Nitrogen oxides (NO_x) in flue gases is an important source of air pollution. It is urgent to remove the NO_x from flue gases. In this review, the removal ways of nitrogen oxides are reviewed in terms of high-temperature and low-temperature selective catalytic reduction (SCR) De-NO_x catalysts. We discuss the high-temperature SCR De-NO_x catalysts including vanadium-based catalysts, iron-based catalysts and molecular sieve-based catalysts. Then, we highlight the low-temperature SCR De-NO_x catalysts such as noble metal-based catalysts, manganese-based catalyst, carbon-based catalysts, etc. We specifically focus on the mechanism studies of SCR De-NO_x catalysts. Finally, we summarize the recent advances in denitrification.

Contents
1 Introduction
2 Process arrangement of SCR denitrification
3 SCR catalysts
3.1 High-temperature catalysts
3.2 Low-temperature catalysts
4 Conclusion