The Use Of Beta-MCM-41 Composite Molecular Sieve As The Support For Ni-Mo Sulfide Catalyst In Hydrodesulfurization

In recent years,the production of clean diesel by hydrotreating and especially by deep hydrodesulfurization?HDS?has attracted increasing attention due to the introduction of rigider legislations and seriouser environmental deterioration.The alteration of catalytic activities due to support may arise as a result of important factors like variation in dispersion and morphology of active component and possible metal support interactions.Combining advantages of zeolites like hydrothemal stablility and strong acid with advantages of mesoporous materials like high specific surface area and turnable pore diameters into a micro-mesoporous composite has attract many attention.In this thesis,a micro-mesoporous composite composing Beta zeolite as core and MCM-41 as shell was synthezed?BM?by hydrothermal method and modified by Na+ ion exchange?NaBM?.Deffenent characterizations and the hydrodesulfurization?HDS?performance of NiMo sulfides supported over NaBM was evaluated with dibenzothiophene?DBT?as the model sulfur-containing molecule.TEM images revealed that zeolite Beta overgrown with an MCM-41 layer and the mesoporous channels were assumed to be oriented outward from the inner Beta core.XRD and N₂ adsorption results indicated that the structure of NaBM remained after ion exchange with Na2C2O4.Compared to modified MCM-41,Beta and their mechanical mixture,NiMo/NaBM showed the highest HDS and hydrogenation activities,which might be attributed to the high specific surface area of the composite and different oxide species dispersion.Comparing to NiMo/Al₂O₃,NiMo/NaBM performed lower DBT conversion but different products selectivities,that CHB showed higher selectivities than BP did.The transforming DBT into BP might be main reason for high DBT conversion over NiMo/Al₂O₃.With temperature increasing,the BP initial selectivity increased and BP hydrogenation also increased over NiMo/NaBM,which could be attributed to high CHB selectivity.Different catalysts performance could be obtain with different ion exchange conditions: defferent anions could cause different structure parameter of composite and Na content and positive ions also could effect catalyst performances.