Process for treating chlorinated off-gas

Abstract

The present application relates to a treatment process of chlorination tail gas, comprising: providing the chlorination tail gas, the chlorination tail gas comprising at least sulfur dioxide gas and hydrogen chloride gas; using sulfuryl chloride to carry out cooling absorption treatment on the chlorination tail gas to obtain absorption liquid and residual tail gas; carrying out at least two-stage methanol absorption treatment on the residual tail gas to obtain hydrogen chloride methanol solution; carrying out desorption treatment on the absorption liquid to obtain desorption tail gas; carrying out acyl chloride synthesis reaction on the desorption tail gas and chlorine under the action of a catalyst to obtain sulfuryl chloride, and the sulfuryl chloride is recycled for the cooling absorption treatment of the chlorination tail gas. The treatment process of the chlorination tail gas can not only realize the recycling of sulfur element, but also can prepare high-purity hydrogen chloride methanol solution, broaden the use of hydrogen chloride gas, and has significant environmental protection and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of chemical waste gas treatment technology, and in particular to a treatment process for chlorinated waste gas. Background Technology

[0002] Currently, in industrial production of 4-chloro-3,5-dimethylphenol, the chlorinated tail gas generated from the use of chlorinating agents (such as thioyl chloride) is mostly separated from hydrogen chloride gas by pressure separation. However, the sulfur dioxide gas separated by this method contains a small amount of tetrachloroethylene, which can react with chlorine gas to form solid hexachloroethane during the synthesis of thioyl chloride, posing a risk of clogging the acyl chloride synthesis reactor. Simultaneously, the separated hydrogen chloride gas also contains a small amount of sulfur, limiting the applications of the prepared hydrochloric acid solution. Furthermore, the pressure separation equipment used in this method not only occupies a large area but also incurs high investment costs.

[0003] Therefore, there is an urgent need to find a more economical and effective method to separate and reuse the chlorinated tail gas generated during the production of 4-chloro-3,5-dimethylphenol, improve the comprehensive utilization value of hydrogen chloride gas and sulfur dioxide gas, and reduce the cost of chlorinated tail gas treatment. Summary of the Invention

[0004] Therefore, it is necessary to provide a treatment process for chlorinated tail gas to address the above problems. This treatment process can not only realize the recycling of sulfur, but also prepare a high-purity hydrogen chloride methanol solution, thus broadening the applications of hydrogen chloride gas and providing significant environmental and economic benefits.

[0005] A process for treating chlorinated tail gas, comprising:

[0006] Provide chlorinated tail gas, said chlorinated tail gas comprising at least sulfur dioxide gas and hydrogen chloride gas;

[0007] The chlorinated tail gas was subjected to cooling and absorption treatment using sulfuryl chloride to obtain an absorbent and residual tail gas.

[0008] The remaining tail gas is subjected to at least two-stage methanol absorption treatment to obtain a hydrogen chloride methanol solution.

[0009] The absorbent is desorbed to obtain desorbed tail gas;

[0010] The desorption tail gas and chlorine are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride, which is then recycled for the cooling and absorption treatment of chlorinated tail gas.

[0011] In one embodiment, in the step of using sulfuryl chloride to cool and absorb the chlorinated tail gas, the cooling and absorption temperature is -30°C to 10°C.

[0012] And / or, in the step of using sulfuryl chloride to cool and absorb the chlorinated tail gas, at least three stages of cooling and absorption treatment are performed.

[0013] In one embodiment, the step of treating the remaining exhaust gas with at least two-stage methanol absorption meets at least one of the following conditions:

[0014] (1) The methanol absorption treatment temperature is -30℃ to 10℃;

[0015] (2) The remaining tail gas is subjected to three-stage methanol absorption treatment;

[0016] (3) When the mass fraction of dimethyl sulfate in the primary methanol absorbent is greater than or equal to 10%, the primary methanol absorbent obtained from the primary methanol absorption treatment is subjected to distillation to separate dimethyl sulfate, distillation tail gas and methanol.

[0017] (4) The methanol absorption tail gas obtained from the final stage methanol absorption treatment is reused in the next stage methanol absorption treatment.

[0018] In one embodiment, the distillation tail gas is recycled to a secondary methanol absorption treatment, and the methanol is further recycled to a methanol absorption treatment.

[0019] In one embodiment, the desorption treatment temperature for the absorbent liquid is between 0°C and 60°C.

[0020] In one embodiment, in the step of performing an acyl chloride synthesis reaction between the desorption tail gas and chlorine gas under the action of a catalyst, at least one of the following conditions is met:

[0021] (1) The molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas is 1.05:1-1.2:1;

[0022] (2) The catalyst is activated carbon, and the particle size of the activated carbon is 4mm-8mm;

[0023] (3) The reaction temperature for the synthesis of acyl chloride is from -20℃ to 0℃.

