the steps of: (a) passing the exhaust

A process for continuously removing one or more nitrogen oxides, carbon monoxide, and hydrocarbons from the exhaust gas from an internal combustion engine, the process comprising a cold-start stage and a warm-running stage, wherein the cold-start stage comprises the steps of: (a) passing the exhaust gas from a time beginning from the start of the engine into a first zone comprising a first catalytic material which is capable of simultaneously reducing the nitrogen oxides, oxidizing the carbon monoxide, and oxidizing the hydrocarbons, wherein the exhaust gas is contacted with the first catalytic material, during the cold-start stage, under reaction conditions during the beginning of the cold-start stage that are not sufficient to oxidize a majority of the hydrocarbons in the exhaust gas; (b) passing the effluent from step (a) to a second zone comprising a sorbent material capable of sorbing hydrocarbons, wherein the effluent from step (a) is contacted with the sorbent under conditions sufficient to sorb hydrocarbons in the effluent from step (a), wherein the sorbent material comprises iron-containing ZSM-5 and iron-containing zeolite Beta, and wherein the sorbent material is hydrothermally treated prior to use in the process; and (c) passing the effluent from step (b) to a third zone comprising a second catalytic material which is capable of oxidizing hydrocarbons, wherein the cold-start stage transitions into the warm-running stage when the temperature in the first zone increases to a temperature sufficient to promote the oxidation of hydrocarbons in the first zone, the warm-running stage comprising the steps of: (d) passing the exhaust gas from the engine into the first zone, wherein the exhaust gas is contacted with the first catalytic material under reaction conditions sufficient to (i) reduce nitrogen oxides and (ii) oxidize carbon monoxide, wherein the reaction conditions during the warm-running stage are sufficient to oxidize a majority of the hydrocarbons in the exhaust gas; (e) passing the effluent from step (d) to the second zone, wherein the effluent from step (d) is contacted with the sorbent material under conditions sufficient to desorb at least a portion of the hydrocarbons sorbed on the sorbent during step (b); and (f) passing the effluent from step (e) to the third zone, wherein the effluent of step (e) is contacted with the second catalytic material under conditions sufficient to oxidize hydrocarbons desorbed from the sorbent in step (e).