CN114989019A - Acidic ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration - Google Patents

Abstract

The invention relates to the technical field of acid liquid recovery and regeneration, and relates to an acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration. The steps include: mixing a lignocellulose raw material and an acid ionic liquid to be treated to perform a hydrothermal reaction; The reaction product is washed with ethanol, and then concentrated to obtain a concentrated solution; water is added to the concentrated solution to precipitate lignin from the concentrated solution to obtain a supernatant; the macromolecular impurities in the supernatant are removed by ultrafiltration, and electrodialysis The ultrafiltration filtrate is treated, then the solution in the electrodialysis mixing chamber is extracted with ether to obtain the organic compound part, and the water in the electrodialysis acid chamber solution is removed to obtain the inorganic acid part; the organic compound part and the inorganic acid part are mixed to obtain a regenerated acidic ionic liquid; The present invention recovers different ionic components by partition for the acidic ionic liquid with complex composition, thereby improving the recovery rate and processing speed of the ionic liquid.

Description

A kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration

technical field

The invention relates to the technical field of acid liquid recovery and regeneration, and relates to a method for recovering acid ionic liquid based on bipolar membrane electrodialysis-ultrafiltration, in particular to the recovery method of acid ionic liquid used as solvent and catalyst in biomass pretreatment and conversion process. Technology for recycling and regeneration.

Background technique

Outstanding features and excellent solvent properties make acidic ionic liquids effective solvents and catalysts for biomass high-value processes such as biomass processing and conversion. Cost issues and lack of effective recovery methods are the main factors restricting the large-scale use of acidic ionic liquids for biomass processing.

Acidic ionic liquids such as triethylammonium bisulfate ([TEA][HSO ₄ ]), 1-butyl-3-methylimidazole bisulfate ([Bmim][HSO ₄ ]), etc., will ionize in solution Organic cations, sulfate ions and hydrogen ions are produced, and it is difficult to directly recover and regenerate all components after biomass processing.

Ultrafiltration technology is widely used in industrial wastewater purification, pharmaceutical industry purification, industrial water treatment and other processes. Ultrafiltration technology is to push different substances in the solution through the ultrafiltration membrane by the pressure difference. Due to the difference in the interception ability of the ultrafiltration membrane to substances of different sizes, the interception of substances in a specific molecular weight range in the solution is realized.

Bipolar membrane electrodialysis is widely used in environmental, chemical, biological and other fields. The bipolar membrane electrodialyzer membrane stack consists of bipolar membranes and anion and cation membranes that pass through a certain order. When a voltage is applied on both sides of the membrane stack, the bipolar membrane can dissociate water, and hydrogen ions and hydroxide ions are obtained on both sides of the membrane, respectively. At the same time, under the selective migration of ions by the electric field and the ion exchange membrane, the anions and cations in the feed liquid of the electrodialyser can be combined with the hydrogen ions and hydroxide ions formed by the dissociation of water. This provides the possibility for the recovery of different ions in the salt solution, the conversion of salts, and the synthesis of acids and bases.

SUMMARY OF THE INVENTION

The invention overcomes the deficiencies of the prior art, and proposes an acidic ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration.

In order to achieve the above objects, the present invention is achieved through the following technical solutions.

A method for recovering acidic ionic liquids based on bipolar membrane electrodialysis-ultrafiltration, comprising the following steps:

1) The lignocellulose raw material and the acidic ionic liquid to be treated are mixed for hydrothermal reaction.

2) Wash the obtained reaction product with ethanol, and then concentrate to obtain a concentrated solution.

3) Water is added to the concentrate to precipitate lignin from the concentrate to obtain a supernatant.

4) The macromolecular impurities in the supernatant are removed by ultrafiltration to obtain an ultrafiltration filtrate.

5) The ultrafiltration filtrate is treated by electrodialysis, then the solution in the electrodialysis mixing chamber is extracted with ether to obtain the organic compound part, and the water in the electrodialysis acid chamber solution is removed to obtain the inorganic acid part.

