Study On The Preparation And Evaluation Of The NiMoW Hydrodesulfurization Catalysts Supported On The Modified Carrier

In this paper, the precursor solution containing the ZSM-5 secondary structural unit(or zeolite nanocluster)was firstly synthesized in the system without alkali metal. The influences of the preparation methods, crystallizing time, crystallizing temperature and the ratio of Si/Al on properties of zeolite nanoclusters were studied. The results of XRD and IR indicated that the zeolite nanoclusters did exist in the precursor solution but the zeolite crystalline particles didn't exist.The effects of nanoclusters prepared at different conditions and the modify methods on the acidity ofγ-Al2O3 were investigated. The modification methods of room temperature impregnation, ultra-audible sound assistanted dispersion , crystallizing at high temperature, dilution method impregnation, mechanically blending were examinated. The characterization results of XRD, IR, Py-IR and TPD indicated that some Br?nsted acid sites formated on the surface ofγ-Al2O3 where ZSM-5 nanoclustes dispersed, and at the same time the ZSM-5 minicrystal particles didn't form. The acidity of modified support rised remarkably but the changes of pore diameter and BET surface were unconspicuous.The Ni-Mo-W hydrodesulfurization catalysts were prepared with the modifiedγ-Al2O3 as support. Then the performances of HDS were evaluated in high pressure micro-reactor with 4,6-DMDBT as model compound, and the products of reaction were analyzed qualitatively and quantitatively using the GC and MS. Compared to the traditional HDS catalyst supported on theγ-Al2O3, the novel catalyst supported on the carrier modified with zeolite nanocluster presented higher conversion and desulfurization of 4,6-DMDBT. The conversion ratio of 4,6-DMDBT rised by 52.4 percentages,and meanwhile the removal ratio of partly hydrogenation sulfcompounds increased. The results revealed that the catalyst supported on modifiedγ-Al2O3 had higher HYD/DDS ratio, wich attributed to the catalyst's stronger acidity and metal compound's higher stacking number originated from the weaker interaction between metal compound and carrier.