LLE data for the ionic liquid 3-methyl-N-butyl pyridinium dicyanamide with several aromatic and aliphatic hydrocarbons

(Liquid + liquid) equilibrium data for ternary systems of several aromatic and aliphatic hydrocarbons with the ionic liquid 3-methyl-N-butylpyridinium dicyanamide were determined at T = 303.15 K and 328.15 K and atmospheric pressure. As aromatics benzene, cumene and p-xylene have been chosen, as paraffins n-hexane and n-nonane were used. The experimental data were regressed and could be adequately correlated with the NRTL model. A logical order in the extraction capacity of 3-methyl-N-butylpyridinium dicyanamide for the different aromatics is obtained: benzene > p-xylene > cumene

Ionic liquids as alternative solvents for aromatics extraction

The objective of this thesis was the development of an extraction process for the removal of multiple aromatics from several petrochemical streams by means of an ionic liquid. Due to environmental legislation, the demand of ‘clean’ fuels is increasing and most likely will increase even more towards fuels with almost zero content of certain aromatics, e.g. benzene and toluene. In particular, the concentration of benzene has to be reduced to = 0.1 wt-% in carburant fuels. Furthermore, the sulphur content of gasoline and diesel fuel has to be decreased to toluene > p-xylene > cumene > 1-hexene > n-hexane > n-heptane and for higher aromatics and cyclic aliphatics 9,10-dihydrophenanthrene > naphthalene > tetralin > decalin. Based on these screening results the ionic liquid [3-Mebupy][DCA] has been chosen for further evaluation due to the high capacity (Dbenzene,[3-Mebupy][DCA] = 0.60 [g/g]) and reasonable selectivity (¿[3-Mebupy][DCA],benzene/n-hexane = 35.3). Subsequent, the two ionic liquids [3-Mebupy][TCM] and [3-Mebupy][TCB] became available, which exhibit an even higher capacity and comparable or slightly lower selectivity (Dbenzene,[3-Mebupy][TCM] = 0.70 [g/g] and Dbenzene,[3-Mebupy][TCB] = 0.74 [g/g]; ¿[3-Mebupy][TCM],benzene/n-hexane = 34.8 and ¿[3-Mebupy][TCB],benzene/n-hexane = 27). Additionally, as petrochemical streams contain numerous components, including heterocycles, the affinity of heteroatoms towards ionic liquids has been studied in comparison to mono-aromatics. Therefore two model feeds containing sulphur aromatic components or nitrogen aromatics and toluene, tetralin and n-heptane have been investigated for the extraction with the same ionic liquids that showed to be promising for feeds containing only aromatic and aliphatic hydrocarbons. It was found that the sulphur and nitrogen containing hetero aromatics thiophene and dibenzothiophene and pyrrol, indole and carbazole are significantly better extracted than aromatic hydrocarbons. In one extraction step up to 80 % of the thiophene and up to 90 % of the dibenzothiophene can be removed while > 99 % of the nitrogen containing aromatics has been removed. Furthermore, the results for the model feeds are compared to real feed experiments in order to investigate the influence of a real petrochemical stream mixture compared to a model feed with a limited number of components. In all cases it was observed that the removal of the aromatic components from the real feed was less, due to competing influences of other components, but still promising. For the real feed experiments the ionic liquid [3-Mebupy][DCA] has been chosen. Whit a suitable candidate defined, the subsequent step is the development of an extraction process based on this ionic liquid. Therefore, a process design for the FCC gasoline model feed based on [3-Mebupy][DCA] comprising the main extraction column with the additional separation and solvent recovery units has been developed with Aspen plus together with an economical feasibility study of the process. The process comprises the main extraction column, a back extraction column for recovery of the ionic liquid that is withdrawn in the raffinate phase by entrainment, an extractive stripper in order to remove the co-extracted aliphatic components from the extract phase and a flash evaporator for separation of the aromatic product from the extraction solvent. Since [3-Mebupy][DCA] is hydrophilic, in contrary to the compounds present in the raffinate phase, the ionic liquid in the raffinate phase can be easily back-extracted by means of water. The results for investment and operational costs for the ionic liquid based process have been compared to a process using sulfolane as extraction solvent, since this is the most conventional solvent for aromatics extraction. It is shown that the investment costs for the ionic liquid based process are up to 42 % lower than for sulfolane and the annual costs for the [3-Mebupy][DCA] process are only 17.8 M€ compared to 32.6 M€ for a sulfolane process. This is due to the higher capacity of the ionic liquid which results in smaller process streams and therewith smaller equipment. The process design is based on the ternary diagrams that can be derived from the components present in the FCC gasoline and reformate model feeds and [3-Mebupy][DCA]. The ternary data have been determined experimentally and correlated with the NRTL model. The data regression for the two model feeds is in good agreement with the experimental data and the RMSD values are in general <0.0324. Additionally, the ternary diagrams for toluene/n-heptane with the three ionic liquids [BMIM][DCA], [BMIM][SCN] and [3-Mebupy][DCA] have been determined. The RMSD-values in this case are <0.0076. Furthermore, an experimental study on the scale-up of the FCC gasoline model feed and a real feed (LCCS) to a rotating disc contactor (RDC) pilot plant with the solvent [3-Mebupy][DCA] provided insight in mass transport and hydrodynamic effects, which is valuable information for an industrial process. Analogous to the LLE-measurements, it was shown that the extraction performance of the RDC column is higher for the model feed than for the real feed. From the FCC gasoline model feed 89 % benzene and 75 % toluene removal was observed while for the real feed 81 % benzene and 71 % toluene could be removed, respectively, with a solvent-to-feed ratio S/F = 4 and 800 rpm. This is due to competing effects of the multiple components in the real feed, which also hampers the mass transfer. Therefore, the mass transfer performance of RDC-column is also higher for the model feed than for the real feed. Besides, comparable hydrodynamic behaviour of the model and real feed has been observed. Since the densities and viscosities of both feeds are comparable, this explains the observed similar data in terms of Sauter means size diameter, hold-up and operational window. The conclusions that can be drawn from this work confirm that ionic liquids are potential solvents for the extraction of aromatic hydrocarbons as well as hetero aromatics containing sulphur and nitrogen. It has been reported that these components can be removed selectively from components as, e.g. olefins, aliphatics and cyclic aliphatics. Moreover, the results obtained with model feeds could be validated by means of real feed experiments on lab scale as well as pilot plant scale. Furthermore, from the conceptual process design based on [3-Mebupy][DCA] it is evident that an ionic liquid based extraction process can be energetically, and thus economically, more favourable than a sulfolane process. However, for the implementation of an ionic liquid extraction process on industrial scale further research has to be carried out in particular with view of the ionic liquid recovery and aromatics removal form the extract phase

