Abstract
Background: The unique physiochemical properties of nanoparticles as compared to their bulk state make them highly useful in the area of catalysis, fuel cell development, photonics, medicines, solar cell and biomedical imaging. The small size structures of nanoparticles are certainly very unstable mainly because of their high surface energies and large surface area. To produce stable nanoparticle, it is important to reduce the particle growth reaction (to avoid agglomeration). The advantage of the use of SBA-15 material as support also includes its high surface-to-volume ratio, variable framework compositions and high thermal stability. Thus SBA-15 exhibits mainly mesoporous structure and possesses a small amount of micropores. The large pore size of this mesoporous material can mitigate the diffusion barrier for the reactants and the products. In some recent technical reports, silica materials with grafted silicon hydride groups have been successfully applied for the synthesis of gold, silver and palladium nanoparticles. With respect to common normal hydrogen reduction, direct reduction of ions followed by varying concentration of metal salt and reduction time, the hydride silica surface offers the controlled shape and size selective metal nanoparticles.
Methods: In the present report, we have exploited the catalytic application of mesoporous silica supported Ru metal nanoparticles for CO2 hydrogenation reaction. Silica hydride groups, possessing reducing properties, grafted to the surface of silica allowed obtaining metal nanoparticles immediately at reducer attachment position. Ru-silica (SBA-15-xRu) catalysts were characterized by different physiochemical methods and tested for CO2 hydrogenation reaction. Results: A series of SBA-15 supported Ru catalysts were prepared with 1, 2 and 3% (by weight) Ru metal loading followed by impregnation method and well-characterized by sophisticated analytical techniques. Among all the SBA-15-xRu catalysts, SBA-15-3Ru catalyst was found to be highly active for hydrogenation of CO2 to formic acid. Low catalyst loading, ligand free approach, simple reaction protocol and catalyst recycling are major merits of this proposed work. Conclusion: In summary, Ru nanoparticles synthesis on the surface of SBA-15 with different structural characteristics was studied. The SBA-15-3Ru catalyst was found to be highly efficient for hydrogenation of CO2 to formic acid. CO2 hydrogenation reaction enjoyed the catalytic system and offered the corresponding hydrogenated reaction product in good yield and selectivity. Good catalyst recycling, low catalyst loading, simple work up procedure and easy catalyst preparation step were the major outcomes of this proposed protocol.Keywords: Ruthenium nanoparticle, carbon sequestration, hydrogenation, formic acid, functionalized ionic liquid.
Graphical Abstract
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