Synthesis and purification process of high-purity chloroformate
By using a bifunctional adsorption system of zirconium-doped SBA-15 mesoporous molecular sieve framework grafted with amphoteric oximes and sterically hindered tertiary amine groups, the problem of removing iron ions and acids in chloroformate synthesis was solved, and high-purity and high-yield chloroformate production was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies struggle to effectively remove trace amounts of iron ions and residual acid during the synthesis of chloroformates, leading to product performance degradation and an inability to meet the stringent requirements of high-end downstream applications.
Using a zirconium-doped SBA-15 mesoporous molecular sieve framework as a support, and grafting amine oxime groups and sterically hindered tertiary amine groups onto the surface, a bifunctional adsorption system was constructed. Combined with inert gas purging and distillation units, selective removal of iron ions and acids was achieved.
It significantly reduces impurity content, improves product color index and distillation yield, avoids the risk of catalytic decomposition and hydrolysis loss, and achieves stable and efficient production of high-purity chloroformate.
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Figure CN121779243A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical synthesis technology, specifically relating to a process for the synthesis and purification of high-purity chloroformate. Background Technology
[0002] Chloroformates, especially as highly reactive organic synthesis intermediates, are widely used in pesticides, pharmaceuticals, initiators, and high-end optical materials due to their unique carbonyl and chlorine atom structures. Currently, the industry primarily uses the bis(trichloromethyl)carbonate (triphosgene, BTC) process for production. This process uses triphosgene and organic solvents (such as toluene) as substrates, preparing the target product through a phosgenation reaction with alcohols. Compared to the traditional gaseous phosgene method, the BTC method has significant advantages in safety and measurement accuracy. However, in the preparation of high-purity, low-color chloroformates, this process is highly susceptible to trace impurities in the reaction system and post-processing, leading to product performance degradation and making it difficult to meet the stringent requirements of high-end downstream applications.
[0003] First, the synthesis of chloroformates is essentially a highly acidic release process. The phosgenation reaction produces an equimolar amount of hydrogen chloride (HCl), and unreacted phosgene typically remains in the reaction system. These highly reactive chlorine-containing media dissolve in organic solvents, creating a highly corrosive reaction environment. In actual industrial production, this corrosive material inevitably corrodes the metal equipment, pipelines, and instruments (usually made of stainless steel), causing trace amounts of iron ions to continuously dissolve and enter the product system. Even if only ppm levels of ferric chloride (FeCl3) are present in the system, its strong Lewis acid nature can significantly reduce the decomposition activation energy of chloroformates. In the subsequent distillation and purification stage, these trace amounts of iron ions introduced by "chlorine corrosion" become "catalytically active centers," inducing violent decomposition of the product, generating carbon dioxide and alkyl chlorides. This leads to instability in the molten pool and a significant increase in product color, severely shortening the product's shelf life and reducing yield.
[0004] To address the issue of acidic residues associated with phosgenation reactions, the industry currently employs a combination of nitrogen purging and water / alkali washing. However, this traditional post-treatment technique has significant inherent drawbacks: limited by gas-liquid equilibrium, low-temperature nitrogen purging is insufficient to completely remove dissolved hydrogen chloride; while water washing can remove residual acid, the highly reactive ester bonds of chloroformates are extremely sensitive to water, easily undergoing hydrolysis side reactions during the washing process, leading to the loss of effective components.
[0005] In summary, there is an urgent need to develop a new process that can remove trace amounts of iron ions and residual acids while avoiding the introduction of moisture and organic leaching, in order to solve the problems of catalytic decomposition and hydrolysis loss in existing technologies. Summary of the Invention
[0006] In view of the above situation and to overcome the defects of the prior art, the purpose of the present invention is to provide a synthesis and purification process for high-purity chloroformate, so as to at least partially solve the problems mentioned in the background art.
