La-Zn复合氧化物的制备及其催化尿素醇解性能研究

Preparation of La-Zn Composite Oxide and Its Catalytic Performance for Alcoholysis of Urea

以金属硝酸盐为前驱体,采用共沉淀法制备出一系列镧基金属复合氧化物(La-M,M=Fe, Co, Ni, Zn)。利用X射线衍射、透射电子显微镜、扫描电子显微镜、X-射线能谱仪等测试方法验证了其复合氧化物结构。在尿素醇解法制备碳酸乙烯酯反应中,La-Zn物质的量比1∶1复合金属氧化物表现出优异的催化性能,140℃下7 h后完全转化时EC选择性达到96.5%,远高于其他La-M和氧化镧(La_(2)O_(3))。此外,La-Zn物质的量比1∶1复合物在尿素醇解制备碳酸乙烯酯反应中表现出比氧化锌(ZnO)更高的稳定性。经五次催化循环后,La-Zn物质的量比1∶1复合氧化物对乙二醇的选择性(86.9%)高于ZnO(77.4%),并且EC产品中Zn元素的浓度是ZnO做催化剂时的1/24。

A series of lanthanum-metal composite oxides(La-M,M=Fe,Co,Ni,Zn)were prepared by a co-precipitation method using metal nitrate as the precursors.The structure of La-M was demonstrated by using X-ray diffraction,transmitted electron microscope,scanning electron microscope,X-ray energy spectrometer.Among them,n(La)∶n(Zn)=1∶1 showed the excellent catalytic performance for urea alcoholysis to ethylene carbonate(EC),where the selectivity reached 96.5%based on a complete conversion after 7 h at 140°C,higher than lanthanum oxide(La_(2)O_(3))and other La-M.Moreover,n(La)∶n(Zn)1∶1 exhibited higher stability than ZnO.After five catalytic cycles,the selective of EC on n(La)∶n(Zn)1∶1(86.9%)was higher than that on ZnO(77.4%),meanwhile,the concentration of Zn in EC products on n(La)∶n(Zn)1∶1 is 1/24 of that on ZnO.