Butadiene purification using polar solvents. Analysis of solution nonideality using data and estimation methods

The classical problem of 1,3-butadiene recovery from steam cracker C ₄ hydrocarbons is reconsidered using modern tools of quantum mechanics and molecular simulation. The effectiveness of N,N-dimethylformamide (DMF) and acetonitrile (ACN) to act as extractive-distillation solvents is explored with an emphasis on the predictive capability of various models. The quantum mechanical method of interest is the COSMO-RS method. The chosen molecular simulation method is the SPEADMD model. These methods are compared to conventional methods such as UNIFAC and "thermodynamic intuition". The COSMO-RS method is found to predict the trends of infinite-dilution activity coefficients quantitatively, but requires a systematic empirical correction to provide accuracy comparable to UNIFAC. It is noted that the COSMO-RS method has a special capability to predict subtle trends. The SPEADMD model is found to provide unique qualitative insights, but requires empirical refinement of the interaction-potential models that is similar to the regression of UNIFAC parameters. This work is intended to serve as an objective framework to evaluate tools-traditional and modern-to predict solution nonideality.