Method for preparing sulfur by using acetamide modified guanidyl water-containing eutectic solvent

Abstract

The invention belongs to the field of valuable resource recovery, and discloses a method for preparing sulfur by using an acetamide modified guanidyl water-containing eutectic solvent. The method comprises the following steps: mixing acetamide modified guanidyl ionic liquid and water to prepare a water-containing eutectic solvent absorbent; the method comprises the following steps: absorbing sulfur dioxide gas by adopting a water-containing deep eutectic solvent absorbent to obtain a SO2-rich water-containing absorbent; h2S gas is introduced into the SO2-rich water-containing absorbent, stirring is carried out at the same time, a Claus reaction is carried out, a reaction product is heated to the temperature above the melting point of sulfur, cooling separation is carried out, and separated sulfur and a regenerated absorbent are obtained. According to the method, the defect that the Claus conversion rate of a traditional absorbent is low under a water-containing system can be overcome, the SO2 conversion rate can be increased to 95.37% by means of the method for preparing the sulfur through the acetamide modified guanidyl water-containing eutectic solvent, and the conversion rate of the sulfur is greatly increased.

Description

Technical Field

[0001] The invention belongs to the field of valuable resource recovery, and in particular relates to a method for preparing sulfur by utilizing acetamide-modified guanidine-containing water-containing deep eutectic solvent. Background Art

[0002] During the high-temperature smelting process of non-ferrous metal sulfur-containing minerals, a large amount of sulfur dioxide (SO2) flue gas is produced. Excessive emission of SO2 will produce a large amount of acid rain, which will harm buildings and trees, and endanger human health. At the same time, SO2 is also an important raw material for chemical production. It can be used to produce common chemical products such as sulfuric acid and sulfur. Therefore, the green and efficient treatment of SO2 in non-ferrous smelting flue gas has become the focus of flue gas purification.

[0003] Traditional flue gas desulfurization methods include calcium method, ammonia method, seawater desulfurization, etc. Although they are widely used, they still have problems such as low by-product utilization, difficult absorbent regeneration, and serious secondary pollution. It is urgent to develop new SO2 adsorbents and realize recycling and regeneration of desulfurization methods. Ionic liquids (ILs) are composed of organic cations and organic (inorganic) anions. They are a kind of salt in a molten state near room temperature. They have the characteristics of anion and cation construction, green and pollution-free, low vapor pressure, and recyclable after desorption. They are extremely efficient desulfurizers. The main desulfurization principle of ILs is to use its functional groups and chemical bonds to physically and chemically absorb SO2 gas, thereby achieving the purpose of capturing SO2.

[0004] At present, the main use of ionic liquids to recover SO2 is to prepare sulfuric acid. However, sulfuric acid will inevitably have high maintenance costs and high risks during storage and transportation, so converting SO2 into a stable substance can effectively solve such problems. Using the liquid-phase Claus reaction to convert SO2 into elemental sulfur is an innovative study to achieve SO2 conversion and recovery. It makes up for the problem of low SO2 utilization after absorption, and also reduces the difficulty of storage and transportation of acid or gas production after SO2 desorption. In addition, the ILs after desorption can be recycled, which minimizes the cost investment from a macro perspective. Most ionic liquids have high viscosity. In actual production, adding water to the absorbent can not only improve the fluidity of the ionic liquid and accelerate the reaction and mass transfer, but also reduce the cost of using the absorbent. However, in current research, the participation of water will significantly reduce the conversion rate of the liquid-phase Claus reaction, and traditional water-containing absorbents are not suitable for the preparation of sulfur. Patent document with publication number CN109876601A discloses a method for converting SO2 into sulfur by coupling Claus reaction in ionic liquid. The method uses ethanolamine lactate to achieve an SO2 conversion rate of 96% in a water-free system, but the SO2 conversion rate is not high in a system containing 30-50wt% water. Therefore, it is urgent to find a method for improving the Claus conversion rate of aqueous ionic liquid. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a method for preparing sulfur by using acetamide-modified guanidine-containing water-containing deep eutectic solvent.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent comprises the following steps: (1) mixing acetamide-modified guanidine-based ionic liquid and water to prepare a water-containing deep eutectic solvent absorbent; (2) using the water-containing deep eutectic solvent absorbent obtained in step (1) to absorb sulfur dioxide gas to obtain a SO2-rich water-containing absorbent; (3) introducing H2S gas into the SO2-rich aqueous absorbent obtained in step (2) while stirring to cause a Claus reaction; (4) The reaction product obtained after step (3) is heated to a temperature above the melting point of sulfur, and then cooled and separated to obtain separated sulfur and regenerated absorbent. In this step, the sulfur is liquefied and agglomerated by heating to the melting point of sulfur, and the sulfur and absorbent are separated after cooling to obtain the regenerated absorbent.

