Bifunctional Catalyst for Decomposition and Oxidation of Nitrogen Monoxide, Composite Catalyst Including the Same for Apparatus to Decrease Exhaust Gas, and Method for Preparation Thereof

Abstract

Disclosed are a bifunctional catalyst for simultaneously removing nitrogen oxide and particulate matters, capable of decomposing nitrogen monoxide and generating nitrogen dioxide through oxidation of nitrogen monoxide, a composite catalyst including the catalyst for simultaneously removing nitrogen oxide and particulate matters used for an apparatus to decrease exhaust gas of diesel vehicles, and a method for preparation thereof. The catalyst and the composite catalyst can be used in a device for reducing exhaust gas contaminants mounted on a diesel vehicle and an exhaust gas purification system comprising the device.

1 . A bifunctional catalyst for simultaneously removing nitrogen oxide and particulate matters (PMs) to enable nitrogen monoxide (NO) decomposition and nitrogen dioxide (NO 2 ) generation through NO oxidation, the bifunctional catalyst comprising:
 a support containing oxides of at least one element selected from a group consisting of titanium (Ti), zirconium (Zr), silicon (Si), aluminum (Al) and cerium (Ce); and   a composite active metal formed by loading a co-catalyst based on at least one metal selected from a group consisting of tungsten (W), molybdenum (Mo), cobalt (Co), manganese (Mn), copper (Cu) and iron (Fe) or metal oxides thereof on top of the support, and loading an active metal based on at least one metal selected from a group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and silver (Ag) on top of the co-catalyst.   
     
     
         2 . The bifunctional catalyst according to  claim 1 , wherein the co-catalyst is loaded in an amount of 0.1 to 30 wt. % relative to a total weight of the support, and the active metal is loaded in an amount of 0.1 to 20 wt. % relative to a total weight of the support. 
     
     
         3 . The bifunctional catalyst according to  claim 1 , wherein the co-catalyst is loaded on an outer surface of the active metal. 
     
     
         4 . The bifunctional catalyst according to  claim 3 , wherein the co-catalyst is loaded on the outer surface of the active metal in an amount of 0.1 to 5 wt. % relative to a total weight of the support. 
     
     
         5 . The bifunctional catalyst according to  claim 1 , wherein an average particle diameter of the support is larger than that of the composite active metal. 
     
     
         6 . The bifunctional catalyst according to  claim 5 , wherein the average particle diameter of the support ranges from 0.02 to 10 μm. 
     
     
         7 . The bifunctional catalyst according to  claim 5 , wherein the average particle diameter of the composite active metal ranges from 0.001 to 0.1 μm. 
     
     
         8 . A method for preparation of a bifunctional catalyst for simultaneously removing nitrogen oxide and particulate matters (PMs) to enable nitrogen monoxide (NO) decomposition and nitrogen dioxide (NO 2 ) generation through NO oxidation, the method comprising:
 (a) loading a co-catalyst based on at least one metal selected from a group consisting of tungsten (W), molybdenum (Mo), cobalt (Co), manganese (Mn), copper (Cu) and iron (Fe) or metal oxides thereof on top of a support containing oxides of at least one element selected from a group consisting of titanium (Ti), zirconium (Zr), aluminum (Al) and cerium (Ce);   (b) loading an active metal based on at least one metal selected from a group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and silver (Ag) or metal oxides thereof on top of the co-catalyst; and   (c) drying, calcining and conducting reduction of the loaded materials after loading the co-catalyst and the active metal.   
     
     
         9 . The method for preparation of a bifunctional catalyst according to  claim 8 , wherein the co-catalyst in step (a) is loaded in an amount of 0.1 to 20 wt. % relative to a total weight of the support, and the active metal in step (b) is loaded in an amount of 0.1 to 10 wt. % relative to a total weight of the support. 
     
     
         10 . The method for preparation of a bifunctional catalyst according to  claim 8 , wherein the co-catalyst and the active metal are simultaneously or sequentially loaded in step (c). 
     
     
         11 . The method for preparation of a bifunctional catalyst according to  claim 8 , wherein step (c) further comprises:
 after simultaneously or sequentially loading the co-catalyst and the active metal and calcining the loaded materials to form a particulate catalyst, loading the co-catalyst on an outer surface of the active metal in the presence of the particulate catalyst; and,   after loading the co-catalyst on the outer surface of the active metal, sequentially drying, calcining and conducting reduction of the loaded active metal.   
     
