助剂Fe和反应修饰剂修饰的Ru催化剂上苯选择加氢制环己烯

Selective Hydrogenation of Benzene to Cyclohexene over the Ru Catalyst Modified by the Promoter Fe and the Reaction Modifiers

共沉淀法制备了Ru-Fe(x)催化剂,并利用X射线衍射(XRD)、X射线荧光光谱(XRF)、N2物理吸附和透射电镜等手段对催化剂进行了表征.结果表明,Ru-Fe(x)催化剂中助剂Fe以Fe3O4形式存在.单独Fe3O4并不能提高Ru催化剂的环己烯选择性.但在加氢过程中Fe3O4可与反应修饰剂ZnSO4反应生成(Zn(OH)2)3(ZnSO4)(H2O)x(x=1 or 3).化学吸附的(Zn(OH)2)3(ZnSO4)(H2O)x(x=1 or 3)在提高Ru催化剂环己烯选择性中起着关键作用.此外,Ru-Fe(x)催化剂的性能还与浆液中的Zn2+浓度和pH值有关.在0.61 mol/L ZnSO4溶液中Ru-Fe(0.47)催化剂不但给出了56.7%的环己烯收率,而且具有良好的稳定性和重复使用性能.化学吸附在Ru表面的Fe2+同样能提高Ru催化剂的环己烯选择性.在0.29 mol/L和0.61 mol/L FeSO4溶液中Ru-Fe(0.47)催化剂上化学吸附Fe2+量近似,性能近似.因为Fe2+和Zn2+性质的差异,在0.29 mol/L和0.61 mol/L FeSO4溶液中Ru-Fe(0.47)催化剂的环己烯选择性分别低于在同浓度的ZnSO4溶液中的.

The Ru-Fe （x） catalysts were prepared by a co-precipitation method. The catalysts were characterized by X-ray diffraction （XRD）, X-fluorescence （XRF）, N2 physisorption and transimission electron microscopy （TEM）. The results showed that the promoter Fe existed as Fe304 in the catalysts. The Fe304 alone could not im- prove the selectivity to cyclohexene of Ru catalyst. However, the Fe3 O4 on the surface could react with the reaction modifier ZnSO4 to form the （Zn（OH）2）3（ZnSO4） （HzO）x（X= 1 or 3） salt. The chemisorbed （Zn（OH）2）3 （ZnSQ） （H2 O）x（X = 1 or 3 ） salt played a key role in improving the selectivity to cyclohexene. Besides, the per- formance of the Ru-Fe （0.47） catalyst was closely related to the concentration of Zn2~ and the pH values of the slur- ry. The Ru-Fe（0.47） catalyst not only gave a cyclohexene yield of 56.7% in the presence of 0.61 mol/L ZnSO4 , but has a good stability and an excellent reusability. The reaction modifier FeSO4 also could enhance the selectivity to cyclohexene of the Ru-Fe（0.47） catalyst since the chemisorbed Fez＋ could not be reduce to the metallic Fe on Ru surface. The Ru-Fe（0.47 ） catalyst exhibited the similar performance in 0.29 mol/L and 0.61 mot/L of FeSO4 solutions due to the similar amounts of the chemisorbed Fe〉. The Ru-Fe （0.47） catalyst showed the lower selectiv- ity to cyclohexene in 0.29 moL/L and 0.61 mol/L of MnSO4 solutions than that in the same concentrations of ZnSQ for the different natures of Fe2＋ and Zn2＋.