Study On The Colloidal Properties Of Residue Hydroprocessing System

The decline in the colloidal stability of residue would cause asphaltene to aggregate and ultimately transform into coke during thermal reaction. Asphaltene deposited on the catalyst and transformed int coke, making catalyst deactived rapidly, during hydroprocessing of heavy oils. So asphaltenes would limit the efficiency of conversion and run time of unit greatly. Therefore, the hydroprocessing performance of residue and the relationship between the colloidal stability variation and coking characteristics were investigated in this thesis.Effect of FCC slurry oil and HVGO on the colloidal stability of residue was studied by mass fraction conductivity method. It was shown that the addition of two fractions exhibited negative effect on the colloidal stability of residue. The disparity in polarity between heavy fraction and residue was the main reason for altering the colloidal stability of residue.Through the investigation on the hydroprocessing performance of different residue, it could be seen that asphaltenes with small size and high sulfur content were easy to convert, and the conversion of corresponding residue was high. The product distribution and colloidal stability were invarious with reaction condition. As the reaction temperature increased, the conversion of residue increased or the colloidal stability of system decreased, and the coke yield increased. At reaction temperature of 420℃, the colloidal stability of residue system was destroyed totally, the sludge formation was found and the coke yield increased remarkablely. As the initial hydrogen pressure increased, the conversion of residue reduced and the colloidal stabililty increased, and the coke yield decreased. As reaction time increase, the conversion of residue increased and the colloidal stability decreased, and the coke yield increased. The change of the colloidal stability was deterimined by the company action of SARA composition and the properties of them.The reaction performance of asphaltenes was influenced by heteroatom content and types of them. The sulfur-carbon bond was weaker than the carbon-carbon bond, so the sulfur-carbon bond was easy to rupture, and the sulfur content in asphaltene decreased as hydroprocessing processed. Nitrogen was mainly present in the aromatic rings located inside the asphaltene molecule, and was difficult to remove. So the nitrogen in asphaltene increased. X-ray photoelectron spectroscopy(XPS) and X-ray absorption near-edge structure spectrum(XANES) were carried out to investigate the type of heteroatom in asphaltene. After hydroprocessing, basic nitrogen relative content increased, carbonoxylate oxygen relative content increased, and thiophene sulfur and sulfoxide relative content decreased. The decreased contene of sulfoxide was consistent with the downtrend of polarity of asphaltene.The rheology and diffused efficiency of residue were influenced by morphology of colloidal particle of asphaltene. The colloidal particle size of asphaltene was characterized by small angle X-ray scattering technology(SAXS). The size of colloidal particle in residue was between 6-9nm. When the SARA compostion was uncomfatible and the solvated power of maltene decreased, asphalene aggregated together and the size increased. After hydroprocessing, the size of asphaltenes particles decreased.At high temperature and pressure, the residue, mixed system and the liquid product after hydroprocessing were shown to be Newton rheology. The viscosity and temperature character fitted to exponential law. Pressure had little impact on the viscosity.