Exhaust Gas Purifier

Abstract

It is intend to provide at low cost an exhaust gas purifier capable of in an internal combustion engine or other combustion instrument mainly driven under excess air conditions, efficiently removing nitrogen oxides from exhaust gas. A nitrogen oxide adsorbent ( 4 ) is disposed in an exhaust passage, which the nitrogen oxide adsorbent ( 4 ) is composed of a lithium composite oxide of the general formula LiAxOy or LiAxPO 4 , containing as constituent elements lithium (Li) and at least one element (A) selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), vanadium (V), chromium (Cr), iron (Fe), titanium (Ti), scandium (Sc), and yttrium (Y). For example, the nitrogen oxide adsorbent ( 4 ) is composed of a lithium composite oxide, such as lithium manganate (LiMnO 3 ), the lithium titanate (Li 2 TiO 3 ) or lithium manganate phosphate (LiMnPO 4 ).

1 . An exhaust gas purifier being installed in an exhaust passage of an internal combustion engine or a combustion instrument, comprising:
 the exhaust gas purifier characterized in that a nitrogen oxide adsorbent is disposed in the exhaust passage, and the nitrogen oxide adsorbent is made of lithium composite oxide of Lithium manganate (LiMn 2 O 4 ) or Lithium manganate phosphate (LiMn 2 O 4 ).   
     
     
         2 . The exhaust gas purifier according to  claim 1 , wherein noble metal is added to the nitrogen oxide adsorbent. 
     
     
         3 . The exhaust gas purifier according to  claim 2 , wherein noble metal is platinum (Pt). 
     
     
         4 . The exhaust gas purifier according to  claim 1 , wherein the nitrogen oxide adsorbent is supported by a support made of at least one of aluminum oxide (Al 2 O 3 ) and anatase titanium oxide (TiO 2 ). 
     
     
         5 . The exhaust gas purifier according to  claim 1 , wherein an additive amount as lithium oxide (Li 2 O) ranges from 10 to 20 weight % in the nitrogen oxide adsorbent. 
     
     
         6 . The exhaust gas purifier according to  claim 1 , wherein nitrogen oxide adsorbent is burned in a range of 400° C. to 500° C. 
     
     
         7 . The exhaust gas purifier according to  claim 2 , wherein adsorbed substance desorbing means is disposed on an exhaust gas upstream side of the nitrogen oxide adsorbent and a combustion apparatus is disposed on an exhaust gas downstream side of the nitrogen oxide adsorbent. 
     
     
         8 . The exhaust gas purifier according to  claim 7 , wherein the combustion apparatus is a fuel lean-burn type. 
     
     
         9 . The exhaust gas purifier according to  claim 1 , wherein the adsorbed substance desorbing means is set to a temperature near the burning temperature or to the burning temperature or less. 
     
     
         10 . The exhaust gas purifier according to  claim 7 , wherein the adsorbed substance desorbing means is set to a temperature near the burning temperature or to the burning temperature or less. 
     
     
         11 . The exhaust gas purifier according to  claim 1 , wherein a sulfur oxide adsorbent is disposed on an exhaust gas upstream side of the nitrogen oxide adsorbent. 
     
     
         12 . The exhaust gas purifier according to  claim 11 , wherein the sulfur oxide adsorbent contains copper oxide and zirconium oxide. 
     
     
         13 . The exhaust gas purifier according to  claim 12 , wherein a metal ratio of copper and zirconium is 1:1 in the sulfur oxide adsorbent. 
     
     
         14 . The exhaust gas purifier according to  claim 11 , wherein adsorbed substance desorbing means is disposed on an exhaust gas upstream side of the sulfur oxide adsorbent and a combustion apparatus is disposed on an exhaust gas downstream side of the nitrogen oxide adsorbent. 
     
     
         15 . The exhaust gas purifier according to  claim 12 , wherein adsorbed substance desorbing means is disposed on an exhaust gas upstream side of the sulfur oxide adsorbent and a combustion apparatus is disposed on an exhaust gas downstream side of the nitrogen oxide adsorbent. 
     
     
         16 . The exhaust gas purifier according to  claim 13 , wherein adsorbed substance desorbing means is disposed on an exhaust gas upstream side of the sulfur oxide adsorbent and a combustion apparatus is disposed on an exhaust gas downstream side of the nitrogen oxide adsorbent.