Process Simulation of Isoprene Recovery from Dilute Fermentation Off-Gas Using Absorption-Desorption

The recovery of biobased isoprene from dilute fermentation off-gas remains a major challenge due to low product concentrations and energy-intensive downstream separations. In this study, a process intensification strategy based on absorption-desorption was developed and evaluated to efficiently recover isoprene from air mixtures. The proposed system integrates absorption using 3-methyltridecane, vacuum degassing, steam stripping, and condensation with multiple recycle loops for solvent, water, and residual isoprene. Of the thermodynamic models examined, the Peng-Robinson equation of state was used for the absorption section while UNIFAC was used for steam stripping. Process optimization demonstrated up to 95% isoprene recovery and 98% product purity while significantly reducing energy consumption. Sensitivity analyses revealed that solvent temperature, solvent-to-feed ratio, and feed isoprene concentration strongly influence process efficiency, with energy demand decreasing from 26 to 10 MJ kg^-1 as feed concentration increased. Compared to literature benchmarks, the proposed design achieved up to 40% reduction in steam usage. These results highlight absorption-based separation as a viable and energy-efficient pathway for recovering volatile hydrocarbons from dilute bioprocess streams and provide design insights for future scale-up and experimental validation.