Optimal Design of an Ionic Liquid (IL)-Based Aromatic Extractive Distillation Process Involving Energy and Economic Evaluation

Abstract

Extractive distillation (ED) can be used to separate mixtures with low relative volatilities that are even close to unity. It is widely adopted for the separation of aromatics and nonaromatics in the petrochemical industry. Selecting a suitable solvent is of paramount importance to ED processes. Ionic liquids (ILs) are increasingly being considered as potential options to replace organic solvents in ED processes due to their favorable properties including high boiling points and extremely low volatilities. In this work, a nonexperimental solvent screening approach, i.e., computer-aided ionic liquid design (CAILD), is employed to identify the optimal ILs. Using a novel design objective and several structural and property constraints on IL, we have identified 1,3-dimethylpyridinium tetrafluoroborate ([C1mPy]­[BF4]) as the best IL solvent by solving a formulated CAILD-based mixed-integer nonlinear programming problem. The separation performance of this IL is further evaluated with rigorous process simulation in Aspen Plus. Besides, process simulation of the aromatic ED process using sulfolane as the benchmark organic solvent is performed. Furthermore, a systematic analysis of the energy consumption and the process economy is conducted by investigating the optimized simulation results of the studied aromatic ED process. The [C1mPy]­[BF4]-based process with an assumed IL price of 50 $/kg can reduce the capital cost by 35.2%, the operating cost by 11.8%, and the total annual cost by 31.2%. The IL price at the break-even point of replacing sulfolane with [C1mPy]­[BF4] in the aromatic ED process is 91.03 $/kg.

Extractive Distillation with Ionic Liquids To Separate Benzene, Toluene, and Xylene from Pyrolysis Gasoline: Process Design and Techno-Economic Comparison with the Morphylane Process

“…These energy consumptions are similar to those found in the literature for similar processes. 23,49 Concerning the solvent recovery column, no energy consumption is required. The number of stages needed to recover [emim][TCM] with a purity of 99.9 wt % was 12 for Process 2A and 10 for Process 2B.…”

“…Lei et al took a price of 91.03 $/kg for the [mmpy][BF 4 ], three times higher than the price established for the sulfolane or NFM. 23 According to this, Process 1 had a solvent investment of 2.7 MM$, related to a process residence time of 0.5 h and 30 $/kg price; Process 2B demands 15 MM$ of investment in the ionic liquid in the same scenario but with a price of 100 $/kg. However, the nonvolatile character of the ionic liquid imposes the advantage of negligible losses of solvent, imposing no make-up requirements; NFM losses in the process are around 250 kg/h, which demands 60 MM$/year operating costs associated with the solvent.…”

“…Indeed, its suitability for the separation of BTX from aliphatics has been recently studied, overcoming the limitations regarding liquid−liquid extraction and improving energy expenses. 22,23 Our research group developed a series of studies evaluating the feasibility of several ionic liquids as mass agents in the extractive distillation of different mixtures {aliphatic + aromatic}. First, an experimental screening of 10 ionic liquids was made to probe the influence of their extractive properties (aromatic selectivity and distribution ratio) on the n-heptane/ toluene relative volatility provided by each one.…”

Ionic liquid‐based in situ product removal design exemplified for an acetone–butanol–ethanol fermentation

“…11,12 Until now, ILs have been widely studied as solvents for gas separations 13,14 (e.g., CO 2 capture, 15 shale gas purification 16 ) and energy intensive liquid-liquid separation. [17][18][19] Additionally, applications of ILs in biotechnology have also been in focus over the past few decades. 20,21 For example, they have been used as extractants for the recovery of various small molecules (e.g., biofuels, [22][23][24] alkaloids, 25,26 amino acids, [27][28][29][30] phenolic compounds, 31 isoprene 32 ) produced by fermentation or by biosynthetic routes.…”

“…Unlike most commonly used organic solvents, ILs have a low‐volatility and are non‐flammable, providing alternatives for the chemical, biochemical and other industries 11,12 . Until now, ILs have been widely studied as solvents for gas separations 13,14 (e.g., CO 2 capture, 15 shale gas purification 16 ) and energy intensive liquid–liquid separation 17–19 . Additionally, applications of ILs in biotechnology have also been in focus over the past few decades 20,21 .…”