Ce and Zr Modified WO3-TiO2 Catalysts for Selective Catalytic Reduction of NOx by NH3

Wenyi Zhao,Cheng Zhang,Shule Zhang,Xin Guo,Yu Wang,Yan Wang,Rongrong Fan,Rong Wang,Zhaoqiang Li

doi:10.3390/catal8090375

Abstract

A series of Ce and/or Zr modified WO3-TiO2 catalysts were synthesized by the impregnation method, which were employed for NH3-SCR reaction. The T50 contour lines of NOx were used to quickly optimize catalyst composition, the Ce20Zr12.5WTi catalyst was considered to be the optimization result, and also exhibited excellent NH3-SCR activity and thermal stability with broad operation temperature window, which is a very promising catalyst for NOx abatement from diesel engine exhaust. The excellent catalytic performance is associated with the formation of Ce-Zr solid solution. The introduction of Zr to CeWTi catalyst facilitated the redox of Ce4+/Ce3+ and the formation of more acid sites, more Ce3+ ions, more oxygen vacancies, larger quantities of surface adsorbed oxygen species and NH3, which were beneficial for the excellent selective catalytic reduction (SCR) performance.

Highlights

Nitrogen oxides (NOx ) resulting from automobiles are major air pollutants, which can cause acid rain, photochemical smog, haze, ozone depletion and direct damages to the respiratory systems of human bodies
A method of “prediction verification” was used to optimize the contents of Ce, Zr, and WTi, with an aim to decrease the amount of optimization experiments
Ce and/or Zr was introduced to WO3 -TiO2 oxides by the impregnation method. Their deNOx performances were evaluated in a simulated real diesel engine exhaust, in order to decrease the amount of optimization experiments, a method of “prediction verification” was used to optimize the contents of Ce, Zr and WTi

Summary

Introduction

Nitrogen oxides (NOx ) resulting from automobiles are major air pollutants, which can cause acid rain, photochemical smog, haze, ozone depletion and direct damages to the respiratory systems of human bodies. Great efforts have been made to the development and application of available technologies for the control of NOx emissions [1,2]. Among these technologies, selective catalytic reduction of NOx with NH3 (NH3 -SCR) has been widely used and considered one of the most effective approaches for NOx control in diesel vehicles. The toxicity of vanadium species and the narrow operation temperature window restrains the practical application of the V-based catalysts for diesel. Great efforts have been made to develop an environmentally-benign selective catalytic reduction (SCR) catalyst with high deNOx performance

Methods

Results

Conclusion