A kind of metal-containing protic deep eutectic solvent specially used for HCl / SO2 absorption-extractive distillation separation

Abstract

The application discloses a kind of design, preparation and its mediation HCl / SO2 mixed gas separation process of metal-containing protic deep eutectic solvent.The absorbent or extractant used in the application is prepared by organic base hydrochloride, metal halide and high-boiling organic solvent three components according to certain molar ratio under heating stirring at 50-90 ℃, and its most important feature is: it has the function of inhibiting HCl dissolution and promoting SO2 absorption.The HCl / SO2 mixed gas separation device proposed in the application is mainly composed of absorption-extraction rectification tower and graphite evaporator.Two parts.The high-purity HCl and SO2 can be obtained at the top of absorption-extraction rectification tower and graphite evaporator respectively after mixed gas is sent into the separation device, and the absorbent or extractant can be recycled.The deep eutectic solvent of the application has the advantages of simple synthesis and low cost, and the HCl / SO2 separation process has the advantages of green and efficient, low energy consumption and low cost compared with high-pressure rectification, water absorption and other traditional separation processes, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention addresses the separation of HCl / SO2 byproducts in chemical production, specifically involving the design and preparation of a type of deep eutectic solvent containing metal protons and its use as a medium in the HCl / SO2 absorption-extraction distillation separation process, belonging to the field of chemical separation. Background Technology

[0002] Hydrogen chloride (HCl) is a highly corrosive and acidic gas. In industrial applications, reactions using chlorinating agents such as SOCl2, including the chlorination of fine chemicals like acyl chloride, cypermethrin, and sucralose, produce nearly equal volumes of HCl and SO2 mixed tail gas (HCl / SO2). Currently, industrial methods for treating HCl / SO2 mixed tail gas can be divided into two categories: (1) Chemical methods: The HCl / SO2 tail gas is first washed with water to generate a hydrochloric acid solution; then, a sodium bicarbonate solution is passed through it for absorption, generating sodium bisulfite; (2) Physical methods: The HCl / SO2 tail gas is compressed by a compressor and then cooled to separate HCl and SO2. Physical methods can separate dry HCl, but they are energy-intensive, and HCl inevitably dissolves in liquefied SO2. Compared to chemical methods, the dry HCl gas obtained by physical methods has a higher economic added value. It is not only a raw material for the synthesis of many chemicals, but also a catalyst for some new processes. Therefore, it is very important to develop new processes for separating HCl / SO2 tail gas under anhydrous conditions. To achieve efficient separation of HCl and SO2 mixtures, the key is to develop a new generation of green, low-cost media and new technologies for enhanced separation.

[0003] Deep eutectic solvents (DESs), as a novel solvent platform under the vision of green chemistry, offer new opportunities for the efficient separation of HCl. DESs are typically produced by Lewis or... Deep eutectic mixtures, formed by the mixing of acidic substances (hydrogen bond donors) and ionic Lewis basic substances (hydrogen bond acceptors) through hydrogen bonding, resulting in a lower freezing point, offer advantages such as wide availability of raw materials, simple synthesis, low cost, and strong gas trapping capabilities. Patent CN109603437B reports a method using diethylene glycol as an absorbent to absorb HCl-containing mixed gases. However, no reports have yet documented the absorption and separation of HCl and SO2 mixed gases in DES.

[0004] This invention discloses a deep eutectic solvent and its mediated HCl / SO2 mixed tail gas separation technology. The deep eutectic solvent is proton-type and contains transition metal ions (denoted as PM-DES), which inhibits HCl dissolution and promotes SO2 absorption. The HCl / SO2 mixed tail gas separation technology is an absorption-extractive distillation separation process, which can effectively separate SO2 and HCl. The PM-DES in this invention has advantages such as simple synthesis steps and low cost, while the separation technology has advantages such as simple process and outstanding separation performance. This invention has good prospects for industrial application. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost design and preparation method for a metal-containing proton-type deep eutectic solvent, as well as a matching HCl / SO2 separation process.

