A method for purifying mercaptans
By using the deprotonation reaction of triethylamine with crude thiol and the low-temperature crystallization acidification regeneration process, the problems of complex equipment, high energy consumption and many side reactions in traditional separation methods are solved, and high-purity thiols are separated efficiently and produced at low cost.
Patent Information
- Application Number
- CN202611241187.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-17
- Publication Date
- 2026-11-06
AI Technical Summary
Existing technologies for separating tert-dodecyl mercaptan from olefins suffer from problems such as complex equipment, high energy consumption, numerous side reactions, and low product purity. In particular, traditional distillation methods are difficult to achieve high-purity separation, and extractive distillation leaves solvent residues that affect product quality.
Triethylamine is deprotonated with crude thiol to form a crystallizable complex. Through low-temperature crystallization and acidification regeneration, the acid-base reaction between thiol and triethylamine salt is used to generate a sparingly soluble salt, achieving solid-liquid separation. The solvent is recovered by vacuum distillation to avoid high-temperature side reactions.
It improves the selectivity of thiols and olefins separation, reduces olefin residue, increases thiols purity and product recovery rate, reduces energy and solvent consumption, avoids side reactions, and ensures good product stability.
Smart Images
Figure CN123042015A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical technology, and more specifically to a method for purifying thiols. Background Technology
[0002] Tertiary dodecyl mercaptans are important organosulfur compounds, commonly used as chain transfer agents or molecular weight regulators in the preparation of styrene-butadiene rubber, nitrile rubber, ABS resin, polystyrene, and other polymer materials. Tertiary dodecyl mercaptans are generally prepared by the addition reaction of olefin feedstocks such as tetrapropylene with hydrogen sulfide. Due to factors such as reaction conversion rate, feedstock composition, and separation conditions, the crude product usually contains a certain amount of unreacted olefins, thiols with different carbon numbers, and catalyst residues. Residual olefins not only reduce the effective content of tertiary dodecyl mercaptans but may also affect their chain transfer efficiency and product performance in subsequent polymerization reactions; therefore, further purification of the crude thiol product is necessary.
[0003] Existing technologies typically employ atmospheric distillation, vacuum distillation, or extractive distillation to separate thiols and olefins. However, industrial tetrapropylene is a mixture of olefins with varying carbon numbers and branching structures, and its boiling range partially overlaps with that of tert-dodecyl mercaptan and other thiols with different carbon numbers. When using conventional distillation methods to obtain high-purity tert-dodecyl mercaptan, more trays, higher reflux ratios, or higher vacuum levels are usually required. This not only complicates the equipment structure and operation but also increases energy consumption for heating, condensation, and vacuum systems. Furthermore, prolonged exposure to high temperatures can lead to side reactions such as oxidation, decomposition, or the formation of disulfides, thus affecting product purity and yield.
[0004] To improve the separation effect of conventional distillation, some existing technologies employ extractive distillation using high-boiling-point polar solvents such as sulfolane. This utilizes the extractant to alter the relative volatility between olefins and tert-dodecyl mercaptan (TDM), followed by recovery distillation to separate the TDM from the extractant. While this method can improve the separation purity of olefins and TDM, it typically requires an extractive distillation column and a solvent recovery column, along with continuous extractant circulation, bottom heating, and reduced pressure operation. This results in a lengthy process, high equipment investment, and high energy consumption. Furthermore, incomplete separation with the high-boiling-point extractant may leave residues in the TDM product, affecting product quality.
[0005] Furthermore, existing technologies can first convert thiols into thiolates and then release them using acidification. However, when strong bases are used to form thiolates or strong acids are used for acidification, excessively strong acid-base conditions may promote thiol oxidation, olefin polymerization, or other side reactions, potentially generating corrosive waste liquid. When using liquid-liquid extraction or water washing for separation, an emulsion layer may form due to the coexistence of thiols, organic solvents, and salt solutions, leading to slow oil-water separation, unclear interfaces, and thiol entrainment losses, affecting the stability of continuous production.
[0006] Therefore, further improvements and development are still needed. Summary of the Invention
[0007] To address the shortcomings of existing technologies and solve the aforementioned problems, a method for purifying thiols is proposed, and the following technical solution is provided: A method for purifying thiols includes the following steps: S1, the crude thiol product is mixed with triethylamine and subjected to a deprotonation reaction to form a mixture containing a crystallizable complex, wherein the crude thiol product contains thiols and alkenes; S2, the mixture is cooled and crystallized, and solid-liquid separation is performed to obtain a solid phase crystal containing the crystallizable complex and a liquid mother liquor containing the olefin; S3 involves acidifying the solid crystals, adjusting the pH to a weakly alkaline state, and then separating the thiols.
