钴分子筛催化剂的制备及其分子筛载体对环己烷氧化选择性的影响

Synthesis of Cobalt Molecular Sieve Catalyst and Influence of the Support on the Selective Oxidation of Cyclohexane

为了考察催化剂载体的孔道结构和择形性能对环己烷部分氧化反应的影响,采用直接水热法制备出了Co/S-1,Co/TS-1以及Co/MCM-41分子筛催化剂.XRD,FT-IR和SEM结果表明合成的样品具有较高的结晶度,晶粒大小均匀,其活性组分钴进入了分子筛骨架.采用氧气为氧化剂,考察了合成的钴催化剂样品对环己烷部分氧化的催化性能,并与CoAPO-5、Co/A l2O3、均相Co(OAc)2.4H2O催化剂以及无催化氧化的结果进行了比较.实验结果表明:分子筛载体能利用其孔道结构和择形性能,降低环己醇(酮)选择性对环己烷转化率的依赖性,且反应的选择性随分子筛载体孔径的增加而下降.孔道较小的Co/TS-1和Co/S-1做催化剂时,过氧化物含量低,环己烷转化率可达5%以上,同时反应总选择性为95%左右.

In order to investigate the influence of the pore structure and shape-selective performance of catalyst support on the selective oxidation of cyclohexane, Co incorporating molecular sieve Co/S-1, Co/TS-1 and Co/MCM-41 were hydrothermally synthesized by one-pot synthesis method. The prepared samples were characterized by XRD, TEM and IR. The results showed that Co had incorporated into the matrix of all samples with good crystallinity and regular particle morphologies. The catalytic performance of the samples for the cyclohexane liquid-phase oxidation into cyclohexanone and cyclohexanol by oxygen was investigated in the absence of solvents. The catalytic activities were also compared with CoAPO-5, Co/Al2O3 as well as Co（OAc）2·4H2O which used as homogeneous catalyst. Experiment results suggested that the use of molecular sieve support improved the cyclohexane conversion as well as the selectivity of cyclohexanol and cyclohexanone, accordingly reduced the dependence of the cyclohexanone and cyclohexanol selectivity on the cyclohexane conversion. The selectivity to cyclohexanone and cyclohexanol was inclined with the increase of the pore diameter of the molecular sieve support. Co/S-1 and Co/TS-1 with the smaller pores showed superior selectivity to Co/MCM-41, CoAPO-5, Co/Al2O3 as well as Co（OAc）2·4H2O 96.7% selectivity to cyclohexanol and cyclohexanone at 5.2% conversion of cyclohexane was obtained over Co/S-1 at 140℃ for 3h.