纳米钛酸盐催化合成碳酸二正丁酯

以廉价的偏钛酸为原料,采用水热法和乙醇热法制备了纳米钛酸盐(简称钛酸盐),并对其进行了X射线粉末衍射和X射线光电子能谱表征。考察了钛酸盐的种类、制备方法、晶型对催化碳酸二甲酯(DMC)与正丁醇酯交换反应的影响。实验结果表明,乙醇热法比水热法制备的钛酸盐粒径小;对于不同的钛酸盐,随钛酸盐碱性的增强,催化活性提高,但由于三价钛的存在,钛酸锂对产物碳酸二正丁酯(DBC)的选择性低于钛酸钡;钛酸钾的催化活性最高,DMC转化率达到65%,DBC选择性达到100%,DBC收率达到65%,并在5次循环使用过程中,催化性能稳定;对于同种钛酸盐,催化活性随粒径的增加而减小;对于钛酸钡,立方相结构的催化活性优于四方相结构。

Synthesis of Dibutyl Carbonate over Nano-Titanate Catalyst

Nano-titanates were prepared from metatitanic acid by ethanol-thermal and hydrothermal methods,and characterized by means of X-ray diffraction(XRD)and X-ray photoelectron spectrometry(XPS).Performance of nano-titanate as catalyst for synthesis of dibutyl carbonate(DBC)from methyl-carbonate(DMC)and n-butanol was investigated.Effects of type,preparation method and crystal structure of nano-titanate on catalytic performance for transesterification were studied.The stronger basicity of nano-titanate was,the higher its catalytic activity was.On potassium titanate,which was the most active among the five titanates and exhibited steady life-time for transesterification,conversion of DMC,selectivity to DBC and yield of DBC were 65%,100% and 65%,respectively.Particle diameter of titanate prepared by ethanol-thermal method was smaller than that prepared by hydrothermal method.Catalytic activity of nano-titanate clearly related to its particle diameter and crystal structure.Smaller particle diameter was preferable to catalytic activity.Barium titanate with cubic crystal structure was more active in transesterification than that with tetragonal crystal structure.