Study On Synthesis And Modification Of KIT-6 Mesoporous Materials And The Corresponding Hydrorefining Performances

With the trend of exploiting crude oil with heavier quality,the distillate processing shows a trend of higher sulfur contents,which including organic macromolecular sulfides that could condensing and coking easily on the active sites of reactions,thus accelerate the activity and selectivity deactivated,the sulfides which not been removed would burning into sulfur oxides and cause pollutions even disasters such as acid rains,so the processing capacity of hydrodesulfurization catalysts still need to be improved,and this thesis is aimed at preparing high efficiency catalysts for desulfurization reactions.In this thesis,KIT-6 mesoporous materials are used as the carriers to analysis the main factors which affect the order and crystallinity of the pore structures including adjusting the aging temperatures,crystallization times and crystallization temperatures.The results shows that the aging temperatures plays a decisive role,which is attributed to its influence on the solubility of the templates,the micelles arrangement order and the silicon source adsorption-polycondensation self-assembly process,and the optimal temperature is 35℃.When the crystallization temperature is higher than 100℃,the crystallization times and temperatures have less influence on the order degree and crystallinity,but the pore diameters and specific surface areas are smaller,which is attributed to the influence on the dissolution-recrystallization times and speeds of silicon source.Secondly,the ordered mesoporous KIT-6 materials synthesizes at different crystallization temperatures are used as the carriers,and the catalysts for hydrodesulfurization of dibenzothiophene are prepared by modified with aluminum and loaded active metals.The results shows that the pore sizes and specific surface areas of the catalysts decreases slightly,but the mesoporous structure of the carriers are well maintained,the acid types and distributions are similar.The reaction results shows that the desulfurization rate of Cat-Al-K6(120℃)is the highest,which is attributed to its larger specific surface area,which is more conducive to the dispersion of metal active phases,and form more "Ni-Mo-S-II" type active phases with short length and high stacking layers.Third,the results shows that under the same reaction conditions,the desulfurization rates of KIT-6 catalysts are higher than that of SBA-15 catalysts with the same pores,which is attributed to the fact that KIT-6 material with three-dimensional space network channels is more conducive to the diffusion of reactants than SBA-15 material with straight channels.Forth,a compare research between the zirconium modified and aluminum modified KIT-6 catalysts are studied,and it is found that the pore structure,active phase distribution and desulfurization rate of the zirconium modified catalyst are better than that of the aluminum modified catalyst,which is attributed to the better dispersion of the active phase and the higher acidity.Finally,iron,copper and zinc as additives are introducing into the zirconium modified KIT-6 catalysts respectively,and characterization results shows that the catalysts’ structures which load different additive metals are similar to the original catalyst,specific surface areas and pore sizes are reduced,but the carrier channel structures maintain well,the dispersion degree of active metals,degree of sulfided and the states of sulfided active phases such as stacking numbers are different,Cu modified is similar to the original catalyst,Fe modified is the worst,Zn modified is the best which improve the catalytic activity to a certain extent,due to the influence of different metal additives for the active phase.