CN104923036A - Method for catching sulfur dioxide by adopting halogenated carboxylic acid ion liquid - Google Patents

Abstract

The invention discloses a method for catching sulfur dioxide by adopting a halogenated carboxylic acid ion liquid. According to the halogenated carboxylic acid ion liquid, halogen is introduced onto carboxylic acid negative ions of a functionalized ionic liquid, the absorbing capacity of sulfur dioxide is improved by utilization of the action of halogen reinforced onto the negative ions and sulfur dioxide, and the electron absorption property of the halogen on the negative ions is utilized to improve the desorption property of carboxylic acid ion liquid, so that efficient reversible absorption of the sulfur dioxide can be realized.

Description

A kind of method adopting halocarboxylate ionic liquid to trap sulfur dioxide

technical field

The invention belongs to the technical field of sulfur dioxide absorption, and in particular relates to a method for trapping sulfur dioxide by using a halogenated carboxylate ionic liquid.

Background technique

In recent years, with the rapid development of economy and society, the sulfur dioxide released by coal combustion has continuously deteriorated the atmospheric environment, and the harm of acid rain has intensified, which has seriously affected human survival and the ecological environment. Therefore, there is an urgent need to control and reduce the emission of sulfur dioxide gas. Therefore, it is of great significance to develop efficient, reversible, economical and environmentally friendly new materials and new processes for absorbing sulfur dioxide gas.

At present, the use of traditional processes such as limestone, ammonia, and organic solvents to absorb sulfur dioxide gas has the advantages of low cost, fast absorption speed, and large absorption capacity. Absorbents are not easy to regenerate and other problems, which do not conform to the principle of sustainable development.

Due to the advantages of good stability, low volatility, strong gas dissolving ability, and designability, ionic liquids provide a good alternative for the industrial absorption of SO2 gas. Many researchers have used experimental and theoretical methods to study the physical solubility of sulfur dioxide gas in different ionic liquids. For example, Huang et al. determined the performance of guanidinium-based ionic liquids containing tetrafluoroborate and bistrifluoromethylsulfonylimide to absorb sulfur dioxide gas, showing that each mole of ionic liquid can absorb 1-2 moles of sulfur dioxide gas under normal pressure. , but little absorption under reduced pressure (Chem. Commun. 2006, 4027). Another method is to use anion-functionalized ionic liquids to chemically absorb sulfur dioxide gas. For example, Han et al. used guanidinolactic acid ionic liquids for the first time to absorb sulfur dioxide gas. Each mole of ionic liquid can absorb 1.7 moles of sulfur dioxide gas under normal pressure. (Angew. Chem., Int. Ed. 2004, 2415). Recently, Wang et al. applied azole-based quaternary phosphine ionic liquids to the chemical absorption of sulfur dioxide gas and obtained good absorption effects (J. Am. Chem. Soc. 2011, 11916).

However, in the current methods of using anion-functionalized ionic liquids to absorb sulfur dioxide, there are common problems such as insufficient absorption capacity, high absorption enthalpy, difficult desorption, and poor cycle performance, which affect its industrial application. Therefore, it is necessary to improve the desorption performance of ionic liquids through the structural design of anion-functionalized ionic liquids, which can not only increase the absorption capacity of ionic liquids for sulfur dioxide, but also reduce the absorption enthalpy, so as to achieve high capacity and low energy consumption of sulfur dioxide absorption.

Contents of the invention

The technical problem solved by the present invention is to provide a method for trapping sulfur dioxide by using a halogenated carboxylate ionic liquid, by introducing a halogen into the anion of the carboxylic acid functionalized ionic liquid, and using the effect of the anion-enhanced halogen and sulfur dioxide to increase the concentration of sulfur dioxide Absorption capacity, and the electron-withdrawing property of the halogen on the anion is used to improve the desorption performance of the ionic liquid, so as to realize the efficient and reversible absorption of sulfur dioxide.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme, a method for trapping sulfur dioxide by using a halogenated carboxylate ionic liquid, characterized in that: the halogenated carboxylate ionic liquid is used as an absorbent to absorb sulfur dioxide gas, during the absorption process , the absorption gas pressure is 0.001-0.1MPa, the absorption temperature is 20-80°C, and the absorption time is 0.5-5h. During the desorption process, the desorption temperature is 60-120°C, and the desorption time is 0.5-1.5h. The halogenated carboxylate ionic liquid is a functionalized ionic liquid with a deprotonated halogenated carboxylic acid compound as an anion, wherein the halogenated carboxylic acid compound is bromoacetic acid, fluoroacetic acid, 2-chlorobutyric acid, 2-bromoisoamyl acid, 4-bromohexanoic acid, 6-bromohexanoic acid, 6-chlorohexanoic acid or 10-bromodecanoic acid, the cation is tetradecyltrihexylphosphine ion, propyltrihexylphosphine ion, butyltrihexylphosphine ion , ethyltributylphosphine ion, tetrabutylphosphine ion, ethylmethylimidazolium ion, butylmethylimidazolium ion or ethyltributylammonium ion.

