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作 者:TANG Jie LIU Gui-hua QI Tian-gui ZHOU Qiu-sheng PENG Zhi-hong LI Xiao-bin 唐杰;刘桂华;齐天贵;周秋生;彭志宏;李小斌(School of Metallurgy and Environment,Central South University,Changsha 410083,China)
机构地区:[1]School of Metallurgy and Environment,Central South University,Changsha 410083,China
出 处:《Journal of Central South University》2022年第4期1147-1160,共14页中南大学学报(英文版)
基 金:Project(51874372)supported by the National Natural Science Foundation of China。
摘 要:Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area through multistep phase transformation of aluminum-bearing substances using intermediate dawsonite as a template.Thermodynamic calculations and experimental results show that increasing the concentration of Na_(2)CO_(3) and(NH_(4))_(2)CO_(3) is remarkably beneficial to the formation of dawsonite and ammonium aluminum carbonate hydroxide,respectively.Based on determination of dissolution and precipitation mechanism,the ultrafine granular gibbsite is converted to the uniform fibrous dawsonite with a ratio of length to diameter over 50,and the fibrous dawsonite changes into the long fibrous ammonium aluminum carbonate hydroxide with a ratio of length to diameter is about 80 in above 70 g/L(NH_(4))_(2)CO_(3) solution.Furthermore,the activated alumina remains fibrous morphology after roasting ammonium aluminum carbonate hydroxide at a slow heating rate,plentiful open mesopore and weak aggregation of particles,which contributes to the high specific surface area of 159.37 m^(2)/g at 1273 K for the activated alumina.The complete transformation of dawsonite to ammonium aluminum carbonate hydroxide and high specific surface area contribute to the purity of the activated fibrous alumina above 99.9%with low Na and Fe content.纤维状活性氧化铝被广泛应用于催化剂、吸附剂和复合材料等领域。本文提出了一种绿色方法,以中间体丝钠铝石为模板,通过含铝物相的多步相变制备具有高纯度和高比表面积的纤维状活性氧化铝。热力学计算和实验结果表明,提高Na_(2)CO_(3)和(NH_(4))_(2)CO_(3)的浓度分别有利于丝钠铝石和碳酸铝铵的形成。根据溶解和沉淀机理,超细粒状氢氧化铝可以转变为长径比大于50的纤维状丝钠铝石,而纤维状丝钠铝石在70 g/L以上的(NH_(4))_(2)CO_(3)溶液中又可以转变为长径比约80的纤维状碳酸铝铵。此外,纤维状碳酸铝铵经缓慢加热分解后得到的活性氧化铝仍可以保持纤维状形态,且大量开放的介孔结构和颗粒间的弱聚集使活性氧化铝在1273 K的焙烧温度下仍具有159.37 m^(2)/g的高比表面积。丝钠铝石完全转化为碳酸铝铵和高比表面积使纤维状活性氧化铝的纯度超过99.9%,且Na和Fe含量较低。
关 键 词:fibers activated alumina specific surface area DAWSONITE ammonium aluminum carbonate hydroxide
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