CN102516092A - Dicarboxylic hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity, and preparation method thereof - Google Patents

Abstract

A class of dibasic carboxylate hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity, its cation is tetraalkyl quaternary ammonium cation or N,N-dialkylimidazolium cation with asymmetric structure, and its anion is dibasic carboxylic acid Hydrogen radical anion, the ionic liquid of the present invention has lower viscosity and melting point, can really meet the requirement of industrial application. The present invention uses tetraalkylammonium chloride quaternary ammonium chloride or N,N-dialkylimidazole chloride and potassium hydrogen carboxylate with asymmetric structure as raw materials, and adopts a microwave method to synthesize the target ionic liquid in one step, and the preparation process is simple and convenient. The product has high yield and purity, no by-products, low synthesis cost, and is very suitable for industrial production. The dibasic hydrogen carboxylate salt ionic liquid with asymmetric chemical structure and weak acidity of the present invention can be used for fast and efficient absorption of _SO2 . The invention discloses its preparation method.

Description

A class of dibasic carboxylate hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity and its preparation method

technical field

The invention relates to a kind of dibasic carboxylate hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity and a preparation method thereof.

Background technique

Ionic liquid is a green solvent or reaction medium newly developed in recent years. It is composed of organic cations and organic or inorganic anions, and is a type of organic molten salt in a liquid state at room temperature or within a range from room temperature to 100 °C. Ionic liquids have many special properties such as "zero" vapor pressure, low melting point, high thermal stability, and high solubility. They are known as a new generation of "green solvents" and have great application prospects in many fields such as chemical engineering. At present, more than 2,000 kinds of ionic liquids have been discovered and reported in the literature. According to the different organic cation precursors, ionic liquids can be roughly divided into four categories: imidazolium salts, pyridinium salts, quaternary ammonium salts, and quaternary phosphonium salts. The anions of ionic liquids are mainly AlCl ₄ ^- , BF ₄ ^- , PF ₄ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , H ₂ PO ₄ ^- , HSO ₄ ^- and other acid ions, and in some cases, it can also be inorganic anions such as Cl ^- , Br ^- , I ^- , NO ₃ ^- , ClO ₄ ^- and so on. At present, there are two main methods for preparing ionic liquids: one-step method and two-step method. The one-step method uses tertiary amines and halogenated alkanes or esters or organic acids as raw materials, and directly adds or neutralizes them in alcoholic solutions or aqueous alcoholic solutions to generate target ionic liquids in one step. This method has simple process, high production efficiency, no by-product formation, and high purity of ionic liquid, but its disadvantages are also obvious, such as fewer types of ionic liquids to be synthesized. The main steps of the two-step method are as follows: the first step is to first react the tertiary amine with the halogenated alkanes to form the quaternary ammonium halide salt, and the second step is to replace the halide anion in the quaternary ammonium salt with the desired target anion, thereby obtaining the target ionic liquid. The advantage of the two-step method is that it can prepare "functionalized" ionic liquids with special properties, but the disadvantages are complex preparation process, high production cost and low yield.

At present, some functionalized ionic liquids containing carboxyl groups have been reported in the literature, and these carboxyl groups are generally grafted on the cationic structure of ionic liquids. Although the ionic liquid thus constituted is also weakly acidic, on the one hand, the properties such as the melting point and viscosity of the ionic liquid are not ideal, and on the other hand, their synthesis process is complicated, the reaction steps are many, and the separation and purification process is not easy. As a result, the production cost of the ionic liquid is also extremely high, which is not practical. H.Ohno et al. (Chem.Commun., 2007, 29, 3089-3091; GreenChem., 2007, 11 (9), 1155-1157) once used tetrabutyl quaternary phosphine or choline as cations to synthesize several weak Acidic dicarboxylic hydrogen salt ionic liquids, but these ionic liquids have a high melting point and a high viscosity, and various physical and chemical properties are not ideal, which greatly limits the application of this type of ionic liquid, which is different from this type of ionic liquid. The unreasonable design of the chemical structure of the cation is closely related. In general, weakly acidic functionalized ionic liquids with low melting point and low viscosity are still relatively scarce, and the production cost of preparing weakly acidic functionalized ionic liquids containing carboxyl groups is still high, and large-scale industrial production of ionic liquids has not yet been achieved. this bottleneck.