[0008] Furthermore, the crude thiol product contains 80% thiol and 20% olefin, and the mass ratio of the thiol to triethylamine is 1-2:1.
[0009] Furthermore, the crude thiol product is mixed with triethylamine in water or an organic solvent.
[0010] Furthermore, the organic solvent is at least one of toluene and n-hexane.
[0011] Furthermore, the organic solvent is a mixture of toluene and n-hexane, with a mass ratio of toluene to n-hexane of 3:1.
[0012] Furthermore, the acidification treatment is carried out using a weak acid, which is at least one selected from carbonic acid, acetic acid, phosphoric acid, citric acid, and oxalic acid.
[0013] Further, in step S3, the pH is adjusted to a weakly alkaline state using an alkaline regulator, wherein the alkaline regulator is a strong base, and the pH is adjusted to 8.0-9.0.
[0014] Further, in step S1, the deprotonation reaction is carried out at a temperature of 25-40°C for 20-40 min; in step S2, the mixture obtained in step S1 is cooled to -5-0°C at a cooling rate of 0.5-1°C / min for 1-3 h.
[0015] Further, the liquid mother liquor obtained in step S2 is subjected to vacuum distillation to recover the organic solvent, and the recovered water or organic solvent is recycled for step S1 to obtain a recovery product rich in olefins.
[0016] Furthermore, the crude thiol product is a crude tert-dodecyl thiol product, which contains tert-dodecyl thiol and dodecene.
[0017] The purification technology for tert-dodecyl mercaptan is mainly based on chemical principles such as deprotonation, low-temperature crystallization, and acid regeneration. In the deprotonation reaction, tert-dodecyl mercaptan undergoes an acid-base neutralization reaction with a weak base such as triethylamine, forming a poorly soluble tert-dodecyl mercaptan-triethylamine salt complex. The selectivity of this reaction depends on the acidic nature of the thiol group (-SH) in the mercaptan molecule, with a pKa value typically between 8 and 10, allowing the weak base to effectively abstract hydrogen atoms and form a stable salt compound. This reaction not only improves the separation coefficient between the target product and impurities but also lays the foundation for subsequent solid-liquid separation. Low-temperature crystallization is a key step in achieving further high-purity separation. By cooling the mixture after the deprotonation reaction to -5 to 0°C, the tert-dodecyl mercaptan-triethylamine salt precipitates from the solution in crystalline form, while nonpolar impurities such as dodecene remain in the liquid mother liquor. This process utilizes the significant differences in the solubility of different substances at low temperatures, thereby achieving efficient separation. Studies have shown that crystallization temperature and cooling rate have a significant impact on crystal purity and morphology; excessively rapid cooling may lead to impurity inclusion or co-crystallization. The acidification and regeneration step is the process of releasing tert-dodecyl mercaptan from the salt complex. By introducing carbon dioxide gas or adding a weakly acidic aqueous solution into the solid crystalline salt, the pH of the system can be adjusted to 8.0-9.0, causing the tert-dodecyl mercaptan-triethylamine salt to dissociate, thereby obtaining a high-purity tert-dodecyl mercaptan product. The mild conditions of this step avoid the side reaction of thiol oxidation to disulfide, while simultaneously achieving the recovery and recycling of triethylamine, significantly reducing production costs. This method utilizes the specific acid-base reaction between triethylamine and tert-dodecyl mercaptan to form a sparingly soluble salt, achieving efficient separation of the target product. The purity of the obtained dodecene product is improved compared to traditional processes, and the purity of the regenerated tert-dodecyl mercaptan also reaches an extremely high level. This result is primarily attributed to the highly efficient solid-liquid phase separation achieved during the low-temperature crystallization process. The tert-dodecyl mercaptan-triethylamine salt precipitates as crystals, while the dodecene remains in the liquid mother liquor. This separation method not only significantly improves product purity but also exhibits excellent separation selectivity. In contrast, traditional distillation techniques, due to their small boiling point differences, struggle to achieve high-purity separation and are prone to increased impurity content due to side reactions. Therefore, this method demonstrates a clear advantage in separation selectivity, providing a more effective technical approach for the purification of tert-dodecyl mercaptan.
[0018] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows: 1. This application involves deprotonating the thiol in the crude thiol product with triethylamine to form a crystallizable complex, followed by low-temperature crystallization and solid-liquid separation of the reaction mixture. By utilizing the mechanism that the thiol-triethylamine crystallizable complex has different solubility and crystallization properties under low-temperature conditions, the complex is precipitated from the reaction mixture in the form of solid crystals, while the olefins remain in the liquid mother liquor. This achieves the effects of improving the selectivity of thiol and olefin separation, reducing the residual amount of olefins in the product, and improving the purity of the thiol.