[0007] The technical solution adopted in this invention is as follows: This invention proposes a process for the synthesis and purification of high-purity chloroformate, comprising the following steps: S1. Using a mixture of bis(trichloromethyl) carbonate and organic solvent as the base, an alcohol compound is added dropwise under temperature control to carry out a phosgenation reaction, resulting in a mixed reaction solution. S2. The mixed reaction solution obtained in step S1 is purged with inert gas to remove free hydrogen chloride and phosgene, and the treated mixed solution is obtained. S3. The mixture after step S2 is passed through an adsorption bed filled with adsorption material for iron removal and acid removal. S4. The purified liquid obtained in step S3 is sent to the distillation unit to separate the solvent and product under negative pressure to obtain high-purity chloroformate. The adsorbent material comprises a zirconium-doped SBA-15 mesoporous molecular sieve framework, and a tertiary amine group and a sterically hindered tertiary amine group grafted onto the surface of the framework.
[0008] In some embodiments of the present invention, in step S1, the organic solvent is toluene; the temperature control conditions include: the temperature is controlled at 40-60°C when dissolving bis(trichloromethyl) carbonate in toluene, and the temperature is controlled at 20±5°C when carrying out the phosgenation reaction; the alcohol compounds include methanol, ethanol, n-butanol and benzyl alcohol.
[0009] In some embodiments of the present invention, the inert gas purging in step S2 is performed using a gas distributor with an aperture of 20-50 μm; the purging gas-liquid ratio is controlled at 5:1 to 10:1, and the purging time is 2-3 hours.
[0010] In some embodiments of the present invention, step S3 employs a dual-column series process, which includes a main adsorption column and a safety column arranged in series; wherein a pre-filter with a filtration accuracy of ≤5μm is provided between the main adsorption column and the safety column, and a post-filter with a filtration accuracy of ≤1μm is provided at the outlet of the safety column; when the hydrogen chloride content at the outlet of the main adsorption column is detected to be >20ppm or the pressure difference is detected to be >0.1MPa, the main adsorption column and the safety column are switched.
[0011] In some embodiments of the present invention, the distillation unit in step S4 uses a falling film evaporator as a reboiler; The pressure drop across the entire distillation column should be controlled to be less than 2 kPa, the absolute pressure at the top of the column should be 20-50 mmHg, and the temperature difference between the reboiler heat medium and the material should be less than 15℃.
[0012] In some embodiments of the present invention, the process further includes regenerating the adsorbent material in step S3, wherein the regeneration includes: The adsorbent material was sequentially eluted with an oxalic acid alcohol solution, eluted with an alkaline alcohol solution, and purged and dried with an inert gas.
[0013] In some embodiments of the present invention, the method for preparing the adsorbent material in step S3 includes the following steps: Step (1): Using P123 as a template agent, tetraethyl orthosilicate as a silicon source, and zirconium oxychloride as a zirconium source, hydrothermal crystallization was carried out under acidic conditions, and Zr-SBA-15 framework was obtained after calcination. Step (2): Disperse the Zr-SBA-15 skeleton in an organic solvent, add 3-cyanopropyltriethoxysilane and N,N-diethyl-3-aminopropyltrimethoxysilane, and carry out a surface grafting reaction to obtain a grafting intermediate; Step (3): The grafting intermediate is suspended in a solution containing excess hydroxylamine hydrochloride, and an alkali is added to adjust the pH to 8-9 to carry out an oxime reaction to obtain the adsorbent material.
[0014] In some embodiments of the present invention, in step (1), the temperature of the hydrothermal crystallization is 100°C and the time is 24 hours; the temperature of the calcination is 550°C.
[0015] In some embodiments of the present invention, the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane in step (2) is 1.5:1 to 2.5:1; the surface grafting reaction is carried out under reflux at 110°C for 24 hours.
[0016] In some embodiments of the present invention, the oxime reaction in step (3) is carried out under reflux at 70-80°C for 24 hours.
[0017] The beneficial effects achieved by this invention are as follows: This invention constructs a bifunctional adsorption system of zirconium-doped SBA-15 loaded with amylopectin and sterically hindered tertiary amines. Combined with process optimization of adsorption followed by distillation, it utilizes the specific chelation mechanism of amylopectin groups for catalytic iron ions and the selective acid capture mechanism of sterically hindered tertiary amine groups in an anhydrous environment. This avoids the catalytic decomposition risk in high-temperature distillation and the hydrolysis loss problem caused by traditional water washing processes, thereby achieving the effect of significantly reducing impurity content and improving product color index and distillation yield. Attached Figure Description
[0018] Figure 1 This is a flowchart of the synthesis and purification process of high-purity chloroformate according to an embodiment of the present invention.
