Study On The Vapor-Liquid Equilibrium Of Binary Carbon Dioxide And Ester Systems

Carbon dioxide (CO₂) is an main kind of greenhouse gases, is an important reason for global warming. Low-carbon economy is the consensus of the people,but at present, fossil fuel energy dominate the use of large amounts of carbon dioxide emissions from the process. How to turn waste into wealth, development and utilization of CO 2 cause for concern. Supercritical carbon dioxide (SC-CO₂) has many special characters, which make it was used in supercritical extraction, extraction of natural products, various chemical reactions, material chemistry. When SC-CO₂ is used as extracting agent, a small amount of alcohol or esters required to improve its solubility. In this paper, High-pressure vapor-liquid equilibrium data for the binary systems of CO₂ +methyl propionate (MP), CO₂ + propyl propionate (PP), CO₂ + ethyl butyrate (EB) and CO₂ + propylene carbonate (PC) were measured,respectively.A set of variable-volume autoclave with a quartz window has been used for experimental determination. High-pressure vapor-liquid equilibrium data (including mole fractions, density, mole volume and vapor-liquid ratio of the liquid phase and the vapor phase) of the four binary Systems have been measured at different temperatures and pressures with isothermal static analytical method.The experimental results show that the solubilities of SC-CO₂ are greater in the four esters.At the same temperature, the mole fractions of esters in vapor increases and the mole fractions of SC-CO₂ in liquid increase as the pressures were increased. At the same pressure, the effects of temperature on solubilities for esters and SC-CO₂ are different. The solubility of SC-CO₂ in the esters decreased,and the solubility of esters in SC-CO₂ increases.The high-pressure GLE data are also calculated with different methods for above four systems.The PR, PRSV and four different mixing rules are used.The Suitability and accuracy of those EOSs are also been discussed.The results show that PRSV equation with var der waals mixing rules, PR equation with the activity coefficient mixing rules are in good agreement.In addition, Henry equation was modified by Peng-Robinson equation. f1 - x1 curves and Henry coefficients of the four systems at the 313 K, 333 K, 353 K and 373 K were obtained by the modified Henry law. Dissolution molar enthalpyΔsol Hm and dissolution molar entropyΔsolSm ofCO₂ in the esters at different temperature were also calculated.