[0007] In the above-mentioned method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, the mass content of water in the water-containing deep eutectic solvent absorbent is 30-70%.

[0008] In the above method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, in step (3), the pressure of the introduced H2S gas is 0.05-0.25 MPa.

[0009] In the above method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, in step (3), the reaction temperature is 30-80° C. and the reaction time is 10-90 min.

[0010] In the above method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, the water-containing deep eutectic solvent absorbent is prepared by the following preparation method: Acetamide (AA) is added to tetramethylguanidine acetate ([TMG]Ac) at 50°C to 80°C, heated and stirred for more than 0.5h, and then mixed with water to prepare a water-containing deep eutectic solvent absorbent ([TMG]Ac-AA).

[0011] In the above-mentioned method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, the molar ratio of the tetramethylguanidine acetate to the acetamide is 3:(1-9).

[0012] In the above-mentioned method for preparing sulfur using acetamide-modified guanidine-containing deep eutectic solvent, preferably, the tetramethylguanidine acetate is prepared by the following preparation method: taking equimolar amounts of 1,1,3,3-tetramethylguanidine and acetic acid respectively dissolved in anhydrous ethanol, adding the obtained solutions to a three-necked flask and a constant pressure funnel respectively, opening the constant pressure funnel to allow 1,1,3,3-tetramethylguanidine and acetic acid to react, after the reaction is completed, removing water and organic solvents through a rotary evaporator, and drying the product to obtain tetramethylguanidine acetate.

[0013] In the above method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, preferably, the reaction is carried out under cold water bath conditions, and the temperature of the cold water bath is 10°C to 20°C.

[0014] The main principle of the present invention is: after the absorbent captures SO2, H2S at a certain pressure is injected into the absorbent containing SO2, so that it undergoes Claus reaction to convert SO2 into valuable resource sulfur element, thus realizing high-value recycling of SO2. The Claus reaction equation is: SO2+2H2S=3S+2H2O. When the absorbent contains a large amount of water, SO2 exists in the aqueous solution as three substances (H2SO3>HSO3 - >SO3 2- ), of which SO3 2- It does not react with H2S. The lower the pH of the absorbent, the closer the type and ratio of its S (IV) are to the left, which is conducive to improving the conversion rate. The SO2 conversion rate increases as the pH in the system decreases, but the increase in the acidity of the system will reduce the SO2 absorption. In order to keep the SO2 absorption and conversion rate of the aqueous system at a high level, the present invention modifies tetramethylguanidine acetate by adding acetamide, thereby achieving the purpose of high absorption and high conversion. The deep eutectic solvent obtained by mixing acetamide and tetramethylguanidine acetate forms a strong hydrogen bond with SO2, so that the absorbed SO2 is mainly present in the aqueous absorbent in the form of hydrogen bonds. The acetamide-modified absorbent not only has a low viscosity and is suitable for reaction and mass transfer, but also the SO2 captured by the aqueous absorbent can be efficiently converted into sulfur, and the absorbed SO2 after modification will not be reduced.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can overcome the shortcomings and defects of low Claus conversion rate in traditional absorbent water-containing systems. The method of preparing sulfur using acetamide-modified guanidine-containing deep eutectic solvent can increase the SO2 conversion rate to 95.37%, greatly improving the sulfur conversion rate.

[0016] (2) The acetamide-modified guanidine-based water-containing deep eutectic solvent used in the present invention is an ideal solvent for capturing acidic gases. It has similar properties to ionic liquids and is obtained by simply mixing two components. Its synthesis steps are simple, the cost is low, and most of it is biodegradable and has a high SO2 absorption capacity.