[0019] 2. This application first acidifies the solid crystal rich in crystallizable complexes with a weakly acidic aqueous solution, and then adjusts the pH of the acidification solution to 8.0-9.0 with an alkaline regulator. It utilizes the mechanism that the thiol-triethylamine crystallizable complex undergoes transformation under acidic conditions and the acidification intermediate further transforms and releases thiols under weakly alkaline conditions. This allows the released thiols to enter the oil phase and separate from the aqueous phase, achieving the effect of regenerating thiols under mild conditions, reducing oxidation and polymerization side reactions caused by strong acids or strong alkalis, and improving product recovery rate and stability.
[0020] 3. This application recovers organic solvents and olefin-rich recoveries by vacuum distilling the liquid mother liquor obtained after low-temperature crystallization. The recovered organic solvents are then recycled for the reaction step of thiols and triethylamine. By utilizing the different volatility of organic solvents and olefins and the ability of organic solvents to repeatedly participate in the compounding process, the application achieves the effects of reducing organic solvent consumption, lowering material handling costs, improving the recovery rate of olefin by-products, and improving process economy. Attached Figure Description
[0021] Figure 1 The chromatogram of the product obtained in Example 1; Figure 2 The chromatogram of the product obtained in Example 2; Figure 3 The chromatogram of the product obtained in Example 3; Figure 4 The chromatogram of the product obtained in Example 4; Figure 5 The chromatogram of the product obtained in Example 5; Figure 6 The chromatogram of the product obtained in Example 7; Figure 7 The chromatogram of the product obtained in Comparative Example 1; Figure 8 The chromatogram is of the product obtained in Comparative Example 2. Detailed Implementation
[0022] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.
[0023] Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, all reagents used in the examples are commercially available.
[0024] A method for purifying thiols includes the following steps: S1, the crude thiol product is mixed with triethylamine and subjected to a deprotonation reaction to form a mixture containing a crystallizable complex, wherein the crude thiol product contains thiols and alkenes; S2, the mixture is cooled and crystallized, and solid-liquid separation is performed to obtain a solid phase crystal containing the crystallizable complex and a liquid mother liquor containing the olefin; S3 involves acidifying the solid crystals, adjusting the pH to a weakly alkaline state, and then separating the oil phase to obtain thiols.
[0025] This application achieves selective separation of thiols and olefins by first deprotonating the crude thiols with triethylamine to form a mixture containing crystallizable complexes, then cooling and crystallizing the mixture and separating the solid and liquid phases, and then subjecting the resulting solid crystals to acidification and weak alkalinity adjustment. By utilizing the difference that thiols can form crystallizable complexes with triethylamine while olefins do not participate in the reaction and are mainly retained in the liquid phase, this method reduces energy consumption and side reactions caused by high-temperature distillation and obtains thiols with high purity.
[0026] Thiol molecules contain a sulfhydryl group with a certain degree of acidity, which can interact with triethylamine to form a crystallizable complex with different polarity and low-temperature solubility than the original thiol. Olefins do not contain active groups that can react with triethylamine, and therefore mainly remain in the liquid mother liquor during cooling. Through solid-liquid separation, thiols can be separated from olefins in the form of complex crystals.
[0027] After treatment with a weak acid, the triethylamine in the obtained solid crystal complex is protonated, altering the binding state between the original thiol and triethylamine, forming a system containing the acidification intermediate. Subsequently, the system is adjusted to a weakly basic state, allowing the acidification intermediate to further transform and release the thiol. The released thiol exhibits compatibility differences with the aqueous phase, forming an oil phase which is obtained through layering.
[0028] The crystallizable complex is a thiol-triethylamine salt.
[0029] The specific reaction process of step S3 is as follows: the solid crystal obtained in step S3 is acidified to obtain thiol-weak acid salt, the pH value is adjusted to weak alkalinity, the thiol-weak acid salt is dissociated, the thiol is released, and the product is an aqueous phase and an oil phase. The oil layer is separated to obtain a high-purity thiol product, and its aqueous phase is...
[0030] The aqueous phase is treated to recover triethylamine, which is then recycled for step S1.
[0031] Furthermore, the crude thiol product contains 80% thiol and 20% olefin, and the mass ratio of triethylamine to thiol is 1-2:1.