Contents of the invention

The purpose of the present invention is to provide a class of dibasic carboxylate hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity and its preparation method.

Technical scheme of the present invention is as follows:

A class of dibasic hydrogen carboxylate ionic liquid with asymmetric chemical structure and weak acidity, which is a quaternary ammonium dibasic hydrogen carboxylate, and its cation is a tetraalkyl quaternary ammonium cation or N, N-dioxane with an asymmetric structure The imidazolium cation, the anion is a dibasic carboxylic acid hydrogen radical anion, and the specific chemical structural formula is:

In the formula: R ₁ is selected from C ₁ ~ C ₃ straight chain hydrocarbon groups, R ₂ is selected from C ₃ ~ C ₆ straight chain hydrocarbon groups, R ₃ is selected from C ₁ ~ C ₃ straight chain or branched saturated or unsaturated saturated alkylene.

In the above-mentioned ionic liquid, the cation of the ionic liquid is preferably a cation such as trimethylbutylammonium, trimethylpropylammonium, triethylbutylammonium or tripropylhexylammonium, or N, N-methyl Cations such as propylimidazole or N,N-methylbutylimidazole.

In the above-mentioned ionic liquid, the dibasic carboxylate anion is preferably a hydrogen anion such as malonic acid, maleic acid, succinic acid or glutaric acid.

Among the above-mentioned ionic liquids, the _R2 preferably has more than two carbon atoms than _R1 , the viscosity of this type of ionic liquid is 20-1000cP, the preferred ionic liquid viscosity is 56-714cP, and its physical and chemical properties are very different. Great improvement, can really meet the requirements of industrial applications.

A method for preparing the described dibasic carboxylate hydrogen salt ionic liquid with asymmetric chemical structure and weak acidity is: with tetraalkyl ammonium chloride quaternary ammonium chloride or N, N-dialkyl chloride with asymmetric structure Imidazole and dibasic potassium hydrogen carboxylate are used as raw materials, and the two are added into a small amount of butanol at the same time in equimolar amounts. The amount of butanol is 0.5 to 3 times the mass of the theoretical ionic liquid. React for 30 seconds under a microwave of 200 to 400W and then take it out. Stir well, then put it into the microwave to react for 15 seconds, then take it out and stir well, then finish the reaction after performing the last step 3-5 times continuously, filter the solution while it is hot, and distill the filtrate under reduced pressure to remove and recover most of the solvent butanol, and the remaining The liquid sample was vacuum-dried for 48 hours to constant weight to obtain a dibasic hydrogen carboxylate ionic liquid with asymmetric chemical structure and weak acidity. The reaction of the process is:

In the present invention, the cation structure of the ionic liquid is asymmetrically designed so that it has a large free space volume, partially overcomes the hydrogen bond between the anions, so that the obtained ionic liquid has a lower melting point and viscosity, making the ionic liquid have a lower melting point and viscosity. Weakly acidic ionic liquids are more practical. In addition, the present invention uses tetraalkylammonium chloride with asymmetric structure or N, N-dialkylimidazole chloride and potassium hydrogen carboxylate as raw materials, and uses a small amount of butanol as a solvent under microwave conditions. One-step synthesis of target ionic liquids. The synthesis method is simple, the product yield and purity are high, there is no by-product, the synthesis cycle is short, the raw material is cheap and easy to obtain, and the cost is low, which is very suitable for industrial production.

The dibasic hydrogen carboxylate salt ionic liquid with asymmetric chemical structure and weak acidity of the present invention can be used for fast and efficient absorption of _SO2 . At 40°C and a _SO2 partial pressure of 100kPa, the _SO2 absorption of the ionic liquid of the present invention can reach more than _1.5molSO2 /mol salt, even at 40°C and a _SO2 partial pressure of 0.4kPa, the absorption amount is also It can reach 0.1-0.5molSO ₂ /mol salt, and because of its low viscosity, it can reach absorption equilibrium in less than 10 minutes, while many functionalized ionic liquids often need several hours to reach absorption equilibrium.

