Encapsulation of active ruthenium species for hydrogenation of carbon dioxide to formic acid in porous hollow spheres of silica

Abstract

The work is dedicated to the encapsulation of active ruthenium species for the hydrogenation of carbon dioxide to formic acid in porous hollow spheres of silica. The porous hollow spheres were obtained via a sol–gel‐based reaction with 1‐dodecyl amine and cetyltrimethylammonium bromide as templates to form both the hollow void and nanospaces in the shells of the porous hollow sphere support. The metallic ruthenium species were encapsulated in the nanospaces of the hollow spheres through the immersion or incipient wetness impregnation method with a methanolic solution of ruthenium species, following the activation process under solvothermal conditions. The results of transmission electron microscopy (TEM) and X‐ray diffraction (XRD) measurements indicate that the highly dispersed active ruthenium species were effectively encapsulated in the nanospaces by adding an aqueous ammonia solution during the immersion process, and an improvement in the catalytic activity for formic acid yield via the hydrogenation of carbon dioxide was observed in the presence of the catalyst prepared with the appropriate amount of ammonia. The activity dramatically improved in the presence of the ruthenium‐encapsulated porous hollow sphere catalyst prepared via the incipient wetness impregnation method due to including the highly dispersed active ruthenium species on the surface and in the nanospaces of the hollow spheres.