Composition of Floccules Formed in Hydrotreated Base Oil

The composition of the floccules formed in hydrotreated base oil was investigated in detail. First, a method of solvent dilution and filtration at low temperature was employed to perform the separation of the floccules in the oil. Second, n-paraffins in the floccules were separated with urea, and carbon number distribution of the floccules was obtained by gas chromatography (GC). Finally, the composition and structure between the floccules and filtrated oils were investigated using gas chromatography-mass spectrometry (GC-MS) and infrared spectroscopy (IR), and their average molecular weights were also measured. The results indicate that the floccules were caused by some hydrocarbon compounds with large average molecular weight, high paraffinic carbon content, and high freezing point. The floccules were composed of a large amount of naphthenes and some paraffins. The naphthenes had longer side branches and lower ring numbers, and the paraffins had longer chains and lower degrees of branching. During slow cooling under static conditions, these hydrocarbon compounds formed a colloidal network, which embodied the oil and dispersed throughout the oil and formed the floccules.