成型条件对CuO-Ce0.5Mn0.5O2成型载体性能的影响

Effect of Forming conditions on Properties of Formed CuO-Ce0.5Mn0.5O2 Support

摘要:

以CuO-Ce0.5Mn0.5O2粉体为原料，采用挤条成型法制备了相应的成型载体，考察了成型过程中不同胶溶剂类型及其含量、焙烧时间及焙烧温度对该成型载体性能的影响，并通过XRD、BET、SEM等手段对载体结构进行了表征，同时对相应的载钯催化剂进行了活性评价。结果表明，胶溶剂的添加可以不同程度的提高载体的抗压强度，改善载体的孔径分布，其中柠檬酸作为胶溶剂载体的抗压强度最大；使用硝酸作为胶溶剂时载体孔径分布向中孔方向集中；不同胶溶剂对载体的比表面积影响不大。固定硝酸质量分数3%，柠檬酸/粘胶剂=4：6，在600 ℃焙烧5h可得到侧压强度98.65 N/cm2、比表面积为36.938 m3/g、孔容0.177 cm3/g的载体，对应载Pd(载体质量的0.5%)催化剂的催化活性较高，在反应总压5 MPa，O2分压6%、反应时间4 h、反应温度65 ℃条件下，DPC收率9.91%。

Abstract:

Formed CuO-Ce0.5Mn0.5O2 supports were prepared by extrusion process using CuO-Ce0.5Mn0.5O2 powder as raw material．The influence of the kinds of peptizers，the calcination temperature，calcination time on the formed supports were investigated,and these supports were characterized by crushing strength test，BET and SEM methods.The results show:all the peptizers can improve the crushing strength of the formed CuO-Ce0.5Mn0.5O2 supports;however, peptizers have little effect on the surface area of the supports. The added citric acid can remarkably increase the crushing strength of the formed CuO-Ce0.5Mn0.5O2 supports.Under the preparation conditions of nitric acid mass fraction of 3%,citric acid /binder mass ratio of 4:6,calcination temperature of 600 ℃ and calcination time of 5h,the crushing strength，surface area and pore volume of the formed CuO-Ce0.5Mn0.5O2 supports can reach 98.65 N/cm,36.938 rn3/g and 0.177 cm3/g,respectively. The corresponding catalyst supported by Pd for direct synthesis of diphenyl carbonate(DPC) had better catalytic activity，and the yield of DPC could achieve 9.91% under Pd loading content (mass fraction) 0.5%, p=5 MPa,p(CO)∶p(O2)= 94∶6, reaction time 4h, reaction temperature 65 ℃