A method for preparing a sodium thiol organic solution

Abstract

The present application relates to a kind of preparation methods of sodium mercaptan organic solution, using the method can obtain the liquid sodium mercaptan solution containing high concentration mercaptan, facilitate the use and storage and transportation of low molecular weight mercaptan and sodium mercaptan;Using the method can produce the solid methyl mercaptan sodium containing more than 85%, can be enriched and recovered in oil and gas mercaptan.The preferred implementation steps of the method include: the mercaptan treated by dehydration is slowly added to the organic solution containing sodium alcoholate, the system temperature is kept unchanged during the process, until the system mercaptan concentration reaches the set value.Or the organic solution containing sodium alcoholate is added to the oil and gas product containing mercaptan, after being mixed sufficiently, sedimentation, the sediment continues to return and mix with raw oil and gas, constantly adsorbing the mercaptan therein, until the mercaptan sodium solution of set concentration is generated, and the mercaptan concentration can be up to 30-60%.

Description

Technical Field

[0001] This technology relates to a method for preparing a sodium thiolate organic solution, specifically an environmentally friendly method for preparing a high-concentration sodium thiolate organic solution. Using this method, a sodium thiolate organic solution containing a high concentration of thiols can be obtained, which is beneficial for the use and storage of low molecular weight thiols and sodium thiolate; this method can also produce high-purity sodium methanethiol with a content of over 85%. Background Technology

[0002] Thiols and sodium thiolates are important organic sulfur raw materials. In particular, methanethiol and sodium methanethiol can be used as raw materials for pesticides, pharmaceuticals, dye intermediates, and as an antidote for hydrogen sulfide poisoning.

[0003] Because of its low boiling point, methanethiol is gaseous at room temperature and is usually stored, transported and used in the form of sodium methanethiol aqueous solution.

[0004] The existing sodium methanethiol production technology uses a batch process. The structure consists of a single reactor that reacts sodium hydrosulfide with dimethyl sulfate to produce methanethiol gas. Then, 3-4 washing tanks connected in series are used to bubble and wash the methanethiol gas with sodium methanethiol solution or dilute alkaline solution to remove impurities such as hydrogen sulfide. The gas then enters fixed primary and secondary absorption tanks where the methanethiol is absorbed by alkaline solution to produce sodium methanethiol solution.

[0005] This technology suffers from low efficiency due to intermittent production, requiring large investments and space-consuming equipment for the same production capacity. Bubble washing results in low cleaning efficiency, low purity of the methanethiol gas produced, and the presence of hydrogen sulfide in the gas. Insufficient washing can easily lead to high sodium sulfide content in the sodium methanethiolate product, causing it to turn reddish. Furthermore, the washing solution is replaced after each batch, resulting in waste and increased costs and pollutant emissions as it is replaced before it is fully degraded. The wastewater generated by this process contains various organic compounds such as sodium methyl sulfate, sodium methanethiolate, methanol, dimethyl sulfide, and dimethyl disulfide, with a COD as high as 100,000 ppm, producing a foul odor in the surrounding air.

[0006] Solid sodium methanethiol contains a lot of water of crystallization, making it difficult to crush. It must be melted by heating before use, and it is also difficult to package. It has a strong odor and can easily cause environmental pollution. Therefore, companies that use sodium methanethiol as a raw material usually purchase sodium methanethiol solution directly.

[0007] At room temperature, the saturation concentration of sodium methanethiol aqueous solution is approximately 20 wt%. Further increases in concentration can lead to crystal precipitation during transportation and storage, causing pipe blockages and inaccurate sodium methanethiol solution content. Therefore, commercially available sodium methanethiol solutions typically have a concentration of 20 wt%, meaning they contain approximately 80 wt% water. This results in high water consumption, low transportation efficiency, and high transportation costs for sodium methanethiol manufacturers. For example, a sodium methanethiol company in Inner Mongolia produces and sells 20 wt% sodium methanethiol solution to customers in the Jiangsu and Zhejiang areas, incurring freight costs as high as 4000 yuan per ton, making transportation very expensive.

