载体性质对Pd催化剂加氢脱硫性能的影响

Effect of support properties on the performance of supported Pd catalysts in hydrodesulfurization

以Si O2、全硅MCM-41(Si-MCM-41)、通过机械混合Si-MCM-41与ZSM-5得到的Z-MCM-41-M以及通过在ZSM-5外部包覆MCM-41制备得到的Z-MCM-41四种材料为载体,制备了四种负载型Pd催化剂。采用XRD、HRTEM、N2吸附-脱附、NH3-TPD手段对Pd催化剂进行了表征;以二苯并噻吩(DBT)为模型化合物,在固定床反应器上对四种催化剂的加氢脱硫(HDS)活性、加氢路径选择性和加氢裂化活性进行了考察,研究了不同类型载体对Pd催化剂加氢脱硫性能的影响。结果表明,载体的性质会显著影响负载型Pd催化剂的加氢脱硫性能。载体的比表面积对负载型Pd催化剂加氢脱硫活性影响不大,但是HYD路径的选择性与载体的孔道结构有关;具有介孔孔道结构有利于加氢路径选择性的提高。酸性载体负载的Pd催化剂表现出较好加氢脱硫活性和加氢选择性,这与氢溢流有关。介孔材料的孔道结构与微孔沸石的酸性有机结合,所得到的Z-M CM-41复合材料是是潜在的贵金属Pd加氢脱硫催化剂优良载体,可有效提升其加氢脱硫活性。

SiO2, siliceous MCM-41（ Si-MCM-41）, physical mixture of Si-MCM-41 and ZSM-5（ Z-MCM-41-M）,and Z-MCM-41 composite obtained by coating MCM-41 on ZSM-5 zeolite particles were prepared and characterized by XRD,HRTEM,N2 adsorption-desorption and NH3-TPD. The performances of the supported Pd catalysts in hydrodesulfurization（ HDS） were evaluated in a fixed-bed reactor with dibenzothiophene（ DBT） as the model sulfur-containing molecule; the effect of support properties on the performance of supported Pd catalysts in HDS was then investigated. The results indicated that the performance in HDS of supported Pd catalysts are significantly influenced by the support properties. Although the specific surface has a minor influence on the HDS activity of the supported Pd catalysts,the hydrogenation（ HYD） selectivity is probably related to the pore structure of support; the mesoporous structure is beneficial to the improvement of HYD selectivity. The acid supports can give the Pd catalysts higher HDS activity,owing to the hydrogen spillover effect. The Z-MCM-41 composite is an excellent support for noble metal Pd catalyst in HDS,which can be ascribed to the synergy of the mesoporous structure of MCM-41 and acidic properties of ZSM-5.