Study On Vapor-liquid Equilibria Of Systems Containing Sulfurs In FCC Gasoline

About80%of gasoline in our country is from the fluid catalytic cracking (FCC)unit, its sulfur content is much higher than in other countries. To meet the sulfurcontent standards, which is more and more strict, gasoline desulfurization becomes anurgent task in our country. The sufficient vapor-liquid equilibrium data are neededboth for the conventional hydrodesulfurization process and the non-traditionalnon-hydrodesulfurization process design. Although some phase equilibrium data forgasoline with sulfur-components have been reported in the literatures, manycompounds are still lack of of the phase equilibrium data. Therefore, it is of greatimportance for the process simulation and designto supple the phase equilibrium databy experiments and appropriate calculated methods.In this study, the VLE data for twelve binary systems containing thiophenes(thiophene and3-methylthiophene) with hydrocarbons (2-methylbutane,2,3-dimethyl-1-butene,2,3-dimethyl-2-butene, n-heptane, toluene and n-dodecane)were measured at atmospheric pressure by using Rose still. These experimental datawere correlated by Wilson model and UNIQUAC model. Besides, they were alsocorrelated by PR equation by the least squares method. The binary parameters of thesethree models were got. The calculated results show that Wilson model is more suitablefor these systems.Due to the diversity of systems containing thiophenes with hydrocarbons and thelimitation of experimental determination, UNIFAC model was used in the work toobtain more equilibrium data for the gasoline with sulfur systems. The experimentalVLE data were fitted to both UNIFAC-Original model and UNIFAC-Dortmund modeland the binary parameters for the pair of UNIFAC groups (C=C-ACS) were obtained.The VLE data of four binary systems containing thiophenes (thiophene and3-methylthiophene) with Olefins (2-methyl-1-butene and2-methyl-2-butene) at101.33KPa were estimated by UNIFAC-Original method and UNIFAC-Dortmundmethod. The estimation data were correlated by Wilson model and the binaryparameters were provided. The results show that UNIFAC-Original model is moresuitable for these systems.Due to the content of the sulfide in the gasline is very little. In this study, VLEdata of dilute solution for four binary systems thiophene+2,3-dimethyl-2-butene,thiophene+n-heptane,3-methylthiophene+2,3-dimethyl-1-butene and 3-methylthiophene+n-heptane were measured at atmospheric pressure by using Rosestill. Comparing with the experimental data within the whole concentration range, itcan be found that the y-x relationship in the dilute sulfide was closer to a quadraticrelationship, it didn’t agree with the Henry’s law, which was a simple linearrelationship.