Zn-Mg复合氧化物催化大豆油甘油解合成单甘酯

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15.0H17.2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2 h,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%。

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

A series of Zn-Mg mixed oxide catalysts with different Zn/Mg molar ratios were prepared by coprecipitation method for the glycerolysis of soybean oil to produce monoglyceride. These catalysts were firstly characterized by XRD, BET, SEM techniques, and the base strength and basicity of catalysts were determined by Hammett indicators. The reaction conditions were then optimized for the preparation of monoglyceride catalyzed by Zn-Mg mixed oxide catalyst. The reusability of Zn-Mg mixed oxide catalyst was studied finally. The results show that changing the Zn/Mg molar ratio can control the base strength, basicity, surface area and pore volume of Zn-Mg mixed oxide catalysts. The activities of Zn-Mg mixed oxide catalysts with different Zn/Mg molar ratio are consistent with the change of basicity, surface area and pore volume, and the maximum activity could be obtained when the Zn/Mg molar ratio reached 0.1. The optimum reaction conditions were as follows: n(glycerol):n(soybean oil)=3:1, reaction temperature 210?C, reaction time 2 h, and catalyst amount 0.6% (base on the mass of soybean oil). Under these conditions, the soybean oil conversion and monoglycerides yield can reach 95.6% and 58.5%, respectively. After recycling five times, the soybean oil conversion remains 80.9%, which means the ZM0.1 catalyst is stable.