SCR Catalyst Testing

Several monolith geometries for SCR are shown in Fig. 15. Fig. 16 shows an example of a monolith. 

The geometry and other parameters of honeycomb catalysts are given in Tables 7 (and 10 below). The behavior of the catalyst may be expressed in numbers related to activity, selectivity, and stability of the catalytic materials. Also, modeling the catalytic system is an important feature. 

For laboratory tests only part of a honeycomb (4, 9 or 36 channels) or powdered material is required. For bench-scale and pilot-scale testing a whole catalyst element will be needed. These testing methods are discussed in this section. 

All three types of reactors mentioned in Table 8 are used for the quaUty control during the preparation and the use of monolithic systems. Additionally, microreactors are used for the development of new catalysts, whereas bench-scale reactors are used for reactor design. Pilot-scale systems have been used for the determination of the activity during the lifetime of the monolith. 

Additionally, in a microreactor the intrinsic kinetics and deactivation behavior of SCR catalysts is studied with flows up to 1.5m h . In both test facilities it is possible to vary all process parameters temperature, the ammonia to nitric oxide feed ratio, the nitric oxide and sulfur dioxide concentrations, the space velocity, and the catalyst geometry. These techniques provide information for somewhat small areas and therefore should always be performed to complement bench- or laboratory-scale activity and selectivity measurements. 

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In general, NO and NO2 are mutually beneficial for NOx reduction over the SCR catalysts tested. That is, the presence of NO enhances the NO2 conversion, and vice versa. This results in the synergistic effects of NO and NO2 in the catalytic reduction of NOx with NH3 over CuZSMS, FeZSMS and V20s/Ti02 catalysts. 

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