Selective catalytic reduction deactivation causes

The major concern in applying selective catalytic reduction is deactivation or poisoning of the catalyst. One cause of deactivation may be catalyst poisons present in the flue gases. 

The catalytic performance and the effect of coke deposition on the activity and selectivity, were found to be strongly dependent on the preparation procedure, on the reduction temperature, and on the type of support. At low reduction temperatures, the deposition of coke on Ni-Al, (Ni-Al-Ti)sg, and Ni-Ti samples decreased the selectivity to ethylene whereas on (Ni-Al-Ti)imp, deposition of coke increased selectivity. At high reduction temperatures, with only the exception of the Ni-Ti catalyst, coke deposition increased the selectivity to the desired product. The pattern of deactivation by coke was also different for the different samples. In Ni-Ti and (Ni-Al-Ti)sg samples, coke formation strongly diminished their activity and simultaneously increased methane production. With Ni-Al and (Ni-Al-Ti)imp samples, coke did not cause an significant deactivation or an increase in methane yield. Finally, catalysts... 

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