[0024] In one embodiment, the chlorinated tail gas is the reaction tail gas generated by a chlorination reaction using thioyl chloride as a chlorinating agent.

[0025] In one embodiment, the thioyl chloride obtained by reacting the desorption tail gas and chlorine gas under the action of a catalyst is recycled for chlorination reaction;

[0026] And / or, in the step of performing the desorption tail gas and chlorine gas in the action of a catalyst to carry out the acyl chloride synthesis reaction, an acyl chloride synthesis tail gas is also obtained. When the mass fraction of hydrogen chloride gas in the acyl chloride synthesis tail gas is greater than or equal to 95%, the acyl chloride synthesis tail gas is recycled to the chlorination reaction; otherwise, the acyl chloride synthesis tail gas is continued to be recycled to the acyl chloride synthesis reaction step.

[0027] In one embodiment, the chlorinated tail gas is the reaction tail gas generated during the chlorination reaction of 3,5-dimethylphenol and thioyl chloride to produce 4-chloro-3,5-dimethylphenol, and the chlorinated tail gas also includes tetrachloroethylene.

[0028] In one embodiment, during the desorption treatment of the absorbent, an desorption solution is also obtained. When the mass fraction of tetrachloroethylene in the desorption solution is greater than or equal to 10%, the desorption solution is used in the chlorination reaction; otherwise, the desorption solution is used in the cooling absorption treatment step.

[0029] In the chlorination tail gas treatment process of this invention, the difference in solubility of sulfur dioxide gas and hydrogen chloride gas in sulfuryl chloride is utilized. At the same time, the characteristic of sulfur dioxide gas liquefying at low temperature is combined with the use of sulfuryl chloride to cool and absorb the chlorination tail gas, so that the sulfur dioxide gas can be completely absorbed by the sulfuryl chloride, and absorbent liquid and residual tail gas are obtained. At this time, the residual tail gas does not contain sulfur dioxide gas, thereby achieving effective separation of sulfur dioxide gas and hydrogen chloride gas. Simultaneously, the remaining tail gas is treated with methanol absorption, which effectively removes the sulfuryl chloride entrained in the tail gas and yields a high-purity hydrogen chloride methanol solution with a purity ≥99%, which can be used to produce high-value-added products (trimethyl orthoacetate, methyl benzoate). The absorbent is then desorbed to remove sulfur dioxide gas, resulting in pure sulfur dioxide gas, i.e., desorbed tail gas. The desorbed tail gas and chlorine are then reacted with acyl chloride to completely convert sulfur dioxide gas into sulfuryl chloride. The prepared sulfuryl chloride can be recycled as an absorbent in the cooling and absorption treatment of chlorinated tail gas, thereby realizing the recycling of sulfur.

[0030] In addition, during the methanol absorption treatment of the remaining tail gas, methanol can react with sulfuryl chloride to produce dimethyl sulfate, which can be used as a methylating agent and has a wide range of applications.

[0031] Therefore, this invention can not only effectively separate sulfur dioxide and hydrogen chloride gas in chlorination tail gas, but also realize the recycling of sulfur element, and at the same time prepare high-purity hydrogen chloride methanol solution, thus broadening the application of hydrogen chloride gas and having significant environmental and economic benefits. Attached Figure Description

[0032] Figure 1 This is a schematic flow diagram of the chlorination tail gas treatment process of the present invention. Detailed Implementation

[0033] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the invention.

[0035] like Figure 1 As shown, the present invention provides a process for treating chlorinated tail gas, comprising:

[0036] Provide chlorinated tail gas, said chlorinated tail gas comprising at least sulfur dioxide gas and hydrogen chloride gas;

[0037] The chlorinated tail gas was subjected to cooling and absorption treatment using sulfuryl chloride to obtain an absorbent and residual tail gas.

[0038] The remaining tail gas is subjected to at least two-stage methanol absorption treatment to obtain a hydrogen chloride methanol solution.

[0039] The absorbent is desorbed to obtain desorbed tail gas;

[0040] The desorption tail gas and chlorine are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride, which is then recycled for the cooling and absorption treatment of chlorinated tail gas.

[0041] In the chlorination tail gas treatment process of this invention, the difference in solubility of sulfur dioxide gas and hydrogen chloride gas in sulfuryl chloride is utilized (at room temperature, the solubility of sulfur dioxide gas in sulfuryl chloride is 12.7%, and the solubility of hydrogen chloride gas in sulfuryl chloride is 0.5%). Simultaneously, taking into account the liquefaction characteristic of sulfur dioxide gas at low temperatures, sulfuryl chloride is used as an absorbent to perform cooling absorption treatment on the chlorination tail gas. During this process, sulfur dioxide gas liquefies and completely dissolves in sulfuryl chloride, thereby ensuring that the sulfur dioxide gas in the chlorination tail gas is completely absorbed by the sulfuryl chloride, yielding an absorbent liquid and residual tail gas. The residual tail gas is hydrogen chloride gas that does not contain sulfur dioxide, thus achieving effective separation of sulfur dioxide gas and hydrogen chloride gas.

