Catalytic conversion of glycerol into solketal with Ga-silicate nanoparticles prepared by aerosol process

Abstract

Here, the aerosol assisted sol-gel process was used as a powerful tool to synthesize silica-based solids with Ga inserted as single-site in the structure. The influence of different parameters on both morphological properties and catalytic activity were studied. Three different materials bearing a Si/Ga ratio of 34, 74 and 148 were synthesized and extensively characterized via N2 physisorption, XRD, TEM, ICP-OES spectroscopy, XPS and 29Si solid state NMR. All materials displayed promising features for catalytic applications such as high surface area (~ 400 m2/g), controlled mesoporosity and narrow particles size distribution. To investigate the coordination number/geometry of the metal center inserted as single site within the silica matrix, a deep structural investigation of the materials was performed via solid state NMR of 71Ga under magic angle spinning (MAS) or static conditions. The understanding and the quantification of the different species is of fundamental importance since it allows to strongly correlate the final properties of the solids with the metal coordination. The challenging study of quadrupolar 71Ga allowed to observe a signal with a maximum at around 140 ppm that can be assigned to a predominant contribution of tetrahedral gallium present as single site in the silica framework