Ionic Liquids for Propene‐Propane Separation

Abstract

This paper presents an extensive study on the feasibility of ionic liquids (IL) for the extractive distillation of propene-propane mixtures. A new experimental method for express screening of non-volatile entrainers was elaborated. A series of ILs and their mixtures were screened at ambient temperature and low pressures. The screening results show that every tested IL turns a low boiler propene into a high boiler and the alkene-to-alkane separation factor can be as low as 0.28. The solubility and separation efficiency can be tuned by adjusting the chemical structures of the ions forming the IL. It was found that shortening of the alkyl substituents of the imidazolium ions leads to a decrease in capacity and to an increase in the separation factor. Interestingly, ILs containing nitrile functionalities in either the cation or the anion showed, in our experiments, enhanced separation ability combined with still good capacities. From our thermodynamic measurements, [EMIM] [[B(CN) 4 ] was proved to be the most promising candidate. Binary mixtures of ILs were also tested and resulted in separation factors and capacities between the values for the individual ILs. For the most promising candidates, also autoclave measurements at elevated temperatures and pressures were carried out. These experiments indicate that the separation ability decreases with growing temperature and loading. In general, our study definitely proves the high potential of ILs to act as entrainers in the extractive distillation of propenepropane mixtures or for the separation of any other low-boiling alkene-alkane mixture.

Imidazolium-based ionic liquids with cyano groups for the selective absorption of ethane and ethylene

“…The effect of the introduction of nitrile groups in the ionic liquids has been previously reported. Enhanced separation abilities were claimed by Mokrushin et al [12] and Xing et al [13] have reported that the introduction of nitrile groups in the alkyl side-chains of imidazolium-based ionic liquids contributed to an increase of the selectivity for the separation of ethylene from ethane -from 1.37 to 1.61 and then to 2.01 introduction of two nitrile groups) -even if the solubility of ethylene significantly decreased.…”

Ionic Liquids for Chloromethane/Isobutane Distillative Separation: Express Screening

“…The procedure developed by our group for propene/propane separation [8] was adapted for the present measurements as follows. First, a chloromethane/isobutane gas mixture of a given composition was prepared by adding defined masses of the two gases to a metal container.…”

Activity coefficients at infinite dilution for organic solutes and water in 1-ethyl-1-methylpyrrolidinium lactate

“…Recently, ILs have been proposed to be used as entrainers for propane/prop-1-ene separation [13] and hexane/hex-1-ene separation [14]. A series of imidazolium-based ILs with different anions were tested at ambient temperature and low pressures [13].…”

“…As for many similar processes it was found that shortening of the alkyl substituent at the cation leads to an increase of the separation factor and decreases capacity. Thus the best substituent at the imidazolium, or others cations are ethyl-or butyl-substituent [7][8][9][11][12][13]. However, only a limited number of ILs have been studied so far for the separation of alkene from alkane and thus no systematic evaluation of their performance as entrainers is possible.…”