| 150BS bright oil is an important kind of high viscosity lubricating base oil. Its main used field is to modulate some oils, such as gas engine oil, gear oil, compressor oil and aircraft hydraulic oil et al. The amount of thickening oil can be reduced greatly using this component. However, only a few refineries can produce this kind of product in China because of the special requirements of raw material and its high investment etc.150BS bright oil produced by Karamay Refinery is a new series of health-friendly products. In comparison with traditional solvent-refined base oil, it has many excellent characteristics, such as high viscosity index, low volatility loss, and low aromatic content. However, the hydro-treated base oil became hazy and emerged floccules in low temperature after the high-pressure hydrogenation unit running for a period. This disadvantage seriously impact on the practical application and marketable credit of this product. So, it is necessary to investigate the cause of floccules formed in the hydro-treated base oil and to find an effective means to overcome such a disadvantage.In this paper, the chemical composition causing the hydro-treated base oil hazy and emergence of floccules in low temperature was identified. According to the property of this chemical composition, the floccules were separated from the hydro-treated base oil and its composition and structure were analyzed. Then, the reasons causing the hydro-treated base oil hazy and emergence of floccules in low temperature was illuminated according to the mechanism producing floccules and processing technology of the hydro-treated base oil. Finally, the influences of floccules on the main properties of the hydro-treated base oil were investigated. There are five chapters in this dissertation:Chapter 1: Liquid-solid chromatography was used to separate the hydro-treated base oil into five different fractions according to their polarities, i.e. saturates, mono-aromatics, di-aromatics, poly-aromatics and polar components, meanwhile, the accuracy and effectiveness of separation were demonstrated by refractive index method and ultraviolet spectrum. Furthermore, the influences of five different component on the hydro-treated base oil were investigated and the results showed that the saturates are main component causing the hydro-treated base oil hazy and emergence of floccules at low temperature. Chapter 2: The floccules were firstly separated from the hydro-treated base oil applying the methods of solvent dilution and filtration at low temperature. Then, n-paraffms were extracted from the floccules using urea and carbon number distribution of the floccules was identified by using chromatography (GC). Lastly, the composition and structure of the floccules and filtrated oils were investigated using mass spectrometry (MS), infrared spectroscopy (IR) and SH/T0729-2004 method. The results indicated that carbon number distribution of the floccules is mostly C15～C40, and the carbon number of high content is around C30. In additional, the floccules were some hydrocarbon compounds with large relative molecular mass and high solidifying point. These hydrocarbon compounds were composed of some alkanes with a longer chain and a lower degree of branching and a large amount of naphthenes with a longer side branch and a lower ring numbers.Chapter 3: During slow cooling under static conditions, the n-paraffins in the floccules firstly formed the nuclei of crystals, which had the shape of discs and a single molecule size thickness. This kind of nuclei can resist dispersing effect of solvent molecules to it. When the temperature was further decreased, some alkanes with a longer chain and a lower degree of branching, and a large amount of naphthenes with a longer side branch and a lower ring numbers deposited on surface of the nuclei. Subsequently, the extended and continuous lamellas were formed, making a colloidal network, which embodied the oil itself. Ultimately, they dispersed into the whole oil and formed the floccules. In additional, in hydro pour point depression (RLW) process, the apertures of hydro-catalyst were narrowed, some alkanes with a longer chain and a lower degree of branching and a large amount of naphthenes with a longer side branch and a lower ring numbers couldn't enter into the apertures of catalyst to be cracked when the catalyst was used after period of time. Finally, these hydrocarbon compounds came into oils and form floccules in the hydro-treated oil.Chapter 4: After the floccules was separated from the hydro-treated oil, the low temperature properties of filtrated oil were obviously improved, and with the increase of the content of floccules separated from hydro-treated oil, low temperature properties of filtrated oil was gradually improved, the viscosity became lower, meanwhile, the oxidation stability was increased. However, the other main properties weren't obviously changed. Chapter 4: According to the characteristics of the hydro-treated base oil such as lower content of wax and larger relative molecular mass, RLW catalyst should be improved and some alkanes with a longer chain and a lower degree of branching, and a large amount of naphthenes with a longer side branch and a lower ring numbers can also enter the apertures of catalyst to participate in cracking reaction. In additional, the iso-dewaxing technology can be adopted to resolve this issue that the hydro-treated oil was hazy and emerged floccules at low temperature. |
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