焙烧温度对铝层柱蒙脱土热稳定性和水热稳定性的影响

Effect of Calcination Temperature on the Thermal and Hydrothermal Stability of Al-Pillared Montmorillonite

以钠基蒙脱土(Na-MMT)和AlCl3为原料,用离子交换法制备了铝层柱蒙脱土(Al-MMT).通过粉末X射线衍射(XRD),热重法(TG),差示扫描量热法(DSC),傅利叶变换红外光谱(FTIR)等测试手段研究了材料热稳定性、水热稳定性及柱化机理.经过500℃高温焙烧后,交联剂经脱水或脱羟基释放出质子攻击蒙脱土四面体层中Si-O-AlⅣ键,硅氧四面体和铝氧四面体发生翻转,与交联剂发生反应生成共价键,形成稳定的层柱黏土材料.在700℃高温下,Al-MMT材料不仅具有较好的热稳定性,而且具有较好的水热稳定性.

Al-pillared montmorillonites （Al-MMT） were synthesized from natural sodium montmorillonite through the exchange of inter-lamellar ions with hydroxyalumina polycations. The thermal and hydrothermal stability as well as the synthesis mechanism of the pillared materials were studied using a X-ray diffraction （XRD）, Fourier transformation infra-red spectra （FT- IR）, thermogravimetric analysis （TG）, and differential scanning calorimetry （DSC）. Results show that protons are liberated by dehydration or dehydroxylation after calcination at 500℃. These protons disrupt the silicon-oxygen-aluminium bridges where there are Al substitutions in the tetrahedral sheet of the montmorillonite. Some of silicon-oxygen and aluminum-oxygen tetrahedra invert to react with the pillaring agents and yield covalent bonds which firmly fix the pillars to the host clay. The Al-MMT are thermally and hydrothermally stable up to 700 ℃.