[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.
[0022] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0023] Reference Figure 1 To address the problems raised in the background art, this invention provides a process for the synthesis and purification of high-purity chloroformate, comprising the following steps: S1. Using a mixture of bis(trichloromethyl) carbonate and organic solvent as the base, an alcohol compound is added dropwise under temperature control to carry out a phosgenation reaction, resulting in a mixed reaction solution. S2. The mixed reaction solution obtained in step S1 is purged with inert gas to remove free hydrogen chloride and phosgene, and the treated mixed solution is obtained. S3. The mixture after step S2 is passed through an adsorption bed filled with adsorption material for iron removal and acid removal. S4. The purified liquid obtained in step S3 is sent to the distillation unit to separate the solvent and product under negative pressure to obtain high-purity chloroformate. The adsorbent material includes a zirconium-doped SBA-15 mesoporous molecular sieve framework, as well as a tert-amine oxime group and a sterically hindered tertiary amine group grafted onto the surface of the framework.
[0024] First, this invention uses zirconium-doped SBA-15 mesoporous molecular sieve (Zr-SBA-15) as a support and constructs an iron ion adsorption system with surface-grafted amylopectin groups. Specifically, the introduction of zirconium atoms significantly enhances the chemical stability and mechanical strength of the silica framework, improves the pressure drop stability of the adsorption bed during continuous operation, and prevents the dissolution of organic impurities. Simultaneously, the amylopectin groups, as specific chelating ligands for iron ions, can selectively capture trace amounts of iron ions from the reaction solution, significantly reducing their content. Since iron ions are the main catalyst for the thermal decomposition of chloroformates, removing iron ions in the pretreatment stage effectively inhibits the catalytic decomposition reaction in the subsequent high-temperature distillation process, thereby reducing the generation of byproducts (such as carbon dioxide and alkyl chlorides) and improving the color index and storage stability of the final product.
[0025] Secondly, this invention utilizes sterically hindered tertiary amine groups grafted onto the framework surface for deacidification, achieving the removal of acidic impurities under anhydrous conditions and improving process yield. By leveraging the steric hindrance effect, the nucleophilic attack of the tertiary amine nitrogen atom on the carbonyl carbon of the chloroformate is suppressed, avoiding the formation of unstable acyl quaternary ammonium salt intermediates, thus ensuring the stability of the chloroformate while capturing HCl. This dry deacidification process replaces traditional water washing or alkaline washing processes, avoiding hydrolytic loss of highly reactive chloroformate due to contact with water, and significantly improving the distillation yield of the target product while ensuring the deacidification effect.
[0026] Furthermore, this invention enhances the safety and stability of the production process by coupling the adsorption unit with the distillation unit. Before the material enters the heat-sensitive distillation section, the adsorption bed removes potentially decomposing metallic impurities and volatile acids. This pre-purification strategy improves the feed environment of the distillation column, prevents secondary reactions caused by the high-temperature enrichment of impurities in the distillation vessel, avoids vacuum fluctuations and column overflow caused by gases generated during decomposition, and provides a stable thermodynamic environment for distillation operations, thus facilitating the continuous and safe operation of the chemical process.
[0027] In summary, this invention constructs a bifunctional adsorption system of zirconium-doped SBA-15 loaded with amylopectin and sterically hindered tertiary amines. Combined with process optimization of adsorption followed by distillation, it utilizes the specific chelation mechanism of amylopectin groups for catalytic iron ions and the selective acid capture mechanism of sterically hindered tertiary amine groups in an anhydrous environment. This avoids the catalytic decomposition risk in high-temperature distillation and the hydrolysis loss problem caused by traditional water washing processes, thereby achieving the effect of significantly reducing impurity content and improving product color index and distillation yield.