[0017] (3) The acetamide-modified guanidine-based water-containing deep eutectic solvent used in the present invention can be reused, thereby realizing the green recycling of the absorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The effect of different water contents of tetramethylguanidine acetate on SO2 conversion efficiency in Comparative Example 1.

[0019] Figure 2 This is a graph showing the effect of different molar mixing ratios of tetramethylguanidine acetate and acetamide on the SO2 conversion efficiency of the aqueous absorbent in Example 1.

[0020] Figure 3 This is a graph showing the effect of different H2S pressures on SO2 conversion efficiency in Example 2.

[0021] Figure 4 This is a graph showing the effect of different water mass fractions on SO2 conversion efficiency in Example 3.

[0022] Figure 5 This is a graph showing the effect of different Claus reaction temperatures on SO2 conversion efficiency in Example 4.

[0023] Figure 6 This is a graph showing the effect of different Claus reaction times on SO2 conversion efficiency in Example 5. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0025] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0026] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0027] Comparative Example 1: This comparative example mainly examines the effect of different water contents of common tetramethylguanidine acetate on SO2 conversion efficiency. The specific steps are as follows: (1) Weigh tetramethylguanidine acetate to prepare aqueous absorbents with water contents of 0%, 30%, 50% and 70% respectively, and conduct subsequent parallel tests. Then take 5g of the aqueous absorbent in a 25mL glass pressure tube, place it in a 30℃ water bath, and heat it for 50ml / min. -1 Pure SO2 gas flow is passed into the absorbent. After continuous flow for 1 hour, the absorbent after adsorbing SO2 is obtained. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0028] (2) Add a stirring rotor to the glass pressure tube containing the absorbent after adsorbing SO2 obtained in step (1), place the pressure tube in a water bath, and set the water bath temperature to 30°C. To ensure sufficient reaction, the H2S pressure needs to be excessive. The H2S pressure is controlled at 0.2MPa by a pressure gauge. Open the valve to allow H2S to contact the absorbent that has absorbed SO2. Control the rotor speed to 200rpm and react for 1.5h.

[0029] (3) Due to the viscosity and loose porosity of sulfur, sulfur is prone to clogging during industrial production and is difficult to separate by flushing and filtration. Therefore, it is urgent to develop a separation method suitable for industrial applications. Based on the physical properties of sulfur's low melting point (119 °C) and the high stability of ionic liquids, and the fact that the Claus reaction releases huge amounts of heat, a method for separating sulfur by heating is used. The mixture obtained in step (2) is heated to 120 °C to melt the sulfur into droplets that precipitate at the bottom of the reactor. After cooling, the sulfur and ionic liquid are directly separated. The SO2 conversion rate is calculated based on the change in the amount of SO2 and the actual weight of sulfur obtained. The effect of ordinary aqueous tetramethylguanidine acetate on the SO2 conversion efficiency is shown in the following figure. Figure 1 shown.

[0030] from Figure 1 It can be seen that when the water content of the ordinary tetramethylguanidine acetate absorbent system is 0%, 30%, 50% and 70wt%, its SO2 conversion rate is 94.58%, 78.64%, 74.51% and 73.81% respectively. From the experimental results, it can be clearly seen that when the water content of the ordinary tetramethylguanidine acetate absorbent increases, the SO2 conversion rate will gradually decrease. The water content of the tetramethylguanidine acetate absorbent is not conducive to the Claus reaction, which leads to a decrease in the SO2 conversion rate.