6) The organic compound part and the inorganic acid part are mixed to obtain a regenerated acidic ionic liquid.

Preferably, in step 1), distilled water is added to the acidic ionic liquid, and the mass fraction of the acidic ionic liquid in the acidic ionic liquid-distilled water mixture is 45%-95%; the mass ratio of the acidic ionic liquid-distilled water mixture to the lignocellulose raw material is: 1-20:1.

Preferably, the temperature of the hydrothermal reaction is 100-170° C., and the reaction time is 10-50 minutes.

Preferably, the ultrafiltration treatment conditions are: molecular weight cutoff of 1K Da-0.65K Da, temperature of 10-50°C, transmembrane pressure of 100-700 kPa, and cross-flow flow rate of 0.1-5.0 ms ^-1 .

Preferably, the ultrafiltration filtrate is diluted with distilled water to reduce the organic ion concentration in the ultrafiltration filtrate to 0.01-2.0 mol/L.

Preferably, the electrodialysis treatment adopts a three-chamber bipolar membrane electrodialysis device, the electrode chamber feed liquid is Na ₂ SO ₄ solution with a concentration of 1.0-10.0 wt.%; the mixing chamber feed liquid is ultrafiltration filtrate, and the acid chamber feed The liquid is a dilute sulfuric acid solution with the same concentration as the feed liquid in the mixing chamber.

More preferably, the initial volume of the solution in each chamber of the three-chamber bipolar membrane electrodialysis device is 0.5-3.0 L, the applied current density is 1-100 mA/cm ² , and the solution flow rate in each zone is 1.0-30.0 L/h.

Further, the ether phase obtained after the ether extraction adopts rotary evaporation to separate the ether and the organic compound part; the electrodialysis acid chamber solution adopts rotary evaporation to remove the water in the acid chamber solution to obtain the inorganic acid.

Further, in the mixing described in step 6), the inorganic acid part and the organic compound part are mixed and reacted at a molar ratio of 1:0.5-1:2.

Further, the acidic ionic liquid to be treated is triethylammonium hydrogen sulfate ionic liquid.

Further, the reaction temperature of the hydrothermal reaction in step 1) is 100-170° C., and the reaction time is 10-50 minutes.

The beneficial effects that the present invention produces relative to the prior art are:

1) The present invention adopts the treatment method based on membrane separation technology to recover the different ionic components of the acidic ionic liquid with complex composition, which improves the recovery rate and processing speed of the ionic liquid. At the same time, the recycling cost of the ionic liquid is reduced.

2) The recovery and regeneration process of complex acidic ionic liquids is converted into partitioned recovery of different ionic components, such as triethylammonium hydrogen sulfate in acidic ionic liquids-[TEA][HSO ₄ ] triethylammonium and Sulfate is converted into triethylamine and sulfuric acid for recovery. It provides the basis for the regeneration process of ionic liquids.

3) This method requires simple equipment, simple process, short processing time, mild conditions and no additional environmental hazards, which is of reference and guidance for expanding the practical application of these complex acidic ionic liquids and other electrolytes with similar compositions sex.

Description of drawings

FIG. 1 is a schematic diagram of the bipolar membrane electrodialysis device used in Examples 1, 2, and 3 of the present invention.

FIG. 2 is a Fourier transform infrared (KBr tablet method) test chart of the regenerated acidic ionic liquid samples obtained in Examples 1, 2, and 3 of the present invention.

FIG. 3 is a test chart of ¹ H-NMR nuclear magnetic resonance (DMSO-d6 is the solvent) of the regenerated acidic ionic liquid samples obtained in Examples 1, 2, and 3 of the present invention.

Figure 4 shows the model and parameters of the ion exchange membrane used in the bipolar membrane electrodialysis used in the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. The technical solutions of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings, but the protection scope is not limited by this.