[0028] In some embodiments, in step S1, the organic solvent is toluene; the temperature control conditions include: controlling the temperature at 40-60°C when dissolving bis(trichloromethyl) carbonate in toluene, and controlling the temperature at 20±5°C during the phosgenation reaction; the alcohol compounds include methanol, ethanol, n-butanol, and benzyl alcohol. This invention employs a segmented temperature control strategy combined with toluene as the medium to optimize the thermodynamic and kinetic environment of the reaction. During the dissolution stage, the temperature range of 40-60°C promotes the thermal dissociation of bis(trichloromethyl) carbonate, generating highly reactive phosgene monomers in situ, constructing a homogeneous reaction system, and preventing local reaction runaway caused by solid residues. During the reaction stage, the low-temperature control at 20±5°C removes the heat generated by the acylation reaction, inhibits the formation of a series of byproducts such as diester carbonate, thereby improving the selectivity of the reaction and reducing the safety risks caused by phosgene volatilization.
[0029] In some embodiments, the inert gas purging in step S2 employs a gas distributor with an pore size of 20-50 μm; the purging gas-liquid ratio is controlled at 5:1 to 10:1, and the purging time is 2-3 hours. The 20-50 μm pore size of the distributor generates high-density microbubbles, significantly increasing the contact surface area between the gas and liquid phases and overcoming the mass transfer resistance of hydrogen chloride in organic solvents. Combined with a gas-liquid ratio of 5:1 to 10:1 and a purging time of 2-3 hours, a high driving force of gas phase partial pressure is maintained, promoting deep desorption of solvated hydrogen chloride and phosgene. This step effectively reduces the content of acidic components in the mixture, lessens the load on subsequent adsorption units, and extends the service life of the adsorbent.
[0030] In some embodiments, step S3 employs a dual-column series process, comprising a main adsorption column and a safety column connected in series. A pre-filter with a filtration accuracy ≤5μm is installed between the main adsorption column and the safety column, and a post-filter with a filtration accuracy ≤1μm is installed at the outlet of the safety column. When the hydrogen chloride content at the outlet of the main adsorption column is detected to be >20ppm or the pressure difference is >0.1MPa, the main adsorption column and the safety column are switched. The dual-column series structure provides a safety buffer for adsorption breakthrough, ensuring that even when the main column is saturated, the safety column can still effectively intercept residual impurities, maintaining the uniformity of the effluent quality. Simultaneously, the pre-filter (≤5μm) removes mechanical impurities from the fluid, preventing physical blockage of the adsorption bed; the post-precision filter (≤1μm) traps any adsorbent powder that may detach, preventing it from entering subsequent distillation units. This design eliminates the risk of solid particles becoming localized hot spots or catalytic centers in the high-temperature environment of the distillation vessel. Combined with automatic switching logic based on chlorine content and pressure difference, it achieves full lifecycle management of the adsorbent and long-term stable operation of the process system.
[0031] In some embodiments, the distillation unit in step S4 uses a falling film evaporator as a reboiler; the overall pressure drop of the distillation column is controlled to be <2 kPa, the absolute pressure at the top of the column is 20-50 mmHg, and the temperature difference ΔT between the reboiler heating medium and the material is ≤15℃. By using a falling film evaporator as a reboiler, the residence time of the material on the heating surface is significantly shortened, reducing the thermal history of the material. Simultaneously, by controlling the overall pressure drop of the column to be less than 2 kPa and maintaining the absolute pressure at the top of the column within the range of 20 to 50 mmHg, the operating temperature of the reboiler is reduced; coupled with strict temperature difference control of no more than 15℃, localized overheating of the wall surface due to excessively high heating medium temperature is avoided. This distillation strategy combining short residence time and low wall temperature synergistically suppresses the thermal decomposition and coking of chloroformate during the separation process, improving solvent recovery efficiency and product purity.
[0032] In some embodiments, the process further includes regenerating the adsorbent material in step S3. Regeneration includes: sequentially rinsing the adsorbent material with an oxalic acid-alcohol solution, rinsing the adsorbent material with an alkaline alcohol solution, and purging and drying the adsorbent material with an inert gas. The oxalic acid-alcohol solution rinsing step utilizes the strong complexing ability of oxalic acid for iron ions, effectively eluting iron ions adsorbed on the metal oxime groups through a competitive coordination mechanism, restoring the metal-capturing active sites of the material. The subsequent alkaline alcohol solution rinsing step utilizes the acid-base neutralization principle to convert the protonated tertiary amine salt back to the free tertiary amine form, regenerating the acid-capturing capacity of the material. The final inert gas purging step removes residual solvent molecules, preventing cross-contamination of the next batch of material. This regeneration scheme significantly reduces the frequency of adsorbent replacement and operating costs, while also reducing solid waste generation, improving the economic and environmental benefits of the process.