Ionic liquids for aromatics extraction. Present status and future outlook

Ionic liquids (ILs) can be used to replace conventional solvents in liquid-liquid extractions of aromatic hydrocarbons. An IL-based extraction process requires fewer process steps and less energy consumption, provided that the mass-based aromatic distribution coefficient and/or the aromatic/aliphatic selectivity are higher than those of the current state-of-the-art solvents such as sulfolane. Only a small number of ionic liquids are able to combine higher mass-based distribution coefficients with selectivities comparable to or higher than those of sulfolane. The most suitable ILs from our analysis are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, and [3-mebupy]B(CN)4. The mass-based distribution coefficients with these four ILs for benzene, toluene, and p-xylene are factors of 1.2-2.5 higher than those with sulfolane, and the aromatic/aliphatic selectivities are up to a factor of 1.9 higher than with sulfolane. Based on the performed analysis, it can be concluded that industrial application of ILs for aromatics extraction has not yet materialized because only four of the total of 121 investigated ILs are considered suitable for aromatic/aliphatic separation. Most of the reported ILs do not provide higher mass-based aromatic distribution coefficients and/or higher aromatic/aliphatic selectivities than those achieved by conventional solvents such as sulfolane

Ionic liquids for aromatics extraction. Present status and future outlook

Ionic liquids (ILs) can be used to replace conventional solvents in liquid-liquid extractions of aromatic hydrocarbons. An IL-based extraction process requires fewer process steps and less energy consumption, provided that the mass-based aromatic distribution coefficient and/or the aromatic/aliphatic selectivity are higher than those of the current state-of-the-art solvents such as sulfolane. Only a small number of ionic liquids are able to combine higher mass-based distribution coefficients with selectivities comparable to or higher than those of sulfolane. The most suitable ILs from our analysis are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, and [3-mebupy]B(CN)4. The mass-based distribution coefficients with these four ILs for benzene, toluene, and p-xylene are factors of 1.2-2.5 higher than those with sulfolane, and the aromatic/aliphatic selectivities are up to a factor of 1.9 higher than with sulfolane. Based on the performed analysis, it can be concluded that industrial application of ILs for aromatics extraction has not yet materialized because only four of the total of 121 investigated ILs are considered suitable for aromatic/aliphatic separation. Most of the reported ILs do not provide higher mass-based aromatic distribution coefficients and/or higher aromatic/aliphatic selectivities than those achieved by conventional solvents such as sulfolane

