A high-efficiency hydrogen chloride separation eutectic absorbent

Abstract

The present application relates to a kind of high-efficiency separation and recovery of hydrogen chloride eutectic absorbent, belong to gas separation and purification technical field.The eutectic absorbent is by quaternary ammonium salt and polyol with certain proportion compound, synthesis raw material is abundant and easy to obtain, synthesis process is simple and easy to operate, and absorbent scale preparation is safe and reliable.The anion and cation of quaternary ammonium salt in eutectic absorbent and the hydroxyl of polyol can provide multiple hydrogen bond acceptor and hydrogen bond donor, which is beneficial to the absorption of hydrogen chloride, and hydrogen chloride can be completely desorbed by heating or reducing pressure, and the regenerated absorbent can be recycled.The absorbent has low cost, small viscosity, good stability and can be recycled, and is a new type of solvent for efficient separation and recovery of hydrogen chloride, which has wide application prospect in separation and recovery of industrial tail gas containing hydrogen chloride.

Description

Technical Field

[0001] This invention belongs to the field of exhaust gas separation and purification, specifically relating to a eutectic absorbent for efficient separation of hydrogen chloride, which can efficiently separate and recover hydrogen chloride from industrial exhaust gas. Background Technology

[0002] In industries such as petroleum, chemical, pharmaceutical, and metallurgy, mixed tail gases containing hydrogen chloride (HCl) are produced. Examples include industrial tail gases emitted during the production of products such as potassium sulfate, PVC, chlorinated hydrocarbons, epichlorohydrin, and chlorine. Hydrogen chloride gas has a strong corrosive and irritating odor, and direct emission poses a significant environmental hazard. Currently, trace amounts of HCl in industrial tail gases are directly absorbed by alkaline solutions to generate chloride salts, resulting in solid waste and resource waste. High-concentration HCl tail gases are mostly treated using water absorption to produce low-concentration hydrochloric acid. While this technology is simple, the added value of the hydrochloric acid product is low, and the process of obtaining pure HCl through hydrochloric acid distillation is energy-intensive, leading to low overall economic benefits of the water absorption method for HCl recovery.

[0003] To address the aforementioned technical issues, various absorbents for HCl absorption and separation have been reported in the literature, including organic solvents, eutectic solvents (DES), and ionic liquids. Organic solvents generally have low boiling points and poor thermal stability; ionic liquids have almost no saturated vapor pressure and good thermal stability, but their viscosity is relatively high. Eutectic absorbents are mixtures composed of hydrogen bond acceptors and hydrogen bond donors in a certain stoichiometric ratio. Their freezing points are significantly lower than the melting points of the individual components, and their properties are similar to ionic liquid materials. The design and synthesis of novel eutectic absorbents, considering their thermal stability, viscosity, and gas absorption capacity, have great application potential in the field of gas separation. Li et al. (Sep. Purif. Technol. 2022, 281, 119994) reported a eutectic solvent composed of choline chloride and lactic acid, oxalic acid, glycolic acid, and glycerol, which has an absorption capacity of approximately 0.18–0.40 g / g for HCl, exhibits good cycle stability, but has poor thermal stability. Wu et al. (Sep. Purif. Technol. 2022, 300, 121799) reported a eutectic absorbent composed of 1,3-dimethyl-2-imidazolinone (DMI), N,N-dimethylurea (DMU), and methylurea (MU), which has an absorption capacity of approximately 0.60 g / g for HCl, and a thermal decomposition temperature of approximately 140 °C. Patent CN109603437A reports a method for separating and recovering HCl gas using diethylene glycol as an absorbent. The concentration of HCl in the absorbent is 20–40 wt% (average absorption capacity is approximately 0.30 g / g), the desorption temperature is 80–150 °C, and the desorption rate is approximately 87%. Patent CN 117339349A reports a method for separating a mixture of light hydrocarbons and HCl using ethylene glycol as the absorbent, where the absorbent is a low-boiling-point organic solvent, resulting in significant solvent consumption during the separation process. Patent CN 116550098A reports a method for separating a mixture of SO2 and HCl acid gases and its application, using an organic amine as the absorbent. After absorbing HCl, a hydrochloride solution is obtained, which is then released through thermal decomposition, producing some hydrochloric acid as a byproduct. Therefore, designing and developing eutectic absorbents with good thermal stability, high absorption capacity, and low viscosity for the separation and recovery of HCl has significant application value.