[0032] This application limits the thiol content in the crude thiol product to 80% and controls the mass ratio of triethylamine to thiol at 1.0:1-2.0:1. By utilizing an appropriate amount of triethylamine, the conversion of thiol to crystallizable complexes is enhanced. This avoids insufficient complexation due to excessive triethylamine dosage while reducing the recovery load and material waste caused by excessive triethylamine, thereby improving the crystallization separation rate of thiol and the purity of the final product. In actual production, the crude thiol product obtained has a thiol content of approximately 80%, an olefin content of approximately 20%, and a very small amount of impurities. However, these are negligible compared to the thiol and olefin contents and are therefore ignored here without detailed discussion.
[0033] The amount of triethylamine added directly affects deprotonation or acid-base equilibrium. When the amount of triethylamine is insufficient, some thiols cannot be converted into crystallizable complexes and remain in the liquid mother liquor, resulting in thiols loss. When the amount of triethylamine is increased to an appropriate range, it can improve the complexation conversion rate of thiols and the amount of crystal precipitation.
[0034] Furthermore, the crude thiol product is mixed with triethylamine in water or an organic solvent.
[0035] This application improves the contact uniformity between triethylamine and thiol by mixing crude thiol with triethylamine in an organic solvent. This utilizes the dissolution and dispersion effects of the organic solvent on thiol, olefin, and triethylamine, promoting the formation of crystallizable complexes and providing a suitable liquid phase environment for subsequent crystallization by changing the solubility of the complex through cooling.
[0036] Thiols and alkenes are typically highly hydrophobic, and organic solvents can form homogeneous or relatively homogeneous reaction systems, reducing mass transfer resistance and allowing triethylamine to fully contact the thiols. After the reaction is complete, as the temperature decreases, the solubility of the crystallizable complex in the organic solvent decreases and crystal nuclei form, while the unreacted olefins still have high solubility, thus enhancing the selectivity of solid-liquid separation.
[0037] Adding too much water to S1 may create a heterogeneous system and affect the dissolution and crystallization behavior of thiols, triethylamine, and their complexes. Therefore, "water / organic solvent" should not be used as a simple example, but the role and content of water need to be clearly defined based on the actual process.
[0038] Furthermore, the organic solvent is at least one of toluene and n-hexane.
[0039] This application utilizes toluene, n-hexane, or a mixture of both as solvents. By taking advantage of toluene's good solubility for thiols, triethylamine, and the reaction system, and n-hexane's good compatibility with nonpolar olefins, the reactants maintain sufficient contact during the deprotonation stage and form a solubility environment conducive to the precipitation of complexes at low temperatures. This improves the stability of the crystallization separation process and the purity of the thiol product.
[0040] Both toluene and n-hexane are organic solvents, but they differ in polarity, aromaticity, and solubility parameters. Toluene facilitates the full dispersion of thiols and triethylamine at the reaction temperature, while n-hexane helps maintain olefins in the liquid phase. By selecting a single solvent or a mixture of solvents, the solubility difference between the crystallizable complex and the olefin can be adjusted, thereby controlling the amount of crystal precipitation and the degree of impurity entrainment.
[0041] Furthermore, the organic solvent is a mixture of toluene and n-hexane, with a volume ratio of toluene to n-hexane of 3:1.
[0042] This application limits the mass ratio of toluene to n-hexane to 3:1, utilizing the synergistic effect of toluene and n-hexane in terms of solubility and low-temperature crystallization performance. This allows thiols and triethylamine to fully contact and form a complex at higher temperatures, while the complex has lower solubility at low temperatures. This shortens the crystallization time, reduces the possibility of impurity encapsulation and olefin co-crystallization, and improves crystal purity and thiols recovery rate.
[0043] A higher proportion of toluene ensures good solubility and mass transfer of the raw materials and triethylamine during the reaction stage; the addition of an appropriate amount of n-hexane reduces the solubility of polar complexes in the mixed solvent while maintaining the solubility of nonpolar olefins. A mass ratio of 3:1 achieves a balance between the solubility requirements during the reaction stage and the crystallization requirements during the crystallization stage.
[0044] Furthermore, the acidification treatment is carried out using a weak acid, which is at least one selected from carbonic acid, acetic acid, phosphoric acid, citric acid, and oxalic acid.
[0045] Weak acids can donate protons to triethylamine, converting it into the corresponding triethylammonium salt. This alters the acid-base balance between triethylamine and thiols, leading to the dissociation or structural transformation of the crystallizable complex. Compared to strong acids, a properly controlled weak acid system can reduce the likelihood of side reactions caused by localized strong acid environments and facilitates the subsequent recovery of free thiols through pH adjustment.
[0046] Different weak acids have different acidity, solubility, anion structure, and properties of forming salts with triethylamine. Therefore, their acidification rate, intermediate state, stratification effect, and subsequent recovery difficulty may vary significantly.