[0008] High-purity solid sodium methanethiol possesses unique properties, but its catalytic performance requires a very low free alkali content. Current technology obtains solid sodium methanethiol by concentrating an aqueous solution. However, due to the association between sodium thiolate molecules and water molecules, the concentration of 20wt% sodium methanethiol requires increased temperature to remove the water of crystallization, and even then, complete removal is difficult. As the temperature rises, the decomposition of sodium methanethiol in its aqueous solution accelerates, continuously generating gaseous methanethiol. This methanethiol continuously escapes from the concentration system, preventing the achievement of the target concentration. Furthermore, the concentrated sodium methanethiol contains large amounts of impurities such as sodium hydroxide, resulting in a high content of free alkali and water of crystallization, leading to poor performance as a catalyst.

[0009] Therefore, there is an urgent need to develop a method for preparing a stable sodium thiolate solution containing high concentrations of thiols at room temperature, so as to facilitate the storage, transportation and use of thiols; and to solve the problem of producing high-purity sodium methanethiolate solid.

[0010] Patent CN109382072A discloses a method for the continuous preparation of high-concentration sodium methanethiol. This method employs a multi-stage reaction, multi-stage absorption, and multi-stage premixing process. An inert gas must be introduced into the preparation system to replace the air, thus isolating it from substances that easily cause side reactions, such as oxygen and carbon dioxide. Different concentrations of sodium methanethiol solutions require different insulation conditions to ensure no crystal precipitation in the system. The sodium methanethiol produced by this method can reach a concentration of over 30%. It must be stored and transported under heat, using nitrogen-sealed insulated and airtight containers; otherwise, crystallization will occur and block the pipelines.

[0011] CN105330577A describes a process for producing high-purity sodium methanethiol. The process involves reacting sodium hydrosulfide solution with dimethyl sulfate to produce methanethiol and sodium sulfate. The resulting methanethiol mixture is then subjected to a four-stage washing process to remove impurities, followed by cyclone separation to remove moisture. The purified methanethiol gas is then absorbed by two stages of alkaline solutions to generate a sodium methanethiol solution. Utilizing the difference in solubility of sodium methanethiol at different temperatures, the concentration of the alkali is adjusted appropriately, and the reaction temperature is controlled to produce a sodium methanethiol solution of the desired concentration, yielding a solution with a content of 40%–50%. After cooling, the sodium methanethiol solution precipitates crystalline solid sodium methanethiol, forming a supersaturated solution at the corresponding temperature. This supersaturated solution is then filtered to obtain solid sodium methanethiol. The solid sodium methanethiol is dried using an airflow dryer, infrared drying oven, electric furnace drying oven, or condenser dryer. The solid sodium methanethiol obtained by this method contains water of crystallization. The drying process cannot completely remove the water of crystallization, resulting in a high sodium hydroxide content in the product, which does not meet the quality requirements for high-purity sodium methanethiol.

[0012] CN201268672Y relates to a sodium methanethiol production system, mainly comprising a reaction unit, a gas cooling unit, a scrubbing unit, a circulating absorption unit, and a waste gas main. The reaction unit consists of multiple reactors, capable of continuously producing methanethiol gas. The scrubbing unit consists of multiple scrubbing towers; replacing the scrubbing liquid in one circulating tank does not affect the normal operation of the entire scrubbing unit. The absorption unit consists of multiple absorption tanks, which can be circulated and rotated to form primary, secondary, and tertiary stages of absorption. All containers potentially emitting odorous gases have vent valves connected to the waste gas main, sending the gas to an incinerator for treatment. Because this process still takes place in an aqueous solution, the final product has a high free alkali content.

