Patent ID: 11969712
Assignee: TOYOTA JIDOSHA KABUSHIKI KAISHA
Field: Chemical engineering (Chemistry)
Classification: CPC B | IPC B

Claim 0:
1. A catalyst for purification of exhaust gas in which Pd-based nanoparticles composed of Pd or Pd oxide and ceria nanoparticles represented by a compositional formula CeO2-x wherein 0≤x<0.5 are supported on a composite metal oxide support containing alumina, ceria, and zirconia, wherein
a molar ratio Ce/Pd of Ce and Pd supported on the composite metal oxide support is 1 to 8,
a proximity α between Pd and Ce is 0.15 to 0.50, wherein the proximity α is determined, based on a Pd distribution map and a Ce distribution map in an element mapping image obtained by energy dispersive X-ray analysis, by the following formula (1):, α
     =
     
      
       
        
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     (
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in the formula (I), I(i, j) represents a luminance value in a section (i, j), which is i-th in a horizontal direction and j-th in a vertical direction, when the Pd distribution map is divided into M pieces in the horizontal direction and N pieces in the vertical direction, Iave represents an average luminance value in the Pd distribution map, T(i, j) represents a luminance value in a section (i, j), which is i-th in a horizontal direction and j-th in a vertical direction, when the Ce distribution map is divided into M pieces in the horizontal direction and N pieces in the vertical direction, and Tave represents an average luminance value in the Ce distribution map, and
a Pd dispersity after a heat-resistance test is 0.8% or more, wherein the heat-resistance test is conducted by heating at 1050° C. for 25 hours while alternately flowing rich gas of 2 vol % H2+10 vol % CO2+3 vol % H2O+N2 in balance and lean gas of 1 vol % O2+10 vol % CO2+3 vol % H2O+N2 in balance at a flow rate of 0.5 L/min every 5 minutes.