Application Of Ultrasonic In Residue Hydroprocessing

Hydrotreating technology is one way to use energy more efficiently for the time being, and has gained considerable attention. High conversion rate could be obtained by using physical treatments to improve residue quality. Four kinds of vacuum residue have been used in this paper. The changes in properties and structural parameters of four vacuum residue samples before and after ultrasonic treatment were analyzed. By focusing on the effect of ultrasonic treatment on vacuum residue hydrotreating effect,the optimized conditions of ultrasonic treatment has been investigated. We have calculated the influence of ultrasonic treatment on asphaltene structure and established some asphaltene models under different conditions by molecular simulation.Ultrasonic treatment plays an important role in controlling the physical properties of vacuum residue, such as the increase in carbon residue value, decrease in average molecular weight and viscosity, which can barely influence the density of vacuum residue. Meanwhile the constitution of residue can be varied including the decrease in the content of saturates, aromatics and asphaltenes, while the increase in the content of resins can lead to an increase in the total content of asphaltenes and resins. The changes of asphaltene structure parameters can reflect the effect of ultrasonic treatment on residue structure. Ultrasonic treatment has changed the structural parameters of residue such as decrease in C Total, CA, RT, RA and RN, and increase of KH. Among the four kinds of residue samples, there is a common trend that the more the content of asphaltenes in feedstock is, the more increase in decrease of average molecular weight and viscosity, the more increase in carbon residue value, the more the increase in the content of resins, the more significant decrease in the aromatic content and the less decrease in the saturates content after ultrasonic treatment of residue would be. Ultrasonic treatment has improved the CSP of vacuum residue by changing the content and distribution of SARA.The siphonage model of residue hydrotreating has successfully explained the improvement of residue hydrotreating with ultrasonic treatment. We took the process of hydrotreating after ultrasonic treatment of vacuum residue, and found that the yield coefficient of coke and residue of above 500 degrees had been decreased. Gas, gasoline, diesel distillate fractions and VGO had been increased. Ultrasonic treatment has a significant effect on the improvement on the removing rate of heteroatom and metal, especially on sculpture atom, nickel atom and vanadium atom. Structure changes of residue caused by ultrasonic treatment has changed the SARA fractions of hydrotreated vacuum residue. The content of saturates and asphaltenes are increased, the content of resins and aromatics are decreased, the CSP of vacuum residue is worse than before.The effect of residue hydrotreating can be influenced by the changes of ultrasonic treatment conditions. We set special orthogonal experiments to analyze the optimized conditions of ultrasonic treatment with different indexes, including viscosity of vacuum residue, light oil yield, gas yield and coke yield. Light oil is the most needed products. Under ultrasonic treatment conditions of 70 min, 750 W and 70℃, the maximum light oil yield was achieved. Taking everything into consideration, the optimized conditions of ultrasonic treatment is that ultrasonic time 70 min, ultrasonic power750 W, ultrasonic temperature 70℃. At the meanwhile, the significant order of effect is ultrasonic power > ultrasonic time > ultrasonic temperatureThe primary cause of catalyst coking in residue hydrotreating is the existence of asphaltene. Ultrasonic treatment reduced the molecular weight of asphaltene, decreased structure parameters of asphaltene, such as RT 、RA、RN、CA、σ and Dy. Ultrasonic treatment also changed the distribution of hydrogen type of asphaltene. Although the changes of asphaltene structure has minified the complexity and the unit of asphaltene molecular, with the incensement of association number the overall complexity of hydrotreated vacuum residue is more complicated than before. We can confirm by IR that the existence form of oxygen atom in Sheng-Li vacuum residue asphaltene is hydroxyl, while in Saudi light vacuum residue asphaltene is carbonyl. Simulate the unit molecular structure of two kinds of asphaltene with the software C hemBioDraw Ultra version 2012. The simulated result is in line with reckoning. The simulation results is reasonable and reliable. The model can vividly reflect the influ ence of ultrasonic treatment on the change of the chemical structure of asphaltene unit pre-and-post hydrotreating. And it’s useful to explain the reasons of the effect of ultrasonic treatment on asphaltene unit at the molecular level.