MODELING OF A TWO-STAGE EXTRACTIVE DISTILLATION PROCESS FOR THE SEPARATION OF 1,3-BUTADIENE FROM PYROLYSIS-DERIVED C₄ FRACTIONS

The separation of 1,3-butadiene from pyrolysis-derived C₄ fractions represents a challenging task due to the multicomponent nature of the feed and the close boiling points of accompanying hydrocarbons. In this study, a two-stage extractive distillation process was investigated using an acetonitrile–water solvent system to address these challenges. A semi-industrial experimental unit consisting of two extractive distillation columns connected in series was developed and analyzed, and the process configuration was supported by Aspen Plus simulation. The feedstock composition was characterized in detail, revealing that 1,3-butadiene constitutes approximately 40 wt.% of the C₄ fraction, accompanied by significant amounts of propylene, butanes, butanes, and a non-negligible C₅ fraction. Component-wise mass flow analysis showed that the absolute butadiene load reaches about 480 kg/h for a total feed flow of 1200 kg/h, emphasizing the need for a robust and flexible separation scheme. These results demonstrate that the separation problem is governed not only by relative composition but also by high throughput and heavy-end loading. The two-stage extractive distillation configuration allows the separation task to be distributed between columns, facilitating selective interaction between the solvent and 1,3-butadiene while managing light and heavy hydrocarbon components. The presented experimental framework and modeling approach establish a consistent methodological basis for evaluating separation efficiency and further optimization of industrial butadiene recovery processes. The findings confirm the suitability of staged extractive distillation for processing complex pyrolysis C₄ streams with high butadiene content.

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