KR20120000853A - Supported liquid membranes comprising room temperaure ioninc liquid blend and a pervaporative-recovery method using them - Google Patents

Abstract

PURPOSE: A supported liquid membrane containing room temperature ionic liquid blend and a prevaporative-recovery method based on the same are provided to improve the prevaporation performance of butanol. CONSTITUTION: A supported liquid membrane includes room temperature ionic liquid(RTIL) blend. The RTIL blend is phosphonium/ammonium ion mixed liquid or phosphonium/oleyl alcohol mixed liquid. The supported liquid membrane is used for prevaporative-recovering butanol. A prevaporative-recovery method for organic materials uses an organic material-water solution as a supplying solution. The supported liquid membrane with the RTIL blend is mounted at a permeation cell. The organic material is butanol.

Description

Supported liquid membranes comprising room temperaure ioninc liquid blend and a pervaporative-recovery method using them

The present invention relates to a support liquid membrane comprising a room temperature ionic liquid (RTIL) blend and a method for recovering pervaporation thereof, and more specifically, to a room temperature ionic having high hydrophobicity and high affinity for organic matter. A support liquid membrane including a liquid phosphonium / ammonium ionic mixed liquid system or a mixed liquid system of phosphonium [Ph3t] [NTF] / oleyl alcohol is used for recovery of butanol pervaporation to minimize the loss of the extraction solvent and to select butanol. The present invention relates to a support liquid membrane for maximizing the degree of permeability and a method for recovering butanol pervaporation.

Ionic liquids can be impregnated in the microporous polymer membrane support and used in the pervaporation recovery method of organic compounds (eg, industrially important alcohols such as ethanol, butanol, etc.). Through RTIL-RTIL or RTIL-organic solvent blending, improvements in stability and resolution of the Supported Ionic Liquid Membrane (SILM) are achieved. U.S. Patent No. 04617125 (October 14, 1986) describes a "method of separation by a support liquid membrane cascade."

As one of the ways to reduce the dependence of petroleum-derived gasoline, the method of producing butanol from biomass (by fermentation using solventogenic clostridial bacteria) is receiving attention again. This is an older technique, which is greatly limited by the butanol production inhibitory effect during fermentation leading to very low final broth concentrations (0.5 to 1.0% by weight).

Pervaporation has been found to be a very preferred separation method because it provides important advantages such as high selectivity, low energy consumption, simplicity and ease of handling. Korean Patent Application No. 10-2002-0006665 describes "Pervaporation apparatus for concentrating volatile fragrance components and concentration method using the same".

RTIL is a new family of designer solvents that are of great interest for research because of the ability to simply match process requirements by selecting the appropriate combination of cations and anions.

They are a wide range of selected or designed specific ionics with properties suitable for organic separations such as high hydrophobicity, very low or zero (0) vapor pressure, wide liquid temperature range, suitable viscosity, high solvent capacity and surface tension in general. It has a high potential as a liquid membrane extractant (LME) as it can be selected from the group of liquids.

Many papers have been reported on the use of ionic liquids in liquid-liquid extraction, whole cell biocatalysts, especially in SILM for gas separation.

Among pervaporation membrane types, support liquid membranes (SLMs) may have high selectivity and flux because molecular diffusion in liquids can be much faster and more selective for specific ions or molecules.

The resolution of SILM depends on several LME parameters. One of the most important parameters is the LME partition coefficient (Kp) of the solute to be separated. This has a direct correlation with LME extraction rate in addition to hydrophobicity (desired solute distribution for water). Another important parameter is the dispersibility directly controlled by the LME viscosity.

Currently, the biggest obstacle to industrial use of SLM is instability (inadequate long-term performance) leading to reduced solute flow and membrane selectivity. In the case of the RTIL-based LME, there is no vapor pressure, so the loss by evaporation is not applicable, and therefore the movement and dissolution to the adjacent phase are the main causes of instability. Even hydrophobic RTILs are known to exhibit an insignificant degree of solubility with the aqueous phase, and these properties, which are further increased by the presence of alcohol solutes and by increasing temperature, are the main triggers for initiating instability mechanisms.

SILM instability mechanisms include reversed micelle formation or emulsification due to the mutual solubility of the aqueous phase and RTIL. The migration of RTIL and the domination of solute and water transport through these microenvironments due to the migration of the micelle to the aqueous phase results in insufficient selective migration through the membrane.