[0042] Optionally, in the step of cooling and absorbing the chlorinated tail gas with sulfuryl chloride, the cooling and absorption temperature is -30°C to 10°C, preferably -20°C to -10°C. This setting further ensures complete liquefaction of sulfur dioxide gas in the chlorinated tail gas, while simultaneously improving the solubility of sulfur dioxide gas in sulfuryl chloride, further ensuring complete absorption of sulfur dioxide gas by sulfuryl chloride, thereby increasing the purity of the separated hydrogen chloride gas, which is beneficial for obtaining a high-purity hydrogen chloride methanol solution subsequently.

[0043] Optionally, in the step of cooling and absorbing the chlorinated tail gas with sulfuryl chloride, the cooling and absorption process can be carried out in one stage, two stages, three stages, or four stages, depending on the proportion of sulfur dioxide in the chlorinated tail gas. The present invention preferably carries out at least three stages of cooling and absorption. This setting is conducive to the complete dissolution of sulfur dioxide in sulfuryl chloride, further improving the separation effect of sulfur dioxide and hydrogen chloride, thereby obtaining hydrogen chloride gas with higher purity.

[0044] Optionally, in the step of using sulfuryl chloride to cool and absorb the chlorinated tail gas, the cooling and absorption treatment level is 3-8, preferably 4-5.

[0045] It is understandable that when the cooling absorption process is multi-stage, sulfuryl chloride, as an absorbent, can be applied to any stage of the cooling absorption process.

[0046] In one embodiment, the device for cooling and absorbing the chlorinated tail gas using thioyl chloride can be a falling film absorber or a spray tower, with the spray tower being preferred in this invention.

[0047] It should be noted that, in addition to hydrogen chloride gas, the remaining exhaust gas obtained above may also contain sulfuryl chloride.

[0048] To effectively remove sulfuryl chloride and improve the purity of hydrogen chloride gas, thereby increasing the purity of the hydrogen chloride methanol solution, this invention involves subjecting the remaining tail gas to at least two stages of methanol absorption treatment. In the first stage of methanol absorption treatment, the sulfuryl chloride entrained in the remaining tail gas reacts with methanol to form dimethyl sulfate, effectively removing the sulfuryl chloride from the hydrogen chloride gas and improving its purity. This results in a high-purity hydrogen chloride methanol solution with a purity ≥99% obtained in the second stage of methanol absorption treatment, suitable for producing high-value-added products such as trimethyl orthoacetate and methyl benzoate.

[0049] For example, the specific steps for preparing trimethyl orthoacetate using hydrogen chloride methanol solution are as follows: first, hydrogen chloride methanol solution is reacted with acetonitrile to form a salt, and then after alcoholysis and distillation, the finished product trimethyl orthoacetate is obtained.

[0050] In addition, the obtained dimethyl sulfate can be used as a methylating agent and has a wide range of applications. It is understood that in the step of treating the remaining tail gas with at least two stages of methanol absorption, the treatment can be selected based on the proportion of thioacryl chloride in the remaining tail gas, such as two-stage, three-stage, or four-stage methanol absorption treatment, etc. The present invention preferably performs three-stage methanol absorption treatment.

[0051] Specifically, the remaining tail gas is subjected to a first-stage methanol absorption treatment to obtain a first-stage methanol absorbent and a first-stage methanol absorption tail gas. The first-stage methanol absorption tail gas is then subjected to a second-stage methanol absorption treatment to obtain a second-stage methanol absorbent and a second-stage methanol absorption tail gas. The second-stage methanol absorbent is a high-purity hydrogen chloride methanol solution. The second-stage methanol absorption tail gas is then subjected to a third-stage methanol absorption treatment to obtain a third-stage methanol absorbent, which is also a high-purity hydrogen chloride methanol solution.

[0052] Considering that during the primary methanol absorption treatment of the remaining tail gas, the sulfuryl chloride entrained in the remaining tail gas will react with methanol to generate dimethyl sulfate, and dimethyl sulfate can be used as a methylating agent with a wide range of applications.

[0053] Therefore, in this invention, the primary methanol absorbent obtained from the primary methanol absorption treatment is subjected to distillation to separate dimethyl sulfate, distillation tail gas, and methanol. The distillation tail gas (i.e., hydrogen chloride gas) is reused in the secondary methanol absorption treatment, and the methanol is further reused in the secondary methanol absorption treatment. This arrangement not only allows for the recovery and reuse of dimethyl sulfate but also improves the recovery rate of hydrogen chloride gas and saves on methanol consumption, thereby reducing production costs.