Detailed ways

Further illustrate the present invention below by embodiment

Embodiment 1: trimethylbutyl quaternary ammonium hydrogen malonate ionic liquid

Add 15.12g (0.1mol) of trimethylbutylammonium chloride, 14.22g (0.1mol) of potassium hydrogen malonate and 15g of solvent butanol into a 250mL reaction flask respectively, react for 30 seconds under 240W microwave, take out and stir Mix well, then put it into the microwave to react for 15 seconds, take it out and stir well, repeat the last step 3 times. After the reaction was completed, filter while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and vacuum-dried at 70°C for 48 hours to obtain the product trimethylbutyl quaternary ammonium hydrogen malonate ionic liquid, and the product yield was 95% %, chloride ion concentration 620ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 54.77%, H: 9.65%, N: 6.38%, measured value C: 54.75%, H: 9.61%, N: 6.41%. ¹ H NMR (DCCl ₃ , 300MHz) δ=2.27(s, 9H, CH3), 0.96(t, 3H, CH3), 1.33-1.39(m, 4H, CH2), 2.36(m, 2H, CH2 ), 3.17 (s, 2H, CH2). Its melting point was not determined by DSC scan and its viscosity was 56 cP at 40°C.

Embodiment 2: trimethylbutyl quaternary ammonium hydrogen succinate ionic liquid

Add 15.12g (0.1mol) of trimethylbutylammonium chloride, 15.62g (0.1mol) of potassium hydrogen succinate, and 30g of butanol as a solvent into a 250mL reaction flask, react under a 240W microwave for 30 seconds, take out and stir Mix well, then put it into the microwave for 15 seconds, take it out and stir well, repeat the last step 5 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product trimethylbutyl quaternary ammonium hydrogen succinate ionic liquid, and the product yield was 96 %, chloride ion concentration 716ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 56.63%, H: 9.94%, N: 6.00%, measured value C: 56.65%, H: 9.91%, N: 6.01%. ¹ H NMR (DCCl ₃ , 300MHz) δ=2.27(s, 9H, CH3), 0.96(t, 3H, CH3), 1.33-1.39(m, 4H, CH2), 2.36(m, 2H, CH2 ), 2.50 (s, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 527 cP at 40°C.

Embodiment 3: Trimethylbutyl quaternary ammonium hydrogen maleate ionic liquid

In 250mL reaction bottle, add trimethylbutyl ammonium chloride 15.12g (0.1mol) respectively, potassium hydrogen maleate or potassium hydrogen fumarate 15.42g (0.1mol) and solvent butanol 20g, in Under the microwave of 240W, react for 30 seconds, take it out and stir well, then put it into the microwave and react for 15 seconds, take it out and stir well, repeat the last step 4 times. After the reaction is completed, filter while it is hot, and rotate the filtrate to remove and recover most of the solvent butanol, and dry it in vacuum at 70°C for 48 hours to obtain the product trimethylbutyl quaternary ammonium hydrogen maleate ionic liquid or trimethylbutanol The base quaternary ammonium hydrogen fumarate ionic liquid has a product yield of 96% and a chloride ion concentration of 680ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 57.12%, H: 9.15%, N: 6.06%, measured value C: 57.11%, H: 9.14%, N: 6.05%. ¹ H NMR (DCCl ₃ , 300MHz) δ=2.27(s, 9H, CH3), 0.96(t, 3H, CH3), 1.33-1.39(m, 4H, CH2), 2.36(m, 2H, CH2 ), 6.36 (s, 2H, CH). Its melting point was not determined by DSC scan, and its viscosity was 87 cP at 40°C.

Embodiment 4: trimethylbutyl quaternary ammonium hydrogen glutarate ionic liquid

Add 15.12g (0.1mol) of trimethylbutylammonium chloride, 17.02g (0.1mol) of potassium hydrogen glutarate and 15g of solvent butanol to a 250mL reaction flask respectively, react for 30 seconds under a 240W microwave, take out and stir Mix well, then put it into the microwave to react for 15 seconds, take it out and stir well, repeat the last step 4 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product trimethylbutyl quaternary ammonium hydrogen glutarate ionic liquid, and the product yield was 98% %, chloride ion concentration 690ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 58.27%, H: 10.19%, N: 5.66%, measured value C: 58.27%, H: 10.17%, N: 5.69%. ¹ H NMR (DCCl ₃ , 300MHz) δ=2.27(s, 9H, CH3), 0.96(t, 3H, CH3), 1.33-1.39(m, 4H, CH2), 2.36(m, 2H, CH2 ), 1.89 (m, 2H, CH2), 2.36 (t, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 606 cP at 40°C.