RTIL is polymerized in an extreme way to produce stable RTIL-based membranes. However, since the solute transfer in these poly (RTIL) is no longer in the liquid phase, the resolution benefit of SILM is substantially lost.

In the present invention, to solve the problem of insufficient butanol flow rate in the conventional support liquid film.

In addition, the present invention is to solve the problem that the LME is moved to the adjacent phase and dissolved.

In addition, the present invention is to improve the butanol pervaporation recovery performance.

In order to solve the above problems, the present invention provides a support liquid membrane wherein the RTIL blend is a phosphonium / ammonium ionic mixed liquid or a mixed liquid of phosphonium / oleyl alcohol.

In addition, the present invention provides a support liquid membrane as described above used for the recovery of butanol pervaporation.

The present invention also provides a method for recovering an organic permeation evaporation method comprising using a organic-water solution as a feed solution and mounting a support liquid membrane including a room temperature ionic liquid blend to a permeation cell, wherein the RTIL blend is phosphonium. / Ammonium ionic mixed liquid or phosphonium / oleyl alcohol.

The present invention also provides a method in which the organic material is butanol.

The extraction solvent loss can be minimized by including the phosphonium / ammonium ionic mixed liquid of the present invention in the support liquid membrane. In addition, loss of extraction solvent can be minimized by including a mixed liquid of phosphonium / oleyl alcohol in the support liquid membrane. In addition, butanol pervaporation performance is improved.

Figure 1 schematically shows a method for producing SILM by blend LME.
Figure 2 schematically shows the pervaporation process.
FIG. 3 shows butanol distribution by a mixture of water-saturated miscibility extractant (EX) organic phases, where ○: EX1 = OA, EX2 = [Ph3t] [NTF], ■: EX1 = [Ph3t ] [DCN], EX2 = [Ph3t] [NTF].
4 shows the Kp of [Ph3t] [DCN] for the constituents of the simulated ABE fermentation broth, and also shows the deviation of the% formation of butyric acid [HB] and its base pair [B-] (pKa of butyric acid is 4.82) .
5A-5D show the pervaporation performance of pure RTIL-based SILM at 1.5% (FIGS. 5A, 5C) and 2.5% (5B, 5D) butanol feed concentrations.
FIG. 6 shows butanol permeation evaporation of pure RTIL-based SILMs ([Ph3t] [NTF], [OMA] [NTF] and [Ph3t] [DCN]) according to the present invention and the conventional literature [Izak et al., 2008A &B; 2009A &B; Thongsukmak et al., 2007; Matsumura et al., 1992, Qureshi and Blaschek, 1999] is a graph comparing butanol pervaporation reported.
7 shows the temperature dependence of permeate flow at 1.5% (A) and 2.5% (B) butanol feed concentrations.
FIG. 8 shows the blended LME based SILM pervaporation performance at 2.5% butanol feed, 60 and 70 ° C. temperatures. Data for 100% [Ph3t] [NTF] and 100% [Ph3t] [DCN] are also provided for comparison.
9A and 9B show normalized (in 8 hours PV) short term stability data for pure RTIL based SILM (a) and blended RTIL based SILM (b). The line in FIG. 9B is intended to better reveal the change in LIM loss, and is not intended to mean a linear function relationship.

According to the present invention, there is provided a support liquid membrane comprising a phosphonium / ammonium ionic mixed liquid system or a mixed liquid system of phosphonium / oleyl alcohol, which can be used for pervaporation recovery of butanol, and a method for recovering butanol pervaporation thereby. do. Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.

RTIL Of OA In blends  by SILM Manufacture

LME should have optimal properties that are important for high resolution. Specifically, the Kp should be high, but at the same time the LME must have a very low affinity for water (good solute extraction rate) and the solute must not have excessive viscosity in order to have a high diffusion rate through SILM.

Blending is a simple but very effective way to fine tune these features in the LME. In order for LME components to be effectively blended, they must be associated with each other. This is tested by conducting a simple miscibility test (vigorous mixing of the TRTI or organic solvent dilution followed by centrifugation to demonstrate that no phase separation occurs after a long period of standing of the blended mixture).

