Abstract
The design of different bimetallic catalysts is an important area of catalytic research in the context of their possible applications in the cascade processes, meeting the requirements of the so-called green chemistry. In this study, such catalysts were obtained by the incorporation of magnesium species into spherical silica, which was in the next step covered with porous silica and modified with ruthenium species. The structure and chemical composition of the materials obtained were determined by XRD measurements, low temperature N2 adsorption/desorption, SEM, ICP-OES and XPS methods. The catalytic activities of materials obtained were tested in 2-propanol decomposition and hydrogenation of levulinic acid. The results obtained confirmed the successful coverage of nanospheres with porous silica. A much higher concentration of ruthenium species was found on the surface of the catalysts than in their bulk. The opposite relationship was observed for magnesium species. The modification of nanospheres with silica had a positive effect on the catalytic activity of the materials obtained. For the most active sample, i.e., Ru/NS/3Mg/NS, 49% of levulinic acid conversion in its hydrogenation process was reported with γ-valerolactone as the only product.
Highlights
Porous materials play a crucial role in heterogeneous catalysis as they facilitate diffusion of the reactants and dispersion of the active phase
Over the years spherical silica has been paid much attention, as it can be applied as a hard template [5,6], a hollow sphere capturing a metal inside, or as a traditional matrix
For instance Niu et al [7] have proposed the synthesis of core–shell-structured silica spheres with large (~14 nm) pores in the core and small pores (2 nm) in the shell with the use of various surfactants
Summary
Porous materials play a crucial role in heterogeneous catalysis as they facilitate diffusion of the reactants and dispersion of the active phase. Other authors have employed silica with core–shell structure to separate basic (APTMS) and acidic (MPTMS) active sites [8]. Such layered systems can be applied for encapsulation of metal nanoparticles to prevent their aggregation [9]. An exemplary process is biomass transformation into fine chemicals that is usually carried out in a liquid medium In such reactions the application of a heterogeneous catalyst would permit easy separation of the catalyst and would eliminate the step of the post-reaction medium neutralization. We proposed the application of a catalyst based on ruthenium and magnesium loaded onto silica, in liquid phase hydrogenation of levulinic acid to GVL. The idea of this work was to localize magnesium species in the pores of spherical silica, which in the step was modified with porous SiO2 and modified with ruthenium
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