低密度薄水铝石晶体的水热生长过程

Hydrothermal Crystal Growth of Very Light Boehmite Product s

对A12(SO4)3-CO(NH2)2-H2O体系在[Al3+]=0.2 mol·L-1、[CO(NH2)2]:[Al3+]=2:1和反应2 h的水热条件下,不同反应温度的晶体生长过程进行了研究,得到呈多孔、针状团簇体状的微米级低密度薄水铝石晶体.采用ICP-AES、XRD、FT-IR、SEM、BET和粒径分布等手段对反应液和产物进行了分析和表征.结果表明,140℃时氢氧化铝凝胶或无定形粉体的析出已大部分完成,温度升高到180℃后,产物的结晶度变好,堆密度从117.2 kg·m-3相应增加到158.2 kg·m-3,比表面也从75.3 m2·g-1增加到88.3 m2·g-1,但平均粒径有所下降.晶体前驱体在550℃焙烧2 h后完全转化为形貌相似并且比表面增加的γ-Al2O3.

The hydrothermal precipitation in the Al-2(SO4)(3)-CO(NH2)(2)-H2O system under the conditions of [Al3+] = 0.2 mol (.) L-1, [CO (NH2)(2)]: [Al3+] = 2:1 and 2 h at different temperatures has been studied. Very light boehmite powders in the form of porous agglomeration of several micron size covered with needle clusters are obtained at above 140 degreesC. The reaction solution and the products are characterized by ICP-AES, XRD, FT-IR, SEM, BET and particle size distribution. The precipitation of aluminum hydroxide gel or amorphous powder is almost completed at 140 degreesC. With the reaction temperature raised to 180 degreesC, crystallinity of the products, whose tap density varies among 117.2 similar to 158.2 kg (.) m(-3), becomes more perfect and the specific surface area increases from 75.3 m(2) (.) g(-1) to 88.3 m(2) (.) g(-1) as well. However, the average diameter decreases moderately. The gamma-Al2O3 powders formed by calcination of aforementioned boehmites at 550 degreesC for 2 h have the same shape and higher specific surface area compared with their corresponding precursors.