INCAPE   05401
INSTITUTO DE INVESTIGACIONES EN CATALISIS Y PETROQUIMICA "ING. JOSE MIGUEL PARERA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Pt encapsulation in zeolite NaA as catalyst for the WGS reaction: surface properties
Autor/es:
FLORENCIA NEGRI; ANA M. TARDITI; YOHANA MARTÍNEZ GALEANO; LAURA M. CORNAGLIA; M. SERGIO MORENO
Lugar:
Santa Fe
Reunión:
Conferencia; VI San Luis conference; 2018
Institución organizadora:
INTEC
Resumen:
Zeolites are crystalline aluminosilicates with a wide range of applications including catalysis, separation, electronics and chemical sensors. Properties like thermal and chemical stability, high surface area and small pore size, become zeolites as potential supports for the development of high performance catalytic systems. One of the main advantages of zeolites as catalyst supports is the ability of introduce several metals on the pore structure, improving reaction selectivity and avoiding metal particle sintering. Between other methods, the incorporation of metals by the encapsulation technique allows to obtain small metal clusters enclosed on the zeolite structure by a direct addition of the metal precursor on the zeolite synthesis gel1,2.The surface properties of Pt-NaA catalyst prepared by encapsulating Pt in the NaA zeolite structure were studied using XPS. The catalysts were prepared by hydrothermal synthesis using two heating sources: conventional heating through a thermal bath and microwave radiation. Two solutions of aluminate and silicate precursors were mixed at 333 K. Then the Pt solution was added drop by drop to the synthesis gel and keeps stirring for 1 hour. The hydrothermal synthesis was carried out at 363 K during 8 hours. By powder x-ray diffraction measurements the formation of pure zeolite NaA was confirmed; further, the absence of the characteristics reflections of Pt suggests the presence of small metal particles. A lower Si/Al surface ratio, comparing with the bulk ratio determined by XRF, was observed for all samples. These results suggest that the Pt particles were preferentially located inside the crystalline structure of the zeolite, in agreement with the TEM observations. TEM images showed a high metal dispersion with particle size between 1.3 and 5.0 nm.The catalytic test in the water gas shift reaction were carried out at 673 K with a ratio H2O/CO = 2. The Pt_NaA catalysts exhibited a good performance, showing a CO conversion of ca. 70 % and a 100 % selectivity to hydrogen. The Pt/Si surface ratio of the used samples did not differ significantly from that of the fresh samples, suggesting that not sintering of the Pt particles occurs under these conditions. These results showed the potential application of the encapsulated method in the preparation of catalytic membranes.