This dissertation comprises two parts: the first is vapor-liquid equilibrium data for the binary system containing maleic anhydride, the second is the calculation of vapor-liquid equilibrium data for the binary systems containing supercritical CO2 and systems containing CH4 at high pressures.It is a good method to recover maleic anhydride using organic solvents from its production tail gas, which can decrease energy consumptions and increase yields. Many abroad companies have applied this method, but most internal companies still use water as the absorption solvent. The phase equilibrium data of the systems anhydride + esters are necessary to design the new process. Thus, five esters were chosen as the prospective organic solvents, and vapor-liquid equilibrium data for these binary systems were measured with ebulliometric method.The Antoine's constants of pure components in above systems will influence the calculated results of vapor-liquid equilibrium, so, in this research, saturated vapor pressures of maleic anhydride, diethyl phthalate, di-n-butyl phthalate, di-isobutyl hexahydrophthalate, di-n-butyl sebacate were measured with a modified ebulliometer and compared with the values in the literatures. All these data were fitted with Antoine Equation,ln( p / kPa) = A-B/(C + T/ K), and the Antoine constants of each pure component were obtained.Three isothermal (413.2 K, 433.2 K and 453.2 K) p - qcurves and three isobaric (2.67 kPa, 5.33 kPa and 8.00 kPa) T_b - qcurves of five binary systems for different feed composition q were measured with a modified ebulliometer. These binary systems included maleic anhydride + dimethyl phthalate, maleic anhydride + diethyl phthalate, maleic anhydride + di-n-butyl phthalate, maleic anhydride + di-isobutyl hexahydrophthalate and maleic anhydride + di-n-butyl sebacate. All these data were also correlated with the NRTL model to obtain vapor-liquid equilibrium T , p , x1 and y1 data. In the process of correlation, the parameters of NRTL model were determined by simplex method.At the same time, UNIFAC group contribution method was used to calculate the isobaric vapor-liquid equilibrium data of systems (maleic anhydride + dimethyl phthalate, maleic anhydride + diethyl phthalate, and maleic anhydride + di-n-butyl phthalate). The results were compared with the correlated results using NRTL model. New group ACCOO was defined, and the interaction parameters have been regressed with the experimental data.In addition, gas-liquid equilibrium data and critical curves for the binary systems containing supercritical CO_2 and systems containing CH4 at high pressures were calculated. Firstly, an equation of state, was determined according to perturbation theory and hard sphere model, which consists of an attractive part and a repulsive part. Using this equation of state, isothermal gas-liquid equilibrium data of systems (CO_2 + dimethyl carbonate, CO_2 + diethyl carbonate and CO_2 + acetate) at high pressures were calculated. At the same time, the critical curves of the systems (CO_2 + dimethyl carbonate, CO_2 + diethyl carbonate, CO_2 + acetate, CH_4 + nitrogen, CH_4 + carbon monoxide, CH4 + CO_2, CH_4 + ethane and CH_4 + propane) were also obtained. These results were compared with those from literatures, and showed good agreement.