碳酸化分解法制备片状氧化铝的研究

发布时间：2018-05-04 02:44

  本文选题：碳酸化分解法 + 片状氧化铝　； 参考：《中南大学》2010年硕士论文

【摘要】： 本文以低浓度铝酸钠溶液为原料,利用二氧化碳气体进行碳酸化分解,通过多种添加剂的相互作用,制备出氢氧化铝前驱体,该前驱体在一定条件下煅烧后得到具有完整六角片状的氧化铝粉体。实验根据碳酸化分解原理和片状氧化铝晶体生长习性,考察了各操作参数对产物晶型结构的影响。 研究发现,铝酸钠溶液苛性比(αK)与苛性碱浓度(NK)对前驱体制备有很大影响,NK增大会降低碳酸化分解效率；但减小NK会降低拟薄水铝石向三水铝石的转化的效率；同时,NK和αK相互制约,影响着反应驱动力的大小；传统碳酸化分解法制备得到的氢氧化铝呈砂状,团聚严重,SEM检测发现,添加硬脂酸作表面活性剂,四氯化钛、焦磷酸钠作为晶型向导剂,得到的前驱体氢氧化铝具有良好片状结构,且降低了团聚程度；XRD检测表明：直接煅烧至1400℃,前驱体氢氧化铝仍然不能完全转化为α-Al2O3，向体系中添加氟化铝,可以明显降低α-Al2O3的转化温度。 综上所述,利用碳酸化分解法制备前驱体氢氧化铝合适的条件为：控制铝酸钠溶液αK=1.7,NK=100g/L,浓度为2.0mol/L,添加10%(质量分数,下同)硬脂酸作表面活性剂,5%氟化铝、3%焦磷酸钠和3%四氯化钛作晶型向导剂,反应气体二氧化碳与氮气1：1混合,混合气体流速为250L/h,于45℃水浴条件下进行碳酸化分解反应,pH=12.0反应达到终点,过滤洗涤后,加入10%异丁醇于100℃下干燥5h。此条件下得到的前驱体在1200℃下煅烧5h即可得到平均粒径为30.13μm,具有明显六角片状结构,表面光滑,边缘平整,珠光效果明显,并且具有较好的耐酸碱能力的α-Al2O3。 采用遮盖率法和SEM测量法对产品的径厚比进行了检测,得到的径厚比分别为39.12和42.09。
[Abstract]:In this paper, aluminum hydroxide precursor was prepared from low concentration sodium aluminate solution by carbonation and decomposition of carbon dioxide gas. The precursor was calcined under certain conditions to obtain a complete hexagonal aluminum oxide powder. According to the decomposition principle of carbonation and the growth habit of flake alumina crystal, the effect of operation parameters on the crystal structure of the product was investigated. It was found that the ratio of causticity of sodium aluminate solution (伪 K) and the concentration of caustic soda (NKK) had a great influence on the preparation of precursor. The increase of NK would decrease the efficiency of carbonation decomposition, but the reduction of NK would decrease the conversion efficiency of pseudoboehmite to tribobsite. At the same time, NK and 伪 K restrict each other, which affect the driving force of reaction, the aluminum hydroxide prepared by traditional carbonation decomposition method is sandlike, and the agglomeration serious SEM results show that adding stearic acid as surfactant, titanium tetrachloride, titanium tetrachloride, titanium tetrachloride, titanium tetrachloride, Using sodium pyrophosphate as crystal guide agent, the precursor aluminum hydroxide has a good flake structure, and the agglomeration degree is reduced. The results show that the precursor is calcined directly to 1400 鈩，

本文编号：1841234