Structure optimization of task-specific ionic liquids targeting low-carbon-emission ethylbenzene production

The production of ethylbenzene from dry gas is a representative of an energy-intensive process in oil refineries, and the distillation process accounts for the major energy consumption and carbon emissions. Due to the increasing energy and environmental challenges, there is a strong demand for new technologies or intensified process designs that enable us to have energy-efficient and sustainable process operations. In this work, an ionic liquid (IL)-based energy-efficient extractive distillation (ED) process with low carbon emission is proposed for the distillation process of ethylbenzene production from dry gas. First, the structure of task-specific ILs is optimized through the computer-aided IL design (CAILD) method with a novel design objective. An ammonium-based IL ethylammonium trifluoromethanesulfonate ([C₂H₈N][TfO]), that has the best objective performance, is identified by solving a mixed-integer nonlinear programming (MINLP) problem. The energy, environmental (carbon emission), and economic performance of this [C₂H₈N][TfO]-based ED process in the ethylbenzene production is then thoroughly evaluated on the basis of optimized process operations in Aspen Plus. For demonstration purposes, a case study for the separation process of an industrial-scale ethylbenzene production in a Chinese refining industry is performed. When compared to the conventional process that is currently used in the petrochemical industry, our proposed [C₂H₈N][TfO]-based ED separation process has 40 % energy (hot utility) savings and a 11 % cost reduction. Notably, the IL-based ED separation process has 40 % lower carbon emissions versus the conventional process, indicating its great potential for sustainable operation in the production of ethylbenzene from dry gas.