成型条件对CuO-Ce0.5Mn0.5O2成型载体性能的影响

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及其用量、焙烧时间及焙烧温度对该成型载体性能的影响,并对成型载体进行了抗压强度测试,且通过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地提高载体的抗压强度,改善载体的孔径分布,其中,柠檬酸作为胶溶剂时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%,m(柠檬酸)∶m(胶粘剂)=4∶6,在600℃焙烧5 h可得到抗压强度98.65 N/cm2、比表面积为36.938 m2/g、孔容0.177 cm3/g的载体,对应载Pd(占载体质量的0.5%)催化剂的催化活性较高,在反应总压5 MPa,p(CO)∶p(O2)=94∶6、反应时间4 h、反应温度65℃的条件下,DPC收率9.91%。

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

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 and their content,calcination temperature,and calcination time on the properties of the formed supports was investigated.These supports were subjected to a crushing strength test,and were characterized by method of BET and SEM.The results show that all the peptizers can improve the crushing strength of the formed CuO-Ce0.5Mn0.5O2 supports;however,those 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 5 h,the crushing strength,surface area and pore volume of the formed CuO-Ce0.5Mn0.5O2 supports can reach 98.65 N/cm2,36.938 m2/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 reach 9.91% under conditions of Pd loading content(mass fraction) 0.5%,p=5 MPa,p(CO)∶ p(O2)=94∶ 6,reaction time 4 h,reaction temperature 65 ℃.