Mg-Al水滑石的制备及其催化合成丙二醇单甲醚的性能

Preparation and Catalytic Properties of Mg-AI Hydrotalcites for Synthesis of Propylene Glycol Monomethyl Ether

分别采用尿素法和滴定共沉淀法(包括高过饱和法和低过饱和法)制备了镁铝水滑石,利用 X 射线衍射、傅里叶变换红外光谱、热重-差热分析和扫描电子显微镜等方法对镁铝水滑石进行表征,并考察了不同方法制备的镁铝水滑石催化环氧丙烷与甲醇进行醚化反应合成丙二醇单甲醚的性能。表征结果显示,尿素法制备的镁铝水滑石结晶度高、晶粒规整均匀。实验结果表明,尿素法制备的镁铝水滑石的催化活性明显好于高过饱和法制备的镁铝水滑石的催化活性,前者在500℃下煅烧6～7 h 后制得的镁铝复合金属氧化物的催化活性更高,可使环氧丙烷转化率达93.8%,丙二醇单甲醚选择性达97.2%,其中丙二醇单甲伯醚的选择性达100.0%。该催化剂使用后无需处理即可重复使用,是一种稳定性好、选择性高的环境友好催化剂。

Mg-Al hydrotalcites （Mg-Al LDH ）were prepared by urea method and titration coprecipitation（ including coprecipitation at high and low supersaturation） separately. The prepared Mg-Al LDH were characterized by means of XRD, FTIR, TG-DTA and SEM, and used as catalysts in synthesis of propylene glycol monomethyl ether from propylene oxide and methanol. Mg-Al LDH prepared by urea method is higher in crystallinity, its crystals are well formed and even in size. Its catalytic activity is significantly higher than that of Mg-A1 LDH prepared by coprecipitation at high supersaturation. It was calcined at 500 ℃ for 6 -7 h to obtain Mg-A1 complex metal oxide （Mg-A1 LDO） and catalytic activity of Mg-A1 LDO become better. Under appropriate reaction conditions and using Mg-A1 LDO as catalyst, conversion of propylene oxide is 93. 8%, selectivities to propylene glycol monomethyl ether and 2-hydroxy propylene glycol monomethyl ether are 97.2% and 100.0%, respectively. The Mg-A1 LDO catalyst can be reused directly for five times without abvious loss of activity and selectivity.