Promotional effect of reduction treatments of PtIn(ferrierite) on its activity in the SCR of NO with methane. Kinetics and novel characterization studies

K-ferrierite co-exchanged with Pt and In (PtIn(ferrierite)), with different pretreatments, is characterized by EXAFS (extended X-ray absorption fine s tructure), TDPAC (time differential perturbed angular correlation), TPR (te mperature-programmed reduction), and hydrogen chemisorption. The presence o f different In and Pt species is correlated with activity and selectivity d uring the NO selective reduction (SCR) with CH4 in the presence of excess o xygen. The reduction of PtIn(ferrierite) catalyst under controlled conditio ns (hydrogen at 350 or 500 degreesC) strongly promotes the activity of the said catalyst, The reduction at 350 degreesC results in the formation of sm all Pt degrees crystals, stable under wet reaction conditions, which probab ly favor both the oxidation of NO to NO2 and the adsorption of the said spe cies, thus increasing the overall reaction rate. The reduction at 500 degre esC further increases the reaction rate because it promotes the formation o f new (InO)(+) active species from the reduction of In2O3 at the catalyst e xternal surface. Small crystals of Pt degrees are also formed when the calc ined catalyst is treated under wet reaction conditions, thus increasing the reaction rate to an extent similar to the one observed for the catalyst re duced at 350 degreesC.