[0006] The technical solution of the present invention is as follows:

[0007] Design a proton-type DES containing metal (denoted as PM-DES). The general formula for a PM-DES structure that meets the conditions is: [QH] + Cl - -z[MCl x ]-yL, where: [QH] + It is a protonated organic cation, M is a metal central ion, L is a central ligand molecule; x is Cl. - The numbers Q, M, L, y, and z represent the material ratios. By changing Q, M, L, y, and z, especially the electron-withdrawing groups on Q, the basicity of Q can be altered, thereby affecting the interaction between PM-DES and HCl and SO2. Specifically, this is achieved by designing the structure and composition of PM-DES to give it the function of inhibiting HCl dissolution while promoting SO2 dissolution as much as possible.

[0008] A typical method for preparing the metal-containing proton-type deep eutectic solvent is as follows: a certain proportion of organic base hydrochloride, metal halide and high-boiling-point organic solvent are heated and stirred at 50-90°C until the mixture becomes a clear and transparent liquid, and then cooled to room temperature to obtain the target deep eutectic solvent.

[0009] An absorption-extraction distillation separation process is characterized by: using a mixture of industrial by-product HCl and SO2 as the gas source, the gas source is fed from the middle of the absorption-extraction distillation column, and the absorbent or extractant is fed from the top of the absorption-extraction distillation column. The absorbent or extractant is dispersed and sprayed downwards by a liquid distributor. The mixed gas is initially separated in the absorption-extraction distillation column, and the top material is high-purity HCl. Part of the bottom material is evaporated in a reboiler and then returned to the bottom of the column, while the other part is transported by a centrifugal pump to a graphite evaporator for desorption and regeneration. High-purity SO2 is obtained at the top of the evaporator, and the regenerated absorbent or extractant PM-DES at the bottom of the evaporator is transported back to the absorption-extraction distillation column for recycling after heat exchange and cooling.

[0010] In the aforementioned type of deep eutectic solvent containing metal protons, preferably, Q is the parent nucleus on the cation, which can be an alkylamine (such as trialkylamine) or a nitrogen-containing aromatic heterocyclic organic base (such as N-alkylimidazole, N-alkylpyridine), etc., and the alkyl chain can be a straight-chain alkyl group of C1 to C4.

[0011] The aforementioned type of deep eutectic solvent containing metal protons, preferably, contains metal halides such as AlCl3, ZnCl2, CuCl, CuCl2, and FeCl3.

[0012] In the aforementioned type of deep eutectic solvent containing metal protons, preferably, the ligand L is sulfolane and 1,3-dimethyl-2-imidazolinone.

[0013] In the aforementioned type of deep eutectic solvent containing metal protons, preferably, x is the number of Cl, taking a value of 1 to 4.

[0014] In the aforementioned type of deep eutectic solvent containing metal protons, preferably, the material ratios y and z are taken as 1 to 3.

[0015] In the above-mentioned absorption-extraction distillation separation process, the separation target is a mixture of HCl and SO2 gas, which is an industrial byproduct of the use of thionyl chloride as a chlorinating agent.

[0016] In the above-mentioned absorption-extraction distillation separation process, preferably, the top operating temperature of the absorption-extraction distillation separation column is 20-30℃, and the bottom operating temperature is 50-80℃.

[0017] In the above-mentioned absorption-extraction distillation separation process, preferably, the operating pressure of the absorption-extraction distillation separation column is 1 to 3 bar, the total number of theoretical plates is 30 to 50, and the feed plate position (counting from the top of the column) is the 15th to the 25th plate.

[0018] In the above-mentioned absorption-extraction distillation separation process, preferably, the desorption temperature of the absorbent or extractant is 80-100℃ (i.e., the operating temperature of the graphite evaporator is 80-100℃).

