Perturbed angular correlation study of the ion exchange of indium into silicalite zeolites

J.M. RAMALLO-LÓPEZ; F.G. REQUEJO; M. RENTERÍA; A.G. BIBILONI; E.E. MIRÓ

HYPERFINE INTERACTIONS

Kluwer Academic Publishers

Lugar: Dordrecht; Año: 1999 vol. 120/ p. 529 - 534

0304-3843

Vol. 120/121Two indium-containing silicalite zeolites (In/H?ZSM5) catalysts prepared by wet impregnationand ionic exchange were characterized by the Perturbed Angular Correlation (PAC)technique using 111In as probe to determine the nature of the indium species. Some of thesespecies take part in the catalytic reaction of the selective reduction (SCR) of NOx withmethane. PAC experiments were performed at 500C in air before and after reduction?reoxidation treatments on the catalysts in order to determine the origin of the differenthyperfine interactions and then the degree of ionic exchange. Complementary catalyticactivity characterizations were also performed.PAC experiments performed on the catalyst obtained by wet impregnation showed thatall In-atoms form In2O3 crystallites while almost 70% of In-atoms form In2O3 in the catalystobtained by ionic exchange. The PAC experiments of both catalysts performed afterthe reduction?reoxidation treatment revealed the presence of two hyperfine interactions, different from those corresponding to indium in In2O3. These hyperfine interactions shouldbe associated to disperse In species responsible of the catalytic activity located in the ionicexchange-sites of the zeolites.