The Effect of mechanical mixing and Porosity on the Activity of Ag and Cu Ion exchanged Zeotypes in the HC-SCR of NOx with Propene
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- Institutt for kjemi 
Abstract The effect of mechanical mixing and porosity of Ag and Cu ion exchanged zeotypes in the hydrocarbon selective catalytic reduction (HC-SCR) of NOx with propene has been investigated. To this effect, mordenite, ZSM-5, and conventional and hierarchical SAPO-34 have been ion exchanged with Ag, Cu, or both simultaneously. Mechanically mixed samples have been prepared using equal parts Ag and Cu zeotypes. The crystallinity of the resulting samples has been verified by XRD, and the metal content has been determined by ICP-MS. The NOx conversion has been measured by a chemiluminescence NOx analyser. It has been found that mechanical mixing causes reduced deNOx activity compared to Cu ion exchanged zeotypes. For simultaneously ion exchanged zeotypes with Ag and Cu, a synergistic effect is seen with smaller pore sizes. Physical separation and diffusion between crystallites is thought to cause the difference between simultaneously ion exchanged and mechanically mixed samples. Moreover, a peak deNOx conversion of 83% has been achieved with simultaneously ion exchanged conventional SAPO-34 at 425°C. This is attributed to differences in local coordination between the simultaneously ion exchanged sample and the mechanically mixed sample. Simultaneous ion exchange is seen to give increased total metal loading compared to Ag and Cu ion exchanged zeotypes.