硅基多孔材料的表征及其对SO2的吸附性能

为增强火山灰反应的强度，提高对SO₂的脱除性能，以粉煤灰为原料采用两步水热合成法制备硅基多孔材料，并对制备的材料进行表征.结果表明:硅基多孔材料整体呈无序形态，主要成分为水化硅酸钙和CaCO₃，属于无定型的非晶相物质；由C、O、Si、Na、Ca等元素构成，主要以SiO₃2-、CO₃2-的形式存在；呈蜂窝和玻璃纤维的网状结构，内部空隙发达，比表面积较大，且存在有大量的吸附水和结合水.利用固定床反应器测定了硅基多孔材料对SO₂的吸附性能，在入口ρ（SO₂）为1 200 mg/m3、吸附温度为50℃、SO₂含氧量为9%、粒度为200目（0.075 mm）的条件下，SO₂的吸附量可达24.87 mg/g，脱硫率可达100%，与钙基吸附剂相比吸附量提高了74%；将吸附SO₂后的硅基多孔材料在700℃下焙烧3 h，可以继续吸附SO₂，重复使用率可达72.24%.由于SO₂在脱除过程中存在一定的化学反应，含氧量的增加能够提高其对SO₂的吸附量.研究显示，硅基多孔材料脱除SO₂的过程是由物理吸附和化学反应相结合的结果，其中由于制备的硅基多孔材料具有较大的比表面积和较为丰富的孔结构，有利于物理吸附；同时，在两步法制备硅基多孔材料的过程中使火山灰反应得到增强也同样提高了SO₂与硅基多孔材料的化学反应，进而增强了化学吸附的效果. 

Characterization of Silicate Based Porous Materials and the Adsorption Properties for SO2

To enhance the reaction activity of pozzolanic and improve SO₂ removal performance, a novel highly porous SO₂ adsorbent has been prepared from fly ash by a two-step hydrothermal reaction in this work. The results indicated that silicate-based porous materials possess a disordered amorphous structure, mainly containing elements of C, O, Si, Na, Ca in the formation of SiO₃2- and CO₃2-. The absorbent presented honeycomb and glass fibrous networks with high porosity and specific surface area and it contains large amount of adsorption water and crystal water. The adsorption performance of SO₂ was determined by the fixed bed adsorption column. When applying the inlet SO₂ concentration of 1200 mg/m3 (mass concentration), a temperature of 50℃, oxygen content of 9%, particle size of 200 mesh (0.075 mm), the amount of adsorbed SO₂ on the silicate based materials could reach 24.87 mg/g with an 100% the desulfurization rate, 74% larger than the adsorption efficiency of a calcium-based adsorbent. The adsorbed SO₂ of silicate based porous material at 700℃ after roasting for three hours can continue to adsorb SO₂, repeat utilization rate can reach 72.24%. Because of a certain chemical reaction, the increase in oxygen content can increase the adsorption capacity of SO₂. The process of removing SO₂ by silicate based porous materials is a result of the combination of physical adsorption and chemical reaction. It is beneficial to physical adsorption because of the large specific surface area and abundant pore structure. Preparation of silicate based porous materials at the same time the two-step processes enhanced the pozzolanic reactions also raised the SO₂ and silicate based porous material of the chemical reactions, thus enhancing the effect of the chemical adsorption.