Mathematical Model of the Microreactor for Kinetic Tests

Once defined the reaction network that describes the different investigated reacting systems and understood the main features of the reaction mechanisms, consistent kinetic schemes and rate expressions were derived, as extensively described in the following. In order to estimate the rate parameters in such expressions, transient experimental data collected over the powdered SCR catalyst were analyzed 

The experimental investigation started firom the study of the simplest reacting system, i.e., including only ammonia and oxygen as reactants. Basically, two main processes are expected to occur in this case, namely the adsorption-desorption of 

at higher temperature, its oxidation by gaseous oxygen. The two processes were addressed sequentially, as discussed in the following. 

The capabihty to adsorb ammonia is an important characteristic of SCR catalysts. Indeed all authors who had previously studied the SCR process for stationary applications agreed that in the SCR reactions ammonia reacts from a strongly adsorbed state [16-21]. Moreover, the aflSnity of such a reactant for the catalyst surface decreases the so-called ammonia slip that is the undesired release of unreacted ammonia from the reactor. Accordingly, a good understanding of the ammonia adsorption-desorption process is strictly required for a correct description of the SCR process. 

Lewis sites for molecularly adsorbed ammonia, and only a minor adsorption of protonated ammonia with low thermal stability was pointed out. On contrary, Amiridis et al. [28] suggested that the V2O5-WO3 interaction generates Br0nsted sites. 

---