Embodiment 1: a kind of acidic ionic liquid recovery and regeneration method based on bipolar membrane electrodialysis-ultrafiltration, the concrete steps are as follows:

1) Mix the acidic ionic liquid with distilled water in proportion, and the mass fraction of the acidic ionic liquid in the mixed solvent is: 80%. After the lignocellulose raw material is pulverized and dried, the mixed solvent and the lignocellulose pulverized particles are mixed in a ratio of 5g/1g. After mixing uniformly, the reaction was carried out at 150° C. for 30 minutes in a reactor.

2) After the reaction, the reaction product was washed with hot ethanol and filtered with a Buchner funnel, and the filtrate was evaporated to remove ethanol to obtain a concentrated solution. The concentrated solution was added with deionized water and left to stand overnight, and then the precipitated lignin was separated by centrifugation. The supernatant was filtered through an ultrafiltration membrane with a molecular weight cut-off of 0.65K Da, and the ultrafiltration membrane used for ultrafiltration treatment pretreated lignin by centrifugal The supernatant was obtained after separation, and the ultrafiltration treatment conditions were: temperature 25°C, transmembrane pressure 400 kPa, cross-flow flow rate: 2.4 ms ^-1 .

3) The filtrate obtained by ultrafiltration treatment is diluted with distilled water, and the treatment goal is to reduce the concentration of triethylammonium ions in the solution to 0.1 mol/L.

4) The electrodialysis treatment adopts a BP-A-BP three-chamber bipolar membrane electrodialysis device, and the electrode chamber feed liquid is Na ₂ SO ₄ solution with a concentration of 5.0 wt.%. The feed liquid of the mixing chamber is the ultrafiltration filtrate obtained after the dilution treatment, and the concentration is calculated by the molar concentration of triethylammonium ions. The acid chamber feed liquid is a dilute sulfuric acid solution with the same concentration as the mixing chamber feed liquid.

5) The initial volume of the solution in each chamber of the electrodialyzer is 1.0 L, the applied current density of the electrodialyzer is 25 mA/cm ² , and the flow rate of the solution in each zone is 15.0 L/h.

6) After the electrodialysis treatment, the solution in the mixing chamber was collected and extracted three times with 300 ml of ether. After the extraction, the ether phases were combined, and the ether and triethylamine were separated by rotary evaporation. At the same time, the acid chamber solution of the electrodialyzer is collected, and the water in the acid chamber solution is removed by rotary evaporation to obtain concentrated sulfuric acid.

7) The triethylamine is slowly dripped with concentrated sulfuric acid, and the obtained concentrated sulfuric acid triethylamine is reacted in a flask containing a certain amount of deionized water in an ice-water bath at a molar ratio of 1:1, and the dropwise addition is completed and incubated for 3 hours. A light yellow liquid was obtained, and the water was removed on a rotary evaporator to obtain a light yellow acidic ionic liquid triethylammonium hydrogen sulfate-[TEA][HSO ₄ ].

In this example, the recovery rate of the acidic ionic liquid [TEA][HSO ₄ ] can reach 93.9%, the current efficiency of the electrodialyzer in the recovery process is 87.4%, and the recovery energy consumption is 12.4 kwh/kg.

Embodiment 2: a kind of acidic ionic liquid recovery and regeneration method based on bipolar membrane electrodialysis-ultrafiltration, the concrete steps are as follows:

1) Mix the acidic ionic liquid with distilled water in proportion, and the mass fraction of the acidic ionic liquid in the mixed solvent is: 80%. After the lignocellulose raw material is pulverized and dried, the mixed solvent and the lignocellulose pulverized particles are mixed in a ratio of 5g/1g. After mixing uniformly, the reaction was carried out at 150° C. for 30 minutes in a reactor.

