NO Reduction Over Noble Metal Ionic Catalysts

Abstract

In last 40 years, catalysis for NO x removal from exhaust gas has received much attention to achieve pollution free environment. CeO 2 has been found to play a major role in the area of exhaust catalysis due to its unique redox properties. In last several years, we have been exploring an entirely new approach of dispersing noble metal ions in CeO 2 and TiO 2 for redox catalysis. We have extensively studiedPt, Rh, Ru) catalysts for exhaust catalysis especially NO reduction and CO oxidation, structure-property relation and mechanism of catalytic reactions. In these catalysts, lower valent noble metal ion substitution in CeO 2 and TiO 2 creates noble metal ionic sites and oxide ion vacancy. NO gets molecularly adsorbed on noble metal ion site and dissociatively adsorbed on oxide ion vacancy site. Dissociative chemisorption of NO on oxide ion vacancy leads to preferential conversion of NO to N 2 instead of N 2 O over these catalysts. It has been demonstrated that these new generation noble metal ionic catalysts (NMIC) are much more catalytically active than conventional nano crystalline noble metal catalysts especially for NO reduction.

Noble metal ion substituted CeO2 catalysts: Electronic interaction between noble metal ions and CeO2 lattice

“…It is an attractive material for catalytic, electronic, optical, electrical, electrochemical, gas sensor and corrosion resistant applications [1][2][3][4][5][6][7][8][9][10]. CeO 2 based materials have been useful in auto exhaust catalysis, hydrogen production, H 2 -O 2 recombination, water gas shift reaction, preferential oxidation of CO and electrodes in fuel cells [1][2][3][4][11][12][13][14][15].…”

“…It is an attractive material for catalytic, electronic, optical, electrical, electrochemical, gas sensor and corrosion resistant applications [1][2][3][4][5][6][7][8][9][10]. CeO 2 based materials have been useful in auto exhaust catalysis, hydrogen production, H 2 -O 2 recombination, water gas shift reaction, preferential oxidation of CO and electrodes in fuel cells [1][2][3][4][11][12][13][14][15]. Details of structure, redox properties, oxygen storage capacities and catalytic activities toward auto exhaust emission have extensively been investigated by research groups of Trovarelli, Fornasiero and Kašpar [1,[16][17][18][19][20][21][22].…”

Synthesis of metal oxides with improved performance using a solvothermal method

“…41), 42) Orthorhombic REFeO 3 (o-REFeO 3 ), with the perovskite structure, is the thermodynamically stable phase, whereas hexagonal REFeO 3 (h-REFeO 3 ) with the P6 3 cm space group exists as a metastable phase. 43) We not only have found that o-and hREFeO 3 can be selectively synthesized by the combination of a suitable choice of starting materials and the addition of suitable amines as additives, 44) but also have demonstrated that the metastable h-REFeO 3 showed a higher activity for the catalytic combustion of CH 4 or C 3 H 6 than o-REFeO 3 .…”

Investigation of strong shock wave interactions with CeO2 ceramic

“…Ceria based materials have been explored for several applications such as heterogeneous catalysis [1,2], gas sensors [3], fuel cells [4], bio-materials [5,6], bio-photonics [7], etc. In many applications, knowledge of the cerium oxidation state is necessary for understanding the properties of the ceria compounds.…”