Synthesis of highly thermostable copper-nickel nanoparticles confined in the channels of ordered mesoporous SBA-15 silica

Abstract

CuNi nanoparticles were effectively confined in the mesopores of SBA-15 silica by a simple incipient wetness impregnation method. After impregnation, the samples were dried at room temperature, which is considered as the key preparation step to obtain high and stable dispersions of the supported CuNi nanoparticles, irrespective of the thermal conditions during the calcination and reduction steps. The catalysts were systematically characterized by powder X-ray diffraction at low and high angles, transmission electron microscopy and nitrogen physisorption, hydrogen temperature-programmed reduction, in situXRD after temperature-programmed reduction, hydrogen chemisorption as well as by catalytic tests for the hydrogenation of cinnamaldehyde in liquid phase. Characterization revealed a strong interaction between Cu and Ni, resulting in improved reducibility as compared to either Cu or Ni monometallic materials. Moreover, the complete interdiffusion of Cu and Ni atoms to form continuous solid alloy solutions is prevented due to the stabilization of Ni by 1 : 1 nickel phyllosilicate. As a result, the bimetallic CuNi/SBA-15 materials present two distinct metallic phases, one rich in copper and another rich in nickel. At the calcination temperature of 500 °C, the materials displayed the highest chemisorption capacity and highest catalytic activity, as well. Nevertheless, the chemoselectivity of supported CuNi/SBA-15 to cinnamyl alcohol or hydrocinnamaldehyde does not depend on the calcination conditions.