The vacuum chamber (chamber) is then simply soaked into the circular pores of a hydrophobic microporous membrane support such as Celgard 2400® or other associable polymer support matrix (eg hydrophobic Solupor® membrane). Degassing to remove the contained air and allow the LME blend to fully absorb and swell into the pores of the support membrane. In addition, the LME should be evacuated during pervaporation so that it does not readily leak out of the pores. Other considerations are LME viscosity, pore size, support matrix form (for stronger capillary force between LME and support matrix) and support matrix thickness (must be as thin as possible for minimum diffusion resistance).

First, blotting a “wet” membrane between two sheets of fine filter paper and gently wiping both sides with a soft lint-free tissue to remove excess LME on the surface of the support membrane. LME-filled support membranes appear translucent or transparent in contrast to the original opaque white appearance of conventional support membranes.

By measuring the mass of the support membrane before and after the absorption and swelling of the LME, the liquid membrane capacity (formerly expressed in% of the original mass of the support) can be calculated.

The physical properties of the LME used in the SILM according to the present invention and the tests for the evaluation of the SILM performance according to the present invention are described in Tables 1 and 2 below.

Type of SILM LME full name
(full name) Abbreviation MW Density, g / cm 3 constitutional formula Trihexyl (tetradecyl) phosphonium bis (trifluoromethylsulfonyl) imide [Ph3t] [NTF] 764.0 1.070

Methyltrioctylammonium bis (trifluoromethylsulfonyl) imide [OMA] [NTF] 648.8 1.105

Trihexyl (tetradecyl) phosphonium dicyamide [Ph3t] [DCN] 549.9 0.898

Oleyl alcohol OA 268.5 0.855

Test for SILM performance evaluation exam shame Parameter to measure
* Affinity for butanol of all RTIL types, LME blends
* pH effect

(See Table 1)
* As a pure LME
As an LME blend
* Temperature = 25 ℃
PH = 3, 5, 7 and 9 for simulated fermentation broth Distribution factor measurements (Kp) for
* Butanol from butanol-water model solution
* Acetone, butanol, acetone, acetic acid, butyric acid from simulated fermentation broth Pervaporation Various butanol feed concentrations: 1.5, 2.5 wt / vol%
Variety of Temperatures: 35, 45, 60, and 70 ° C * Separation factor
* Butanol% in permeate
* Flow (butanol, water) SILM stability Short-term stability Various butanol feed concentrations: 1.5, 2.5 wt% / vol%
Variety of Temperatures: 35, 45, 60, and 70 ° C * Liquid film loss%
(Normalized for 8 hour pervaporation)

Butanol  And other broth  Distribution of ingredients

The partition coefficient (Kp) is the ratio of butanol (or specific solute) concentrations in the organic phase C _OP and the aqueous phase C _AP under equilibrium, as shown in equation (1):

The shake flask method was used for the dispensing experiment. Since it is difficult to measure C _OP directly, it is assumed that the volume of each phase does not change after equilibrium, i.e., (V _AP ) _i = (V _AP ) _eq and (V _OP ) _i = (V _OP ) _eq Approximate values were obtained through the solute balance of Equations 2 and 3 below.

In the above, C and V refer to solute concentration and phase volume respectively, and the subscripts i, eq, OP and AP refer to initial conditions, equilibrium conditions, organic and aqueous phases respectively.

Known concentrations of butanol-water solution were mixed with the water-saturated extract to the total liquid volume in a sealable vessel with a different aqueous: organic volume ratio. The mixture was thoroughly stirred and mixed, left to equilibrate for 1 day, then centrifuged to separate the phases, all under temperature controlled conditions (T = 25 ° C.). In addition, butanol distribution by liquid film extractant blend (biphasic mixture) was studied. In addition, the distribution of the constituents of the simulated fermentation broth by extractant was studied at constant organic: aqueous phase volume ratio, temperature, and component concentration. For the pH control test, the pH was adjusted by adding a 26% NH4OH solution to the simulated fermentation broth prior to the extraction step, and the properties were measured using a Thermo Orion pH meter and probe. In addition, the equilibrium concentration of the simulated broth constituents was determined by gas chromatography analysis, while the equilibrium pH was confirmed using a pH strip due to the limited volume of the equilibrated aqueous phase that could be sampled.