[0013] CN102976987A A method for co-producing sodium methanethiol and dimethyl sulfide, characterized in that: its specific steps include:

[0014] (1) Reaction stage: Equal amounts of sodium hydrosulfide solution are added to four identical reactors to form a series connection. Chloromethane gas is introduced into the four reactors in sequence under negative pressure. By controlling the reaction temperature, pure methanethiol gas can be obtained.

[0015] (2) Absorption stage: Add equal amounts of sodium hydroxide solution to three identical absorption vessels. After the methanethiol gas generated in step (1) is saturated by the three-stage absorption of sodium hydroxide solution, a sodium methanethiol solution can be obtained.

[0016] (3) Processing stage: The reaction solution obtained in step (1) is introduced into a separator and allowed to stand. The upper oily liquid is taken to obtain the dimethyl sulfide solution.

[0017] This method involves complex procedures and numerous equipment, requiring four stages of series reaction and three stages of absorption saturation. Although the yield of sodium methanethiol reaches over 80%, the resulting sodium methanethiol solution is still a low concentration of no more than 21.34%. Summary of the Invention

[0018] The purpose of this invention is to provide a simple, pollution-free, and environmentally friendly method for preparing a high-concentration sodium thiolate organic solution. This method yields a liquid sodium thiolate solution containing a high concentration of thiols, facilitating the use, storage, and transportation of low molecular weight thiols and sodium thiolate. It can also produce high-purity solid sodium methanethiol with a content exceeding 85%. Because the preparation is carried out in a non-aqueous environment, the thiols react completely, the product does not hydrolyze, there is no air pollution, and the process does not generate wastewater.

[0019] A method for preparing a sodium thiolate organic solution includes the following steps: mixing a dehydrated thiolate with a water content ≤0.5% with an organic solution containing sodium thiolate until the thiolate concentration in the system reaches a set value.

[0020] More specifically, dehydrated thiols with a water content of ≤0.5% can be slowly and continuously added to an organic solution containing sodium alkoxide for mixing and reaction. At this time, the thiols begin to generate sodium thiolate, and the generated sodium thiolate continues to complex with the thiols entering the system until the thiols concentration in the system reaches the set value.

[0021] The present invention selects thiols according to the product type, without particular limitation, preferably monothiols, or hydrocarbon oils or gases containing monothiols; more preferably methanethiol, ethanethiol, propanethiol, mixed thiols, or oil and gas products containing dissolved methanethiol, ethanethiol, and mixed thiols.

[0022] This invention also provides a more specific method for preparing a sodium thiolate organic solution using dissolved entrained oil and gas products such as methanethiol, ethanethiol, and mixed thiols: The sodium thiolate-containing organic solution is thoroughly mixed with the thiol-containing oil and gas products, followed by sedimentation and separation. The sodium thiolate sediment is then returned to be mixed with the thiol-containing oil and gas products, continuously adsorbing and enriching the thiols until a sodium thiolate solution of a predetermined concentration is generated. The thiol concentration in the enriched solution can reach up to 30-60% using this invention, and the process is pollution-free and emission-free.

[0023] The sodium alkoxide is selected according to the product type, and preferably it is one or more of sodium methoxide, sodium ethoxide and sodium ethylene glycol.

[0024] In this invention, the organic solution containing sodium alkoxide typically includes an alcohol, preferably a monohydric alcohol, a dihydric alcohol, or a mixture thereof. The monohydric alcohol is preferably methanol, ethanol, butanol, or octanol, and the dihydric alcohol is preferably ethylene glycol, methyl ethylene glycol, or propylene glycol.

[0025] The present invention also provides a more preferred sodium alkoxide-containing organic solution, wherein the sodium alkoxide content in the sodium alkoxide-containing organic solution is 5%~45% by mass, the alcohol content is 55~95%, the alcohol ether content is 0~10%, and the amide content is 0~0.8% by mass; preferably, the sodium alkoxide content is 10%~40%, more preferably 15%~35%; the alcohol content is 60%~90%, more preferably 65%~85%; the alcohol ether content is 0.5%~6%, more preferably 1%~5%; and the amide content is preferably 0.1%~0.6%, more preferably 0.2%~0.5%.

