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在MⅡ与MⅢ的摩尔比为1(MⅡ代表Mg2+和Cu2+等,MⅢ代表Al3+等)及不同Cu与Mg的摩尔比(3:1,1:1,1:3,1:19)的条件下合成了CuMgAl类水滑石,并进行了元素分析、X射线衍射、扫描电子显微镜、Fourier变换红外(infrared,IR)光谱仪、热重-差热分析及Brunauer-Emmett-Teller比表面积表征。结果表明:在Cu与Mg的摩尔比小于1时,可以得到纯水滑石物相,在Cu/Mg比较大时,由于Jahn-Teller效应,层状结构不稳定,出现Al(OH)3及Cu的氢氧化物或氧化物相。随着Cu含量的增加,CuMgAl类水滑石的结晶度增加,层间碳酸根离子的对称性减少,热稳定性下降。500℃时煅烧CuMgAl类水滑石其层状结构已完全破坏,此时可以形成MgO,Cu形成CuAlO4晶相。Al的氧化物没有出现在煅烧后的氧化物中。500℃煅烧的氧化物比表面积最大。
Under the condition that the mole ratio of MⅡ to MⅢ is 1 (MⅡ stands for Mg2 + and Cu2 + etc., MⅢ stands for Al3 + etc.) and different molar ratios of Cu to Mg (3: 1, 1: 1, 1: 3, 1: 19) CuMgAl hydrotalcites were synthesized and characterized by elemental analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, TG-DTA and Brunauer-Emmett-Teller surface area. The results show that the pure hydrotalcite phase can be obtained when the mole ratio of Cu to Mg is less than 1. When the Cu / Mg ratio is large, the layered structure is unstable due to the Jahn-Teller effect and Al (OH) 3 and Cu Hydroxide or oxide phase. With the increase of Cu content, the crystallinity of CuMgAl hydrotalcite increases, the symmetry of interlayer carbonate ions decreases, and thermal stability decreases. The layered structure of CuMgAl-type hydrotalcite calcined at 500 ℃ has been completely destroyed, at this time, MgO can be formed, and Cu forms CuAlO4 crystal phase. Al oxides do not appear in the calcined oxide. The calcined oxide at 500 ℃ has the largest specific surface area.