A Study On The Kinetics Of Manganese Oxide Supported On Palygorskite Catalyst For Low Temperature SCR

The technology is widely used in fixed and moving resources on ammonia selective catalytic reduction of nitrogen oxide emissions.SCR is a useful way to solve the pollution brought by the nitrogen oxide. A large number of previous studies of palygorskite supported manganese oxide catalysts (MnOx/PG) show that, this is a new type of low-temperature DeNOx catalyst. It also shows a high SCR efficiency at low temperature. With using the prepared by impregnation of MnOx/PG catalyst, the DeNOx efficiency can reach more than 95% at 473 K. The MnOx/PG catalyst has large business development potential, wide application prospect and further research value.This paper takes the prepared by impregnation of MnOx/PG catalyst for research object. Catalyst for denitration experiments was taken in a tubular fixed bed reactor. Experiments show that, on the manganese load mass fraction of catalyst 10%MnOx/PG 10%, when the particle diameter is 40?60 mesh, Gas Hour Space Velocity of 29400 h-1, the effect of internal and external diffusion can be neglected.This paper focuses on kinetics of MnOx/PG catalyst ammonia selective catalytic reduction NO in the 398?548 K temperature range. When ammonia is excessive, the SCR reaction can be regarded as a first-order reaction, with an activation energy of Ea=42.13 kJ·mol-1, pre exponential factor A=2.5549* 105 s-1; when the amount of ammonia is insufficient, the activation energy can be reduced, the transformation of the SCR reaction rate controlling step would happen. And the mass transfer of ammonia would become rate controlling step. Analysis of the use of the exponential rate equation shows that, in the process of transformation, the reaction order of ammonia is increased; the reaction order of NO will decline.In the aspect of microscopic reaction mechanism, proposed the following mechanism map hypothesis:ammonia is first adsorbed on the PG vector, and then transferred to the active center of manganese element on activation. The adsorption state oxygen will help promoting the activation of manganese on ammonia which can generate water and N-.N-seems either to reaction with gas phase NO by E-R reaction mechanism, or to reaction with adsorption state NO by L-H mechanism (only in low temperature,473 K below) approach to generate N2O, N2O then decompose into N2. There may be L-H mechanism and E-R mechanism of the common phenomenon in low temperature. E-R mechanism occupied a dominant role at higher temperature.