     
         12 . The method for preparation of a bifunctional catalyst according to  claim 11 , wherein the co-catalyst is loaded on the outer surface of the active metal in an amount of 0.1 to 10 wt. % relative to a total weight of the support. 
     
     
         13 . A composite catalyst for an exhaust gas reducing device mounted on a diesel vehicle, comprising. the catalyst for simultaneously removing nitrogen oxide and particulate matters as set forth in  claim 1 . 
     
     
         14 . The composite catalyst according to  claim 13 , further comprising beta-zeolite, an inorganic binder and a dispersant. 
     
     
         15 . The composite catalyst according to  claim 13 , wherein the catalyst for simultaneously removing nitrogen oxide and particulate matters is contained in an amount of 30 to 95 wt. % relative to a total weight of the composite catalyst. 
     
     
         16 . The composite catalyst according to  claim 14 , wherein the inorganic binder is any one selected from a group consisting of alumina, titania and silicone, and an amount of the inorganic binder ranges from 0.5 to 5 wt. % relative to a total weight of the composite catalyst. 
     
     
         17 . The composite catalyst according to  claim 14 , wherein the dispersant is water or alcohol. 
     
     
         18 . A method for preparation of a composite catalyst for an exhaust gas reducing device mounted on a diesel vehicle, the method comprising:
 (a) loading a co-catalyst based on at least one metal selected from a group consisting of tungsten (W), molybdenum (Mo), cobalt (Co), manganese (Mn), copper (Cu) and iron (Fe) or metal oxides thereof on top of a support containing oxides of at least one element selected from a group consisting of titanium (Ti), zirconium (Zr), aluminum (Al) and cerium (Ce);   (b) loading an active metal based on at least one metal selected from a group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and silver (Ag) or metal oxides thereof on top of the co-catalyst;   (c) drying, calcining and conducting reduction after loading the co-catalyst and the active metal, to thereby obtain a catalyst powder; and   (d) mixing the catalyst powder with beta-zeolite, an inorganic binder and a dispersant to produce a composite catalyst.   
     
     
         19 . The method for preparation of a composite catalyst according to  claim 18 , wherein the catalyst powder is added in an amount of 30 to 95 wt. % relative to a total weight of the composite catalyst, the inorganic binder is any one selected from a group consisting of alumina, titania and silicon, and the dispersant is water or alcohol. 
     
     
         20 . A device for reducing exhaust gas contaminants, comprising. the catalyst for simultaneously removing nitrogen oxide and particulate matters as set forth in  claim 1  forth in  claim 13 . 
     
     
         21 . The device for reducing exhaust gas contaminants according to  claim 20 , further comprising:
 a catalyst coated honeycomb fabricated by coating a honeycomb with the catalyst for simultaneously removing nitrogen oxide and particulate matters or the composite catalyst for an exhaust gas reducing device; and   a filter, wherein the filter is connected to the catalyst coated honeycomb.   
     
     
         22 . The device for reducing exhaust gas contaminants according to  claim 20 , further comprising:
 a catalyst coated honeycomb fabricated by coating a honeycomb with the catalyst for simultaneously removing nitrogen oxide and particulate matters or the composite catalyst for an exhaust gas reducing device; and   a filter for trapping particulate matters, wherein the filter is connected to the catalyst coated honeycomb.   
     
     
         23 . The device for reducing exhaust gas contaminants according to  claim 20 , further comprising:
 a catalyst coated honeycomb fabricated by coating a honeycomb with the catalyst for simultaneously removing nitrogen oxide and particulate matters or the composite catalyst for an exhaust gas reducing device; and   a catalyst coated diesel particulate filter (DPF) trap formed by coating an inner side of the DPF with the catalyst for simultaneously removing nitrogen oxide and particulate matters or the composite catalyst for an exhaust gas reducing device, wherein the catalyst coated DPF trap is connected to the catalyst coated honeycomb.   
     
     
         24 . An exhaust gas purification system comprising the device for reducing exhaust gas contaminants as set forth in  claim 20 . 
     
     
         25 . The exhaust gas purification system according to  claim 24 , further comprising a reducing agent supplying device. 
     
     
         26 . A device for reducing exhaust gas contaminants, comprising. the composite catalyst for an exhaust gas reducing device as set forth in  claim 13 .