Vapor Pressure Measurement of 2-Pentenenitrile and Vapor–Liquid Equilibrium for Its Mixtures with 2-Methyl-3-Butenenitrile and 2-Methyl-2-Butenenitrile

2-Methyl-3-butenenitrile, a key intermediate in the industrial production of Nylon-66, is often accompanied by two other by-products, 2-methyl-2-butenenitrile and 2-pentenenitrile, which have been proven to affect the production yield and quality of Nylon-66. Pure 2-pentenenitrile is a commercial synthetic intermediate for many chemical products and bioactive substances. As important foundational data for designing large-scale separation and purification processes for these three compounds are lacking, the saturated vapor pressure of pure 2-pentenenitrile was measured over the temperature range 298.5 K to 401.4 K, and vapor–liquid equilibrium (VLE) data for the binary systems (2-methyl-3-butenenitrile + 2-pentenenitrile, 2-methyl-2-butenenitrile + 2-pentenenitrile) were determined at pressures of 50.0 kPa and 100.0 kPa. In order to better utilize these experimental data for the design of large-scale separation distillation processes, the experimental saturated vapor pressure data of pure 2-pentenenitrile were well correlated using the Antoine equation, yielding an average relative deviation of 0.92%. For all binary systems, the thermodynamic consistency of the VLE results was verified using both the point test and the direct test. The binary VLE data were correlated with the Wilson and NRTL activity coefficient models, and the corresponding model parameters were obtained by regression, which can help to obtain complete data in the whole mole fraction range for industrial separation design.