Ionic liquids for aromatics extraction. Present status and future outlook

Ionic liquids (ILs) can be used to replace conventional solvents in liquid-liquid extractions of aromatic hydrocarbons. An IL-based extraction process requires fewer process steps and less energy consumption, provided that the mass-based aromatic distribution coefficient and/or the aromatic/aliphatic selectivity are higher than those of the current state-of-the-art solvents such as sulfolane. Only a small number of ionic liquids are able to combine higher mass-based distribution coefficients with selectivities comparable to or higher than those of sulfolane. The most suitable ILs from our analysis are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, and [3-mebupy]B(CN)4. The mass-based distribution coefficients with these four ILs for benzene, toluene, and p-xylene are factors of 1.2-2.5 higher than those with sulfolane, and the aromatic/aliphatic selectivities are up to a factor of 1.9 higher than with sulfolane. Based on the performed analysis, it can be concluded that industrial application of ILs for aromatics extraction has not yet materialized because only four of the total of 121 investigated ILs are considered suitable for aromatic/aliphatic separation. Most of the reported ILs do not provide higher mass-based aromatic distribution coefficients and/or higher aromatic/aliphatic selectivities than those achieved by conventional solvents such as sulfolane

Desulfurization and denitrogenation of gasoline and diesel fuels by means of ionic liquids

Ionic liquids can extract mono- and poly-aromatic sulfur and nitrogen compounds from gasoline and diesel and they perform better than conventional solvents. The extraction capacity of several ionic liquids for these heterocyclic compounds is determined and compared to the extraction capacity for aromatic hydrocarbons. Furthermore, the experimental results obtained are evaluated in view of the results reported in literature. It is shown that the ionic liquids investigated in this work are able to extract sulfur as well as nitrogen-containing aromatics in preference to aromatic hydrocarbons. Moreover, the ionic liquids [3-mebupy]N(CN)2, [4-mebupy]N(CN)2 and [bmim]C(CN)3 are superior to sulfolane, which has been used as a benchmark and also outperform the ionic liquids reported in literature so far. Finally, it has been shown that nitrogen-containing hetero-aromatics are significantly better extracted than sulfur-containing hetero-aromatics

Sharing five years of pilot plant experience on aromatics extraction with ionic liquids

Since 2004 pilot plant trials have been conducted with various contactors and different ionic liquids for petrochemical model feeds as well as real refinery feeds. Our pilot plant contains several columns (rotating disc contactor, Kuhni, pulsed disc and donut column) with a height of 6 m and 5 cm diameter. Up to 100 kg of ionic liquid and 200 L of feed are applied in experiments. In this paper the hydrodynamic and mass transfer performance of a rotating disc contactor has been characterised for toluene/heptane, a model FCC (fluid catalytic cracker) feed and a real LCCS (Light Catalytically Cracked Spirit) refinery feed using 3-methyl-N-butyl-pyridinum dicyanamide as the ionic liquid. Experiments with the real LCCS feed demonstrated comparable extraction performance to the model FCC feed. Over the past five years the same batches of ionic liquids have been repeatedly regenerated by evaporation and reused. The studies revealed that, although coloration occurs, the extraction performance of the ionic liquids has not changed even after several years of usage. After the real LCCS refinery feed experiments, validation with the toluene/heptane model feed confirmed unchanged extraction performance

Long term pilot plant experience on aromatics extraction with ionic liquids

Since 2004, we have been conducting pilot plant trials with various contactors and different ionic liquids for petrochemical model feeds as well as real refinery feeds. Our pilot plant contains a Rotating Disc Contactor with a height of 6 m and a diameter of 60 mm. Up to 100 kg of ionic liquid and 200 L of feed are applied in experiments. In this paper, the hydrodynamic and mass transfer performance of a rotating disc contactor has been characterized for toluene/n-heptane, a model FCC feed and a real LCCS refinery feed using 3-methyl-N-butyl-pyridinum dicyanamide ([3-mebupy]N(CN)(2)) as the ionic liquid. Experiments with the real LCCS feed demonstrated comparable extraction performance to the model FCC feed. Over the past 5 years, the same batches of the ionic liquid have been repeatedly regenerated by evaporation and reused. Our studies revealed that, although coloration occurs, the extraction performance of the ionic liquids has not changed even after several years of usage. After the real LCCS refinery feed experiments, validation with the toluene/n-heptane model feed confirmed unchanged extraction performance. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental fil

Liquid-Liquid equilibria for the three ternary systems (3-methyl-N-butylpyridinium dicyanamide + toluene + heptane), (1-butyl-3-methylimidazolium dicyanamide + toluene + heptane) and (1-butyl-3-methylimidazolium thiocyanate + toluene + heptane) at T = (313.15 and 348.15)K and p = 0.1 MPa

Liquid-liquid equilibrium data for the ionic liquids 3-methyl-N-butylpyridinium dicyanamide ([3-Mebupy][DCA]), 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]), and 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) with toluene and heptane were investigated at T = (303.15 and 328.15) K and atmospheric pressure. The experimental data were regressed and could be correlated adequately with the nonrandom two-liquid model. The results show that the extraction capacity of the three investigated ionic liquids is in the order of: [3-Mebupy][DCA] > [BMIM][DCA] > [BMIM][SCN]