Effect Of Surface Modification Of Siliceous MCM-41 By Alkali Metal Ion Exchange On The Performance Of Its Supported Ni-W And Co-Mo In Deep Hydrodesulfurization

Mesoporous MCM-41, as one of perfect supports for deep hydrodesulfurization (HDS) catalysts, offers high surface area, mild acidity and relatively high thermal stability as well as an adjustable uniform pore. It was studied that the effect of surface modification of siliceous MCM-41 by alkali metal ion exchange on the Ni-W and Co-Mo in deep HDS, meanwhile, this dissertation was addressed on the research the influence of the quinoline on the catalysts by using dibenzothiophene (DBT) as model compound, and the following results have been obtained.: The siliceous MCM-41 (Si-MCM-41) and pure siliceous (T-MCM-41) were synthesized with sodium silicate hydrate and TEOS respectively. And the siliceous MCM-41 was modified by ion exchange method with alkali metal ion (K+, Na+). The results of XRD and N2 adsorption isotherm indicate that Si-MCM-41 has the physical properties of typical mesoporous zeolite; Surface area, pore volum and pore radius of K-MCM-41 and Na-MCM-41, especially Na-MCM-41 were reduced, but their the structural properties were retained as well as the mesoporous zeolite's. T-MCM-41 has highest surface area, big pore volume and pore radius in the MCM-41, it also does the most well-regulated pore structure. The results of XRF also indicate that K-MCM-41 and Na-MCM-41 were modified by K+ and Na+, they also contain Al respectively. And the results of FT-IR show that there are some B, L acid sites, K-MCM-41and Na-MCM-41 haven't the B, L acid sites, and T-MCM-41 don't have them yet.Ni-W catalysts supported by the different MCM-41 were prepared. It was also studied that the effects of the modified supports and quinoline on the HDS catalysts by using a model compound DBT. It is indicated that the negative effect of the modified supports on the HDS reaction of these catalysts. Hydrogenation path was severely restrained by themodified supports of Ni-W catalysts, whereas, hydrogenolysis path was promoted by this, especially the K-MCM-41. Ni-W/Si-MCM-41 catalyst have highest hydrogenation activity. Ni-W/T-MCM-41 catalyst do the lowest HDS activity because the hydrogenation and hydrogenolysis activity are both lower. When quinoline was existed, the hydrogenation reactivity was restrained under whole reaction temperature. Meanwhile, the HDS and hydrogenolysis reactivity were promoted under the low temperature, while they were both restrained at high temperature. So the effects of the modified supports and quinoline are different. It is confirmed by the results of UV-Vis and TPR that the active sites of hydrogenation is correlated with the octahedral coordinated Ni species, while the hydrogenolysis activity of Ni-W is related with the reducibility of NiO-WO3 species. Meanwhile, it is also confirmed by the results of FT-IR and TPR that some relationships were existed between the hydrogenation reactivity and the acid sites, the reducibility of the active sites. So, it can be included that there was a synergy between the acid support and the active sites, which involve the spillover hydrogen migration, may exist on the surface of catalysts.Co-Mo catalysts supported by the different MCM-41 were prepared. It was also studied that the effects of the modified supports and quinoline on the HDS catalysts by using a model compound DBT. The HDS and hydrogenolysis activities of Co-Mo/T-MCM-41 are highest in these catalysts. The hydrogenolysis path and hydrogenation path of Co-Mo catalysts supported by the modified supports were both restrained respectively. When quinoline was existed, the activities of HDS, hydrogenolysis and hydrogenation over the Co-W catalysts were all restrained under the reaction temperature. The results of N2 adsorption isotherm and FT-IR of different MCM-41, along with TPR and UV-Vis of catalyst also show that MCM-41 have some relationships with disperse and reducibility of active species. The results also show: when quinoline was existed, the properties of K-MCM-41 and Na-MCM-41 supported Ni-W catalysts are better than the other two, however, the performances of different MCM-41 supported Co-Mo catalysts were r...