[0031] Embodiment 1: This example mainly examines the effect of modification of tetramethylguanidine acetate and acetamide at different molar mixing ratios on SO2 conversion efficiency. The specific steps are as follows: (1) Take equimolar amounts of tetramethylguanidine and acetic acid and dissolve them in an appropriate amount of anhydrous ethanol, respectively. Add the obtained tetramethylguanidine solution and acetic acid solution to a three-necked flask and a constant pressure funnel, respectively. Open the constant pressure funnel to allow the reaction to proceed. The reaction is carried out in a cold water bath (15°C). After the reaction, water and organic solvents are removed by rotary evaporation. The final product is dried under vacuum at 60°C for 48 h to remove moisture, thereby obtaining tetramethylguanidine acetate ([TMG]Ac). Then, at 80°C, different molar amounts of acetamide (AA) (molar ratios of 3:0, 3:1, 2:1, 1:1, 1:2, and 1:3, respectively) are added to [TMG]Ac for parallel experiments. The mixture is heated and stirred for 1 h to obtain [TMG]Ac-AA absorbent, which is then prepared with water to prepare absorbents with a water content of 50 wt%. Take 5 g of the water-containing absorbent in a 25 mL glass pressure tube and place it in a 30°C water bath. Heat 50 ml min -1 Pure SO2 gas flow is passed into the absorbent. After continuous flow for 1 hour, the absorbent after adsorbing SO2 is obtained. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0032] (2) Add a stirring rotor to the glass pressure tube containing the SO2 absorbent, place the pressure tube in a water bath, and set the water bath temperature to 30°C. To ensure sufficient reaction, the H2S pressure needs to be excessive. The H2S pressure is controlled at 0.2MPa by a pressure gauge. Open the valve to allow H2S to contact the absorbent that has absorbed SO2. Control the stirring rotor speed to 200rpm and react for 1.5h.

[0033] (3) The mixture obtained in step (2) is heated to 120°C to melt the sulfur into droplets and precipitate at the bottom of the reactor. After cooling, the sulfur and the ionic liquid are directly separated. The SO2 conversion rate is calculated based on the change in the amount of SO2 and the actual weight of sulfur obtained. The effects of different molar mixing ratios of tetramethylguanidine and acetamide on the SO2 conversion efficiency are shown in the following table. Figure 2 shown.

[0034] from Figure 2It can be seen that the Claus conversion rate of the synthesized deep eutectic aqueous absorbent [TMG]Ac-AA is significantly higher than that of the [TMG]Ac aqueous absorbent. As the content of acetamide increases, its SO2 conversion rate increases significantly, and when the molar ratio of [TMG]Ac and AA is 1:1, the SO2 conversion rate is the highest, and its conversion rate is 95.37%. The conversion rate of the original [TMG]Ac aqueous absorbent is only 74.51%. The addition of acetamide increases the Claus conversion rate of the [TMG]Ac aqueous absorbent by nearly 20%. This may be because the synthesized deep eutectic solvent [TMG]Ac-AA and SO2 form a strong intramolecular hydrogen bond, which makes the interaction energy between DES and SO2 higher than the interaction energy of the [TMG]Ac] absorption process. When the molar ratio of tetramethylguanidine acetate and acetamide exceeds 1:1, as the content of acetamide continues to increase, the SO2 conversion rate shows a downward trend. This may be because with the large amount of acetamide added, the alkalinity of the system increases, resulting in a part of the sulfur dioxide absorbed by the absorbent being converted into SO3 2- exists in the form of SO3 2- It is difficult to react with H2S to generate elemental sulfur, resulting in a decrease in SO2 conversion rate.

[0035] Embodiment 2: This example mainly examines the effect of different H2S pressures on SO2 conversion efficiency. The specific process is as follows: (1) Weigh 5 g of the acetamide-modified absorbent [TMG]Ac-AA prepared in Example 1 with the optimal molar ratio of [TMG]Ac to AA being 1:1 and 5 g of H2O in a beaker to prepare an absorbent with a water content of 50 wt%. Take 5 portions of the water-containing absorbent, each weighing 5 g, and place them in a 25 mL glass pressure tube for parallel testing. Place them in a 30°C water bath and heat them at 50 ml / min. -1 Pure SO2 gas flow is passed into the absorbent, and the absorbent after adsorbing SO2 is obtained after 1 hour. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0036] (2) Add a stirring rotor to the glass pressure tube containing SO2 absorbent, place the pressure tube in a water bath, and set the water temperature to 30°C. Use a pressure gauge to control the H2S pressure to 0.05, 0.10, 0.15, 0.20, and 0.25 MPa, respectively. Open the valve to allow H2S to contact the absorbent that has absorbed SO2. Control the stirring speed to 200 rpm and let it react for 1.5 hours. The results of the effect of different H2S pressures on SO2 conversion efficiency are shown in the figure. Figure 3 shown.

