Promotional effect of reduction treatments of PtInFerrierite on its activity in the SCR of NO with methane. Kinetics and Novel Characterization studies

GUTIERREZ, L. B. ; RAMALLO-LÓPEZ, J. M.; IRUSTA, S.; MIRÓ, E. E.; REQUEJO, F. G.

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Lugar: Washington; Año: 2001 vol. 105 p. 9514 - 9523

1520-6106

K-ferrierite co-exchanged with Pt and In (Ptln(ferrierite)), with different pretreatments, is characterized by EXAFS (extended X-ray absorption fine structure), TDPAC (time differential perturbed angular correlation), TPR (temperature-programmed reduction), and hydrogen chemisorption. The presence of different In and Pt species is correlated with activity and selectivity during the NO selective reduction (SCR) with CH 4 in the presence of excess oxygen. The reduction of PtIn(ferrierite) catalyst under controlled conditions (hydrogen at 350 or 500 °C) strongly promotes the activity of the said catalyst. The reduction at 350 °C results in the formation of small Pt° crystals, stable under wet reaction conditions, which probably favor both the oxidation of NO to NO 2 and the adsorption of the said species, thus increasing the overall reaction rate. The reduction at 500 °C further increases the reaction rate because it promotes the formation of new (InO) + active species from the reduction of In 2O 3 at the catalyst external surface. Small crystals of Pt° are also formed when the calcined catalyst is treated under wet reaction conditions, thus increasing the reaction rate to an extent similar to the one observed for the catalyst reduced at 350 °C.