Selective Catalytic Reduction plasma

The oxidation of NO to N02 can be considered an advantage when combining plasma with selective catalytic reduction, as it is well-known that at low temperature the efficiency of NO reduction by SCR strongly depends on the N02 concentration in the gas. An oxidation pre-treatment of the gas by non-thermal plasma, prior to the SCR reactor greatly enhances the performance of SCR at temperatures below 500 K. Therefore, the PE-SCR technique is very promising for efficient NO reduction. 

Mok, Y.S., Dors, M. and Mizerazcyk, J. (2004) Effect of reaction temperature on NOx removal and formation of ammonium nitrate in nonthermal plasma process combined with selective catalytic reduction, IEEE Trans. Plasma Sci. 32, 799-807. 

Broer, S. and Hammer, T. (2000) Selective catalytic reduction of nitrogen oxides by combining a non-thermal plasma and a V205-W03/Ti02 catalyst, Appl. Catal. B Env. 28, 101-11. 

Demidouk, V., Ravi, V., Chae, J.-O. et al. (2005) Pt-Al203 catalyst and discharge plasma pre-treatment techniques for enhancing selective catalytic reduction of nitrogen oxides A comparative study, React. Kinet. Catal. Lett. 85, 239-44. 

At present the most effective available after-treatment techniques for NO, removal under lean conditions are ammonia selective catalytic reduction (SCR) [1-3] and NO, storage reduction (NSR) [4—6]. Indeed, three-way catalysts (TWCs) are not able to reduce NO, in the presence of excess oxygen, because they must be operated at air/ fuel ratios close to the stoichiometric value. Also, non-thermal plasma (NTP) and hydrocarbon-selective catalytic reduction (HC-SCR) are considered, although they are still far from practical applications. 

A great effort is underway to develop reliable aftertreatment systems for lowering NOx emissions from diesel and LB engines. A variety of approaches have been proposed for NOx aftertreatment of advanced vehicles including lean NOx catalysts (LNC), NOx storage and reduction (NSR) catalysts, selective catalytic reduction with urea (urea-SCR), and plasma-assisted catalysis (PAC). Lean NOx catalysts are mainly designed to reduce NOx with unburned hydrocarbons already included in the exhaust stream in the presence of O2 but result in... 

Many of recent works on the plasma-catalyst process for NQr removal arc based on PCC system. Because of the similarity in the catalytic reactions between the PEC process and the conventional SCR process, NO.r removal method using PEC system is also referred to as plasma-enhanced selective catalytic reduction (PE-SCR) process [109], Table 4 summarizes the current status of NO r removal using the PE-SCR process. It should be noticed that the use of proper chemical reducing agent is necessary to achieve reductive decomposition of NO.r even with the plasma-catalyst system. To optimize the reductive decomposition of NO.r, therefore, it is necessary to find proper reducing agent together with a catalyst. The main role of NTP in the PEC system is the partial conversion of NO to NO . This partial oxidation of... 

Miessner, H. Francke, K.-P. Rudolph, R. and Hammer, T. NOx removal in excess oxygen by plasma-enhanced selective catalytic reduction Catal. Today. 2002. 75. 325-330... 

Catalytic activity in the homogeneous gas-phase conversion of nitrogen oxides and carbon monoxide to nitrogen and carbon dioxide was observed to be most effective for the atomic ions Fe+, Os+, and Ir+ out of the investigation of 29 different transition metal cations M+ [462]. The overall catalytic scheme that was established in this study consists of the three catalytic cycles shown in Fig. 1.94. The catalysis occurs in two steps in which NO is first reduced to N2O. An analogous three-step catalytic reduction of NO2, in which NO2 is first reduced to NO, was also discovered. The three cycles in Fig. 1.94 were characterized with laboratory measurements of reactions of each of the three nitrogen oxides NO2, NO, and N2O with the different transition metal ions in an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer [462]. 

---