镁铝复合氧化物催化合成丙二醇乙醚

以硝酸镁、硝酸铝和氨水为原料，通过共沉淀方法制备了一系列镁铝水滑石材料，经过焙烧处理后作为碱催化剂用于丙二醇乙醚的催化合成。采用X射线衍射、热分析、SEM、DTA-TG和CO^_2-TPD等手段对所制备的催化剂进行表征，结果表明，在实验范围所制备的催化剂均具有典型的镁铝水滑石结构。采用高压固定床反应器对催化剂进行活性评价，考察了形成沉淀的pH、晶化方式、原料中镁与铝物质的量比及焙烧温度等对镁铝水滑石及其衍生物的结构和催化活性的影响，研究了碱性与催化剂活性之间的关系，结果表明，镁与铝物质的量比为3和550 ℃焙烧的催化剂具有良好的催化合成丙二醇乙醚活性。超声晶化的方式可以提高镁铝水滑石衍生物的碱强度，但对镁与铝物质的量比不同的催化剂活性有着不同的影响。在（350～550） ℃，焙烧温度的提高可以增大催化剂的碱强度和碱量，催化活性也有显著提高，但进一步升高焙烧温度，催化剂的表面碱强度和碱量有所下降，催化活性也随之降低。

Catalytic synthesis of propylene glycol monoethyl ether over hydrotalcite derivates

Mg-Al hydrotalcites were prepared by co-precipitation method and characterized by XRD, thermal analysis, SEM、DTA-TG and CO₂-TPD. The results showed that the catalysts prepared had hydrotalcite-type structure. The synthesis of propylene glycol monoethyl ether from ethanol and propylene oxide was studied in a high pressure fixed-bed reactor using calcined hydrotalcites as the solid-base catalysts. The effects of pH for precipitation, crystallization method, Mg/Al molar ratio and calcination temperature on the structure and catalytic activity of hydrotalcites and their derivatives were investigated, as well as the relationship between the activity and alkalinity. The results showed that Mg-Al hydrotalcite derivatives with Mg/Al molar ratio of 3 and calcined at 550 ℃ exhibited excellent activity for synthesis of propylene glycol monoethyl ether. Ultrasonic-assisted crystallization enhanced alkalinity of the calcined hydrotalcites, with different effects on the activity for catalysts with different Mg/Al molar ratio. At （350-550） ℃, alkalinity and quantity of basic centers (and hence catalytic activity) firstly increased and then declined with enhancement of calcination temperature.