摘要
研究了利用乙二醇共浸渍方法制备高分散的二氧化硅负载钴催化剂,该催化剂有效地提高了乳酸乙酯的气相加氢反应活性。系统地考察了钴金属负载量、乙二醇与硝酸钴摩尔比、醇种类和焙烧温度等制备参数对四氧化三钴纳米粒子物性的影响。乙二醇与硝酸钴摩尔比和醇种类对二氧化硅负载的四氧化三钴纳米粒子大小有显著影响。与常规的浸渍方法相比较,共浸渍过程中的乙二醇增强了二价钴粒子和载体二氧化硅之间的相互作用力,从而引起金属钴分散度的提高以及四氧化三钴纳米粒子粒径从16 nm降到5 nm以下;金属钴的高分散与无定型硅酸钴的形成密切相关;同时显著地提高了乳酸乙酯的加氢活性,在反应条件下(2.5MPa、160°C和10%(w,质量分数)Co/SiO_2)乳酸乙酯的转化率从69.5%提高到98.6%,1,2-丙二醇的选择性达到98.0%。利用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、N_2吸脱附实验、H_2程序升温还原(H_2-TPR)等表征手段对共浸渍制备的Co/SiO_2催化剂结构和形貌进行了表征分析。
Highly dispersed Co catalysts supported on SiO_2 were prepared in the presence of ethylene glycol（EG） by co-impregnation and tested in the vapor-phase hydrogenolysis of ethyl lactate to 1,2-propanediol.The synthesis parameters of Co metal loading,ratio of EG to cobalt nitrate,type of alcohol and calcination temperature,which influenced the physical properties of the Co_3O_4 nanoparticles,were investigated through the use of X-ray diffraction（XRD）.It revealed that the ratio of EG to cobalt nitrate and the type of alcohol significantly affected the particle size of Co_3O_4 supported on SiO_2.During co-impregnation with EG,the interaction between Co^（2＋） and the SiO_2 support was strongly enhanced,resulting in the high dispersion of cobalt species and the decrease of Co3O4 particle size from 16 nm to below 5 nm;the significantly enhanced cobalt dispersion was associated with the formation of amorphous cobalt silicate.Meanwhile the conversion of ethyl lactate was greatly improved to 98.6% from 69.5%,with 98.0% selectivity of 1,2-propanediol over 10%（w,mass fraction）Co/SiO_2 catalysts under the given reaction conditions（2.5 MPa and 160 °C）.The obtained catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,N_2 adsorption-desorption measurements,and H_2 temperature-programmed reduction（H_2-TPR） methods.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2016年第6期1511-1518,共8页
Acta Physico-Chimica Sinica
基金
supported by the National High-Tech Research and Development Program of China(863)(2012AA101806)
National Natural Science Foundation of China(21306195,51276183)~~
