Synthesis, characterization, and catalytic activity of nitridated magnesium silicate catalysts

Abstract

Amorphous and crystalline magnesium silicates (MgSils) were prepared by sol–gel and template-assisted hydrothermal synthesis methods, respectively. The obtained materials were nitridated with NH3 at 300, 500, and 800 °C for 24 and 48 h generating nitridated MgSil catalysts. The catalysts were characterized by XRD, FTIR, TG–MS, N2-physisorption, Hammett indicators, and elemental analysis methods. MgSils nitridated at 300 °C were found to be more active for the Knoevenagel condensation reaction, compared to those nitradated at 500 or 800 °C. A larger amount of nitrogen was incorporated in the framework of amorphous MgSil compared to the crystalline MgSil. FTIR analysis indicated the presence of NHx species, which were known to form upon reaction between NH3 and M-OH groups. It was also found that the presence of Si–OH and Mg–OH groups along with the basic –NH2 functional groups is responsible for the enhanced catalytic activity of the low-temperature nitridated catalysts.