Process for the Removal of Harmful Substances from Exhaust Gases of Combustion Engines and Catalyst for Carrying Out Said Process

Abstract

An integrated system for treatment of exhaust gases includes a NO x -storing component, an in situ ammonia-generating component, an ammonia-storing component, and an ammonia (NH 3 )—SCR-component. A process for treatment of exhaust gas includes (i) storing of NO x under lean exhaust gas conditions in a NO x -storing component; (ii) in situ conversion of the stored NO x to ammonia (NH 3 ) under rich exhaust gas conditions; (iii) storing of the ammonia (NH 3 ) in a NH 3 -storing component under rich exhaust gas conditions, and (iv) reaction of NH 3 with NO x under lean exhaust gas conditions. Thereby, the partial steps of storing of NO x and conversion of NH 3 with NO x are carried out at least partially and/or temporarily simultaneously and/or parallelly.

1 . A catalytic process for the removal of NO x  from the exhaust gases of lean engines in the cyclic lean/rich operational mode, which comprises at least the following partial steps:
 (i) storing of NO x  under lean exhaust gas conditions in at least one NO x -storing component,   (ii) in situ conversion of the stored NO x  to ammonia (NH 3 ) under rich exhaust gas conditions,   (iii) storing of the NH 3  in at least one NH 3 -storing component under rich exhaust conditions,   (iv) reaction of NH 3  with NO x  under lean exhaust gas conditions,   wherein the partial steps of storing of NO x - and reaction of NH 3  run at least temporarily and/or partially simultaneously and/or parallelly, characterized in that the catalytic components which cause said partial steps (i) to (iv) are in a physical contact.   
     
     
         2 . A process according to  claim 1 , wherein the catalytic components which are required for carrying out the different partial steps form a spatially and/or functionally contiguous system. 
     
     
         3 . A process according to  claim 2 , wherein at least two of the catalytic components are present on a common substrate or on a jointed substrate system. 
     
     
         4 . A process according to  claim 1 , wherein the storing of NH 3  as well as the NH 3  conversion according to the SCR-process takes place by means of the same catalytic component. 
     
     
         5 . A process according to  claim 1 , wherein for the storing of NO x  all materials are applied, which, due to their chemical properties, are able to interact with nitric oxides. 
     
     
         6 . A process according to  claim 1 , wherein the spatially and/or functionally contiguous system contains catalytic components, which are used for the generation of ammonia, for storing ammonia and for the conversion of ammonia to nitrogen. 
     
     
         7 . A process according to  claim 1 , wherein the catalytic components are applied onto a body selected from honeycomb structures, pellets, beads, and extrudates. 
     
     
         8 . A process according to  claim 1 , characterized in that the catalytic components contain at least one of the materials from the group (1) and at least one acidic solid from the group (2):
 group (1) consisting of Pt, Pd, Rh, Ir and Ru, each alone or in mixture, being present on a carrier material selected from: oxides, mixed oxides, phosphates and sulfates of Al, Si, Zr, Ti, Ce, the earth alkali metal elements and rare earth elements; heteropoly acids; zeolites; as well as mixtures thereof; and   group (2) consisting of zeolites, heteropoly acids, sulfated zirconium oxides or zirconium phosphates; as well as mixtures thereof.   
     
     
         9 . A process according to  claim 8 , characterized in that said zeolite from group (2) has a Si/Al ratio of more than 3. 
     
     
         10 . A process according to  claim 8 , characterized in that said zeolite from group (2) is selected from the group consisting of pentasiles, Y-zeolite, USY, DAY, mordenite and zeolite-β. 
     
     
         11 . A process according to  claim 8 , characterized in that said catalytic components contain a further component consisting of iron-exchanged zeolite, preferably an iron-exchanged and/or rare earth element-exchanged zeolite. 
     
     
         12 . A process according to  claim 8 , characterized in that the amount of the sum of the noble metals in the total mass of the catalytic components is in the range 0.1 to 5 weight-%. 
     
     
         13 . A process according to  claim 8 , characterized in that the amount of acidic solid from group (2) in the total mass of the catalytic components is in the range of from 5 to 95 weight %. 
     
     
         14 . Use of catalytic components for a catalytic process for the removal of NO x  from the exhaust gases of lean engines in the cyclic lean/rich operational mode, which comprises at least the following partial steps:
 (i) storing of NO x  under lean exhaust gas conditions in at least one NO x -storing component,   (ii) in situ conversion of the stored NO x  to ammonia (NH 3 ) under rich exhaust gas conditions,   (iii) storing of the NH 3  in at least one NH 3 -storing component under rich exhaust conditions,   (iv) reaction of NH 3  with NO x  under lean exhaust gas conditions,   wherein the partial steps of storing of NO x  and reaction of NH 3  run at least temporarily and/or partially simultaneously and/or parallelly, characterized in that the catalytic components which cause said partial steps (i) to (iv) are in a physical contact.   
     
     
         15 . Use of catalytic components containing at least one of the materials from the group (1) and at least one acidic solid from the group (2):
 (1) Pt, Pd, Rh, Ir and Ru, each alone or in mixture, being present on a carrier material selected from: oxides, mixed oxides, phosphates and sulfates of Al, Si, Zr, Ti, Ce, the earth alkali metal elements and rare earth elements; heteropoly acids; zeolites; as well as mixtures thereof;   (2) zeolites, heteropoly acids, sulfated zirconium oxides or zirconium phosphates; as well as mixtures thereof;   for a catalytic process for the removal of NO from the exhaust gases of lean engines in the cyclic lean/rich operational mode, which comprises at least the following partial steps:   (i) storing of NO x  under lean exhaust gas conditions in at least one NO x -storing component,   (ii) in situ conversion of the stored NO to ammonia (NH 3 ) under rich exhaust gas conditions,   (iii) storing of the NH 3  in at least one NH 3 -storing component under rich exhaust conditions,   (iv) reaction of NH 3  with NO x  under lean exhaust gas conditions,   wherein the partial steps of “storing of NO x ” and “reaction of NH 3 ” run at least temporarily and/or partially simultaneously and/or parallelly, characterized in that the catalytic components which cause said partial steps (i) to (iv) are in a physical contact.   
     
     
         16 . The method of  claim 15  wherein the catalytic components further contain an oxide of a metal selected from alkali metal elements, earth alkali metal elements, rare earth elements, zirconium and titanium. 
     
     
         17 . The method of  claim 15  wherein the catalytic components further contain an inorganic compound of a metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, In, Ga, Ag and Sn. 
     
     
         18 . The method of  claim 8  wherein the catalytic components further contain an oxide of a metal selected from alkali metal elements, earth alkali metal elements, rare earth elements, zirconium and titanium. 
     
     
         19 . The method of  claim 8  wherein the catalytic components further contain an inorganic compound of a metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, In, Ga, Ag and Sn.