[0047] Preferably, the weak acid is carbonic acid.
[0048] Further, in step S3, the pH is adjusted to a weakly alkaline state using an alkaline regulator, wherein the alkaline regulator is a strong base, and the pH is adjusted to 8.0-9.0.
[0049] Preferably, the alkalinity regulator includes at least one of sodium hydroxide and potassium hydroxide.
[0050] This application uses sodium hydroxide and potassium hydroxide alkaline regulators to control the pH of the acidification solution at 8.0-9.0. The controlled weak alkaline environment promotes the conversion of acidification intermediates and releases free thiols, while avoiding excessive alkalinity of the system that could cause thiols to re-form thiols or undergo oxidation side reactions, thereby improving the thiols release rate, oil-water separation effect and product stability.
[0051] The alkaline regulator can consume the acid remaining in the acidification process and regulate the acid-base balance among triethylamine, weak acid, and thiols. Within the pH range of 8.0-9.0, the acidification intermediate can be converted towards free thiols, and the released hydrophobic thiols enter the oil phase, while the triethylammonium salt and inorganic salts are mainly retained in the aqueous phase, thus achieving phase separation.
[0052] When the pH is too low, the intermediate may not be fully converted to the target thiol, or residual acid in the system may cause side reactions; when the pH is too high, the thiol may be deprotonated again, increasing its distribution in the ionic phase and affecting the oil phase yield.
[0053] Further, in step S1, the deprotonation reaction is carried out at a temperature of 25-40°C for 20-40 min; in step S2, the mixture obtained in step S1 is cooled to -5-0°C at a cooling rate of 0.5-1°C / min for 1-3 h.
[0054] Compared with the prior art, the present invention has the following significant advantages: High separation selectivity and high purity: The specific acid-base reaction between triethylamine (a weak base) and tert-dodecyl mercaptan forms a sparingly soluble salt, while having no effect on nonpolar dodecene. Highly efficient separation of the solid and liquid phases is achieved through low-temperature crystallization, resulting in significantly higher purity dodecene compared to traditional processes, and the regenerated tert-dodecyl mercaptan also exhibits extremely high purity.
[0055] To avoid side reactions and ensure high product quality: Triethylamine is selected as the complexing agent, with moderate alkalinity (pKb≈3.0), avoiding side reactions such as thiol oxidation (forming disulfides) and olefin polymerization caused by strong alkalis such as sodium hydroxide at high temperatures or high concentrations. Simultaneously, the mild CO2 acidification regeneration step further guarantees the product's color and stability.
[0056] The process conditions are mild and energy consumption is low: Compared to traditional distillation, which requires heating to over 200°C, this method mainly involves complexation at room temperature and crystallization at low temperatures (-5 to 0°C), significantly reducing energy consumption. Furthermore, triethylamine has a low boiling point (89°C), making it easy to recover and recycle through vacuum distillation, thus reducing production costs.
[0057] Environmentally friendly, with no pollution from waste: The entire process does not use strong acids or alkalis and does not produce saline wastewater. Triethylamine can be recycled in a closed loop, making it highly economical and meeting the requirements of green chemical production.
[0058] This invention solves the emulsification problem: traditional alkaline washing methods often result in severe emulsification due to changes in interfacial tension, making it difficult to separate into layers. The present invention separates the components by forming solid crystalline salts, completely avoiding the emulsification problem in liquid-liquid extraction and exhibiting strong operational stability.
[0059] This application controls the deprotonation reaction temperature at 25-40℃ and the reaction time at 20-40 min, and then cools it to -5-0℃ at a cooling rate of 0.5-1.0℃ / min before crystallizing for 1-3 h. By using suitable reaction temperature and time, the thiol and triethylamine can fully form a crystallizable complex. Controlled cooling is used to form a suitable number of uniformly grown crystal nuclei, reducing olefin entrainment, impurity encapsulation, and co-crystallization caused by rapid cooling, thereby improving crystal purity, crystallization yield, and process repeatability.
[0060] If the reaction temperature is too low, the system viscosity will be high and the mass transfer rate will be slow, which may lead to incomplete complexation. If the temperature is too high, it may increase the risk of side reactions and increase energy consumption. 20-40 minutes provides the necessary time for acid-base equilibrium and complexation formation between triethylamine and thiol.
[0061] During cooling crystallization, the cooling rate determines the rate at which the system's supersaturation is established. Excessive cooling will generate a large number of fine crystal nuclei in a short time, easily entraining the mother liquor and olefins; appropriately reducing the cooling rate promotes orderly crystal growth. Controlling the final temperature between -5 and 0℃ can reduce the solubility of crystallizable complexes while avoiding excessively low temperatures that could cause solvent freezing, increased energy consumption, or the co-precipitation of non-target components.
