碳酸钾改性SiO_(2)-Al_(2)O_(3)复合气凝胶制备及脱碳特性

Preparation and decarburization characteristics of SiO_(2)-Al_(2)O_(3) composite aerogel modified by potassium carbonate

本文对碳酸钾改性SiO_(2)-Al_(2)O_(3)复合气凝胶的制备、K_(2)CO_(3)碳酸化特性及再生循环脱碳特性进行了研究,采用固定床反应器研究负载率对CO_(2)吸附的影响,结合SEM、BET对样品微观结构进行分析。结果表明,Na_(2)CO_(3)碱熔烧结过程中,Si-O-Si、Si-O-Al键断裂,晶相结构被破坏,莫来石的共价键转化为霞石的离子键;经正交试验以气凝胶比表面积为衡量指标确定最佳煅烧条件为:900℃、反应60 min、Na_(2)CO_(3)添加比例0.5;K_(2)CO_(3)负载量越多,载体表面相应活性位点越少,且负载量为30%时,CO_(2)吸附量最大为2.86 mmol·g^(−1);过量K_(2)CO_(3)会堵塞孔结构,破坏CO_(2)扩散,降低扩散和利用效率;介孔孔体积百分比由94.21%下降至89.32%,说明活性组分K_(2)CO_(3)主要填充在介孔;经过10次循环-再生试验,吸附剂的CO_(2)吸附量下降幅度为10.49%,吸附剂孔隙结构稳定,脱碳性能优良。

The preparation of potassium carbonate modified SiO_(2)-Al_(2)O_(3) composite aerogel,the carbonation characteristics of K_(2)CO_(3) and the decarbonization characteristics of the regeneration cycle were studied.Using a fixed bed reactor to study the effect of loading rate on CO_(2) adsorption.Analyze the microstructure of samples combined with SEM and BET.The results show that during the Na_(2)CO_(3) alkali fusion and sintering process,the Si-O-Si and Si-O-Al bonds are broken,the crystal structure is destroyed,and the covalent bond of mullite is transformed into ionic bond of nepheline.The orthogonal test uses the specific surface area of the aerogel to determine the best calcination system as follows:900℃,60 min reaction,and 0.5 Na_(2)CO_(3)addition ratio.The more K_(2)CO_(3)loading,the fewer K_(2)CO_(3)active sites can be attached to the surface of the carrier.When the load is 30%,the maximum CO_(2)adsorption capacity is 2.86 mmol·g^(-1).Excessive K_(2)CO_(3)will block the pore structure,destroy CO_(2)diffusion,and reduce diffusion and utilization efficiency.The volume percentage of mesopores decreased from 94.21%to 89.32%,indicating that the active component K_(2)CO_(3)was mainly filled in the mesopores.After 10 cycles-regeneration tests,the CO_(2)adsorption capacity of the adsorbent decreased by 10.49%,the pore structure of the adsorbent was stable,and the decarburization performance was excellent.