[0054] It is understandable that methanol can be applied to any stage of methanol absorption treatment.

[0055] Optionally, when the mass fraction of dimethyl sulfate in the primary methanol absorbent is greater than or equal to 10%, the primary methanol absorbent is subjected to distillation.

[0056] In one embodiment, gas chromatography is used to determine the mass fraction of dimethyl sulfate in the primary methanol absorption solution.

[0057] Optionally, in the step of subjecting the remaining tail gas to at least two stages of methanol absorption treatment, the methanol absorption tail gas obtained from the final stage methanol absorption treatment is reused in the previous stage methanol absorption treatment. This configuration can further improve the recovery rate of hydrogen chloride gas.

[0058] It is understood that when the remaining tail gas is subjected to three-stage methanol absorption treatment, the tail gas obtained from the three-stage methanol absorption treatment is reused in the two-stage methanol absorption treatment.

[0059] In one embodiment, the apparatus for treating the remaining tail gas with methanol absorption can be a falling film absorber or a spray tower, preferably a spray tower.

[0060] In this invention, the absorbent obtained above is subjected to desorption treatment to desorb sulfur dioxide from the absorbent, resulting in desorption tail gas and desorption liquid, wherein the mass fraction of sulfur dioxide in the desorption tail gas is 85%-90%.

[0061] It should be noted that during the desorption process of this invention, the liquefied sulfur dioxide will be converted from liquid to gaseous state and desorbed simultaneously with the sulfur dioxide gas dissolved in the absorbent.

[0062] Optionally, the desorption solution can be used in the cooling absorption process. It is understood that when the cooling absorption process is multi-stage, the desorption solution can be used in any stage of the cooling absorption process.

[0063] Optionally, in the step of desorption treatment of the absorbent liquid, the desorption treatment temperature is 0°C to 60°C, preferably 30°C to 40°C. This setting allows for better desorption of sulfur dioxide from the absorbent liquid, thereby increasing the desorption rate of sulfur dioxide.

[0064] It should be noted that in this invention, the remaining tail gas is subjected to at least two stages of methanol absorption treatment to obtain a hydrogen chloride methanol solution, and the absorption liquid is subjected to desorption treatment to obtain desorbed tail gas. These two steps are not sequential and can be performed simultaneously or separately.

[0065] In this invention, the desorption tail gas and chlorine obtained above are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride. The sulfuryl chloride is then recycled for the cooling and absorption treatment of chlorination tail gas. This setup ensures that sulfur dioxide gas is completely converted into sulfuryl chloride, and the prepared sulfuryl chloride can be reused as an absorbent in the cooling and absorption treatment of chlorination tail gas, i.e., recycled throughout the entire reaction system, thereby achieving the recycling of sulfur.

[0066] Optionally, the molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas is 1.05:1-1.2:1, preferably 1.05:1-1.1:1. This setting allows the sulfur dioxide gas to react more fully with the chlorine gas and be completely converted into thioacryl chloride.

[0067] Optionally, in the step of the desorption tail gas and chlorine gas undergoing acyl chloride synthesis reaction under the action of a catalyst, the catalyst is activated carbon with a particle size of 4mm-8mm, and the acyl chloride synthesis reaction temperature is -20℃ to 0℃, preferably -10℃ to -5℃. This setting can further improve the reaction efficiency of the thioacyl chloride synthesis reaction.

[0068] In one embodiment, the activated carbon is coconut shell activated carbon.

[0069] Optionally, in the step of reacting the desorption tail gas and chlorine gas with a catalyst to carry out the acyl chloride synthesis reaction, an acyl chloride synthesis tail gas is also obtained, which can be reused in the acyl chloride synthesis reaction step.

[0070] In one embodiment, in the step of performing an acyl chloride synthesis reaction between the desorption tail gas and chlorine gas under the action of a catalyst, the acyl chloride synthesis reaction is carried out in a tubular reactor.

[0071] It is understood that the chlorination tail gas treatment process provided by the present invention is mainly used to treat chlorination tail gas including sulfur dioxide gas and hydrogen chloride gas. The chlorination tail gas is mainly generated by chlorination reaction. Optionally, the chlorination tail gas is reaction tail gas generated by chlorination reaction using sulfuryl chloride as chlorinating agent.

[0072] Optionally, the sulfuryl chloride obtained by reacting the desorption tail gas and chlorine gas under the action of a catalyst can be recycled for chlorination reaction. It can be understood that in this case, sulfuryl chloride acts as a chlorinating agent.

[0073] Optionally, in the step of reacting the desorption tail gas and chlorine gas with a catalyst to synthesize acyl chloride, an acyl chloride synthesis tail gas is also obtained. When the mass fraction of hydrogen chloride gas in the acyl chloride synthesis tail gas is greater than or equal to 95%, the acyl chloride synthesis tail gas is recycled back to the chlorination reaction; otherwise, the acyl chloride synthesis tail gas is continued to be recycled back to the acyl chloride synthesis reaction step. This arrangement can further improve the recycling of hydrogen chloride gas and sulfur dioxide gas, and reduce the generation of waste gas, wastewater, and solid waste.

