Selective catalytic reduction with ammonia (NH3-SCR) is an effective, well-established method to eliminate nitrogen oxides (NOx) in oxygen excess for stationary and mobile applications. Titania-supported vanadia catalysts are traditionally used for NH3-SCR. This type of catalyst is effective in the range 300-450°C, but the NOx reduction efficiency decreases at both lower and higher temperatures. The efficiency of the NH3-SCR process can be improved significantly by using catalysts based on copper-exchanged zeolites and zeotypes, due to their high activity around 200°C. Solid-state ion-exchange in a mixture of copper oxide and zeolite is an efficient way to prepare such catalysts, but this process usually requires high (&gt;700°C) temperatures. The ion-exchange can be considerably affected by appropriate choice of atmosphere during the process. Here, powder mixtures of CuI2O or CuIIO and zeolite with either CHA, MFI or *BEA framework structure were exposed to well-defined gas atmospheres at constant temperature. After the treatment, the SCR activity of the samples was determined by steady state and transient flow reactor experiments, and the physicochemical properties of the samples were characterized with bulk and surface sensitive characterization techniques. Furthermore, first-principles calculations were used to investigate the energetic conditions for the ion-exchange process. We show that in the presence of ammonia, copper becomes mobile at considerably lower temperatures, &lt; 250°C, than conventionally used in solid-state ion-exchange (typically 700-800°C). The treatment in ammonia can be used to prepare copper-exchanged zeolites, active for NH3-SCR, on a time scale below 5−10 h, irrespective of zeolite framework structure. The influence of the treatment conditions on the copper-exchange and the mechanism of the reaction-driven ion-exchange process will be presented and discussed. Such copper-exchanged zeolite structures with high copper loading are potentially interesting catalysts for a number of technical applications.

Copper mobility in zeolite-based SCR catalysts

254th National Meeting (2017)

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