[0033] In some embodiments, the method for preparing the adsorbent material in step S3 includes the following steps: Step (1): Using P123 as a template agent, tetraethyl orthosilicate as a silicon source, and zirconium oxychloride as a zirconium source, hydrothermal crystallization was carried out under acidic conditions, and Zr-SBA-15 framework was obtained after calcination. Step (2): Disperse the Zr-SBA-15 skeleton in an organic solvent, add 3-cyanopropyltriethoxysilane and N,N-diethyl-3-aminopropyltrimethoxysilane, and carry out a surface grafting reaction to obtain a grafting intermediate; Step (3): The grafting intermediate is suspended in a solution containing excess hydroxylamine hydrochloride, and an alkali is added to adjust the pH to 8-9 to carry out the oxime reaction to obtain the adsorbent material.
[0034] In step (1), a sol-gel hydrothermal crystallization method is used, employing block copolymer P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide) as a template directing agent to in-situ dope zirconium atoms into the silica framework. This constructs a high specific surface area ordered mesoporous structure while simultaneously enhancing the framework's chemical corrosion resistance and mechanical strength through the introduction of zirconium-oxygen bonds. Steps (2) and (3) employ a post-grafting-in-situ conversion strategy. First, organic functional groups are firmly anchored to the pore surface via covalent bonds through a silane coupling agent's co-condensation reaction. Then, under mild conditions, cyano groups are converted into amine oxime groups with high complexing activity towards iron ions through a mild oxime reaction. This preparation route ensures uniform dispersion and high loading rate of bifunctional groups within the mesopores, avoiding pore blockage and imparting excellent anti-leakage properties to the material, making it suitable for continuous flow industrial purification environments.
[0035] In some embodiments, in step (1), the hydrothermal crystallization temperature is 100°C and the time is 24 hours; the calcination temperature is 550°C. The hydrothermal crystallization process at 100°C for 24 hours promotes the deep condensation of inorganic species at the micelle interface, improves the compactness and order of the pore walls, and establishes the structural stability of the material under subsequent harsh chemical environments. The high-temperature calcination treatment at 550°C completely removes the organic template agent without destroying the integrity of the skeleton, clears the mass transfer channels, and exposes highly active surface silanol sites, providing sufficient reaction centers for subsequent functional group grafting.
[0036] In some embodiments, the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane in step (2) is 1.5:1 to 2.5:1; the surface grafting reaction is carried out under reflux at 110°C for 24 hours. By controlling the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane to be between 1.5:1 and 2.5:1, the distribution density of iron removal sites and acid removal sites on the pore surface is optimized. While prioritizing the efficient capture of catalytic iron ions, sufficient acid capture capacity is maintained, achieving a synergistic balance between the two purification functions. The reflux reaction at 110°C for 24 hours provides the activation energy required to overcome surface steric hindrance, promotes the full condensation between the silane coupling agent and the silanol groups on the framework surface, forms a dense and strong covalent bond layer, improves the loading of functional groups and the solvent erosion resistance, and extends the service life of the adsorbent material.
[0037] In some embodiments, the oxime reaction in step (3) is refluxed at 70-80°C for 24 hours. The reaction temperature of 70-80°C provides the necessary activation energy for the nucleophilic addition of hydroxylamine to cyano groups, ensuring high conversion efficiency while preventing the decomposition of the heat-sensitive hydroxylamine reagent and the thermal degradation of the organic linker arm; the reaction time of up to 24 hours overcomes the diffusion and mass transfer resistance of the reactants in the confined mesoporous channels, ensuring that the cyano groups on the surface of the deep channels are fully converted into amylopyroxime groups with high complexing activity to iron ions, thereby maximizing the effective chelating capacity of the adsorbent material.
[0038] The present invention will be further described below by way of specific embodiments.
[0039] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods already existing in the art; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.