[0074] For example Figure 1 As shown, further, the chlorination tail gas in this invention is the reaction tail gas generated during the chlorination reaction of 3,5-dimethylphenol and thioyl chloride to produce 4-chloro-3,5-dimethylphenol. At this time, the chlorination tail gas also includes tetrachloroethylene. It can be understood that the chlorination tail gas includes not only sulfur dioxide gas and hydrogen chloride gas, but also tetrachloroethylene and a mixture of phenols.

[0075] When the chlorination tail gas is the reaction tail gas generated during the chlorination reaction of 3,5-dimethylphenol and sulfuryl chloride to produce 4-chloro-3,5-dimethylphenol, the chlorination tail gas also includes tetrachloroethylene. When sulfuryl chloride is used as an absorbent to cool and absorb the chlorination tail gas, in addition to the sulfur dioxide in the chlorination tail gas being liquefied and completely dissolved in the sulfuryl chloride, the tetrachloroethylene in the chlorination tail gas will also be completely dissolved in the sulfuryl chloride because it can be mixed with sulfuryl chloride in any proportion. Thus, the sulfur dioxide gas and tetrachloroethylene in the chlorination tail gas are completely absorbed by the sulfuryl chloride, resulting in an absorbent liquid and residual tail gas that does not contain sulfur dioxide gas or tetrachloroethylene.

[0076] The remaining exhaust gas is subjected to at least two-stage methanol absorption treatment to obtain a hydrogen chloride methanol solution.

[0077] The absorbent is desorbed to obtain desorbed tail gas and desorbed liquid. The desorption treatment temperature is 0℃ to 60℃, preferably 30℃ to 40℃. This setting allows for better desorption of sulfur dioxide from the absorbent, increasing the desorption rate of sulfur dioxide. Simultaneously, it further prevents the tetrachloroethylene dissolved in the sulfuryl chloride from vaporizing and desorbing from the absorbent, ensuring complete separation of sulfur dioxide gas and tetrachloroethylene. This results in a desorbed tail gas free of tetrachloroethylene, meaning the sulfur dioxide gas does not contain tetrachloroethylene. This avoids the risk of tetrachloroethylene reacting with chlorine to form solid hexachloroethane during subsequent sulfuryl chloride synthesis, which could clog the acyl chloride synthesis reactor.

[0078] Considering that the greater the amount of tetrachloroethylene dissolved in the absorbent, the higher the possibility that tetrachloroethylene will be carried out by sulfur dioxide gas during the desorption process, this invention controls the separation standard of sulfur dioxide gas and tetrachloroethylene by controlling the content of tetrachloroethylene in the desorption liquid, so as to obtain clean sulfur dioxide gas and prevent tetrachloroethylene from being carried out and reacting with chlorine to form solid hexachloroethane, thereby posing a risk of clogging the acyl chloride synthesis reaction device.

[0079] Therefore, when the mass fraction of tetrachloroethylene in the desorption solution is greater than or equal to 10%, the desorption solution is reused in the chlorination reaction; otherwise, the desorption solution is reused in the cooling absorption treatment. This allows for better control of the tetrachloroethylene content in the desorption solution, preventing tetrachloroethylene from being carried out by the desorption tail gas, further ensuring the separation effect of tetrachloroethylene and sulfur dioxide gas, while also further improving the recovery and utilization of each component, reducing the generation of waste, improving environmental protection, and lowering production costs.

[0080] In one embodiment, the mass fraction of tetrachloroethylene in the desorption solution is determined by gas chromatography or distillation.

[0081] In one embodiment, the desorption treatment method can be thermal desorption, air stripping desorption, or negative pressure desorption, and the present invention preferably uses thermal desorption.

[0082] In one embodiment, the steps of the heating desorption method are as follows: the absorbent is placed in the device, heated to 30-40°C, and then stirred to gradually vaporize SO2 gas and HCl gas and separate them from thioacryl chloride.

[0083] Therefore, this invention can not only effectively separate sulfur dioxide and hydrogen chloride gas in chlorination tail gas, but also realize the recycling of sulfur element, and at the same time prepare high-purity hydrogen chloride methanol solution, thus broadening the application of hydrogen chloride gas and having significant environmental and economic benefits.

[0084] In addition, since sulfur dioxide gas does not need to be purified, it can be directly used in the synthesis reaction of thioacryl chloride to prepare thioacryl chloride, thereby simplifying the process route.

[0085] The treatment process for the chlorinated tail gas will be further described below through specific embodiments.

