(89a) Phase Equilibria of Organic Sulfur Compounds for the Development of Sulfur Removal Processes

Environmental concerns have led many countries worldwide to apply stricter regulations on sulfur levels in liquid fuels. These regulations place many challenges for the refining industries. Separation process design to accomplish the removal of sulfur compounds requires knowledge of vapor-liquid equilibria (VLE) of sulfur compounds with hydrocarbons, particularly their activity coefficients at infinite dilution. However, the investigations concerning the systems containing sulfur compounds are scarce. Therefore, more measurements are needed to develop the estimation methods and the thermodynamics models in the dilute systems.

The VLE of sulfur compounds and hydrocarbons published in the open literature have been reviewed and updated with our measurements. We have determined over 100 VLE data sets of systems containing sulfur compounds found in petroleum refinery streams (mercaptans, sulfides, disulfides, thiophenes, and tetrahydrothiophene) in different hydrocarbons (alkanes, alkenes, cyclic, aromatic, and oxygenated components) with a variety of apparatuses (recirculation still, comparative ebulliometer, dilutor, and static total pressure). Measurements for determining phase equilibria of organic sulfur compounds will be continued and more data will be published in the near future. The challenges of the VLE measurements for systems containing sulfur compounds are discussed. The simulation of the behavior of diethyl sulfide in hydrocarbon distillation is presented as a case study. The case study is based on the experimental results from laboratory scale 15 stage Oldershaw type column of Ikari A, Hatate Y and Maruyama A, (1985), Chem. Eng. Comm., vol 34, p. 241-251. The parameters of the Wilson activity coefficient model were optimized based on our measured data and previously published literature data. The effect of Murphree vapour phase efficiencies on the sensitivity of the simulation is discussed.