[0040] Example 1: Step (1): Using P123 as a template agent, tetraethyl orthosilicate as a silicon source, and zirconium oxychloride as a zirconium source, the raw material ratio of the reaction system was set according to the molar ratio of P123: tetraethyl orthosilicate: zirconium oxychloride: HCl: H2O of 0.017:1.0:0.05:5.9:195. According to the above molar ratio, P123 was dissolved in a mixed solution of deionized water and HCl. After complete dissolution by stirring, zirconium oxychloride and tetraethyl orthosilicate were added sequentially under stirring at -40℃. The mixture was pre-hydrolyzed by vigorous stirring at 40℃ for 24 hours, and then transferred to a high-pressure reactor for hydrothermal crystallization at 100℃ for 24 hours. The product was filtered, washed with water until neutral, dried, and then calcined at 550℃ for 6 hours to obtain the Zr-SBA-15 framework.
[0041] Step (2): Take the dried Zr-SBA-15 skeleton and disperse it in anhydrous toluene at a solid-liquid ratio of 1:50. Under nitrogen protection, add 3-cyanopropyltriethoxysilane and N,N-diethyl-3-aminopropyltrimethoxysilane, wherein the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane is 2:1. The mixture is refluxed and stirred at 110°C for 24 hours. After the reaction is complete, centrifuge and wash three times with toluene and ethanol respectively, and dry under vacuum at 60°C to obtain the grafting intermediate.
[0042] Step (3): The above grafting intermediate was suspended in a methanol / water (volume ratio 1:1) mixed solution, excess hydroxylamine hydrochloride was added, and anhydrous sodium carbonate was slowly added to adjust the pH to 8.5. The system was heated to 75°C and refluxed for 24 hours to carry out the oxime reaction. The reaction product was filtered, washed alternately with large amounts of deionized water and ethanol until the filtrate was neutral, and finally dried under vacuum at 60°C for 12 hours to obtain the adsorbent material.
[0043] S1. Add bis(trichloromethyl) carbonate to toluene, add N,N-dimethylformamide catalyst, start stirring and heat to 50°C to completely dissolve the bis(trichloromethyl) carbonate. Then lower the reactor temperature to 20°C. Under temperature control, slowly add benzyl alcohol dropwise to the reactor. During the dropwise addition, control the reaction temperature at 20±5°C. After the dropwise addition is complete, maintain the reaction temperature for 5 hours to obtain a mixed reaction solution.
[0044] S2. After the reaction is complete, nitrogen gas is introduced into the mixed reaction liquid using a gas distributor. The purging gas-liquid ratio (nitrogen volume / reaction liquid volume) is controlled at 8:1, and the purging time is 2.5 hours to remove free hydrogen chloride and phosgene, resulting in the treated mixture.
[0045] S3. The treated mixture is pumped into the adsorption unit. The adsorption unit consists of a main adsorption column and a safety column arranged in series, both filled with the adsorbent material prepared above. The mixture first passes through a pre-filter with a filtration accuracy of 5 μm, and then sequentially through the main adsorption column and the safety column for iron removal and acid removal. The purified liquid passes through a post-filter with a filtration accuracy of 1 μm located at the outlet of the safety column to intercept trace amounts of powder.
[0046] S4. The purified liquid is sent to the distillation unit. The distillation unit uses a falling film evaporator as a reboiler. The overall pressure drop of the distillation column is controlled to be <2 kPa, the absolute pressure at the top of the column is 20-50 mmHg, and the temperature difference between the reboiler heat medium and the material is ΔT ≤ 15℃. First, the solvent toluene is separated, and then the fraction is collected to obtain high-purity benzoyl chloroformate product.
[0047] Example 2: The only difference from Example 1 is: In step S1, the alcohol compound used is anhydrous ethanol, the temperature is controlled at 40°C when dissolving bis(trichloromethyl) carbonate in toluene, and the temperature is controlled at 15°C when carrying out the phosgenation reaction; in step S2, the purging gas-liquid ratio is controlled at 5:1; the purging time is 2 hours.
[0048] In step (2) of the preparation of the adsorbent material, the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane is adjusted to 1.5:1.
[0049] Example 3: The only difference from Example 1 is that in step S1, the alcohol compound used is n-butanol, the temperature is controlled at 60°C when dissolving bis(trichloromethyl) carbonate in toluene, and the temperature is controlled at 25°C when carrying out the phosgenation reaction. In step S2, the purge gas-liquid ratio is controlled at 10:1, and the purge time is 3 hours.