Pervaporation

In a pervaporation apparatus a known concentration of butanol-water solution was used as feed solution (FIG. 2). The prepared SILM was mounted in a permeation cell, the feed flow rate was set to an appropriate level to minimize concentration bias, and the dialysate was recycled to the feed tank. The feed temperature was controlled and a vacuum pump was used to provide driving force downstream of the membrane. The permeate was concentrated and collected in a cold trap using liquid nitrogen as the freezing agent. A steady state was achieved by always allowing at least 1 hour pervaporation equilibrium prior to collecting the final permeate sample. At least 2 liters of feed solution was used and there was no noticeable change in feed butanol concentration after 1.5 to 2.5 hours of actual pervaporation. This is very important as SILM has very high flow characteristics compared to dense polymer membranes.

SILM  Performance evaluation

1. Pure liquid film extractant

[Ph3t] [NTF] is one of the most reported non-imidazolium based RTILs for the main reason for its applicability in the extraction process since it is very hydrophobic and has a mild inhibitory effect against various bacteria. The obtained Kp = 1.1 is in good agreement with the known numerical value (Kp = 1.00) based on the solvation parameter model. In such ionic liquids, the biggest cause for solute distribution is the capacity for dipole interactions and the H-bond basicity / H-bond receptor.

[Ph3t] [DCN] has a much higher butanol partition coefficient than [Ph3t] [NTF]; This must be due to the anion causing the Kp difference, where [DCN]> [NTF]. This tendency is caused by a much stronger hydrogen bond strength between [DCN] and butanol than with [NTF].

Butanol Kp measurement in extractant (T = 25 ° C) Extractant Kp S.D. * [Ph3t] [NTF] 1.10 0.16 [OMA] [NTF] 1.44 0.07 [Ph3t] [DCN] 7.49 0.09 OA 3.32 0.18

Butanol Kp (1.44) for [OMA] [NTF] is slightly larger than that of [Ph3t] [NTF] (1.10). Since these anions are the same, some difference in these distribution characteristics must be due to their respective cations.

Kp measurement 3.3 of OA for butanol is preferred over the values reported in other previous studies such as 3.2, 3.6 and 3.8. Several possible mechanisms for butanol-OA affinity can be identified; Larger capacities for hydrophobic-hydrophobic and dispersion interactions between each alkyl moiety are most certain.

2. Blend Liquid Extractor

The butanol distribution by the liquid film extractant blend is highly dependent on the blend component concentration: Blend Kp increases or decreases as the volume fraction of the extractant component (as pure extractant) with higher Kp increases. It decreases with increasing volume fraction of the extractant component having Kp (FIG. 3). The non-linear functional relationship of this relationship (represented by the OA- [Ph3t] [NTF] system) is the result of various solvent-solvent and solvent-solute interactions. The [Ph3t] [NTF]-[Ph3t] [DCN] systems exhibit a first-order relationship in cosolvency, which consists of the same cation type. These results may indicate that for RTIL-RTIL blends, the similarity of the bulkier cations may be one of the larger factors of the first functional aspect of the blend solvation properties.

All of the extractants studied were known to have the capacity to co-extract acetone, ethanol, acetic acid and butyric acid from the simulated fermentation broth with butanol. Among the three non-organic acid constituents, the partition preference is in the order of butanol> acetone> ethanol. Clearly, the hydrophobicity of these compounds is an important factor for the distribution tendency. [Ph3t] [NTF] and [OMA] [NTF] are very similar to the acetone distribution at about 60-80% and very similar to ethanol at about 10% of their respective partition values for butanol.

[Ph3t] [DCN] distributes acetone and ethanol with a butanol partition value of about 10%. OA distributes acetone and ethanol at 20% and 10%, respectively, for the corresponding butanol partition values. Co-extraction of chemically similar but untargeted solutes can cause problems when applying this method.

[Ph3t] [DCN] shows very high partitioning capacity for organic acids at acidic pH levels (see FIG. 4). The high partition value of organic acids is due to the formation of organic acid-extractant complexes. [Ph3t] [DCN] is a representative tetraalkylphosphonium ionic liquid that has been found to form a hydrated complex of unseparated organic acid. Since complex formation occurs only when these acids are in unseparated form, pH adjustment has been found to be a very effective and convenient way to control the distribution of organic acids (pKa values of acetic acid and butyric acid are 4.76 and 4.82, respectively; At about pH 7, complete dissociation of these ions is expected, which corresponds to their lowest distribution.)

