Purification of isobutane remains a fundamental step in the production of a cleaner alkylated gasoline, and the distillation operation employed for this separation is notoriously energy-intensive and a significant contributor to environmental impacts. To address these challenges, this work proposes vapor recompression (VR) as an intensified alternative process to fully electrify the conventional column–reactor configuration used in n-butane isomerization and separation. An external VR scheme was designed and globally optimized with the objective of minimizing total annualized cost. The optimized VR configuration showed a clear economic advantage, achieving an approximate 13.83% reduction in costs over a 10-year horizon with a break-even time of 7.13 years. Additionally, overall energy demand was reduced by 74%, and operational safety was enhanced, as the boiler is required only during plant start-up and shutdown. To account for economic uncertainty, a sensitivity analysis was conducted to evaluate the effects of fluctuations in electricity and steam prices. Environmental performance was further assessed through CO2 emissions using different national electricity emission factors. While emission reductions depend strongly on grid carbon intensity, regions with low-carbon electricity mixes show significant mitigation potential. Overall, VR emerges as a promising strategy to improve the economic and environmental sustainability of industrial processes.
Figueiredo et al. (Sat,) studied this question.