[0050] In step (2) of the preparation of the adsorbent material, the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane is adjusted to 2.5:1.
[0051] Example 4: The only difference from Example 1 is that in step (3) of the preparation of the adsorbent material, the reaction temperature is controlled at 70°C, the pH is adjusted to 8.0, and the reflux time is 24 hours.
[0052] Example 5: The only difference from Example 1 is that in step (3) of the preparation of the adsorbent material, the reaction temperature is controlled at 80°C, the pH is adjusted to 9.0, and the reflux time is 24 hours.
[0053] Example 6: After running the process described in Example 1 for a period of time, when the hydrogen chloride content at the outlet of the main adsorption column is detected to be >20 ppm, the main adsorption column and the safety column are switched, and the offline main adsorption column is regenerated, including: rinsing the adsorbent material with a methanol solution containing 5 wt% oxalic acid to remove adsorbed iron ions, rinsing the adsorbent material with a methanol solution containing 1 wt% triethylamine to regenerate tertiary amine groups, and purging and drying the adsorbent material with hot nitrogen to constant weight. The regenerated adsorption column is then reconnected to the system as a safety column, and the synthesis and purification of benzoyl chloroformate are carried out according to the process parameters of Example 1.
[0054] Comparative Example 1: The difference from Example 1 is that step S3 is omitted. After the inert gas purging in step S2, the treated mixture is directly fed into the distillation unit without intermediate water washing or adsorption treatment. The remaining parameters are kept as close as possible to those of Example 1.
[0055] Comparative Example 2: The difference from Example 1 is that the adsorbent used in step S3 is pure SBA-15 molecular sieve powder that has not been doped with zirconium and has not been grafted with any organic functional groups. The remaining steps are the same as in Example 1.
[0056] The final products obtained in Examples 1-6 and Comparative Examples 1-2 were tested for quality indicators.
[0057] Test method: Purity: Determined by gas chromatography (GC). The instrument was an Agilent 7890B equipped with a flame ionization detector (FID). An HP-5 capillary column (30m × 0.32mm × 0.25μm) was used. The injection port temperature was 220℃, the detector temperature was 250℃, and the column temperature was programmed.
[0058] Yield: The molar yield based on the amount of alcohol fed is calculated using the formula: (actual moles of product / theoretical moles of alcohol fed) × 100%.
[0059] Colorimetric properties (APHA): Determined using a colorimeter in accordance with GB / T 3143-1982 "Determination of color of liquid chemical products (Hazen units - platinum - cobalt color number)".
[0060] Residual iron content: determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were digested with nitric acid using microwave before analysis.
[0061] Residual acidity: determined by automatic potentiometric titration. A T5 automatic potentiometric titrator was used, with titration performed using 0.01 mol / L NaOH standard solution, expressed as HCl.
[0062] The data from the above tests were analyzed, and the results are shown in Table 1.
[0063] Table 1
[0064] Analysis of the results in Table 1 shows that, compared with Comparative Example 1, the residual iron content in Comparative Example 1 before distillation was 3500 ppb. Iron ions, acting as Lewis acids, catalyze the decomposition of chloroformate during distillation, leading to a decrease in product yield to 88.5%, purity to 96.50%, and an increase in product color to 60 APHA. Example 1, using the adsorbent material of this invention, reduced the residual iron content to below 10 ppb through the chelating effect of the amine oxime groups. This reduction in iron content inhibited the thermal decomposition reaction, resulting in a product yield of 98.2%, purity of 99.85%, and a color reduction to 5 APHA during distillation.
[0065] A comparison of data from Example 1 and Comparative Example 2 shows that while Comparative Example 2, using only pure SBA-15, could partially reduce the iron content (to 1200 ppb) through physical adsorption, its removal efficiency for residual acid (220 ppm) and iron ions was inferior to that of Example 1 due to the lack of specific adsorption groups. The residual acid and iron ions affected the product stability during distillation, resulting in lower product color (45 APHA) and yield (92.0%) compared to Example 1. This indicates that the amylopectin groups and sterically hindered tertiary amine groups on the framework surface play a crucial role in the synergistic removal of impurities.