[0062] Further, the liquid mother liquor obtained in step S2 is subjected to vacuum distillation to recover the organic solvent, and the recovered water or organic solvent is recycled for step S1 to obtain a recovery product rich in olefins.
[0063] This application recovers organic solvents by vacuum distilling the liquid mother liquor after low-temperature crystallization and recycling it for deprotonation reaction, while obtaining olefin-rich recoveries. By utilizing the differences in volatility and distillation behavior between organic solvents and olefins, the solvents and olefins can be recovered separately, reducing the consumption of fresh solvents and the discharge of organic waste liquid, improving the utilization value of olefin by-products and reducing purification process costs.
[0064] The liquid mother liquor after crystallization mainly contains organic solvents, olefins, and small amounts of uncrystallized thiols or triethylamine. By reducing the pressure, the boiling temperature of the organic solvents can be lowered, allowing solvents such as toluene and n-hexane to be distilled off under milder conditions, while the relatively high-boiling-point or less volatile olefin components are enriched in the residue.
[0065] The recovered solvent is purified and reused in S1, which can maintain the solubility and crystallization properties of the system and realize material recycling.
[0066] This application specifically defines the target product as crude tert-dodecyl mercaptan containing tert-dodecyl mercaptan and dodecene. By utilizing the difference that the thiol group contained in tert-dodecyl mercaptan can form a crystallizable complex with triethylamine, while dodecene does not have a corresponding acidic active group and is mainly retained in the liquid phase, this application solves the problem that tert-dodecyl mercaptan and residual olefins have similar boiling ranges and are difficult to separate efficiently using ordinary distillation. This achieves the effects of improving the purity of tert-dodecyl mercaptan, reducing the content of residual olefins, and improving the performance of downstream applications.
[0067] Tertiary dodecyl mercaptan contains a thiol group, enabling it to participate in triethylamine-mediated acid-base bonding and complex crystallization processes. Dodecene, containing only carbon-carbon double bonds, does not form a corresponding crystallizable complex with triethylamine under the same conditions. During low-temperature crystallization, tertiary dodecyl mercaptan enters the solid phase along with the complex, while dodecene remains in the liquid phase with the organic solvent, forming a separation process that combines chemoselectivity and phase selectivity.
[0068] Furthermore, the crude thiol product is a crude tert-dodecyl thiol product, which contains tert-dodecyl thiol and dodecene.
[0069] Example 1 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 400g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 1.0℃ / min and cool it down to -5℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 8 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0070] Example 2 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 600g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 0.8℃ / min and cool it down to -5℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 8 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0071] Example 3 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 800g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the mixture of tert-dodecyl mercaptan-triethylamine salt from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 0.5℃ / min and cool it down to -5℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 8 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0072] Example 4 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 400g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 1.0℃ / min and cool it down to 0℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 9 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0073] Example 5 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 600g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 0.8℃ / min and cool it down to 0℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 9 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0074] Example 6 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 800g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 0.5℃ / min and cool it down to 0℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. A certain amount of water is added and carbon dioxide is continuously introduced. After the reaction, sodium hydroxide is added to maintain the pH of the system at 9 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate solution can be neutralized with sodium hydroxide to remove triethylamine, and then reused.
[0075] Example 7 A method for purifying tert-dodecyl mercaptan is as follows: S1. Take 1000g of crude thiol product and 400g of triethylamine and add them simultaneously to an organic mixture of toluene and n-hexane and stir. Heat to 40℃ to prepare tert-dodecyl thiol-triethylamine salt. S2. Take the tert-dodecyl mercaptan-triethylamine salt mixture from step S1 and add it to the crystallizer for circulating cooling. Control the cooling rate at 1.0℃ / min and cool it down to -5℃ for isothermal crystallization. After 1 hour of constant-temperature crystallization, crystallization is complete, and the liquid mother liquor rich in dodecene is discharged. S3. The solid crystal rich in tert-dodecyl mercaptan-triethylamine salt is heated to obtain a tert-dodecyl mercaptan-triethylamine salt solution. Citric acid is added first to react, and then potassium hydroxide is added to maintain the pH of the system at 8 to obtain tert-dodecyl mercaptan. The lower layer containing triethylamine bicarbonate brine is discharged, and the upper layer of tert-dodecyl mercaptan is collected. The lower layer containing triethylamine bicarbonate salt water is neutralized with sodium bicarbonate to remove triethylamine, and the solution can be reused.
