渣油悬浮床加氢水溶性催化剂预硫化研究Ⅰ硫化条件对硫化催化剂物种及分散度的影响

Study on the sulfurization of water-soluble catalysts for slurry-bed hydroprocessing of residue Ⅰ Effect of sulfurization conditions on the species and dispersity of the sulfurized catalysts

通过对在不同阶段中和不同条件下所获得的硫化产物的XRD和TEM分析发现,镍盐在临氢加热前的硫化产物是结晶程度较低的NiS2,临氢加热后变为结晶程度较高的NiS和Ni7S6,它们的分散状态没有明显地改变;钼酸盐在临氢加热前的硫化产物为部分硫代钼酸盐,临氢加热后变为微晶态MoS2,其分散状态明显提高,临氢加热是两种催化剂前体的硫化过程中的重要阶段。助硫化剂NH4Cl的加入对镍盐的硫化产物的各种物理和化学存在状态都没有产生显著的影响,它是钼酸盐硫化过程中不可缺少的助剂,当NH4Cl加入量增大时,XRD分析未发现其本体化学组成有变化,其结晶程度有所降低,晶粒度由6.6nm降至3.6nm。分散介质的种类对催化剂的分散效果产生了显著的影响。以钼酸盐为例,密度和黏度更大的克拉玛依常压渣油更有利于硫化产物的分散,与采用润滑油基础油为分散介质时相比,其晶粒度由3.0nm降低至2.0nm,且外观形态由粒径较小(50nm～100nm)的较致密的颗粒变为粒径较大(100nm～500nm)的呈现蓬松球壳结构的絮状团块。

The catalyst precursors for slurry-bed hydroprocessing of residue need to be sulfurized for higher catalytic activity. In this study, two of the most important precursors described above, ammonium molybdate and nickel nitrate, are sulfurized. Sodium sulfide is employed as the sulfrization reagent and ammonium chloride is employed as the auxiliary sulfurization reagent. The sulfruization is carried out in three stages: Stage 1. Precursors are sulfurized directly in water-solution; Stage 2. Precursors are sulfurized in water-oil emulsification; Stage 3. The sulfurized catalysts, which have been dispersed in the media, are heated in the presence of hydrogen. XRD is employed to recognize the crystalline components in the sulfurization products, and the crystal-grain size is calculated using Scherrer's equation. TEM is employed to observe the form and size of the particles of the products. It is observed that nickel nitrate is transferred into micro-crystallized NiS_2 firstly, and crystallized to NiS and Ni_7S_6 after heated under hydrogen, with little change in particle sizes and crystal-grain sizes; while molybdate is transferred into crystallized thioxomolybdate before the heating, and micro-crystallized MoS_2 finally, with great increase in their particle sizes and great decrease in their crystal-grain sizes, thus it can be concluded that the heating under hydrogen is an important stage in the sulfurization of both precursors. According to the result of XRD, the addition use of ammonium chloride in sulfurization does not affect the chemical composition, the particle size or the crystalline-grain size of the sulfurized product of nickel salt. But the molybdate cannot be sulfurized at all without the existence of NH_4Cl. When the amount of NH_4Cl added rises up, it is shown by XRD that its chemical composition does not vary much, but the crystalline size is slightly decreased, and the particle of the product turns to be larger and looser. The viscosity and density of the dispersion media affect the particle size and the crystalline-grain size of the sulfurization products remarkably. When the Kelamayi vacuum residue, which has a higher viscosity and density, is used as the dispersion media, the crystalline-grain size is smaller than that of the lubricant used as the dispersion media and the shape of the particles turns from compact to loose.