[0004] This invention designs a eutectic absorbent for efficient separation of hydrogen chloride, which can further improve the thermal stability and absorption selectivity of the absorbent, and recover HCl from industrial tail gas at low cost. Summary of the Invention

[0005] The present invention aims to provide a eutectic absorbent for efficient separation of hydrogen chloride. This absorbent can efficiently absorb and separate hydrogen chloride from industrial exhaust gas. The absorbent has a high HCl absorption capacity and good stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a eutectic absorbent for highly efficient separation of hydrogen chloride, wherein the absorbent has hydrogen bond acceptors and hydrogen bond donors, the absorbent absorbs hydrogen chloride of different concentrations in industrial tail gas under certain conditions, and the eutectic absorbent desorbs hydrogen chloride under certain temperature and pressure after absorption, the desorbed absorbent can be reused, and the absorbent has good cycle stability. The absorbent achieves highly efficient absorption and separation of HCl by forming multi-site hydrogen bonds with HCl.

[0007] The absorbent is a compound of quaternary ammonium salt and polyol in a specific ratio under certain conditions. This absorbent absorbs and desorbs hydrogen chloride under specific temperature and pressure. The structural formula of the quaternary ammonium salt in the eutectic absorbent is as follows:

[0008]

[0009] Wherein, the following conditions are met:

[0010] R1, R2, R3, and R4 are H or C. n H 2n+1 (n is an integer and 0 ≤ n ≤ 10);

[0011] For Cl - ,Br - NO3 - SO4 - ClO4 - OTf - At least one of the following. Wherein, the quaternary ammonium salt is one or more in combination.

[0012] The polyols in the eutectic absorbent include polyethylene glycol, polypropylene glycol, and compounds with the general structural formula C0. n H 2n+2-x (OH) x One or more of the polyols of (n, x≥2).

[0013] The molar ratio of quaternary ammonium salt to polyol in the eutectic absorbent is 1:(0.1-10).

[0014] The reaction temperature of the quaternary ammonium salt and polyol is 0–120 °C.

[0015] HCl is absorbed by forming strong hydrogen bonds with the eutectic absorbent, and can be desorbed by heating and / or depressurization. Preferably, the absorbent absorbs HCl at a temperature of 10–40°C and an absorption pressure of 0.1 MPa–4.0 MPa; the absorbent desorbs HCl at a temperature of 60–120°C and a desorption pressure of 0.1 kPa–1.0 MPa, and the desorbed absorbent can be recycled.

[0016] The absorbent can treat industrial exhaust gas containing hydrogen chloride gas, preferably, the concentration of hydrogen chloride in the industrial exhaust gas is 0.1% to 90%.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The eutectic absorbent provided by this invention has a higher HCl absorption capacity and better thermal stability than organic solvents and existing DESs; compared with pure ionic liquid absorbents, it has lower viscosity and lower synthesis cost; hydrogen chloride in the absorbent can be rapidly desorbed by heating and / or reducing pressure, and the absorbent is easy to regenerate and recycle.

[0019] The following description is based on specific embodiments. Detailed Implementation

[0020] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0021] Example 1

[0022] This embodiment provides an absorbent, the preparation method of which is as follows:

[0023] Weigh 0.1 mol (13.62 g) of tetramethylammonium nitrate into a 100 mL flat-bottomed conical flask, and weigh 0.02 mol (8.00 g) of polyethylene glycol 400 into the flat-bottomed conical flask. The reaction temperature is controlled at 70 °C and stirred for 6 h until the reaction is complete.

[0024] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 40 °C and 0.1 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0025] Example 2

[0026] This embodiment provides an absorbent, the preparation method of which is as follows:

[0027] Weigh 0.10 mol (6.75 g) of methylamine hydrochloride into a 100 mL flat-bottomed conical flask, and weigh 0.60 mol (37.24 g) of ethylene glycol into the flask. The reaction temperature is controlled at 90 °C and stirred for 6 h until the reaction is complete.

[0028] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 30 °C and 0.1 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0029] Example 3

[0030] This embodiment provides an absorbent, the preparation method of which is as follows:

[0031] Weigh 0.02 mol (6.45 g) of tetrabutylammonium bromide and place it in a 100 mL flat-bottomed conical flask. Weigh 0.10 mol (20.00 g) of polyethylene glycol 200 and add it to the flat-bottomed conical flask. Control the reaction temperature at 90 °C and stir for 4 h to complete the reaction.

[0032] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 40 °C and 0.2 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0033] Example 4

[0034] This embodiment provides an absorbent, the preparation method of which is as follows:

[0035] Weigh 0.10 mol (15.17 g) of butyltrimethylammonium chloride and place it in a 100 mL flat-bottomed conical flask. Weigh 0.20 mol (21.22 g) of diethylene glycol and add it to the flat-bottomed conical flask. Control the reaction temperature at 40 °C and stir for 4 h to complete the reaction.

