Zn-Mg复合氧化物催化大豆油甘油解合成单甘酯

Synthesis of Monoglyceride by Glycerolysis of Soybean Oil over Zn-Mg Mixed Oxide Catalyst

采用共沉淀法制备了一系列不同Zn、Mg物质的量比的Zn-Mg复合氧化物,将其用于催化大豆油甘油解合成单甘酯（MG）,采用XRD、氮气吸附-脱附仪、SEM、TEM对Zn-Mg复合氧化物结构与性能进行了表征,并测定了催化剂的表面碱强和碱量。优化了合成单甘酯的工艺条件,并考察了Zn-Mg复合氧化物的重复使用性能。结果表明,改变Zn、Mg物质的量比不仅可以调控Zn-Mg复合氧化物的碱强与碱量,还可以调控其比表面积、孔容等结构参数;不同Zn、Mg物质的量比复合氧化物的催化活性变化趋势与其碱强度（H）在15.0〈H〈17．2间碱量变化趋势相一致；n（Zn）／n（Mg）=0．1时，复合氧化物（ZM0．1）具有最好的催化甘油解反应活性；使用该催化剂合成单甘酯的适宜条件为：n（甘油）：n（大豆油）=3：1，反应温度210℃，反应时间2h，催化剂用量为大豆油质量的0．6％，该条件下大豆油转化率达95．6％，单甘酯收率为58．5％。ZM0．1催化剂重复使用4次时大豆油转化率仍达80．9％。

A series of Zn-Mg mixed oxide with different Zn-Mg molar ratio were prepared by coprecipitation method and used for catalyzing the glycerolysis of soybean oil to produce monoglyceride（MG）.These catalysts were characterized by XRD,nitrogen adsorption-desorption,SEM and HRTEM techniques.Their base strength and basicity were determined by Hammett indicators.The reaction conditions for the synthesis of monoglyceride were optimized.Additionally,the reuse of catalyst was investigated.The results showed that the base strength,basicity surface area and pore volume of Zn-Mg mixed oxide catalysts could be tuned by changing the Zn-Mg molar ratio.The change trend of catalytic activity of Zn-Mg mixed oxide was consistent with the trend of its base strength（H） in the range of15.0 - 17.2.The Zn-Mg mixed oxide catalyst with a Zn and Mg molar ratio of 0.1（denoted as ZM0.1） showed the best catalytic activity.It was found that a molar ratio of glycerol to soybean oil 3∶1,a reaction temperature of 210 ℃,a reaction time of 2 h,and catalyst amount 0.6%（base on the mass of soybean oil） were optimum for the production of monoglyceride from soybean oil.Under theseconditions,the conversion of soybean oil and yield of monoglyceride could reach 95.6% and 58.5%,respectively.After four recycling,the conversion of soybean oil still remained 80.9 %.