The hydrogenation of furfural to furfuryl alcohol was performed in the presence of a Co/SBA-15 catalyst. High selectivity (96 %) at a conversion higher than 95 % is reported over this catalytic system. As the conversion of furfural to furfuryl alcohol occurs over metallic Co sites, the effect of reduction temperature, H2 pressure, and reaction temperature were studied. Optimum reaction conditions were: 150 °C, 1.5 h, 2.0 MPa of H2 . The catalyst was recyclable, and furfuryl alcohol was recovered with a purity higher than 90 %. The effect of the solvent concentration was also studied. With a minimum of 50 wt % of solvent, the selectivity to furfuryl alcohol and the conversion of furfural remained high (both over 80 %). Likewise, the activity of the catalyst is maintained even in pure furfural, which confirms the real potential of the proposed catalytic system. This catalyst was also used in the hydrogenation of levulinic acid to produce γ-valerolactone selectively.

NiO and NiO-CuO polycrystalline rodlike nanoparticles were confined and stabilized within the channels of ordered mesoporous SBA-15 silica by a simple and viable approach consisting in incipient wetness impregnation of the calcined support with aqueous solutions of metal nitrates followed by a mild drying step at 25 °C and calcination. As revealed by low- and high-angle XRD, N2 adsorption/desorption, HRTEM/EDXS and H2 TPR analyses, the morphostructural properties of NiO-CuO nanoparticles can be controlled by adjusting their chemical composition, creating the prerequisites to obtain high performance bimetallic catalysts. Experimental evidence by in situ XRD monitoring during the thermoprogrammed reduction indicates that the confined NiO-CuO nanoparticles evolve into thermostable and well-dispersed Ni-Cu heterostructures. The strong Cu-Ni and Ni-support interactions demonstrated by TPR and XPS were put forward to explain the formation of these new bimetallic structures. The optimal Ni-Cu/SBA-15 catalyst (i.e., Cu/(Cu+Ni) atomic ratio of 0.2) proved a greatly enhanced reducibility and H2 chemisorption capacity, and an improved activity in the hydrogenation of cinnamaldehyde, as compared with the monometallic Ni/SBA-15 or Cu/SBA-15 counterparts, which can be associated with the synergism between nickel and copper and high dispersion of active components on the SBA-15 host. The unique structure and controllable properties of both oxidic and metallic forms of Ni-Cu/SBA-15 materials make them very attractive for both fundamental research and practical catalytic applications.

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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 situ XRD 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.

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Stabilization of transition metals in nano-phyllosilicate phases generated by digestion of mesoporous silica is reported as an efficient route for the formation of highly dispersed metallic nanoparticles with outstanding catalytic activity.

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