Influence of calcination temperature on Fe/HBEA catalyst for the selective catalytic reduction of NOx with NH3.

A serious of Fe/HBEA catalysts were prepared by impregnation methods under different calcination temperatures, and their catalytic activity in selective catalytic reduction (SCR) of NOx with ammonia were tested. The influence of calcination temperature on the microstructures of zeolite support, iron species, redox ability and reactant adsorption ability was investigated in detail by various characterization methods. Results showed that calcination temperature showed significantly influence on catalytic activity and selectivity of serial Fe/HBEA catalysts in NH3-SCR reaction. Some agglomeration of Fe/HBEA catalyst occurred at high calcination temperature (especially above 850°C), which result in drastic decrease of surface area and pore volume of Fe/HBEA catalysts. Meanwhile, the surface Lewis and Brönsted acidity of zeolite did not change when the calcination temperature was below 750°C, but significantly decreased above 850°C. Furthermore, high temperature aging led to some reduction migration of iron ions out of ion exchange sites on the Fe/HBEA catalyst. Consequently, iron oxide clusters are mainly formed upon Fe migration, which contributed to the SCR activity above 450°C. The deactivation of Fe/HBEA catalysts calcined at high temperatures was ascribed to surface area and pore volume decrease, Lewis and Brönsted acid sites inhibition, and the loss of iron ions and formation of iron oxide clusters.