2) After the reaction, the reaction product was washed with ethanol and filtered with a Buchner funnel, and the filtrate was evaporated to remove ethanol to obtain a concentrated solution. The concentrated solution was added with deionized water and left to stand overnight, and then the precipitated lignin was separated by centrifugation. The supernatant was filtered through an ultrafiltration membrane with a molecular weight cut-off of 0.65K Da, and the ultrafiltration membrane used for ultrafiltration treatment pretreated lignin by centrifugal The supernatant was obtained after separation, and the ultrafiltration treatment conditions were: temperature 25°C, transmembrane pressure 400 kPa, cross-flow flow rate: 2.4 ms ^-1 .

3) The filtrate obtained by ultrafiltration treatment is diluted with distilled water, and the treatment target is to reduce the concentration of triethylammonium ion in the solution to 0.2 mol/L.

4) The electrodialysis treatment adopts a BP-A-BP three-chamber bipolar membrane electrodialysis device, and the electrode chamber feed liquid is Na ₂ SO ₄ solution with a concentration of 5.0 wt.%. The feed liquid of the mixing chamber is the ultrafiltration filtrate obtained after the dilution treatment, and the concentration is calculated by the molar concentration of triethylammonium ions. The acid chamber feed liquid is a dilute sulfuric acid solution with the same concentration as the mixing chamber feed liquid.

5) The initial volume of the solution in each chamber of the electrodialyzer is 1.0 L, the applied current density of the electrodialyzer is 25 mA/cm ² , and the flow rate of the solution in each zone is 15.0 L/h.

6) After the electrodialysis treatment, the solution in the mixing chamber was collected and extracted three times with 300 ml of ether. After the extraction, the ether phases were combined, and the ether and triethylamine were separated by rotary evaporation. At the same time, the acid chamber solution of the electrodialyzer is collected, and the water in the acid chamber solution is removed by rotary evaporation to obtain concentrated sulfuric acid.

7) The method of slowly dripping triethylamine with concentrated sulfuric acid, react the obtained concentrated sulfuric acid and triethylamine in a flask containing a certain amount of deionized water in an ice-water bath at a molar ratio of 1:1, and keep the temperature for 3 hours after the dripping is completed. A light yellow liquid was obtained, and the water was removed on a rotary evaporator to obtain a light yellow acidic ionic liquid triethylammonium hydrogen sulfate-[TEA][HSO ₄ ].

In this example, the recovery rate of the acidic ionic liquid [TEA][HSO ₄ ] can reach 95.4%, the current efficiency of the electrodialyzer in the recovery process is 89.4%, and the recovery energy consumption is 26.8 kwh/kg.

Embodiment 3: a kind of acidic ionic liquid recovery and regeneration method based on bipolar membrane electrodialysis-ultrafiltration, the concrete steps are as follows:

1) Mix the acidic ionic liquid with distilled water in proportion, and the mass fraction of the acidic ionic liquid in the mixed solvent is: 80%. After the lignocellulose raw material is pulverized and dried, the mixed solvent is mixed with the lignocellulose pulverized particles at a ratio of 5g/1g. After mixing uniformly, the reaction was carried out at 150° C. for 30 minutes in a reactor.

2) After the reaction, the reaction product was washed with ethanol and filtered with a Buchner funnel, and the filtrate was evaporated to remove ethanol to obtain a concentrated solution. The concentrated solution was added with deionized water and left to stand overnight, and then the precipitated lignin was separated by centrifugation. The supernatant was filtered through an ultrafiltration membrane with a molecular weight cut-off of 0.65K Da, and the ultrafiltration membrane used for ultrafiltration treatment pretreated lignin by centrifugal The supernatant was obtained after separation, and the ultrafiltration treatment conditions were: temperature 25°C, transmembrane pressure 400 kPa, cross-flow flow rate: 2.4 ms ^-1 .

3) The filtrate obtained by ultrafiltration treatment is diluted with distilled water, and the treatment target is to reduce the concentration of triethylammonium ion in the solution to 0.3 mol/L.