[0019] This invention, for the first time, proposes a metal-containing proton-type deep eutectic solvent and its mediated absorption-extraction distillation separation process for HCl / SO2 separation. The absorbent or extractant is inexpensive and simple to prepare; the separation process is simple and yields good separation results. Furthermore, compared to traditional separation processes such as high-pressure distillation and water absorption, this process offers advantages such as lower energy consumption, lower cost, and greater practicality. Attached Figure Description

[0020] The attached figure is a schematic diagram of an HCl / SO2 absorption-extraction distillation separation process provided by the present invention. Wherein: T-1 is the absorption-extraction distillation column, E-1 is the graphite evaporator, E-2 is the reboiler, E-3 is the condenser, E-4 is the heat exchanger, and P-1 and P-2 are centrifugal pumps. Detailed Implementation

[0021] The present invention will be further illustrated by the following examples.

[0022] Example 1. N,N-dimethylaniline hydrochloride (DMA·HCl), ZnCl2 and sulfolane were heated and stirred at 90°C in a molar ratio of 1:1:1 until the mixture became a clear and transparent liquid. Then, it was cooled to room temperature to obtain a deep eutectic solvent, denoted as DMA·HCl+ZnCl2+sulfolane (1:1:1).

[0023] Example 2. N,N-dimethylaniline hydrochloride (DMA·HCl), ZnCl2 and 1,3-dimethyl-2-imidazolinone (DMI) were heated and stirred at 90°C in a molar ratio of 1:1:2 until the mixture became a clear and transparent liquid. Then, it was cooled to room temperature to obtain a deep eutectic solvent, denoted as DMA·HCl+ZnCl2+DMI (1:1:2).

[0024] Example 3. Triethylamine hydrochloride (TEA·HCl), ZnCl2 and sulfolane were heated and stirred at 90°C in a molar ratio of 1:1:1 until the mixture became a clear and transparent liquid. Then, it was cooled to room temperature to obtain a deep eutectic solvent, denoted as TEA·HCl+ZnCl2+sulfolane (1:1:1).

[0025] Example 4. 2-methylpyridine hydrochloride (2MP·HCl), ZnCl2 and sulfolane were heated and stirred at 80°C in a molar ratio of 1:1:2 until the mixture became a clear and transparent liquid. Then, it was cooled to room temperature to obtain a deep eutectic solvent, denoted as 2MP·HCl+ZnCl2+sulfolane (1:1:2).

[0026] Examples 5-26. Examples 5-26 were synthesized using the same steps as in Example 1, and the solubility of HCl and SO2 under different absorption temperatures and gas partial pressures was determined, and the separation factor was calculated (the test method can be found in Sep. Purif. Technol., 2023, 324, 124538). The specific results are shown in Table 1:

[0027] Table 1. HCl and SO2 concentrations in DES under different conditions. s solubility in

[0028]

[0029] Examples 27-36. DMA·HCl + ZnCl2 + sulfolane (1:1:1) was selected as the absorbent or extractant, and the HCl / SO2 was separated using the absorption-extraction distillation separation process shown in the attached diagram: a mixed gas of 25% HCl and 75% SO2 from industrial by-products was used as the gas source, with a flow rate of 100 Nm³. 3 / h, the gas source is fed from the middle of the absorption-extractive distillation column (the 22nd tray from the top of the column), and DMA·HCl + ZnCl2 + sulfolane (1∶1∶1) is fed from the top of the absorption-extractive distillation column, with a feed liquid-to-gas ratio of 0.0215m. 3 / m 3 The total theoretical number of plates is 45. The top temperature of the absorption-extractive distillation column is controlled at 25℃, and the bottom temperature at 50℃. The mixed gas undergoes preliminary separation in the absorption-extractive distillation column. The top product is high-purity HCl. Part of the bottom product is evaporated in the reboiler and then refluxed to the bottom of the column. The other part is pumped out by a centrifugal pump and sent to a graphite evaporator for desorption at 100℃. The top of the evaporator yields high-purity SO2, and the bottom of the evaporator yields a regenerated liquid of DMA·HCl + ZnCl2 + sulfolane (1∶1∶1). After heat exchange in E-4 and cooling in E-3, the regenerated liquid is sent back to the absorption-extractive distillation column for recycling. The HCl and SO2 gas streams produced during the separation process are collected and absorbed using NaOH solution. The purity of HCl is determined to be 99.9% and the purity of SO2 to be 99.2% by titration of sulfite and Cl ion concentrations.