[0086] It should also be noted that the raw materials involved in the embodiments and comparative examples of this invention can all be purchased from the market. Among them, the thioyl chloride was purchased from the market (≥98%, purchased from Maclean's), and the methanol solution was purchased from the market and was of analytical grade (≥99.8%, purchased from Changshu Hongsheng Fine Chemical Co., Ltd.).

[0087] Furthermore, the compositions of the residual tail gas and the acyl chloride synthesis tail gas involved in the embodiments of this invention are all gas phase compositions measured by gas chromatography, wherein the gas chromatography analysis conditions are as follows:

[0088] Chromatographic column: DB-1 capillary column (30m × 0.53mm, 1.5μm);

[0089] Analysis conditions: column oven temperature 35℃, valve box temperature 110℃, detector temperature 205℃;

[0090] Carrier gas: Helium, flow rate 5 mL / min, reference gas flow rate 15 mL / min, constant column flow rate and make-up flow rate 10 mL / min;

[0091] Injection method: split injection, split ratio of 5:1, injection volume of 250 μL.

[0092] Example 1

[0093] The chlorination tail gas in this embodiment is the reaction tail gas generated during the chlorination reaction of 3,5-dimethylphenol and thioyl chloride to produce 4-chloro-3,5-dimethylphenol. The chlorination tail gas includes hydrogen chloride gas, sulfur dioxide gas, and tetrachloroethylene.

[0094] The chlorinated tail gas was passed into a spray tower containing sulfuryl chloride for cooling and absorption treatment at a temperature of -15°C. The absorbent and residual tail gas were separated, wherein the residual tail gas consisted of 93% hydrogen chloride gas and 7% sulfuryl chloride.

[0095] The remaining tail gas is passed into a spray tower containing a methanol solution for primary methanol absorption treatment at a temperature of -15°C, yielding primary methanol absorbent and primary methanol absorption tail gas. The mass fraction of dimethyl sulfate in the primary methanol absorbent is 8%. Then, the primary methanol absorption tail gas is passed into a spray tower containing a methanol solution for secondary methanol absorption treatment at a temperature of -15°C, yielding secondary methanol absorbent and secondary methanol absorption tail gas. The secondary methanol absorbent is a 99.4% pure hydrogen chloride methanol solution, and the secondary methanol absorption tail gas is reused in the primary methanol absorption treatment.

[0096] The absorbent obtained above was subjected to desorption treatment at a desorption temperature of 35°C, yielding desorption tail gas and desorption liquid. The desorption tail gas consisted of 88% sulfur dioxide gas, 9% hydrogen chloride gas, and 3% thioacryl chloride, while the desorption liquid contained 8% tetrachloroethylene by mass. The desorption liquid was then reused in a cooling absorption treatment, while the desorption tail gas and chlorine gas were simultaneously passed into a tubular reactor containing a catalyst for acryl chloride synthesis. The catalyst was activated carbon with a particle size of 6 mm. The molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas was 1.08:1, and the temperature was -8°C, yielding thioacryl chloride and acryl chloride synthesis tail gas. The acryl chloride synthesis tail gas contained 96% hydrogen chloride by mass. The thioacryl chloride and acryl chloride synthesis tail gas were then reused in a chlorination reaction.

[0097] Example 2

[0098] The only difference between Example 2 and Example 1 is that the above-mentioned chlorinated tail gas is passed into a spray tower containing sulfuryl chloride for cooling and absorption treatment. The temperature of the cooling and absorption treatment is -20°C, and the absorbent liquid and the remaining tail gas are separated. The remaining tail gas consists of 95% hydrogen chloride gas and 5% sulfuryl chloride.

[0099] The remaining tail gas is passed into a spray tower containing a methanol solution for primary methanol absorption treatment at a temperature of -20°C, yielding primary methanol absorbent and primary methanol absorption tail gas. The mass fraction of dimethyl sulfate in the primary methanol absorbent is 6%. Then, the primary methanol absorption tail gas is passed into a spray tower containing a methanol solution for secondary methanol absorption treatment at a temperature of -20°C, yielding secondary methanol absorbent and secondary methanol absorption tail gas. The secondary methanol absorbent is a 99.6% pure hydrogen chloride methanol solution, and the secondary methanol absorption tail gas is reused in the primary methanol absorption treatment.

[0100] The absorbent obtained above is subjected to desorption treatment at a desorption temperature of 30°C, yielding desorption tail gas and desorption liquid. The desorption tail gas consists of 90% sulfur dioxide gas, 8% hydrogen chloride gas, and 2% thioacryl chloride. The desorption liquid contains 8% tetrachloroethylene by mass. The desorption liquid is then reused in a cooling absorption treatment. Simultaneously, the desorption tail gas and chlorine gas are passed together into a tubular reactor containing a catalyst for acryl chloride synthesis reaction. The catalyst is activated carbon with a particle size of 4 mm. The molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas is 1.05:1, and the temperature is -10°C, yielding thioacryl chloride and acryl chloride synthesis tail gas. The acryl chloride synthesis tail gas contains 95% hydrogen chloride by mass. The thioacryl chloride and acryl chloride synthesis tail gas are then reused together in a chlorination reaction.