[0037] from Figure 3It can be seen that when the hydrogen sulfide pressure is 0.05, 0.10, 0.15, 0.20, and 0.25MPa, the SO2 conversion rate is 64.12%, 78.53%, 97.95%, 97.36%, and 95.87%, respectively. The experimental results show that when the hydrogen sulfide pressure is less than 0.15MPa, as the pressure increases, its conversion rate also increases significantly; when the hydrogen sulfide pressure is greater than 0.15MPa, as the pressure continues to increase, its conversion rate remains almost unchanged, and then decreases slightly. This is because when the pressure is too low, hydrogen sulfide does not reach the stoichiometric ratio and the reaction is not complete. When the hydrogen sulfide pressure is excessive, a small amount of sulfur will dissolve in the absorbent, reducing the actual sulfur yield.

[0038] Embodiment 3: This example mainly examines the effect of different water content in the absorbent on the SO2 conversion efficiency. The specific steps are as follows: (1) Weigh different masses of H2O and acetamide modified absorbent [TMG]Ac-AA to prepare acetamide modified absorbents with different mass percentages, wherein the water content is 30%, 40%, 50%, 60% and 70%, wherein [TMG]Ac-AA (1:1) is prepared according to the optimal molar ratio of [TMG]Ac to AA of 1:1 in Example 1. Take 5 g of absorbents with different water contents in 25 mL glass pressure tubes, place them in a 30°C water bath, and heat for 50 ml min. -1 Pure SO2 gas flow is passed into the absorbent. After continuous flow for 1 hour, the absorbent after adsorbing SO2 is obtained. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0039] (2) Add a stirring rotor to the glass pressure tube containing SO2 absorbent, place the pressure tube in a water bath, and set the water temperature to 30°C. Set the hydrogen sulfide pressure to 0.15MPa, open the valve to allow H2S to contact the absorbent that has absorbed SO2, control the stirring rotor speed of the water bath to 200rpm and let it react for 1.5h. The results of the effect of different water content absorbents on SO2 conversion efficiency are shown in the figure. Figure 4 shown.

[0040] from Figure 4 It can be seen that when the water content of the absorbent is 30%, 40%, 50%, 60%, and 70%, the SO2 conversion rate is 98.46%, 98.17%, 97.95%, 92.13%, and 87.34%, respectively. The experimental results show that the SO2 conversion rate decreases with the increase of the water content in the absorbent. This is because the more water in the system, the lower the SO2 content of the absorbent, and the absorbed SO2 will dissolve in water to generate SO3 2- , and SO3 2- It is difficult to react with H2S to generate elemental sulfur, resulting in a decrease in SO2 conversion rate.

[0041] Embodiment 4: This example mainly examines the effect of different Claus reaction temperatures on SO2 conversion efficiency. The specific process is as follows: (1) Weigh 6 parts of 5g H2O and 5g acetamide modified absorbent [TMG]Ac-AA to prepare acetamide modified absorbent with 50% water content for parallel experiments, wherein [TMG]Ac-AA (1:1) is prepared according to the optimal molar ratio of [TMG]Ac and AA of 1:1 in Example 1. Take 5g of the water-containing absorbent in a 25mL glass pressure tube. Place it in a water bath and set the water bath temperature to 30℃, 40℃, 50℃, 60℃, 70℃ and 80℃ respectively. Add 50ml·min -1 Pure SO2 gas flow is passed into the absorbent. After continuous flow for 1 hour, the absorbent that adsorbs SO2 is obtained. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0042] (2) Add a stirring rotor to the glass pressure tube containing SO2 absorbent, place the pressure tube in a water bath, and set the water temperature to 30℃, 40℃, 50℃, 60℃, 70℃, and 80℃. Set the hydrogen sulfide pressure to 0.15MPa, open the valve to allow H2S to contact the absorbent that has absorbed SO2, and control the stirring rotor to 200rpm to allow it to react for 1.5h. The results of the effect of different Claus reaction temperatures on SO2 conversion efficiency are shown in the figure. Figure 5 shown.

[0043] from Figure 5 It can be seen that when the temperature is 30℃, 40℃, 50℃, 60℃, 70℃, and 80℃, the SO2 conversion rates are 97.95%, 98.54%, 98.77%, 98.3%, 97.45%, and 97.02%, respectively. When the temperature range is 30~50℃, as the temperature increases, the SO2 conversion rate shows a slightly upward trend. When the temperature is greater than 50℃, the SO2 conversion rate gradually begins to decrease. This is because when the temperature begins to rise, the SO2 captured by the absorbent is desorbed from it by heat, which improves the reaction mass transfer effect. However, the Claus reaction is an exothermic reaction. Once SO2 and H2S come into contact, a large amount of heat will be released. If the system temperature is too high, the forward reaction will be inhibited. According to the experimental results, the optimal reaction temperature of the absorbent is 30℃ in terms of comprehensive economy.

