Au/CeO2-cube催化1,3-丙二醇氧化酯化反应性能

摘要

Au nanoparticles supported on CeO2 nanocubes were successfully prepared by a deposition-precipitation method and tested for the oxidative esterification of 1,3-propanediol. The catalyst was characterized by inductively coupled plasma atomic emission spectrometry, transmission electron microscope (TEM), X-ray diffraction, and X-ray photoelectron spectroscopy. The different parameters which may affect catalytic performance, such as dosage of urea, the calcination temperature of CeO2 nanocubes, the calcination temperature of Au/CeO2-cube, Au loading and the loading temperature were investigated. The optimized preparation conditions of Au/CeO2-cube were obtained as follows: the mass ratio of urea/ceria 6, the calcination temperature of CeO2 nanocubes 400℃,the calcination temperature of Au/CeO2-cube 200℃,Au loading 1.5% and the loading temperature 80℃. Under the condition of 100℃, pressure of O22 MPa, the mole ratio of 1,3-propanediol to Au 75.5 and the reaction time 4 hours, the conversion of 1,3-propanediol was 97.5% and the selectivities to methyl 3-hydroxypropionate and dimethyl malonate were 90.1% and 6.1%, respectively. It was found that the catalytic performance decreased slightly when used catalyst was calcined at 200℃ for 2 h to burn the surface poisoning substance and recycled four times. This was mainly caused by the fact that Au particle size grew larger in the process of catalytic reaction. It was found that nano Au elemental catalyst particles with the size of 2.0-4.0 nm supported on CeO2 favors for the 1,3-propanediol oxidative esterification.%采用沉积-沉淀法制备了高活性的Au/CeO2-cube催化剂,并对催化剂进行了电感耦合等离子发射光谱、透射电镜、X射线衍射和X射线光电子能谱表征.将制得的催化剂用于1,3-丙二醇选择性氧化酯化反应,考察了沉淀剂尿素的用量、CeO2-cube载体焙烧温度、催化剂焙烧温度、Au负载量和沉积温度对反应性能的影响,结果表明:尿素和CeO2-cube的质量比为6、沉积温度80℃、CeO2-cube焙烧温度400℃、催化剂焙烧温度200℃制备的1.5%Au/CeO2-cube,具有最优的催化活性.在100℃、O2分压2 MPa、1,3-丙二醇和Au的物质的量比为75.5的条件下反应4 h,1,3-丙二醇的转化率达到97.5%,3-羟基丙酸甲酯和丙二酸二甲酯的选择性分别达到90.1%和6.1%.将用过的催化剂在200℃焙烧2 h烧掉表面的中毒物质后循环使用4次,催化性能略有降低,性能下降主要是由催化反应过程中Au颗粒粒径的长大造成的;催化剂上2.0~4.0 nm左右的具有少量Auδ+的负载纳米Au单质颗粒有助于醇的氧化酯化反应.