VLE and viscosity modeling of N-methyl-2-pyrrolidone (NMP) + water (or 2-propanol or 2-butanol) mixtures by cubic-plus-association equation of state

Abstract

Abstract N-methyl-2-pyrrolidone (NMP) due to its special characteristics is an efficient solvent that has numerous industrial and practical applications. Moreover, its mixtures with organic solvents and water have scientifically and practically great of interest. In this theoretical study, the cubic plus association equation of state was utilized to model vapor-liquid equilibrium of water-NMP, 2-propanol-NMP, and 2-butanol-NMP mixtures over a temperature range of 343.15 K–380.15 K, 353.15 K–373.15 K, and 373.15 K, respectively. Four and two association sites were considered for water and studied alcohols, respectively, while NMP was treated as both an “inert” compound and a “cross-associating” compound. NMP as an inert compound resulted in poor correlation results, whereas a high level of accuracy was achieved when considered as a cross-associating compound. Accordingly, hydrogen bonds between NMP carbonyl group and water (or alcohol) hydrogen were taken into consideration. Satisfactory model-correlated results were obtained by both temperature-dependent and temperature-independent binary adjustable parameters (BAPs) for all studied mixtures. In the following, the density of water-NMP, 2-propanol-NMP, and 2-butanol-NMP liquid mixtures was predicted using temperature-independent BAPs over a temperature range of 293.15 K–343.15 K, 298.15 K–303.15 K, and 288.15 K–323.15 K with absolute average relative deviation (AARD) of 6.20%, 7.53%, and 6.16%, respectively. Furthermore, the dynamic viscosity of water-NMP, 2-propanol-NMP, and 2-butanol-NMP liquid mixtures was satisfactorily calculated by CPA EoS and free volume theory (CPA-FV) using a simple quadratic mixing rule. The applied approach calculating the dynamic viscosity was efficient enough to represent minimum and maximum values available in experimental data properly.