Selective reduction of NO x by liquid hydrocarbons with supported HPW–metal catalysts

Abstract

The catalytic multifunctional system based on H 3PW 12O 40·6H 2O (HPW), Pt and support (Zr–Ce or Zr–Ti mixed oxides) has been investigated for lean NO x storage and reduction. It was applied in the NO x storage and reduction (NSR) concept by including a cyclic operation of short NO x storage (oxygen rich phase) and reduction (hydrocarbon rich phase: hexane). For NO x reduction, the assistance of hydrogen is one of the key parameters possibly as a result of the regeneration of metallic sites active for mild oxidation of the hydrocarbon (by forming C x H y O z ). The difference in oxygen mobility of supports (higher in the case of Zr–Ce than for Zr–Ti) became another strategic parameter for catalyst selection since the possibility of total hydrocarbon oxidation. The influence of temperature was also considered for optimizing NO x storage and reduction.