Abstract: MCM-41 with high nitrogen content was prepared by nitridation of MCM-41 with NH3 at high flow rate and low temperature. The highest nitrogen content (mass fraction) of about 26.0% was achieved in NH3 with a flow rate of 400 ml/min at 950 ℃ for 12 h. The NH3 flow rate and nitridation temperature were the key factors that influenced the nitrogen content of the nitrided MCM-41 samples, whereas the silicon source and alkali source had little effect. The nitrogen content of the nitrided samples was stable when the nitridation time was over 12 h. X-ray diffraction, N2 adsorption, transmission electron microscopy, X-ray photoelectron spectroscopy, and 29Si MAS NMR results indicated that the mesopore framework of parent MCM-41 was well preserved after nitridation. Moreover, nitrogen was incorporated into the framework of MCM-41. The nitrided MCM-41 with high nitrogen content exhibited high basic catalytic activity for Knoevenagal condensation of malononitrile and benzaldehyde owing to the slight damage of nitridation at low temperature to the framework of MCM-41.

Key words: MCM-41, nitridation, basic catalysis, Knoevenagal condensation