[0066] Data from Examples 2 and 3 show that the process described in this invention is suitable for the synthesis of chloroformates from alcohols with different carbon chain lengths, such as ethanol and n-butanol, and the product indicators all meet the requirements. Data from Example 6 shows that the adsorption performance of the adsorbent material did not significantly decrease after regeneration, indicating that the adsorbent material has good structural stability and regeneration performance.
[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.
Claims
1. A process for synthesizing and purifying high-purity chloroformate, characterized in that, Includes the following steps: S1. Using a mixture of bis(trichloromethyl) carbonate and organic solvent as the base, an alcohol compound is added dropwise under temperature control to carry out a phosgenation reaction, resulting in a mixed reaction solution. S2. The mixed reaction solution obtained in step S1 is purged with inert gas to remove free hydrogen chloride and phosgene, and the treated mixture is obtained. S3. The mixture after step S2 is passed through an adsorption bed filled with adsorption material for iron removal and acid removal. S4. The purified liquid obtained in step S3 is sent to a distillation unit to separate the solvent and product under negative pressure to obtain high-purity chloroformate. The adsorbent material comprises a zirconium-doped SBA-15 mesoporous molecular sieve framework, and a tertiary amine group and a sterically hindered tertiary amine group grafted onto the surface of the framework.
2. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, In step S1, the organic solvent is toluene; the temperature control conditions include: the temperature is controlled at 40-60℃ when dissolving bis(trichloromethyl) carbonate in toluene, and the temperature is controlled at 20±5℃ when carrying out the phosgenation reaction; the alcohol compounds include methanol, ethanol, n-butanol and benzyl alcohol.
3. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, In step S2, the inert gas purging is performed using a gas distributor with an aperture of 20-50 μm; the purging gas-liquid ratio is controlled between 5:1 and 10:1, and the purging time is 2-3 hours.
4. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, Step S3 employs a dual-column series process, which includes a main adsorption column and a safety column arranged in series. A pre-filter with a filtration accuracy of ≤5μm is installed between the main adsorption column and the safety column, and a post-filter with a filtration accuracy of ≤1μm is installed at the outlet of the safety column. When the hydrogen chloride content at the outlet of the main adsorption column is detected to be >20ppm or the pressure difference is >0.1MPa, the main adsorption column and the safety column are switched.
5. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, The distillation unit in step S4 uses a falling film evaporator as a reboiler. The pressure drop across the entire distillation column should be controlled to be less than 2 kPa, the absolute pressure at the top of the column should be 20-50 mmHg, and the temperature difference between the reboiler heat medium and the material should be less than 15℃.
6. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, The process further includes regenerating the adsorbent material in step S3, wherein the regeneration includes: The adsorbent material was sequentially eluted with an oxalic acid alcohol solution, eluted with an alkaline alcohol solution, and purged and dried with an inert gas.
7. The synthesis and purification process of high-purity chloroformate according to claim 1, characterized in that, The preparation method of the adsorbent material in step S3 includes the following steps: Step (1): Using P123 as a template agent, tetraethyl orthosilicate as a silicon source, and zirconium oxychloride as a zirconium source, hydrothermal crystallization was carried out under acidic conditions, and Zr-SBA-15 framework was obtained after calcination. Step (2): Disperse the Zr-SBA-15 skeleton in an organic solvent, add 3-cyanopropyltriethoxysilane and N,N-diethyl-3-aminopropyltrimethoxysilane, and carry out a surface grafting reaction to obtain a grafting intermediate; Step (3): The grafting intermediate is suspended in a solution containing excess hydroxylamine hydrochloride, and an alkali is added to adjust the pH to 8-9 to carry out an oxime reaction to obtain the adsorbent material.
8. The synthesis and purification process of high-purity chloroformate according to claim 7, characterized in that, In step (1), the hydrothermal crystallization temperature is 100°C and the time is 24 hours; the calcination temperature is 550°C.
9. The synthesis and purification process of high-purity chloroformate according to claim 7, characterized in that, In step (2), the molar ratio of 3-cyanopropyltriethoxysilane to N,N-diethyl-3-aminopropyltrimethoxysilane is 1.5:1 to 2.5:1; the surface grafting reaction is carried out under reflux at 110°C for 24 hours.
10. The synthesis and purification process of high-purity chloroformate according to claim 7, characterized in that, The oxime reaction in step (3) is carried out under reflux at 70-80°C for 24 hours.