[0076] Example 8 Compared with Example 1, in this example, 1000g of crude thiol product and 1000g of triethylamine were simultaneously added to an organic mixture of toluene and n-hexane and stirred, and the mixture was heated to 40°C to prepare tert-dodecyl thiol-triethylamine salt.
[0077] Example 9 Compared to Example 1, in this example, the crude thiol product and triethylamine were directly mixed without solvent, and all other conditions were the same.
[0078] Under this method, crystallization is completed in 3 hours.
[0079] Example 10 Compared to Example 1, in this example, the crude tert-dodecyl mercaptan product and triethylamine are simultaneously added to water and stirred together.
[0080] Under this method, crystallization is completed in 1.4 hours.
[0081] Comparative Example 1 Compared to Example 1, triethylamine was not added, and all other conditions were the same.
[0082] Comparative Example 2 Compared to Example 1, sodium hydroxide was added in S3 to maintain the pH of the system at 7, while other conditions remained the same.
[0083] The relative peak areas of dodecene and tert-dodecyl mercaptan obtained in Examples 1-7 and Comparative Examples 1-2 were measured by gas chromatography-mass spectrometry, and the results are shown in Table 1 below.
[0084] Table 1. Test results of dodecene and tert-dodecyl mercaptan obtained in Examples 1-7 and Comparative Examples 1-2 As shown in Table 1, after treatment with the purification method described in this application, the tert-dodecyl mercaptan obtained in each embodiment exhibited good purification effects, while effectively reducing the residual dodecene in the product. A comparison between the embodiments and the comparative example without triethylamine shows that adding triethylamine to the system and subsequent low-temperature crystallization significantly improves the separation effect between tert-dodecyl mercaptan and dodecene. This is because triethylamine can form a crystallizable complex with tert-dodecyl mercaptan with specific crystallization properties, while dodecene does not participate in the above-mentioned action and is mainly retained in the liquid mother liquor during the cooling crystallization process. Thus, selective separation of tert-dodecyl mercaptan and dodecene is achieved through solid-liquid separation. Therefore, the participation of triethylamine in the formation of a crystallizable complex combined with low-temperature crystallization for solid-liquid separation is an important factor in improving the purification effect of tert-dodecyl mercaptan.
[0085] Further comparison of examples using different amounts of triethylamine shows that, within the scope examined in this application, the purification effect of tert-dodecyl mercaptan generally improves with increasing triethylamine dosage, and the dodecene residue decreases accordingly. This indicates that the amount of triethylamine affects the degree to which tert-dodecyl mercaptan forms crystallizable complexes. When the amount of triethylamine is low, some tert-dodecyl mercaptan may not fully participate in complexation crystallization, resulting in insufficient separation between it and dodecene. As the amount of triethylamine increases, the degree to which tert-dodecyl mercaptan forms crystallizable complexes increases, which is beneficial for it to enter the solid phase under low-temperature conditions, while dodecene remains in the liquid phase, thereby further improving the selectivity of solid-liquid separation. At the same time, when triethylamine continues to be added in excess, the purification effect does not continue to show the same degree of improvement, indicating that there is a relatively suitable range for the use of triethylamine. Continuing to increase its dosage has a limited promoting effect on the purification effect, and may also increase the load on subsequent triethylamine recovery and material processing.
[0086] Examples under different final crystallization temperatures and pH conditions demonstrate that good purification of tert-dodecyl mercaptan can be achieved within the low-temperature crystallization range and weakly alkaline adjustment range defined in this application. This indicates that the purification method of this application has a certain process adaptability range for crystallization temperature and final pH, and does not rely on a single operating point, which is beneficial to improving the operational stability and process tolerance in actual production. Low-temperature crystallization can reduce the solubility of the tert-dodecyl mercaptan-triethylamine crystallizable complex in the system, promoting its precipitation from the liquid phase; at the same time, by controlling an appropriate cooling process, the amount of liquid mother liquor and impurities such as dodecene carried by the crystals can be reduced, thereby improving the crystallization separation effect.
[0087] A comparison of examples and comparative examples using different final pH values shows that pH adjustment after acidification treatment has a significant impact on the regeneration and final purification of tert-dodecyl mercaptan. When the system is adjusted to a suitable weakly alkaline range, it facilitates the further conversion of the acidification intermediate and the release of free tert-dodecyl mercaptan, allowing the released tert-dodecyl mercaptan to form an oil phase and separate from the aqueous phase. However, when the final pH deviates from the suitable range, the release of tert-dodecyl mercaptan and the subsequent phase separation effect are affected, leading to an increase in impurities in the product. Therefore, controlling the system within a suitable weakly alkaline range after acidification treatment is an important process condition to ensure sufficient regeneration of tert-dodecyl mercaptan and achieve better purification results.
