Study Of Ni-Mo-W Supported Hydrodesulfurization Catalysts Via Meso-microporous Composite Zeolites As Carrier

In this paper, the meso-microporous composite zeolite(Mβ) withβsecondary structural building units was synthesized by the nanocluster assembly of microporous zeolite through the two steps method. The mesostructures with the high acidity and hydrothermal stability was obtained, after investigating the influence of crystallizing time, crystallizing temperature and the ratio of Si/Al on the performance of the mesostructures, and the strength of acidity was similar to that of Hβzeolite. The results of XRD, BET, NH3-TPD, IR and Py-IR indicate that theβsecondary structural building units are successfully incorporated to the the pore wall of the mesoporous structures, which contributes a lot to the strong acidity and extraordinary hydrothermal stability of the synthesized mesoporous structures.With regard to the complexity and high cost (mainly because the use of templates) of the hydrothermal method above, the secondary structural building units (or zeolite nanoclusters) were first used to coat onto theγ-Al₂O₃ (marked SBU), and the influence of the methods to modify, the quantity of the nanoclusters and the ratio of Si/Al were investigated. The results of XRD, BET, NH₃-TPD, IR, Py-IR and HRTEM show thatβzeolite nanoclusters can be uniformly dispersed on the surface ofγ-Al₂O₃ and the acidity ofγ-Al₂O₃ is greatly improved, while the surface, pore diameter and pore volume of modifiedγ-Al₂O₃ change little.Two kinds of hydrodesulfurization (HDS) catalysts were prepared by depositing Ni-Mo-W-P on Mβand modifiedγ-Al₂O₃ respectively. Then their performances of HDS were evaluated through high pressure micro-reactor with 4,6-DMDBT as model compound. Comparing to catalyst supported byγ-Al₂O₃, the conversion and desulfurization of 4,6-DMDBT under catalyst supported by Mβimproved a lot, becauce the incorporation of Mβwith strong acidity, large pore volume and pore diameter reduces the steric hindrance of sulfocompound and increase the proportion of direct hydrogenalysis route. The conversion and desulfurization of 4,6-DMDBT under catalyst supported by modifiedγ-Al₂O₃ also improved remarkably, because the high capacity channel ofγ-Al₂O₃ and high acidity of zeolite nanoclusters decrease the steric hindrance of 4,6-DMDBT and increase the activity of HDS to sulfocompound with partly hydrogenation. The most important thing was that the ratio of desulfuration and conversion was raised remarkbly.The desulfurization mechanism of zeolite nanoclusters modifiedγ-Al₂O₃ was primarily studied. And the results proved that the interaction between metal and support was diminished and the dump of active component was increased greatly, which led to its high activity of hydrogenization.