Crystalline walled SBA-15 with large pore size were prepared using alkali and alkali earth metal ions (Na+, Li+, K+ and Ca2+). For this work, the ratios of alkali metal ions (Si/metal ion) ranged from 2.1 to 80, while the temperatures tested ranged from 500 to 700 °C. The SBA-15 prepared with Si/Na+ ratios ranging from 2.1 to 40 at 700 °C exhibited both cristobalite and quartz SiO2 structures in pore walls. When the Na+ amount increased (i.e., Si/Na increased from 80 to 40), the pore size was increased remarkably but the surface area and pore volume of the metal ion-based SBA-15 were decreased. When the SBA-15 prepared with Li+, K+ and Ca2+ ions (Si/metal ion = 40) was thermally treated at 700 °C, the crystalline SiO2 of quartz structure with large pore diameter (i.e., 802.5 Å) was observed for Ca+2 ion-based SBA-15, while no crystalline SiO2 structures were observed in pore walls for both the K+ and Li+ ions treated SBA-15. The crystalline SiO2 structures may be formed by the rearrangement of silica matrix when alkali or alkali earth metal ions are inserted into silica matrix at elevated temperature.
Desulfurization Characteristics of Fuel-Born Alkali and Alkali Earth Metal Compounds in Coal Ashes from Lab-Scale Experiment to Real-Scale Monitoring of CFBC and PC Boiler