[0088] Furthermore, as can be seen from the examples using different acidifying agents and alkaline regulators, the acidification and regeneration step of this application is not limited to a single acidification system. Using a carbonic acid system formed from carbon dioxide or other weak acids for acidification, followed by adjusting the pH of the system with a suitable alkaline regulator, can achieve the dissociation of crystallizable complexes and the release of tert-dodecyl mercaptan. This indicates that this application utilizes the acid-base balance between weak acid acidification and subsequent weak alkaline adjustment. Its technical effect does not originate from a specific acid or base, but rather from the gentle control of the system's acid-base state, altering the binding state between triethylamine and tert-dodecyl mercaptan, ultimately achieving the regeneration and separation of tert-dodecyl mercaptan.
[0089] In summary, this application utilizes a combination of triethylamine selective action, low-temperature crystallization solid-liquid separation, and weak acid acidification and weak base adjustment to first separate tert-dodecyl mercaptan from dodecene in the form of a crystallizable complex, and then release it under mild conditions to obtain tert-dodecyl mercaptan, thus forming a continuous purification mechanism of "selective complexation—low-temperature crystallization—solid-liquid separation—acidification regeneration". Compared with schemes that do not involve triethylamine complexation crystallization or have unsuitable acid-base adjustment conditions, this application can more effectively reduce the residue of impurities such as dodecene in the tert-dodecyl mercaptan product, improve the purification effect of tert-dodecyl mercaptan, and also has the advantages of mild process conditions, wide operating range, and easy material recycling.
[0090] Compared to traditional distillation processes that primarily rely on differences in volatility for separation, this application utilizes the differences in chemical action and low-temperature crystallization behavior between tert-dodecyl mercaptan and dodecene to achieve selective separation. This eliminates the need for prolonged high-temperature distillation of all materials, reducing energy consumption during heating and minimizing potential side reactions under high-temperature conditions. Furthermore, triethylamine and organic solvents can be recovered and recycled through subsequent separation, further reducing material consumption and production costs. Therefore, this application not only ensures effective purification of tert-dodecyl mercaptan but also demonstrates good process economics and industrial application potential.
[0091] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for purifying mercaptans, characterized by, Includes the following steps, S1, the crude thiol product is mixed with triethylamine and subjected to a deprotonation reaction to form a mixture containing a crystallizable complex, wherein the crude thiol product contains thiols and alkenes; S2, the mixture is cooled and crystallized, and solid-liquid separation is performed to obtain a solid phase crystal containing the crystallizable complex and a liquid mother liquor containing the olefin; S3 involves acidifying the solid crystals and then adjusting the pH to a weakly alkaline state to obtain thiols.
2. The method for purifying mercaptans according to claim 1, characterized by, The crude thiol product contains 80% thiol and 20% olefin, and the mass ratio of the thiol to triethylamine is 1-2:
1.
3. The method for purifying mercaptans according to claim 1, characterized by, The crude thiol product is mixed with triethylamine in water or an organic solvent.
4. The method for purifying thiols according to claim 3, characterized in that, The organic solvent is at least one of toluene and n-hexane.
5. The method for purifying mercaptans according to claim 4, characterized by, The organic solvent is a mixture of toluene and n-hexane, with a mass ratio of toluene to n-hexane of 3:
1.
6. The method for purifying thiols according to claim 1, characterized in that, The acidification treatment is carried out using a weak acid, which is at least one of carbonic acid, acetic acid, phosphoric acid, citric acid, and oxalic acid.
7. The method for purifying thiols according to claim 1, characterized in that, In step S3, the pH is adjusted to a slightly alkaline state using an alkaline regulator, wherein the alkaline regulator is a strong base, and the pH is adjusted to 8.0-9.
0.
8. The method for purifying thiols according to claim 1, characterized in that, In step S1, the deprotonation reaction is carried out at a temperature of 25-40°C for 20-40 min. In step S2, the mixture obtained in step S1 is cooled to -5-0°C at a cooling rate of 0.5-1°C / min for 1-3 h.
9. The method for purifying thiols according to claim 3, characterized in that, The liquid mother liquor obtained in step S2 is subjected to vacuum distillation to recover the organic solvent, and the recovered water or organic solvent is recycled for step S1 to obtain a recovery product rich in olefins.
10. The method for purifying thiols according to claim 1, characterized in that, The crude thiol product is a crude tert-dodecyl thiol product, which contains tert-dodecyl thiol and dodecene.