[0036] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 10 °C and 1.0 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0037] Example 5

[0038] Weigh 0.10 mol (20.78 g) of octyltrimethylammonium chloride and place it in a 100 mL flat-bottomed conical flask. Weigh 0.10 mol (10.61 g) of diethylene glycol and 0.10 mol (15.02 g) of triethylene glycol and add them to the conical flask at the same time. Control the reaction temperature at 40 °C and stir for 4 h to complete the reaction.

[0039] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 30 °C and 3.0 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0040] Example 6

[0041] Weigh 0.05 mol (8.28 g) of tetraethylammonium chloride and 0.05 mol (16.12 g) of tetrabutylammonium bromide and place them in a 250 mL flat-bottomed conical flask. Weigh 0.50 mol (31.04 g) of ethylene glycol and 0.50 mol (100.00 g) of polyethylene glycol 200 and add them to the flat-bottomed conical flask. The reaction temperature is controlled at 40 °C and stirred for 4 h until the reaction is complete.

[0042] Add 2.00 g of the above eutectic absorbent to a 10 mL absorption bottle. Pass pure HCl gas (flow rate of 50 mL / min) into the absorption bottle at 30 °C and 4.0 MPa. Record the mass change of the absorption bottle at intervals until the absorption reaches equilibrium. The absorbent after absorbing HCl is desorbed by heating and depressurization.

[0043] Example 7

[0044] The absorbent provided in Example 4 was subjected to a cyclic absorption-desorption test. Specifically, 5.00 g of absorbent was added to a 20 mL absorption bottle, and HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle at 30 °C and 0.1 MPa. The mass change of the absorption bottle was recorded at intervals until absorption reached equilibrium. The saturated absorbent was then desorbed by heating and reducing the pressure (60 °C and 30 kPa). After five consecutive absorption-desorption cycles, the results are shown in Table 1. The absorbent provided in this example exhibits stable performance.

[0045] Table 1. Absorption-desorption cycle stability test of absorbent for hydrogen chloride gas.

[0046]

[0047] As shown in Table 1, the absorbent of the present invention exhibits good stability in the absorption of hydrogen chloride over 5 cycles and has good regeneration performance.

[0048] Comparative Example 1

[0049] This comparative example provides an absorbent, specifically EG: ethylene glycol.

[0050] Comparative Example 2

[0051] This comparative example provides an absorbent, specifically DEG: diethylene glycol.

[0052] Comparative Example 3

[0053] This comparative example provides an absorbent, specifically ChCl-EG (1:2): choline chloride and ethylene glycol.

[0054] The absorption effect of the absorbents provided in Comparative Examples 1-3 on hydrogen chloride gas was tested using the following method: 2.00 g of absorbent was added to a 10 mL absorption bottle, and pure HCl gas (flow rate of 50 mL / min) was introduced into the absorption bottle at 30 °C and 0.1 MPa. The mass change of the absorption bottle was recorded at intervals until the absorption reached equilibrium. The absorbent after absorbing HCl was desorbed by heating and depressurization.

[0055] Table 2 shows the test results of the absorption effect of the absorbents provided in Examples 1-7 on hydrogen chloride gas and the test results of the absorption effect of the absorbents provided in Comparative Examples 1-3 on hydrogen chloride gas.

[0056] From Table 2, the following points can be concluded: Compared with the absorbents provided in Comparative Examples 1-3, the absorbents provided in Examples 1-6 of the present invention can achieve efficient absorption and separation of hydrogen chloride gas.

[0057] Table 2. Test results of the absorbent's absorption effect on hydrogen chloride gas.

[0058]

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A highly efficient eutectic absorbent for separating hydrogen chloride, characterized in that: The eutectic absorbent has an absorption temperature of 10–40°C and an absorption pressure of 0.1 MPa–4.0 MPa for the tail gas containing hydrogen chloride. The absorbent desorbs hydrogen chloride at a temperature of 60–120°C and a desorption pressure of 0.1 kPa–1.0 MPa. The concentration of hydrogen chloride in the exhaust gas ranges from 0.1% to 90%. The eutectic absorbent is synthesized by compounding a quaternary ammonium salt and a polyol in a molar ratio of 1:(0.1-10) at a temperature of 0-120 °C. The structural formula of the quaternary ammonium salt in the eutectic absorbent is as follows: Where R1, R2, R3, and R4 are H or C. n H 2n+1 (n is an integer and 0 ≤ n ≤ 10); NO3 - SO4 - ClO4 - OTf - At least one of them; The quaternary ammonium salt is one or more in combination; The polyol in the eutectic absorbent includes one or more of polyethylene glycol and polypropylene glycol.

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