[0044] Embodiment 5: This example mainly examines the effect of different Claus reaction times on SO2 conversion efficiency. The specific steps are as follows: (1) Weigh 5g H2O and 5g acetamide modified absorbent [TMG]Ac-AA (1:1) and mix to prepare acetamide modified absorbent with 50% water content. Take 5g of the water-containing absorbent into a 25mL glass pressure tube and place it in a water bath. Set the water bath temperature to 30℃. Add 50ml·min -1 Pure SO2 gas flow is passed into the absorbent. After continuous flow for 1 hour, the absorbent after adsorbing SO2 is obtained. The change in mass of the absorbent before and after absorption is recorded using an electronic balance.

[0045] (2) Add a stirring rotor to the glass pressure tube containing SO2 absorbent, place the pressure tube in a water bath, control the water bath temperature to 30°C, set the hydrogen sulfide pressure to 0.15MPa, open the valve to allow H2S to contact the absorbent that has absorbed SO2, control the water bath speed to 200rpm, and let it react for different times. The results of the effect of different Claus reaction times on SO2 conversion efficiency are shown in the figure. Figure 6 shown.

[0046] from Figure 6 It can be seen that when the Claus reaction time is 10min, 30min, 60min, 90min, and 120min, the SO2 conversion rates are 66.64%, 74.16%, 84.36%, 97.95%, and 98.11%, respectively. In the entire Claus reaction, the SO2 conversion rate is the fastest within the first ten minutes of the reaction, and the SO2 conversion rate can reach 66.64%. After that, as time increases, the SO2 conversion rate slowly increases, and at 90min, the reaction is nearly complete. According to the experimental results, the optimal reaction time of the absorbent is 90min in terms of comprehensive economy.

Claims

1. A method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent, characterized in that: The following steps are involved: (1) mixing acetamide-modified guanidine-based ionic liquid and water to prepare a water-containing deep eutectic solvent absorbent; (2) using the water-containing deep eutectic solvent absorbent obtained in step (1) to absorb sulfur dioxide gas to obtain a SO2-rich water-containing absorbent; (3) introducing H2S gas into the SO2-rich aqueous absorbent obtained in step (2) while stirring to cause a Claus reaction; (4) The reaction product obtained after step (3) is heated to a temperature above the melting point of sulfur, and then cooled and separated to obtain separated sulfur and regenerated absorbent.

2. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent according to claim 1, characterized in that: The mass content of water in the water-containing deep eutectic solvent absorbent is 30-70%.

3. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent according to claim 1, characterized in that: In step (3), the pressure of the introduced H2S gas is 0.05~0.25MPa.

4. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent according to claim 1, characterized in that: In step (3), the reaction temperature is 30-80°C and the reaction time is 10-90 minutes.

5. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent according to claim 1, characterized in that: The water-containing deep eutectic solvent absorbent is prepared by the following preparation method: At 50°C to 80°C, add acetamide to tetramethylguanidine acetate, heat and stir for more than 0.5h, and then prepare a water-containing deep eutectic solvent absorbent with water.

6. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent according to claim 5, characterized in that: The molar ratio of the tetramethylguanidine acetate to the acetamide is 3:(1-9).

7. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent as claimed in claim 5, characterized in that: The tetramethylguanidine acetate is prepared by the following preparation method: taking equimolar amounts of 1,1,3,3-tetramethylguanidine and acetic acid respectively dissolved in anhydrous ethanol, adding the obtained solutions into a three-necked flask and a constant pressure funnel respectively, opening the constant pressure funnel to allow 1,1,3,3-tetramethylguanidine and acetic acid to react, removing water and organic solvent after the reaction is completed, and drying to obtain tetramethylguanidine acetate.

8. The method for preparing sulfur using acetamide-modified guanidine-containing water-containing deep eutectic solvent as claimed in claim 7, characterized in that: The reaction is carried out in a cold water bath at a temperature of 10°C to 20°C.

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