STABILITY AND MICROWAVE SYNTHESIS OF COBALT-CONTAINING MESOPOROUS MOLECULAR SIEVES

Cobalt-containing mesoporous molecular sieves (Co-MCM-41) with different cobalt contents were synthesized by the microwave irradiation method and using inorganic salt sodium silicate and cobalt chloride as raw materials,and cetyl trimethyl ammonium bromide as template agent.The physicochemical properties of the as synthesized Co-MCM-41 were characterized by various techniques such as X-ray diffraction,Fourier transform infrared spectroscopy,temperature programmed reduction, transmission electron microscope,and N_2 adsorptiun-desorption technique,and the stability of the synthesized Co-MCM-41 was also investigated.The results show that well-ordered Co-MCM-41 can be synthesized when the molar ratio n(SiO_2):n(CoO) in the starting material is between 1.0:0.05 and 1.0:0.2.The specific surface area of the synthesized mesoporous molecular sieve decreases with the increasing of the amount of cobalt added,and the pore size of synthesized samples slightly increases.The synthesized Co-MCM-41 still has a mesostructure after calcination at 750℃for 3 h,but the mesostructure is damaged after calcination at 850℃for 3 h.On the other hand,the mesostructure of the synthesized sample is still retained after hydrothermal treatment at 100℃for 5 d,but the specific surface area greatly decreases,and the synthesized sample exhibits a worm-like mesoporous structure.