Embodiment 5: Trimethylpropyl quaternary ammonium hydrogen succinate ionic liquid

Add 13.72g (0.1mol) of trimethylpropylammonium chloride, 15.62g (0.1mol) of potassium hydrogen succinate and 30g of butanol as a solvent to a 250mL reaction flask, and react under a 240W microwave for 30 seconds, take out and stir Mix well, then put it into the microwave for 15 seconds, take it out and stir well, repeat the last step 5 times. After the reaction was completed, filter while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and vacuum-dried at 70°C for 48 hours to obtain the product trimethylbutyl quaternary ammonium hydrogen succinate ionic liquid, the product yield was 95% %, chloride ion concentration 612ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 54.77%, H: 9.64%, N: 6.39%, measured value C: 54.75%, H: 9.61%, N: 6.39%. ¹ H NMR (DCCl ₃ , 300MHz) δ=2.27(s, 9H, CH3), 0.90(t, 3H, CH3), 1.44(m, 2H, CH2), 2.36(t, 2H, CH2), 2.71 (s, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 408 cP at 40°C.

Embodiment 6: triethylbutyl quaternary ammonium hydrogen succinate ionic liquid

Add 19.38g (0.1mol) of triethylbutylammonium chloride, 15.62g (0.1mol) of potassium hydrogen succinate, and 30g of butanol as a solvent into a 250mL reaction flask, and react under a 240W microwave for 30 seconds, take out and stir Mix well, then put it into the microwave for 15 seconds, take it out and stir well, repeat the last step 5 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product triethylbutyl quaternary ammonium hydrogen succinate ionic liquid, and the product yield was 96 %, chloride ion concentration 530ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 61.06%, H: 10.61%, N: 5.08%, measured value C: 61.03%, H: 10.64%, N: 5.09%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.92(t, 3H, CH3), 1.15(t, 9H, CH3), 1.24-1.38(m, 2H, CH2), 1.49-1.62(m, 2H , CH2), 2.23 (s, 4H, CH2), 3.12 (t, 2H, CH2), 3.20-3.28 (q, 6H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 481 cP at 40°C.

Embodiment 7: triethylbutyl quaternary ammonium hydrogen maleate ionic liquid

Add triethylbutylammonium chloride 19.38g (0.1mol) respectively in 250mL reaction bottle, potassium hydrogen maleate or potassium hydrogen fumarate 15.42g (0.1mol) and solvent butanol 20g, in Under the microwave of 240W, react for 30 seconds, take it out and stir well, then put it into the microwave and react for 15 seconds, take it out and stir well, repeat the last step 4 times. After the reaction is completed, filter while it is hot, and the filtrate is rotary evaporated to remove and recover most of the solvent butanol, and vacuum-dried at 70°C for 48 hours to obtain the product triethylbutyl quaternary ammonium hydrogen maleate ionic liquid or triethylbutyl The base quaternary ammonium hydrogen fumarate ionic liquid has a product yield of 97% and a chloride ion concentration of 725ppm. Its chemical structural formula is:

or

Characterization results: elemental analysis theoretical value C: 61.51%, H: 9.95%, N: 5.12%, measured value C: 61.49%, H: 9.93%, N: 5.16%. ¹ HNMR (DCCl ₃ , 300MHz) δ=0.91(t, 3H, CH3), 1.15(t, 9H, CH3), 1.22-1.37(m, 2H, CH2), 1.48-1.62(m, 2H, CH2), 3.12 (t, 2H, CH2), 3.17-3.31 (q, 6H, CH2), 6.06 (s, 2H, CH). Its melting point was not determined by DSC scan, and its viscosity was 82 cP at 40°C.

Embodiment 8: triethylbutyl quaternary ammonium hydrogen glutarate ionic liquid

Add 19.38g (0.1mol) of triethylbutylammonium chloride, 17.02g (0.1mol) of potassium hydrogen glutarate and 15g of solvent butanol to a 250mL reaction flask respectively, react for 30 seconds under a 240W microwave, take out and stir Mix well, then put it into the microwave to react for 15 seconds, take it out and stir well, repeat the last step 4 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product triethylbutyl quaternary ammonium hydrogen glutarate ionic liquid, and the product yield was 98% %, chloride ion concentration 570ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 62.25%, H: 10.80%, N: 4.84%, measured value C: 62.23%, H: 10.82%, N: 4.82%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.92(t, 3H, CH3), 1.16(t, 9H, CH3), 1.22-1.36(m, 2H, CH2), 1.47-1.62(m, 2H , CH2), 1.88-1.97 (m, 2H, CH2), 2.36-2.39 (t, 4H, CH2), 3.11 (t, 2H, CH2), 3.17-3.32 (q, CH2). Its melting point was not determined by DSC scan, and its viscosity was 714 cP at 40°C.

