Measurements and modeling of high-pressure phase behavior of binary CO 2–amides systems

Abstract

High-pressure vapor–liquid equilibrium (VLE) data were measured for binary CO 2– N, N-dimethylformamide, CO 2– N, N-diethylformamide and CO 2– N, N-dibutylformamide systems at various temperatures (318.2–398.2 K) and pressure up to 25 MPa. These CO 2– N, N-dimethylformamide, CO 2– N, N-diethylformamide and CO 2– N, N-dibutylformamide systems exhibits type-I phase behavior, which is characterized by an uninterrupted critical mixture curve which has a maximum in pressure. The solubility of N, N-dimethylformamide, N, N-diethylformamide and N, N-dibutylformamide for the CO 2– N, N-dimethylformamide, CO 2– N, N-diethylformamide and CO 2– N, N-dibutylformamide systems increases as the temperatures increases at constant pressure. The CO 2– N, N-dimethylformamide, CO 2– N, N-diethylformamide and CO 2– N, N-dibutylformamide systems have continuous critical mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of CO 2 and N, N-dimethylformamide, N, N-diethylformamide or N, N-dibutylformamide. Also, three phases were not observed of any of the systems studied. In each systems, the mixture critical point increases as the temperatures increases, and also the mixture critical pressure does as molecular weight increases. The experimental results for CO 2– N, N-dimethylformamide, CO 2– N, N-diethylformamide and CO 2– N, N-dibutylformamide systems is modeled using the Peng–Robinson equation of state. A good fit of the calculated data is obtained with the Peng–Robinson equation of state.