[0026] Depending on the intended use of the sodium thiolate organic solution, this invention allows for the selection of whether and how much alcohol ether or amide is present in the sodium thiolate organic solution. The preferred alcohol ethers are ethylene glycol butyl ether and propylene glycol butyl ether, and the preferred amide is dimethylformamide.

[0027] The oil and gas products of this invention preferably refer to naphtha, gasoline, solvent oil, mixed solvent, light hydrocarbons, liquefied petroleum gas, and natural gas produced in coal and petroleum mining and processing.

[0028] In this invention, the content of thiols and water in the system is preferably ≤0.5%, and the thiols can be obtained through a dehydration process. This invention does not particularly limit the reaction temperature; the reaction can usually be carried out at room temperature. The preferred reaction temperature is 20℃~45℃. Heat will be generated during the reaction, and it is best to maintain a system temperature difference below 15℃, more preferably below 10℃, to control the temperature of the preparation system.

[0029] The method of this invention achieves the reaction of thiols in an organic solution of sodium alkoxide to generate dissolved sodium thiolate. In the prior art, a sodium thiolate solution of a first concentration is typically prepared using sodium hydroxide solution and methanethiol gas; then, methanethiol gas is introduced into the first concentration sodium thiolate solution to prepare a sodium thiolate solution of the target concentration; during the preparation process, the oxygen content in the preparation system is controlled to be lower than a preset oxygen content.

[0030] The inventors discovered that thiols are more soluble in alcohols than water and have stronger acidity than alcohols. When thiols encounter sodium alkoxide, which is also soluble in alcohols, a rapid displacement reaction occurs, displacing the alcohol from the sodium alkoxide and generating a more stable sodium thiolate with higher solubility. This reaction is fast and complete, and even when sodium alkoxide is in excess, thiols will not overflow the system and cause pollution. The generated sodium thiolate molecules have the property of complexing with thiols with higher polarity, allowing more thiols in the system to be complexed and absorbed, maintaining stability. This ultimately yields a stable organic solution of sodium thiolate containing 30%–60% thiols at room temperature. This solution contains a high concentration of thiols and does not produce sodium thiolate crystals. During storage and transportation, the solvent isolates the solution from air, preventing it from reacting with oxygen, decomposing, or polluting the environment. The free alkali content in the system is extremely low, resulting in higher reactivity than aqueous solutions and making it more convenient and efficient to use. The solution solidifies below 5°C but quickly melts into a homogeneous liquid upon increasing the temperature, without any change in concentration.

[0031] The following reaction occurs in this invention:

[0032] C2H5ONa + CH3SH = CH3SNa + C2H5OH

[0033] CH3SNa+CH3SHn=CH3SNa.(CH3SH)n(n=1-3)

[0034] The inventors discovered that the sodium thiolate complexation reaction has the following characteristics: sodium thiolate readily forms complexes with highly polar molecules, such as water > thiol > alcohol. Therefore, sodium thiolate more readily complexes with water, and the greater the polarity, the more molecules it complexes. For example, sodium thiolate can complex up to 5 water molecules, 3 thiol molecules, and 1 alcohol molecule. Therefore, if the system contains water, water molecules will occupy the complexation sites first, reducing the solubility of thiol and promoting the hydrolysis of sodium thiolate to form sodium hydroxide impurities. Thus, the above reaction requires controlling the water content of each material in the system to be low. Based on these reasons, in the reaction using sodium hydroxide aqueous solution to absorb methanethiol, the generated sodium methanethiol will first form a stable complex with water in the system, namely sodium methanethiol hydrate, and will not complex with methanethiol molecules, ensuring that the methanethiol content in the solution at room temperature can only reach 20%.

