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Synthesis and characterization of metallic catalysts of Ni, Co, Pt and Pd supported on molecular sieves MCM-41 type

Abstract:

A mesoporous material MCM-41 was prepared and used as support for four catalysts containing the metallic catalytic precursors of Ni, Co, Pd and Pt. The XRD pattern of the support showed the four typical reflections of this type of material, with a structure contraction after surfactant removal by calcination. The catalysts Ni/MCM-41, Co/MCM-41, Pt/MCM-41 and Pd/MCM-41 presented the reflections at low angle, but with much higher structural disorder. It was appreciated a retention of the mesoporous structure of the starting material and high surface areas. Additionally, it was possible to observe and identified the oxide phases in the diffraction range (30-45°/2θ) presented in all solids. Oxidation states of incorporated metal, and possible oxides in which are found some of them, were obtained by X-ray photoelectron spectroscopy, corroborating by this technique the presence of metals at surface level. Surface morphology of the solids under study was observed by transmission electron microscopy. The conversion of cyclohexen and the selectivity towards cyclohexane indicated that fresh catalysts show certain degree of intrinsic activity, which depends on the metallic character of the studied solids.