Coprecipitation synthesis of Si-modified mesoporous alumina with high thermal stability from coal fly ash

摘要

Si-modified mesoporous alumina with high thermal stability was synthesized from coal fly ash through a facile coprecipitation method using NH_4HCO_3 and NH_4Al(SO_4)_2. The effects of Si dopant contents on the characterization of alumina were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, N_2 adsorption-desorption method and transmission electron microscopy. The results show that the introduction of Si effectively inhibits the phase transformation of mesoporous alumina from γ-Al_2O_3 to α-Al_2O_3. Compared with alumina obtained without Si dopant, the specific surface area of mesoporous alumina with adding 12 wt% Si improved from 5.2 to 227.5% by increasing the calcination temperature from 500 to 1200 °C, respectively. The specific surface area, pore volume and pore size of mesoporous alumina with 12 wt% Si calcined at 1100 °C are 149 m~2/g, 0.52 cm~3/g and 8.9 nm, respectively.