[0101] Example 3

[0102] The only difference between Example 3 and Example 1 is that the above-mentioned chlorinated tail gas is passed into a spray tower containing sulfuryl chloride for cooling and absorption treatment. The temperature of the cooling and absorption treatment is -10°C, and the absorbent liquid and the remaining tail gas are separated. The remaining tail gas consists of 90% hydrogen chloride gas and 10% sulfuryl chloride.

[0103] The remaining tail gas is passed into a spray tower containing a methanol solution for primary methanol absorption treatment at a temperature of -10°C, yielding primary methanol absorbent and primary methanol absorption tail gas. The mass fraction of dimethyl sulfate in the primary methanol absorbent is 8%. Then, the primary methanol absorption tail gas is passed into a spray tower containing a methanol solution for secondary methanol absorption treatment at a temperature of -10°C, yielding secondary methanol absorbent and secondary methanol absorption tail gas. The secondary methanol absorbent is a 99.2% pure hydrogen chloride methanol solution, and the secondary methanol absorption tail gas is reused in the primary methanol absorption treatment.

[0104] The absorbent obtained above was subjected to desorption treatment at a desorption temperature of 40°C, yielding desorption tail gas and desorption liquid. The desorption tail gas consisted of 85% sulfur dioxide gas, 11% hydrogen chloride gas, and 4% thioacryl chloride. The desorption liquid contained 8% tetrachloroethylene by mass. The desorption liquid was then reused in a cooling absorption treatment. Simultaneously, the desorption tail gas and chlorine gas were introduced together into a tubular reactor containing a catalyst for acryl chloride synthesis. The catalyst was activated carbon with a particle size of 8 mm. The molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas was 1.1:1, and the temperature was -5°C, yielding thioacryl chloride and acryl chloride synthesis tail gas. The acryl chloride synthesis tail gas contained 97% hydrogen chloride by mass. The thioacryl chloride and acryl chloride synthesis tail gas were then reused together in a chlorination reaction.

[0105] Example 4

[0106] Example 4 differs from Example 1 only in that the secondary methanol absorption tail gas is further fed into a spray tower containing methanol solution for tertiary methanol absorption treatment. The tertiary methanol absorption treatment temperature is -15℃, resulting in tertiary methanol absorption liquid and tertiary methanol absorption tail gas. The tertiary methanol absorption tail gas is reused in the secondary methanol absorption treatment, and all other conditions are the same.

[0107] The three-stage methanol absorption solution obtained in this embodiment is a hydrogen chloride methanol solution with a purity of 99.6%.

[0108] Example 5

[0109] The only difference between Example 5 and Example 1 is that the mass fraction of dimethyl sulfate in the primary methanol absorbent is 11%. The primary methanol absorbent is passed into a distillation unit for distillation to obtain dimethyl sulfate, hydrogen chloride, and methanol. The hydrogen chloride and the tail gas from the primary methanol absorption are then passed together into a spray tower containing a methanol solution for secondary methanol absorption treatment. Methanol is then reused in the secondary methanol absorption treatment, and all other conditions are the same.

[0110] The secondary methanol absorption solution obtained in this example is a hydrogen chloride methanol solution with a purity of 99.5%.

[0111] Example 6

[0112] The only difference between Example 6 and Example 1 is that the mass fraction of tetrachloroethylene in the desorption solution is 12%, and the desorption solution is used in the chlorination reaction; all other conditions are the same.

[0113] The secondary methanol absorption solution obtained in this embodiment is a hydrogen chloride methanol solution with a purity of 99.0%.

[0114] Example 7

[0115] The only difference between Example 7 and Example 1 is that the mass fraction of hydrogen chloride gas in the acyl chloride synthesis tail gas is 85%, and the acyl chloride synthesis tail gas is passed into a tubular reactor containing a catalyst to carry out the acyl chloride synthesis reaction. All other conditions are the same.

[0116] The secondary methanol absorption solution obtained in this example is a hydrogen chloride methanol solution with a purity of 99.5%.

[0117] Example 8

[0118] Example 8 differs from Example 1 only in that the chlorinated tail gas is passed into a spray tower containing sulfuryl chloride for a three-stage cooling absorption treatment. Specifically, the chlorinated tail gas is subjected to a first-stage cooling absorption treatment, a second-stage cooling absorption treatment, and a third-stage cooling absorption treatment in sequence. The temperature of the first-stage cooling absorption treatment, the second-stage cooling absorption treatment, and the third-stage cooling absorption treatment are all -15°C. The absorbent liquid and the remaining tail gas are separated. The remaining tail gas consists of 95% hydrogen chloride gas and 5% sulfuryl chloride. All other conditions are the same.