Embodiment 9: tripropylhexyl quaternary ammonium hydrogen succinate ionic liquid

Add 26.39g (0.1mol) of tripropylhexylammonium chloride, 15.62g (0.1mol) of potassium hydrogen succinate and 70g of butanol as a solvent into a 250mL reaction flask, react under a 240W microwave for 30 seconds, take it out and stir well , then put it into the microwave for 15 seconds to react, take it out and stir well, repeat the last step 5 times. After the reaction was completed, filter while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and vacuum-dried at 70°C for 48 hours to obtain the product tripropylhexyl quaternary ammonium hydrogen succinate ionic liquid, the product yield was 95% , Chloride ion concentration 596ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 66.04%, H: 11.38%, N: 4.05%, measured value C: 66.06%, H: 11.34%, N: 4.09%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.88(t, 3H, CH3), 0.90(t, 9H, CH3), 1.29(m, 4H, CH2), 1.31(m, 2H, CH2), 1.36 (m, 2H, CH2), 1.44 (m, 6H, CH2), 2.36 (t, 8H, CH2), 2.71 (s, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 603 cP at 40°C.

Example 10: N, N-methylpropylimidazole hydrogen succinate ionic liquid

Add 16.06 g (0.1 mol) of N, N-methylpropylimidazole chloride, 15.62 g (0.1 mol) of potassium hydrogen succinate and 45 g of solvent butanol into a 250 mL reaction flask respectively, and react under a 240W microwave for 30 Take it out in seconds and stir well, then put it in the microwave to react for 15 seconds, take it out and stir well, repeat the last step 5 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product N, N-methylpropylimidazole hydrogen succinate ionic liquid, the product yield The rate is 97%, and the chloride ion concentration is 590ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 54.53%, H: 7.49%, N: 11.57%, measured value C: 54.51%, H: 7.48%, N: 11.54%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.90(t, 3H, CH3), δ=1.70(m, 2H, CH2), 3.72(s, 3H, CH3), 4.04(m, 2H, CH2 ), 6.76-7.29 (s, 3H, CH), 2.71 (s, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 328 cP at 40°C.

Example 11: N, N-methylbutylimidazole hydrogen succinate ionic liquid

Add 1746g (0.1mol) of N,N-methylbutylimidazole chloride, 15.62g (0.1mol) of potassium hydrogen succinate and 45g of butanol as a solvent into a 250mL reaction flask, and react under a 240W microwave for 30 seconds Take it out and stir well, then put it in the microwave to react for 15 seconds, then take it out and stir well, repeat the last step 5 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product N,N-methylbutylimidazole hydrogen succinate ionic liquid, the product yield The rate is 96%, and the chloride ion concentration is 623ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical value C: 56.23%, H: 7.87%, N: 10.93%, measured value C: 56.25%, H: 7.84%, N: 10.94%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.96(t, 3H, CH3), 3.63(s, 3H, CH3), 1.33(m, 2H, CH2), 1.77(m, 2H, CH2), 3.73 (t, 2H, CH2), 6.76-7.29 (s, 3H, CH), 2.63 (s, 4H, CH2). Its melting point was not determined by DSC scan and its viscosity was 243 cP at 40°C.

Example 12: N, N-methylbutylimidazole hydrogen glutarate ionic liquid

Add respectively 17.46g (0.1mol) of N,N-methylbutylimidazole chloride, 17.02g (0.1mol) of potassium hydrogen glutarate and 35g of solvent butanol to a 250mL reaction flask, and react under a 240W microwave for 30 Take it out in seconds and stir well, then put it in the microwave to react for 15 seconds, take it out and stir well, repeat the last step 5 times. After the reaction was completed, it was filtered while it was hot, and the filtrate was rotary evaporated to remove and recover most of the solvent butanol, and dried in vacuum at 70°C for 48 hours to obtain the product N, N-methylbutylimidazole hydrogen glutarate ionic liquid. The rate is 97%, and the chloride ion concentration is 610ppm. Its chemical structural formula is:

Characterization results: elemental analysis theoretical values C: 57.76%, H: 8.20%, N: 10.36%, measured values C: 57.77%, H: 8.21%, N: 10.34%. ¹ H NMR (DCCl ₃ , 300MHz) δ=0.96(t, 3H, CH3), 3.63(s, 3H, CH3), 1.33(m, 2H, CH2), 1.77(m, 2H, CH2), 3.73 (t, 2H, CH2), 6.76-7.29 (s, 3H, CH2), 1.88-1.97 (m, 2H, CH2), 2.36-2.39 (t, 4H, CH2). Its melting point was not determined by DSC scan, and its viscosity was 394 cP at 40°C.

Example 13:

Accurately weigh 10 g of triethylbutyl quaternary ammonium hydrogen succinate ionic liquid (the product of Example 6) and place it in the absorption tank (the volume of the absorption tank is 100 mL), at 40 ° C, feed _SO into the absorption tank to carry out Absorption, the pressure tends to balance within 10 minutes, indicating that the absorption of SO ₂ by the ionic liquid has reached equilibrium. It is calculated that when the _SO2 partial pressure is 0.4kPa, the molar ratio of the _SO2 absorption to the ionic liquid is 0.49, and when the _SO2 partial pressure is 100kPa, the molar ratio of the _SO2 absorption to the ionic liquid is 1.76.

Claims (6)

1. one type has asymmetric chemical structure and weakly acidic di-carboxylic acid hydrogen salt ionic liquid; It is characterized in that: ionic liquid is a quaternary ammonium di-carboxylic acid hydrogen salt; Its positively charged ion is the tetraalkyl quaternary ammonium cation or the N of unsymmetric structure; N-dialkylimidazolium positively charged ion, negatively charged ion are di-carboxylic acid hydrogen root negatively charged ion, and chemical structural formula is:

In the formula: R ₁Be selected from C ₁～C ₃Straight-chain alkyl, R ₂Be selected from C ₃～C ₆Straight-chain alkyl, R ₃Be selected from C ₁～C ₃The saturated or undersaturated alkylene of straight or branched.

2. one type according to claim 1 has asymmetric chemical structure and weakly acidic di-carboxylic acid hydrogen salt ionic liquid; It is characterized in that: described ionic liquid positively charged ion is trimethylammonium butyl ammonium, trimethylammonium propyl ammonium, triethyl butyl ammonium or tripropyl hexyl ammonium cation; Perhaps N; N-methyl-propyl imidazoles or N, N-methylbutyl glyoxaline cation.

3. one type according to claim 1 has asymmetric chemical structure and weakly acidic di-carboxylic acid hydrogen salt ionic liquid, it is characterized in that: the hydrogen root negatively charged ion that described di-carboxylic acid root negatively charged ion is propanedioic acid, maleic acid, Succinic Acid or pentanedioic acid.

4. one type according to claim 1 has asymmetric chemical structure and weakly acidic di-carboxylic acid hydrogen salt ionic liquid, it is characterized in that: described R ₂For it compares R ₁Many two above carbonatomss.

5. one kind prepares that claim 1 is described to have asymmetric chemical structure and an ion liquid method of weakly acidic di-carboxylic acid hydrogen salt; It is characterized in that: with chlorination tetraalkyl quaternary ammonium or the chlorination N with unsymmetric structure, N-dialkylimidazolium and di-carboxylic acid hydrogen potassium are raw material, both etc. mole join in the butanols simultaneously; The butanols consumption is 0.5～3 times of theoretical ionic liquid quality; Takes out after 30 seconds in reaction earlier under the microwave of 200～400W and to stir, put into the microwave reaction again and takes out after 15 seconds and stir, one step of back repeat 3～5 times continuously after end react; With the solution filtered while hot; Underpressure distillation filtrating to be to remove and to reclaim most of solvent butanols, and remaining liq sample vacuum-drying 48h to constant weight, is promptly got and has asymmetric chemical structure and weakly acidic di-carboxylic acid hydrogen salt ionic liquid.

6. according to claim 1 have asymmetric chemical structure and a weakly acidic di-carboxylic acid hydrogen salt ionic liquid, it is characterized in that can be used for SO ₂Absorption rapidly and efficiently.