[0035] The advantages of this invention are: the method of this invention can obtain a sodium thiolate solution containing a high concentration of thiols, which remains stable at room temperature, is not prone to crystallization or decomposition, does not readily react with oxygen, and does not pollute the environment. When the reactants are thiols from oil and gas, various thiols from oil and gas are enriched and recovered.

[0036] Based on the aforementioned complexation principle, in the absence of water influence, sodium thiolate dissolved in alcohol can be concentrated and dried, especially under vacuum, to produce a high-purity, high-concentration solid. Therefore, this invention also provides a method for preparing high-purity solid sodium thiolate using the aforementioned sodium thiolate organic solution. Specifically, the method involves vacuum concentrating and drying the sodium thiolate organic solution obtained using this invention, preferably a solution without excessive complexation with thiols, to obtain a high-purity solid sodium thiolate product. This method can produce solid sodium thiolate products with a content of 85% or higher, even around 90%.

[0037] The high-purity solid sodium thiolate obtained by the method of this invention contains no water of crystallization and has a low free alkali content. Due to its high content of active substances and extremely low free alkali content, this solid sodium thiolate can be used as an excellent raw material and additive, and is particularly suitable for the synthesis of triazine herbicides. Detailed Implementation

[0038] The present invention is illustrated below with specific embodiments, which are not intended to limit the scope of the invention.

[0039] Example 1

[0040] A method for generating high concentrations of sodium thiolate includes the following steps:

[0041] Prepare a 20% sodium ethoxide organic solution. Dissolve 20 kg of solid sodium ethoxide in a solvent consisting of 75 kg of ethanol and 5 kg of ethylene glycol butyl ether. Dehydrate the C4 liquid hydrocarbons containing thiols using a coalescer to reduce the water content to below 0.5%, maintaining the system temperature at 25–35°C. Mix the mixture with the 20% sodium ethoxide organic solution using a static mixer, and then allow it to settle in a settling tank. The heavy component containing sodium thiols at the bottom of the tank is then mixed with the liquid hydrocarbons containing thiols and allowed to settle until the sodium thiols content in the heavy component solution at the bottom of the tank reaches 40%. The organic sulfur concentration in the C4 liquid hydrocarbons can be reduced to as low as 5 ppm.

[0042] Example 2

[0043] Solid sodium ethoxide was dissolved in a mixed solvent consisting of 75% methanol, 20% ethylene glycol, and 5% propylene glycol butyl ether to prepare a solution with a sodium ethoxide concentration of 38%. Methanethiol was then bubbled into this solution, and the system temperature was controlled at 25-30°C until the methanethiol content reached 50%. The solution was a homogeneous liquid at room temperature. After being placed in a refrigerator at 5°C for one hour, the viscosity of the system increased. Upon returning to room temperature, it returned to its original homogeneous liquid state.

[0044] Example 3

[0045] Methanethiol gas was slowly passed into a methanol solution containing 18% sodium methoxide, and the system temperature was maintained at 35-45°C to generate a methanol solution containing 22% sodium methanethiol. The solution was concentrated by vacuum distillation at a maximum temperature of 50°C, and then dried in a vacuum oven at 80°C for two hours. The content of solid sodium methanethiol was determined to be 88.5%.

[0046] Example 4

[0047] A methanol solution containing 25% sodium methoxide is pumped into two two-stage packed towers connected in series and parallel to establish a liquid-phase circulation. Natural gas containing 150 ppm methanethiol and 50 ppm ethanethiol is continuously fed into the first-stage packed tower. The second-stage packed tower ensures deep removal of organic sulfur from the natural gas. After the mercaptan content in the circulating liquid of the first-stage packed tower reaches 40%, the natural gas is switched to directly enter the second-stage packed tower. The circulating liquid of the first-stage packed tower is discharged from the system, resulting in a mixed mercaptan organic solution with a mercaptan content of 40%. The second-stage tower continues to absorb mercaptan from the natural gas. After the enriched liquid of the first-stage tower is discharged, a new sodium methoxide solution is introduced to continue enriching mercaptan from the natural gas. This process can enrich and recover mercaptan and other organic sulfur from natural gas, achieving deep removal of organic sulfur from the natural gas.

