Effect of Si precursor on structural and catalytic properties of nanosize magnesium silicates

Abstract

Two Si precursors, inorganic (sodium silicate) and organic (tetraethoxy silane), were used to synthesize magnesium silicate (MgSil) nanomaterials. The effect exerted by the nature of Si precursors on the morphology and structural properties of the samples was studied by chemical analyses, X-ray diffraction, HRTEM, FTIR spectroscopy, XPS, N2 adsorption, solid-state NMR spectroscopy and TPD of CO2 and NH3 techniques. The characterization results show that MgSil-org sample possessed hollow nanospheres which are composed of small platelets and sheets; in contrast, MgSil-inorg sample showed nanotubular structure due to more alkaline nature of the inorganic Si precursor. Additionally, MgSil-org sample have different textural characteristics, acidic and basic properties. MgSil-org sample have higher surface areas, more uniform mesoporous pores, and more number of acidic and basic sites as well as higher activities in transesterification of tributyrin and esterification of palmitic acid with methanol than MgSil-inorg sample. MgSil-org sample is stable and showed excellent reusability for more than five cycles without any loss of activity in transesterification and esterification reactions.