Advances in Selective Catalytic Reduction of NO with Methane

The removal of nitrogen monoxide from combustion exhaust gas is recognized as one of the most important and urgent targets in catalysis research. In the last decade, the utilization of hydrocarbons as reducing agents has received much attention for the selective catalytic reduction (SCR) of nitric oxide. Using CH4 as the reducing agent for SCR of NO2 has particularly attracted interest, owing to the fact that methane exists in nearly all of the combustion exhausts. This paper summarized the advance in SCR of NO2 with methane in recent years. The status of the catalysts for CH4-SCR of NOx including metal-exchanged zeolites and metal oxides was also introduced. The reaction mechanism was also discussed, and it was indicated that the formation of NO2 was the key step for CH4-SCR of NOx. Combining with our own research work, we briefly described the methods and techniques used for improving the catalyst activity. The methods used to improve the catalyst activity can be divided into two sides. One is the melioration of catalyst preparation, the other is to add some additives in the catalysts. For the new techniques used in CH4-SCR of NOx we put our stress on the microwave. At last, we forecasted the difficulties for CH4-SCR of NOx and the research direction we should strive in the future.