[0030] When the feed gas flow rate is maintained at 100 Nm 3 Under the condition of constant h, different PM-DES types, HCl / SO2 volume ratio in feed gas, top / bottom operating temperatures of absorption-extraction distillation column, feed liquid-gas ratio, and theoretical plate number / feed plate position were changed to form other embodiments, and the results are summarized in Table 2.

[0031]

Claims

1. A metal-containing proton-type deep eutectic solvent for HCl / SO2 absorption-extraction distillation separation, characterized in that, The composition is [QH]. + Cl - ·z[MCl x ]·yL, where: [QH] + It is a protonated organic cation, wherein the parent nucleus of the organic cation is Q, and Q is an alkylamine or a nitrogen-containing aromatic heterocyclic organic base, wherein the alkyl chain of the alkylamine is a straight-chain alkyl group of C1 to C4; MCl x It can be AlCl3, ZnCl2, CuCl, CuCl2, or FeCl3; L is sulfolane or 1,3-dimethyl-2-imidazolinone; In eutectic solvents containing metal protons, [QH] + Cl - ,MCl x The molar ratio of L is 1:z:y, where the values ​​of y and z are independently selected from 1 to 3, and are adjusted by changing [QH]. + Cl - ,MCl x The parameters L, y, and z can be used to modify the interaction between the metal-containing proton-type eutectic solvent and HCl and SO2.

2. The method for preparing a metal-containing proton-type deep eutectic solvent for HCl / SO2 absorption-extraction distillation separation according to claim 1, characterized in that, Organic base hydrochloride, metal halide and high-boiling-point organic solvent are heated and stirred at 50-90°C in a molar ratio until the mixture becomes a clear and transparent liquid. Then, it is cooled to room temperature to obtain the target eutectic solvent.

3. The absorption-extraction distillation process for a metal-containing proton-type deep eutectic solvent used for HCl / SO2 absorption-extraction distillation separation according to claim 1, characterized in that: The gas separation unit consists of an absorption-extraction distillation column and a graphite evaporator. A mixture of HCl and SO2 is fed from the middle of the absorption-extraction distillation column, while a metal proton-containing eutectic solvent is fed from the top of the column. The solvent is dispersed and sprayed downwards by a liquid distributor. The mixture undergoes preliminary separation in the absorption-extraction distillation column, with the top material being high-purity HCl. Part of the bottom material is returned to the column bottom after evaporation in a reboiler, while the other part is pumped to the graphite evaporator for desorption and regeneration. High-purity SO2 is obtained at the top of the graphite evaporator, and the regenerated metal proton-containing eutectic solvent at the bottom of the evaporator is recycled back to the absorption-extraction distillation column after heat exchange.

4. The absorption-extraction distillation process for a metal-containing proton-type deep eutectic solvent used for HCl / SO2 absorption-extraction distillation separation according to claim 3, characterized in that: The top operating temperature of the absorption-extraction distillation column is 20–30℃, the bottom operating temperature is 50–80℃, and the desorption temperature of the metal proton-type deep eutectic solvent is 80–100℃.

5. The absorption-extraction distillation process for a metal-containing proton-type deep eutectic solvent used for HCl / SO2 absorption-extraction distillation separation according to claim 3, characterized in that: The operating pressure of the absorption-extraction distillation column is 1 to 3 bar, the total number of theoretical plates is 30 to 50, and the feed plate is the 15th to 25th from the top of the column.

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