The halogenated carboxylate ionic liquid of the present invention is preferably tetradecyltrihexylphosphine 6-bromohexanoic acid.

The halogenated carboxylate ionic liquid of the present invention is tetraalkylphosphine hydroxide, dialkylhydroxide formed by tetraalkylphosphine halide, dialkylimidazolium halide salt or tetraalkylammonium halide through anion exchange reaction. Imidazole or tetraalkyl ammonium hydroxide and halogenated carboxylic acid compounds are prepared by equimolar neutralization reaction at normal temperature and pressure for 6-24h.

Compared with traditional limestone, ammonia, organic solvents, conventional ionic liquids and other functionalized ionic liquids, the halogenated carboxylate ionic liquid of the present invention has the following advantages: (1) using highly stable non-amine functionalized ions The liquid is an absorbent, which avoids the loss and volatilization of the solvent before and after the system absorbs sulfur dioxide gas, and significantly speeds up the reaction; The effect of the gas significantly increases the absorption capacity; (3) Due to the electron-attracting effect of the halogen, the charge on the anion is dispersed, reducing the absorption enthalpy of the sulfur dioxide gas, and making the absorbed sulfur dioxide gas easy to desorb.

Detailed ways

The above-mentioned contents of the present invention are described in further detail below through the embodiments, but this should not be interpreted as the scope of the above-mentioned themes of the present invention being limited to the following embodiments, and all technologies realized based on the above-mentioned contents of the present invention all belong to the scope of the present invention.

Example 1

Select different kinds of tetraalkylphosphine halides, dialkylimidazolium halide salts or tetraalkylammonium halides respectively to form tetraalkylphosphine hydroxides, dialkyl imidazole hydroxides or tetraalkylammonium hydroxides through anion exchange reaction. The formed hydroxides are reacted with different kinds of halogenated carboxylic acid compounds according to the molar ratio of 1:1 at normal temperature and pressure for 6-24 hours to obtain different kinds of halogenated carboxylate ions as shown in Table 1 liquid.

In a 5mL glass container with an inner diameter of 1cm, add 0.002mol of the different types of halocarboxylate ionic liquids prepared above, and then slowly introduce sulfur dioxide gas at a flow rate of 40mL/min, absorbing the gas pressure at 0.1MPa, and controlling the temperature at At 20°C, the absorption time is 0.5h for sulfur dioxide absorption. During the absorption process, the electronic analytical balance is used for weighing. The absorption results of sulfur dioxide gas are shown in Table 1.

Table 1 Effects of different kinds of halocarboxylate ionic liquids on SO2 gas absorption

Among them, mol/mol IL represents the amount of sulfur dioxide gas absorbed per mole of ionic liquid (the same as above).

Example 2

Add 0.002mol of tetradecyltrihexylphosphine 6-bromohexanoic acid into a 5mL glass container with an inner diameter of 1cm, and then slowly introduce sulfur dioxide gas at a flow rate of 40mL/min. Set different absorption gas pressure, absorption temperature and The absorption time is for the absorption of sulfur dioxide gas, and the electronic analytical balance is used for weighing during the absorption process. The absorption results of sulfur dioxide gas are shown in Table 2.

Table 2 Effects of different absorption conditions on the absorption of sulfur dioxide gas by tetradecyltrihexylphosphine 4-bromohexanoic acid

Compared with Table 1, combined with Table 2, it can be seen that the absorption amount of sulfur dioxide gas will change significantly depending on the absorption temperature and the absorption gas pressure. The higher the absorption temperature or the lower the absorption gas pressure, the halogenated carboxyl The lower the amount of sulfur dioxide gas absorbed by the acid radical ionic liquid, the lower the absorption temperature or the higher the pressure of the absorbed gas, the higher the amount of sulfur dioxide gas absorbed by the halogenated carboxylate ionic liquid.