Pervaporation Performance Evaluation

1. Pure LME SILM

In general, the separation coefficient increases with increasing temperature but exhibits an optimal mode at 60 ° C., while the butanol flow continues to increase with increasing temperature (FIGS. 5A and 5B). The same trend is reflected in pervaporation separation index (PSI) values (FIGS. 5C and 5D).

[Ph3t] [DCN] SILM has a high separation coefficient (for both butanol feed concentrations) of about 90, butanol flow of about 165 g / m2h and higher feed concentrations (2.5 weights) at lower feed concentrations (1.5 wt%). %) Showed good performance at a butanol flow of about 320 g / m 2 h. In particular, at higher butanol feed concentrations, [Ph3t] [NTF] and [OMA] [NTF] provide nearly similar flows even though the separation coefficient of [Ph3t] [NTF] is higher than that of [OMA] [NTF]. . These results indicate that there is a higher efficiency for [Ph3t] [NTF] than [OMA] [NTF] as LME as it can provide a thicker product stream in butanol. This trend in SILM flow values can be related to the ionic liquid Kp in the sequence [Ph3t] [DCN] (7.5)> [OMA] [NTF] (1.4)> [Ph3t] [NTF] (1.1). This is because, according to the solution-diffusion model, the high affinity of RTIL to butanol (indicated by Kp) results in high permeability (and therefore flow) (FIGS. 5A-5D).

Comparison of the results with the performance of other membranes reported in the literature shows that SILM-based pervaporation is indeed very desirable as the upper limit of the membranes reported so far can easily be broken by the two ionic liquid types studied (Fig. 6).

The temperature dependence of butanol and water flow was found to follow the Arrhenius equation (FIG. 7). Butanol flow is more affected by temperature than water flow, which appears to be due to the lipophilic properties of the ionic liquid. In SILM, the temperature sensitivity of the butanol flow is [Ph3t] [DCN]> [OMA] [NTF]> as indicated by the apparent activation energy obtained (about 10.5, 14.1 and 14.2 kcal / mol respectively at 2.5% butanol feed). Follow the sequence [Ph3t] [NTF]. These results demonstrate that [Ph3t] [DCN] -based SILMs require lower energy for butanol permeation and are very efficient in butanol recovery (FIG. 7).

2. Blend LME SILM

For these SILMs, only temperatures close to optimum pervaporation performance (60 and 70 ° C.) were initially studied. As expected, the performance of the blend LME based SILM is generally in the middle of the performance of each component (as pure LME) in the blend in terms of butanol flow.

From the butanol distribution results of the RTIL-RTIL or RTIL-OA blends, the blend Kp is always the result of the first / non-first-order combination of component Kp and volume ratio, and thus a similar trend is expected for butanol permeation (FIG. 8). .

For the separation coefficient, blends containing oleyl alcohol (20% [Ph3t] [NTF] -80% OA and 50% [Ph3t] [NTF] -50% OA) showed a significant improvement. This appears to be due to the synergistic effect of their favorable hydrophobicity (very low mutual solubility with water; see Table 1) and higher capacity and lower viscosity for butanol distribution of OA.

In Tables 4 to 6, butanol performance of the conventional liquid film and the butanol performance of the support liquid film according to the present invention were compared.

From the above, it can be seen that the support liquid membrane including the RTIL blend according to the present invention has a higher butanol flow rate than the conventional liquid membrane, and has the same or higher separation coefficient and the LM loss rate is minimized, which can be advantageously used for recovery of butanol pervaporation. have.

Blend LME system SILM Stability

The actual pervaporation time ranged from just 1.5 to 2 hours, but was normalized to 8 hour operation to better compare LM losses with other prior art. Initial stability data for pure RTIL-based SILMs showed insufficient performance: 6-16 wt% LME loss for 1.5% butanol feed and 11-54 wt% LME loss for 2.5% butanol feed at 60-70 ° C. Reported (FIG. 9A). Resistance to liquid film loss was found to be greatly influenced by both feed concentration and operating temperature, following the order [Ph3t] [NTF]> [OMA] [NTF]> [Ph3t] [DCN]. High alcohol concentrations in the hot and aqueous phases increase the RTIL-water intersolubility and decrease the RTIL surface tension, which increases the formation of RTIL emulsion droplets that can easily separate from the pore-impregnated RTIL phases and lead to SILM instability Let's go.