[0119] The secondary methanol absorption solution obtained in this example is a hydrogen chloride methanol solution with a purity of 99.6%.

[0120] Example 9

[0121] The only difference between Example 9 and Example 1 is that the obtained thioacryl chloride is used in a spray tower containing thioacryl chloride for cooling and absorption treatment, and the acryl chloride synthesis tail gas is used in the chlorination reaction. All other conditions are the same.

[0122] The secondary methanol absorption solution obtained in this example is a hydrogen chloride methanol solution with a purity of 99.5%.

[0123] 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.

[0124] 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 process for treating chlorinated tail gas, characterized in that, include: Provide chlorinated tail gas, said chlorinated tail gas comprising at least sulfur dioxide gas and hydrogen chloride gas; The chlorinated tail gas was subjected to cooling and absorption treatment using sulfuryl chloride to obtain an absorbent and residual tail gas. The remaining tail gas is subjected to at least two-stage methanol absorption treatment to obtain a hydrogen chloride methanol solution. The absorbent is desorbed to obtain desorbed tail gas; The desorption tail gas and chlorine are subjected to an acyl chloride synthesis reaction under the action of a catalyst to obtain sulfuryl chloride, which is then recycled for the cooling and absorption treatment of chlorinated tail gas.

2. The chlorination tail gas treatment process according to claim 1, characterized in that, In the step of using sulfuryl chloride to cool and absorb the chlorinated tail gas, the cooling and absorption temperature is -30°C to 10°C. And / or, in the step of using sulfuryl chloride to cool and absorb the chlorinated tail gas, at least three stages of cooling and absorption treatment are performed.

3. The chlorination tail gas treatment process according to claim 1, characterized in that, In the step of treating the remaining tail gas with at least two-stage methanol absorption, at least one of the following conditions is met: (1) The methanol absorption treatment temperature is -30℃ to 10℃; (2) The remaining tail gas is subjected to three-stage methanol absorption treatment; (3) When the mass fraction of dimethyl sulfate in the primary methanol absorbent is greater than or equal to 10%, the primary methanol absorbent obtained from the primary methanol absorption treatment is subjected to distillation to separate dimethyl sulfate, distillation tail gas and methanol. (4) The methanol absorption tail gas obtained from the final stage methanol absorption treatment is reused in the next stage methanol absorption treatment.

4. The chlorination tail gas treatment process according to claim 3, characterized in that, The distillation tail gas is recycled to the secondary methanol absorption treatment, and the methanol is recycled to the methanol absorption treatment.

5. The chlorination tail gas treatment process according to claim 1, characterized in that, In the step of desorbing the absorbent, the desorption temperature is from 0°C to 60°C.

6. The chlorination tail gas treatment process according to claim 1, characterized in that, In the step of reacting the desorption tail gas and chlorine gas with a catalyst to synthesize acyl chloride, at least one of the following conditions must be met: (1) The molar ratio of sulfur dioxide gas to chlorine gas in the desorption tail gas is 1.05:1-1.2:1; (2) The catalyst is activated carbon, and the particle size of the activated carbon is 4mm-8mm; (3) The reaction temperature for the synthesis of acyl chloride is from -20℃ to 0℃.

7. The chlorination tail gas treatment process according to any one of claims 1-6, characterized in that, The chlorinated tail gas is the reaction tail gas generated by chlorination reaction using thioyl chloride as the chlorinating agent.

8. The chlorination tail gas treatment process according to claim 7, characterized in that, The sulfuryl chloride obtained by reacting the desorption tail gas and chlorine gas under the action of a catalyst is also recycled for chlorination reaction; And / or, in the step of performing the desorption tail gas and chlorine gas in the action of a catalyst to carry out the acyl chloride synthesis reaction, an acyl chloride synthesis tail gas is also obtained. When the mass fraction of hydrogen chloride gas in the acyl chloride synthesis tail gas is greater than or equal to 95%, the acyl chloride synthesis tail gas is recycled to the chlorination reaction; otherwise, the acyl chloride synthesis tail gas is continued to be recycled to the acyl chloride synthesis reaction step.

9. The chlorination tail gas treatment process according to claim 7, characterized in that, The chlorinated tail gas is the reaction tail gas generated during the chlorination reaction of 3,5-dimethylphenol and thioyl chloride to produce 4-chloro-3,5-dimethylphenol, and the chlorinated tail gas also includes tetrachloroethylene.

10. The chlorination tail gas treatment process according to claim 9, characterized in that, In the step of desorbing the absorbent, an desorbent is also obtained. When the mass fraction of tetrachloroethylene in the desorbent is greater than or equal to 10%, the desorbent is used in the chlorination reaction; otherwise, the desorbent is used in the cooling absorption treatment step.

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