过渡金属改性的Pd/TS-1催化氢、氧直接合成H_2O_2的性能

利用等体积浸渍法制备了M-Pd/TS-1(M=Ce,La,Pt,Fe,Co,Ni,Cr,Mn,Zn,Cd,Cu)系列催化剂,并将制得的催化剂用于常压下氢、氧直接合成过氧化氢的反应。考察了M的类型及负载量对M-Pd/TS-1催化剂催化性能的影响。结果表明,M选Ce时,催化剂的性能最好。Ce的最佳掺入量,n_(Ce)/(n_(Ce)+n_(Pd))=0.5%。对Ce改性与未改性的催化剂进行了TEM及静态化学吸附分析,结果表明,掺入Ce可使Pd在TS-1分子筛表面的粒度及分散度得到改善。考察了n_(O_2)/n_(H_2)比,气体流量,反应时间等反应条件对H_2转化率、H_2O_2选择性及收率的影响。在相对优化的工艺条件下,即n_(O_2)/n_(H_2)=3,气体流量为25 mL·min~(-1),反应时间为3 h时,H_2O_2,的收率可达到25.7%,TOF值为18.7 mol·mol~(-1)·h~(-1),此时溶液中H_2O_2的质量百分数为0.8%。

Performance of Transition Metal Modified Pd/TS-1 in Direct Synthesis of Hydrogen Peroxide from H2 and O2

M-Pd/TS-1(M=Ce, La, Pt, Fe, Co, Ni, Cr, Mn, Zn, Cd, Cu) catalysts were prepared by incipient wetness impregnation and their performance was evaluated for the direct synthesis of hydrogen peroxide from hydrogen and oxygen at atmospheric pressure. The effect of transition metal and the doping amount were studied on the activity of M-Pd/TS-1 catalyst. The catalysis evaluation results show that M-Pd/TS-1 catalyst doped with cerium significantly enhances the catalytic activity and the optimal molar ratio of Ce/(Ce+Pd) is 0.5%. The Ce-Pd/TS-1 and Pd/TS-1 catalysts were characterized by transmission electron microscopy(TEM) and chemical adsorption. The results indicate that the catalyst doped with cerium can improve the dispersivity of Pd on the surface of the TS-1 support and decrease the Pd particle size effectively. The influence of factors on H₂ conversion and H₂O₂ yield were examined such as n_O2/n_H2 molar ratio, gas flow rate and reaction time. The yield of H₂O₂, the mass percentage of H₂O₂ and turn-over frequency(TOF) are up to 25.7%, 0.8% and 18.7 mol·mol^-1·h^-1, respectively, after 3 h reaction at n_O2/n_H2 of 3 with 25 mL·min^-1 gas flow rate.