4) The electrodialysis treatment adopts a BP-A-BP three-chamber bipolar membrane electrodialysis device, and the electrode chamber feed liquid is Na ₂ SO ₄ solution with a concentration of 5.0 wt.%. The feed liquid of the mixing chamber is the ultrafiltration filtrate obtained after the dilution treatment, and the concentration is calculated by the molar concentration of triethylammonium ions. The acid chamber feed liquid is a dilute sulfuric acid solution with the same concentration as the mixing chamber feed liquid.

5) The initial volume of the solution in each chamber of the electrodialyzer is 1.0 L, the applied current density of the electrodialyzer is 20 mA/cm ² , and the flow rate of the solution in each zone is 15.0 L/h.

6) After the electrodialysis treatment, the solution in the mixing chamber was collected and extracted three times with 300 ml of ether. After the extraction, the ether phases were combined, and the ether and triethylamine were separated by rotary evaporation. At the same time, the acid chamber solution of the electrodialyzer is collected, and the water in the acid chamber solution is removed by rotary evaporation to obtain concentrated sulfuric acid.

7) Using the method of slowly dripping triethylamine with concentrated sulfuric acid, the obtained concentrated sulfuric acid and triethylamine were reacted in a flask containing a certain amount of deionized water in an ice-water bath at a molar ratio of 1:1, and the dripping was completed and incubated for 3 hours. A light yellow liquid was obtained, and the water was removed on a rotary evaporator to obtain a light yellow acidic ionic liquid triethylammonium hydrogen sulfate-[TEA][HSO ₄ ].

In this example, the recovery rate of the acidic ionic liquid [TEA][HSO ₄ ] can reach 95.8%, the current efficiency of the electrodialyzer in the recovery process is 90.3%, and the recovery energy consumption is 43.4 kwh/kg.

It can be seen from Figure 1 that acidic ionic liquids such as [TEA][HSO ₄ ] will ionize three ions of TEA ⁺ (triethylammonium), H ⁺ and SO ₄ ^2- in solution. After biomass treatment, by-product biomass-based cation C ^X+ and biomass-based anion A ^X- , together with TEA ⁺ , SO ₄ ^2- and H ⁺ maintain the charge balance of the solution. Through the three-chamber bipolar membrane electrodialysis device shown in Figure 1, when an electric field is applied on both sides of the membrane stack, SO ₄ ^2- in the feed liquid of the mixing chamber is transferred to the acid chamber (right chamber) through the anion exchange membrane under the action of the electric field. , forming a sulfuric acid solution with H ⁺ produced in the acid chamber. At the same time, the OH ^- generated in the mixing chamber (left chamber) will neutralize H ⁺ and TEA ⁺ in the solution successively to generate water and triethylamine (TEA). The main reactions that occur in the mixing chamber are shown below. Then, triethylamine is separated by ether extraction, distillation, etc., and reacted with sulfuric acid to generate an aqueous solution of [TEA][HSO ₄ ]. Further removal of excess water yields [TEA][HSO ₄ ].

OH ^- +H ⁺ → H ₂ O (1)

OH ^- +TEA ⁺ → H ₂ O + TEA (2)

It can be seen from Figure 2 that the absorption peak positions of the IR spectra of the acid ionic liquid [TEA][HSO ₄ ] samples recovered and regenerated in Examples 1, 2 and 3 of the present invention are similar to those of the original [TEA][HSO ₄ ] samples. match. It is illustrated that the acid ionic liquid samples recovered and regenerated in Examples 1-3 have characteristic functional groups consistent with the original ionic liquid samples. It can be seen from Fig. 3 that the H NMR liquid of the acid ionic liquid [TEA][HSO ₄ ] sample recovered and regenerated in Examples 1, 2 and 3 of the present invention is the same as that of the original [TEA][HSO ₄ ] sample. The peak positions of the spectrum are consistent, which further shows that the recovery of the sample in the present invention can maintain its original chemical structure and composition, that is, the acid ionic liquid recovery and regeneration method based on bipolar membrane electrodialysis-ultrafiltration according to the present invention can achieve acidity. Efficient recovery and regeneration of ionic liquid [TEA][HSO ₄ ] samples.