Example 3

Nitrogen gas is slowly introduced into the tetradecyltrihexylphosphine 6-bromohexanoic acid that has absorbed sulfur dioxide gas, the flow rate is 40mL/min, the pressure is 0.1MPa, the desorption temperature is controlled at 120°C, and the desorption time is 0.5h. Electronic analytical balance weighing shows that the sulfur dioxide gas absorbed by the halogenated carboxylate ionic liquid has been completely desorbed.

Weigh different kinds of halogenated carboxylate ionic liquids that have absorbed sulfur dioxide gas with an electronic analytical balance and add them to a 5mL glass container with an inner diameter of 1cm, and then slowly feed nitrogen gas with a flow rate of 40mL/min and a pressure of 0.1MPa. The desorption temperature and desorption time, the desorption results are shown in Table 3.

Table 3 Effect of different kinds of halocarboxylate ionic liquids on the desorption of sulfur dioxide gas

Example 4

In order to investigate the reversible cycle of halocarboxylate ionic liquids in the process of trapping sulfur dioxide gas, sulfur dioxide and nitrogen were alternately fed into tetradecyltrihexylphosphine 6-bromohexanoic acid ionic liquid with a gas flow rate of 40 mL/min. The pressure is 0.1MPa, the adsorption and desorption time are both 0.5h, the adsorption temperature is controlled at 20°C, the desorption temperature is controlled at 120°C, 30 cycles are carried out, and the electronic analytical balance weighs the sulfur dioxide absorption range of 4.30~4.40 mol/ mol IL, the absorption amount did not decrease significantly, indicating that the halocarboxylate ionic liquid has good reversible cycleability.

The basic principles, main features and advantages of the present invention have been shown and described above. On the premise of not departing from the spirit and scope of the present invention, the present invention also has various changes and improvements, and these changes and improvements all fall into the claimed invention. range.

Claims (4)

1. A method for trapping sulfur dioxide using a halogenated carboxylate ionic liquid is characterized in that: the halogenated carboxylate ionic liquid is used as an absorbent to absorb sulfur dioxide gas, and in the absorption process, the absorption gas pressure is 0.001-0.1MPa, The absorption temperature is 20-80°C, and the absorption time is 0.5-5h. During the desorption process, the desorption temperature is 60-120°C, and the desorption time is 0.5-1.5h. The halogenated carboxylate ionic liquid is based on the The protonated halogenated carboxylic acid compound is an anionic functionalized ionic liquid, wherein the halogenated carboxylic acid compound is bromoacetic acid, fluoroacetic acid, 2-chlorobutyric acid, 2-bromoisovaleric acid, 4-bromohexanoic acid, 6- Bromohexanoic acid, 6-chlorohexanoic acid or 10-bromodecanoic acid, the cation is tetradecyl trihexyl phosphine ion, propyl trihexyl phosphine ion, butyl trihexyl phosphine ion, ethyl tributyl phosphine ion, tetradecyl trihexyl phosphine ion, Butylphosphine ion, ethylmethylimidazolium ion, butylmethylimidazolium ion or ethyltributylammonium ion. 2. The method for trapping sulfur dioxide by using a halogenated carboxylate ionic liquid according to claim 1, characterized in that: said halogenated carboxylate ionic liquid is tetradecyltrihexylphosphine 6-bromohexanoic acid. 3. according to claim 1 and 2 described methods adopting halogenated carboxylate ionic liquid to trap sulfur dioxide, it is characterized in that: take tetradecyltrihexylphosphine 6-bromohexanoic acid as absorbent in order to absorb sulfur dioxide gas, During the absorption process, the absorption gas pressure is 0.1MPa, the absorption temperature is 20°C, and the absorption time is 0.5h. The amount of sulfur dioxide gas absorbed per mole of tetradecyltrihexylphosphine 6-bromohexanoic acid is 4.34mol. During the desorption process, the desorption temperature was 120° C., the desorption time was 0.5 h, and the sulfur dioxide absorbed by tetradecyltrihexylphosphine 6-bromohexanoic acid was completely desorbed. 4. The method for trapping sulfur dioxide using a halogenated carboxylate ionic liquid according to claim 1, characterized in that: said halogenated carboxylate ionic liquid is made of tetraalkylphosphine halides, dialkylimidazolium halides or Tetraalkylphosphine hydroxide, dialkyl imidazolium hydroxide or tetraalkyl ammonium hydroxide and halogenated carboxylic acid compound formed by anion exchange reaction of tetraalkyl ammonium halide, through equimolar neutralization reaction at normal temperature and pressure 6-24h prepared.