AACH在柠檬酸铝制备多孔氧化铝中的应用研究  

Application of AACH in Porous Alumina Preparationfrom Aluminum Citrate

作　　者：石志霞[1] 余章龙[2] 张碧田[1] 王星明[1] 储茂友[1] 段华英[1] 

机构地区：[1]北京有色金属研究总院矿物资源与冶金材料研究所,北京100088 [2]北京化工大学理学院,北京100029

出　　处：《稀有金属》2012年第1期115-119,共5页Chinese Journal of Rare Metals

基　　金：国家自然科学基金面上项目(50672012)资助

摘　　要：针对从简单铝盐(AlCl3,Al(NO3)3等)体系中制备化学品氧化铝易发生凝聚而导致颗粒分散性差的问题,提出利用柠檬酸作为铝的络合剂,并采用碳酸铝铵(AACH)作为中间体制备多孔氧化铝的方法。将柠檬酸铝溶液调节到一定pH值后,滴加到碳酸氢铵溶液中可以得到结晶良好的AACH固体,再通过简单焙烧后即可得高比表面积的多孔球型Al2O3产品。通过对原料碳酸氢铵和柠檬酸铝的物质的量之比β、反应体系pH值、反应温度及陈化时间对铝转化率α的影响的研究发现,在β=2,pH=9,室温25℃,陈化8 d,有50%的柠檬酸铝转化为AACH。同时推测出,由于AACH的形成受柠檬酸,铝酸钠,碳酸氢铵三重络合-缓冲体系的限制,首先需要调节柠檬酸铝,其pH值大于9后缓慢释放出Al(OH)4-,Al(OH)4-再同碳酸氢铵反应易得到结晶良好的AACH晶体。TG-DTA热分析和XRD测试表明:300℃下AACH可完全分解为不定型氧化铝,700和1400℃下焙烧可分别得到γ-Al2O3,α-Al2O3。SEM和TEM测试表明,所得AACH粒径约为15μm,并由大量长度为500 nm左右的纳米棒组成,700℃焙烧后得到形貌不变,含有大量孔径为1～5 nm微孔、BET比表面积为235 m2.g-1的多孔氧化铝。For solving the poor dispersion problem when chemical alumina produced from simple aluminum solutions such as AlCl3,Al（NO3）3 etc.,ammonium aluminum carbonate hydroxide（AACH） was considered as an intermediate for producing porous alumina from aluminum citrate（AlCit） solution with the aid of chelating ability between Al and Cit groups.Well crystallized AACH particles could be obtained when AlCit solution with a certain pH value was adding into the NH4HCO3 solution,and then,porous alumina with spherical shape could be obtained after AACH roasted.The effects of β value（proportion of NH4HCO3 to AlCit）,pH value,reaction temperature and aging time on conversion ratio α（transforming aluminum citrate into AACH）were emphatically studied.A α value of 50% could be obtained under the conditions of β=2,pH=9,25 ℃ and aging time of 8 d.Meanwhile,the AACH forming mechanism could be summarized under the triple buffer systems： Cit,aluminates and bicarbonate groups.The pH value of AlCit solution should be adjusted to about 9 for Al（OH）-4releasing continuously.And then,AACH could be formed steady when adding the adjusted AlCit solution into NH4HCO3 solution.TG-DTA and XRD characterizations showed that AACH was decomposed completely at about 300 ℃.Moreover,γ-Al2O3 and α-Al2O3 were formed by AACH roasted at 700 and 1400 ℃,respectively.The SEM and TEM characterizations showed that AACH crystalline had a diameter of 15 μm composed of many 500 nm nano-rods and this structure was kept in the obtained γ-Al2O3 product.Moreover,the obtained γ-Al2O3 had many micro pores with diameter of 1～5 nm and a BET surface of 235 m2 · g-1 due to the gas librating when AACH was roasted at 700 ℃.

关 键 词：柠檬酸铝 碳酸铝铵 氧化铝 碳酸氢铵 

分 类 号：TF813[冶金工程—有色金属冶金]