Ag2O/SiO2纳米复合催化剂制备及其催化性能研究

由喷雾燃烧法制备含Ag2O质量分数为8%和12%的Ag2O/SiO2纳米复合催化剂,采用SEM、XRD和FT-IR技术对催化剂及其前驱体进行表征,考察样品焙烧、活化中形貌和微观结构的变化.表征结果显示了处理过程中样品粒径和活性中心等变化情况,且两个催化剂变化情形一致.以分子氧为氧化剂,采用气相环己烷一步环氧化生成环氧环己烷反应,对催化剂进行活性测试,考察Ag2O负载量、实验温度、O2和原料气流速对催化剂性能的影响,并将两个催化剂活性测试结果进行比较.结果表明,8%Ag2O/SiO2纳米复合催化剂催化性能优于12%Ag2O/SiO2纳米复合催化剂;一定实验条件下,用8%Ag2O/SiO2纳米复合催化剂进行催化,环己烷转化率低于9.2%时,环氧环己烷选择性最高可达95.2%.

Preparation and Catalytic Properties of Silica Supported Silver Oxide Complex Nanocatalyst

Silica supported silver oxide complex nanocatalysts were prepared by Atomizing-combustion method with different Ag/Si ratios.The catalyst precursor and complex nanocatalysts were characterized by Scanning Electron Microscopy(SEM),X-ray Diffraction(XRD)and Fourier Transform Infrared(FT-IR).The characterization results indicate that the diameter of Ag2O become smaller and the active centers of catalyst are changed after the roasting and activation,the change situation of 8% Ag2O/SiO2 complex nanocatalyst is similar to 12% Ag2O/SiO2 complex nanocatalyst.Using molecular oxygen as oxidant,the catalysis activity on oxydehydrogenation of cyclohexane was tested.It succeeded in gainning the epoxycyclohexane via one-step chemical combination of cyclohexane.The effects of Ag2O loading and reaction conditions including reaction temperature,oxygen velocity and material gas velocity on catalyst performance were also investigated.After comparing the activity tested results of the two complex nanocatalysts,it is found that the oxydehydrogenation performance of 8% Ag2O/SiO2 complex nanocatalyst is exceeded to 12% Ag2O/SiO2 complex nanocatalyst for the target production.Under certain reaction conditions,for the catalysis of 8% Ag2O/SiO2 complex nanocatalyst,the conversion of cyclohexane is 9.2%,the selectivity of epoxycyclohexane can reach 95.2%.