The above content is a further detailed description of the present invention in combination with the specific preferred embodiments, and it cannot be considered that the specific embodiments of the present invention are limited to this. Below, some simple deductions or substitutions can also be made, all of which should be regarded as belonging to the invention and the scope of patent protection determined by the submitted claims.

Claims (10)

1. an acidic ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration, is characterized in that, comprises the following steps: 1) Mix the lignocellulose raw material and the acidic ionic liquid to be treated for hydrothermal reaction; 2) washing the obtained reaction product with ethanol, and then concentrating to obtain a concentrated solution; 3) adding water to the concentrated solution to precipitate lignin from the concentrated solution to obtain a supernatant; 4) removing macromolecular impurities in the supernatant by ultrafiltration to obtain ultrafiltration filtrate; 5) The ultrafiltration filtrate is treated by electrodialysis, then the solution in the electrodialysis mixing chamber is extracted with ether to obtain the organic compound part, and the water in the electrodialysis acid chamber solution is removed to obtain the inorganic acid part; 6) The organic compound part and the inorganic acid part are mixed to obtain a regenerated acidic ionic liquid. 2. A method for recovering acidic ionic liquid based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, wherein in step 1), distilled water is added to the acidic ionic liquid, and the acidic ionic liquid-distilled water mixture is added to the acidic ionic liquid. The mass fraction of acidic ionic liquid is 45%-95%; the mass ratio of acidic ionic liquid-distilled water mixture and lignocellulose raw material is: 1-20:1. 3. A kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, is characterized in that, the temperature of hydrothermal reaction is 100-170 ℃, and the reaction time is 10-50 minutes. 4. a kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, is characterized in that, ultrafiltration processing condition is: molecular weight cut-off is 1K Da-0.65K Da, temperature 10- 50°C, transmembrane pressure 100-700kPa, cross-flow flow rate: 0.1-5.0 ms ^-1 . 5. a kind of acidic ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, is characterized in that, ultrafiltration filtrate is diluted with distilled water, and the organic ion concentration in the ultrafiltration filtrate is reduced to 0.01-2.0mol/L. 6. a kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1 is characterized in that, electrodialysis treatment adopts three-chamber bipolar membrane electrodialysis device, and the electrode chamber feed liquid is Na _{2 SO4} solution with a concentration of 1.0-10.0 wt.%; the mixing chamber feed liquid is ultrafiltration filtrate, and the acid chamber feed liquid is a dilute sulfuric acid solution with the same concentration as the mixing chamber feed liquid. 7. a kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 6, is characterized in that, each chamber solution initial volume of three-chamber bipolar membrane electrodialysis device is 0.5-3.0 L, The applied current density is 1-100 mA/cm ² , and the solution flow rate in each zone is 1.0-30.0 L/h. 8. a kind of acid ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, is characterized in that, the ether phase that obtains after ether extraction adopts rotary evaporation to separate ether and organic compound part; Electrodialysis The acid chamber solution uses rotary evaporation to remove the water in the acid chamber solution to obtain inorganic acid. 9. a kind of acidic ionic liquid recovery method based on bipolar membrane electrodialysis-ultrafiltration according to claim 1, is characterized in that, the mixing described in step 6) is by inorganic acid part and organic compound part by 1: 0.5-1:2 molar ratio for mixing reaction. 10 . A method for recovering acidic ionic liquid based on bipolar membrane electrodialysis-ultrafiltration according to claim 1 , wherein the acidic ionic liquid to be treated is triethylammonium hydrogen sulfate ionic liquid. 11 .

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