| The selective catalytic reduction (SCR) with ammonia is the most effective and widely used technology for the elimination of NOx emitted from stationary power stations and diesel engines. However, current commercial SCR catalysts such as V2O5/TiO2 and V2O5-WO3/TiO2 have to be operated in the temperature range at 300-400℃, resulting in complicated processes and higher costs. For this reason, a large amount of research has been conducted, and several processes have been proposed to the low temperature SCR technology, which can optimize the process configuration."Fast SCR" technology and the research and development of the low temperature SCR catalyst have been two most potential low temperatures SCR technology. However, few studies have been reported on the "Fast SCR" on carbon based SCR catalyst, the combination of these two technologies may be get high NOx removal efficiency at low temperature. Consequently, the key research point of the present work is the combination of "Fast SCR" reaction and activated carbon based V2O5 (V2O5/AC) catalyst. The influences of the relevant factors on the NOx removal performance have been investigated. Based on the above results, the mechanism of the "Fast SCR" on the V2O5/AC catalyst has been discussed. The present study has achieved the following results:1. The influences of various preparation parameters on the NOx removal performance of the V2O5/AC catalyst have been investigated and optimized by activity test and the relevant characterization technology. Base on the above results, an optimal catalyst preparation parameters and reactive conditions have been achieved:the prepared 3% V2O5/AC catalyst by the optimal catalyst preparation can achieve stable NOx removal performance at the conditions of 450 ppm NO,500 ppm NH3,5%O2,3%H2O,250℃and 72000 L/(kg-h) space velocity. At the same time, a high selectivity can be achieved.2. Base on the predecessors'studies, the performance and mechanism of the NO2 adsorption on activated carbon have been investigated. An adsorption and desorption model has been proposed. It is proposed that micropores in AC act as a nano-reactor for the formation of-C(ONO2) complexes, which is the sum of NO2 adsorption on existing-C(O) and disproportionation of adsorbed NO2.3. The "Fast SCR" reaction on the V2O5/AC catalyst has been investigated by various test methods such as the activity test, transient response test, temperature programmed desorption (TPD) and infrared spectra (IR). Particularly, the N2O and NH4NO3 side reactions have also been investigated. The results suggest that the V2O5/AC catalyst exhibits high activity and selectivity in the SCR reaction with feed gas containing both NO and NO2. In present of NO2, an increase of NOX reduction form 26% to 94% can be achieved at a temperature as low as 150℃without the formation of NH4NO3.4. Based on the above research, the mechanism of the "Fast SCR" reaction on V2O5/AC catalyst has been discussed. A preliminary mechanism model has been proposed. It is proposed that the nitrate complexes adsorbed on the V2O5/AC catalyst can be reacted as intermediates of the "Fast SCR" reaction and the conversion to NO. The adsorbed nitrate complexes can accelerate the process of V4+oxidized to V5+... |
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