[0048] Example 5

[0049] Prepare an organic solution with a ratio of ethylene glycol:sodium ethoxide:dimethylformamide = 94.5:5:0.5. Mix one part of this solution thoroughly with three parts of cracked gasoline, allowing it to settle. The mercaptan content in the gasoline decreased by 95%, and the thiophene content decreased by 75%. Continue mixing the bottom sediment with three parts of fresh gasoline, allowing it to settle, repeating this process 30 times. After 30 cycles, the mercaptan content in the sediment was measured to be 9.5%, and the thiophene content was 4%. The results show that the dimethylformamide was carried away by the gasoline, and the bottom consisted of an ethylene glycol solution containing sodium mercaptan and thiophene.

Claims

1. A method for preparing a sodium thiolate organic solution, characterized in that... The preparation method includes the following steps: Thiols with a dehydrated water content ≤0.5% are mixed with an organic solution containing sodium alkoxide until the thiol concentration in the system reaches a set value; wherein the thiol refers to thiols, ethanethiol, propanethiol, or oil and gas products such as naphtha, gasoline, light hydrocarbons, liquefied petroleum gas, and natural gas produced during coal and petroleum mining and processing that contain mixed thiols; sodium alkoxide refers to one or more of sodium methoxide, sodium ethoxide, and sodium glycol; the mass percentage content of sodium alkoxide in the organic solution containing sodium alkoxide is 5%~45%, the alcohol content is 55~95%, the alcohol ether content is 0~10%, and the amide content is 0~0.8%, wherein the alcohol is a monohydric alcohol, a dihydric alcohol, or a mixture thereof; the reaction temperature is 20℃~45℃.

2. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that... After thoroughly mixing the organic solution containing sodium alkoxide with the oil and gas products containing thiols, the mixture is allowed to settle and separate. The sodium alkoxide precipitate is then returned to be mixed with the oil and gas products containing thiols, continuously adsorbing the thiols therein until a sodium alkoxide solution of a set concentration is generated.

3. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that... The monohydric alcohol is methanol, ethanol, butanol or octanol, and the dihydric alcohol is ethylene glycol, methyl ethylene glycol or propylene glycol.

4. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that, The sodium alkoxide organic solution contains 10% to 40% sodium alkoxide by mass, 60% to 90% alcohol, 0.5% to 6% alcohol ether, and 0.1% to 0.6% amide.

5. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that, The sodium alkoxide content in the organic solution containing sodium alkoxide is as follows: sodium alkoxide content is 15%~35%, alcohol content is 65%~85%, alcohol ether content is 1%~5%, and amide content is 0.2%~0.5%.

6. The method for preparing sodium thiolate organic solution according to claim 4 or 5, characterized in that, The alcohol ether is ethylene glycol butyl ether or propylene glycol butyl ether, and the amide refers to dimethylformamide.

7. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that, When thiols are mixed with organic solutions containing sodium alkoxides, the content of thiols and water in the system shall be ≤0.5%.

8. The method for preparing sodium thiolate organic solution according to claim 1, characterized in that, During the preparation process, the temperature difference of the system should be kept below 15℃.

9. The method for preparing sodium thiolate organic solution according to claim 8, characterized in that, During the preparation process, the temperature difference of the system is kept below 10℃, and the temperature of the preparation system is controlled.

10. A method for preparing solid sodium thiolate using the method for preparing sodium thiolate organic solution according to claim 1, characterized in that... The obtained sodium thiolate organic solution is concentrated and dried to obtain solid sodium thiolate product.