The short term stability of the blend was found to be very similar to the most stable RTIL used in the blend, [Ph3t] [NTF]. These are in the range of 10 to 14% LM loss for 8 hour run normalization.

conclusion

1. Compared to the performance of dense polymer membranes, very high values of selectivity and flow were obtained using SILM made by phosphonium and ammonium-based RTILs. The general trend is that flow and selectivity performance increases with increasing evaporation temperature, but temperature limits are shown for the separation coefficient.

[Ph3t] [DCN] -based SILMs exhibited the highest performance at a separation factor of about 65 at lower temperatures (35 and 45 ° C), with a first-order relationship up to about 90 at higher temperatures at 1.5% butanol feed. Increased to.

The separation coefficient in the 2.5% butanol feed also increased with increasing temperature, but the optimum value (about 90) was obtained at 60 ° C. and then decreased to about 70 at higher temperature (70 ° C.). Both butanol flow and PSI continued to increase with increasing temperature. For butanol flow, maximum values of about 165 and 320 g / m 2 h were obtained at 1.5% and 2.5% butanol feed concentrations, respectively. PSI values of 4,000 to 26,000 (1.5% butanol feed) and 5,000 to 36,000 (2.5% butanol feed) were obtained for the considered temperature range (35 to 70 ° C.).

The separation coefficient of [Ph3t] [NTF] is higher than that of [OMA] [NTF], especially in the thicker feed solution, while [Ph3t] [NTF] and [OMA] [NTF] show nearly similar values for butanol flow. Indicates. This trend is also seen with higher PSI values for [Ph3t] [NTF]. This result indicates that [Ph3t] [NTF] has a higher efficiency than [OMA] [NTF] as LME as [Ph3t] [NTF] can provide a thicker product stream in butanol.

Permeate flow is directly related to the butanol distribution capacity (Kp) of the used RTIL in the order [Ph3t] [DCN] (7.5)> [Ph3t] [NTF] (1.1) ≒ [OMA] [NTF] (1.4) Indicates.

2. For SILMs made by phosphonium containing RTILs that form complexes with organic acids, pH control of the feed solution can be very effective to minimize the migration of organic acids through the SILM.

3. The performance of blended LME based SILMs is generally in the middle of the performance of each component of the blend (as pure LME) in terms of butanol flow. Blends containing oleyl alcohol (20% [Ph3t] [NTF]-80% OA and 50% [Ph3t] [NTF]-50% OA) showed a significant increase in the separation coefficient, especially at 70 ° C. % (Based on pure [Ph3t] [NTF] SILM). This appears to be due to their favorable hydrophobicity (very low mutual solubility with water), higher capacity for butanol distribution of OA and lower synergistic effects.

The use of RTIL-RTIL or RTIL-oleyl alcohol dilution blends significantly increased the SILM stability and proved to not significantly reduce pervaporation performance. For the most unstable RTIL ([Ph3t] [DCN]), blending it with [Ph3t] [NTF] from 50 to 80% reduces LM loss from 54% to 11 to 15%, while reducing butanol flow by about 41%. Only decrease (average). The resulting butanol flow (170-200 g / m 2 h) of the blend is similar to that generally obtained by polymers and mixed-matrix membranes.

Claims (4)

In a Supported Liquid Membrane comprising a Room Temperature Ionic Liquid (RTIL) blend,
And the RTIL blend is a phosphonium / ammonium ionic mixed liquid or a phosphonium / oleyl alcohol mixed liquid.
The method according to claim 1,
A support liquid membrane used for butanol pervaporation recovery.
In the organic permeation evaporation recovery method comprising using an organic-water solution as a feed solution, and mounting a support liquid membrane comprising a room temperature ionic liquid blend to the permeation cell,
Said RTIL blend is a phosphonium / ammonium ionic mixed liquid or a phosphonium / oleyl alcohol mixed liquid.
The method according to claim 3,
The organic material is butanol.

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