Development of energy‐optimum aromatic extraction processes using ionic liquid [EMIM][NTf2]

Abstract

There is industrial incentive to extract aromatics from ethylene cracker feeds, but the conventional sulfolane solvent was found not economical by Meindersma and coworkers. Ionic liquids (ILs) have long been considered alternative aromatic extraction solvents. This work develops energy‐optimum aromatic extraction processes for an ethylene cracker feed using IL solvents. We avoid pitfalls of using simplified feeds and a priori thermodynamic property estimates, with the largest set of experimentally regressed UNIQUAC binary parameters for the IL, 1‐ethyl‐3‐methylimidazolium bis([trifluoromethyl]sulfonyl)imide ([EMIM][NTf2]). We screen process energy and operating conditions for [EMIM][NTf2] and sulfolane at varying aromatic feed contents and find [EMIM][NTf2] favorable at low aromatic feed contents. Adding light and heavy components of the ethylene cracker feed necessitates process modifications. Our novel steam‐assisted extractive distillation developed for [EMIM][NTf2] is also suitable for sulfolane. We show that the [EMIM][NTf2] solvent can reduce 10.7% of energy consumption compared to sulfolane using the same novel process.

Evaluation of thermophysical data, COSMO‐SAC predictions, and feed simplifications for aromatic extraction process simulation using ionic liquid [EMIM][NTf2]

“…Figure 1 and extractive distillation ($348-448 K) processes, as discussed in our associated modeling work. 52 We show the predicted IDAC for hydrocarbon components over the full process temperature range in Figures S1-S3 of the Supplement Material, demonstrating consistency of extrapolated predictions at higher temperatures.…”

“…We lower weights of: (1) data that are apparent outliers; (2) datasets with large numbers of data points that dominate the regression at the expense of other datasets; and (3) single‐temperature point data. Preserving trends of temperature dependency is important, since none of the experimental data covers the operating temperature ranges of the liquid extraction (~323–373 K) and extractive distillation (~348–448 K) processes, as discussed in our associated modeling work 52 . We show the predicted IDAC for hydrocarbon components over the full process temperature range in Figures S1–S3 of the Supplement Material, demonstrating consistency of extrapolated predictions at higher temperatures.…”

“…Process development and optimization are described in detail in our associated work. 52 The aromatic extraction process configuration begins with an aromatic extractor where a hydrocarbon is fed to the bottom and solvent is fed to the top. An aliphatic product, raffinate exits the top of the extractor and an aromatic extract exits the bottom of the extractor.…”

“…We use a design that is developed and optimized using the UNIQUAC regression and minimally simplified ethylene cracker feed composition. Process development and optimization are described in detail in our associated work 52 …”

“…Solvent feed rate controls aromatic purity. Aromatic purity control requires special consideration.Our associated work52 outlines why independent control of the EDC bottom temperature is important for controlling solvent heat load and avoiding high grade steam usage. The EDC bottom temperature is…”