Synthesis of 3-chloropropynyl and p-chlorobenzaldehyde

Abstract

The present application relates to the technical field of fine chemical product synthesis, and in particular to a synthesis method of 3-chloropropynyl co-production of p-chlorobenzaldehyde, which comprises the following steps: mixing propargyl alcohol, a solvent, an ionic liquid catalyst, a cocatalyst DMF and a polymerization inhibitor p-tert-butyl catechol, heating and slowly adding p-chlorobenzylidene dichloride dropwise into the mixture, collecting the generated 3-chloropropynyl crude product at the tail gas outlet, cooling after the reaction is completed, and sequentially reducing pressure rectification of 3-chloropropynyl, the remaining propargyl alcohol and the solvent, and p-chlorobenzaldehyde product through a rectification tower. The present application solves the problems of using toxic and hazardous chemicals chlorinating agent in the production of existing 3-chloropropynyl, and generating a large amount of toxic waste acid gas or low-value byproducts, and the problem of low utilization rate of chlorine atom in the existing direct hydrolysis method of p-chlorobenzaldehyde, and reduces environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of fine chemical product synthesis technology, specifically to a method for synthesizing 3-chloropropyne and p-chlorobenzaldehyde. Background Technology

[0002] 3-Chloropropyne is an important chemical raw material, mainly used in the synthesis of electroplating intermediates, pharmaceutical intermediates, and pesticide intermediates. It can be used to synthesize pharmaceuticals such as fenvalerate and pesticides such as propyrin, and is also an excellent metal corrosion inhibitor and rust preventant. p-Chlorobenzaldehyde is mainly used as a pharmaceutical, pesticide, and dye intermediate. In pharmaceuticals, it is used to manufacture products such as phenalool and aminophenylbutyric acid. In pesticides, it can be used in the synthesis of fungicides such as tebuconazole, plant growth regulators such as uniconazole, and insecticides such as chlorfenapyr.

[0003] The chlorination process of propynyl alcohol is the main method for producing 3-chloropropyne. The chlorinating agents used mainly include thionyl chloride, phosphorus chloride, and carbonyl chloride. CN202849284 mentions reacting propynyl alcohol with phosphorus trichloride under pyridine as an acid-binding agent, with a yield of 85%. This method has drawbacks such as pyridine being a foul-smelling liquid and difficulty in recovery under acidic conditions. CN99802124.5 mentions preparing propynyl alcohol from propynyl alcohol with carbonyl chloride under the action of an amide catalyst, with a yield of only about 65%. Furthermore, carbonyl chloride is a highly toxic substance, requiring sophisticated equipment and complex operation. CN 107473930 B mentions a method using phosphorus trichloride chlorination in a tubular reactor, with a yield of only 90%, and may also suffer from low-quality byproduct phosphorous acid.

[0004] The main methods for preparing p-chlorobenzaldehyde include gas-phase oxidation of p-chlorotoluene, liquid-phase oxidation, electrochemical oxidation, and chlorination hydrolysis. Oxidation methods result in low conversion rates and selectivity for p-chlorotoluene, making it difficult to control the degree of oxidation. Currently, the chlorination hydrolysis method of p-chlorotoluene is the primary method used in my country's industrial production. Under light or with an initiator, the side-chain methyl group of p-chlorotoluene is chlorinated. The chlorinated product is then hydrolyzed in the presence of a catalyst to obtain p-chlorobenzaldehyde. The hydrolysis reaction commonly uses metal halides such as FeCl3, CuCl2, SnCl2, or zinc salts as catalysts. However, the large amount of catalyst used results in residues in the product, affecting its color. Furthermore, the process generates a significant amount of wastewater, posing considerable safety and environmental risks.

[0005] As can be seen from the above production processes of 3-chloropropyne and p-chlorobenzaldehyde, the two products are produced using different processes. The reactions have low atom economy and both generate low-value-added byproducts or large amounts of waste acid gas, which can easily cause environmental pollution.

[0006] Therefore, there is an urgent need to find a safe and environmentally friendly method for producing 3-chloropropyne and p-chlorobenzaldehyde, so that it can have greater industrial application value. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for the co-production of p-chlorobenzaldehyde from 3-chloropropyne. Using propynyl alcohol as a raw material, 3-chloropropyne and p-chlorobenzaldehyde are obtained through dichlorochlorination of p-chlorobenzylene under the action of a catalyst. This method solves the problems of existing 3-chloropropyne production methods that use toxic and hazardous chlorinating agents and generate large amounts of toxic waste acid gas or low-value-added byproducts; and addresses the issue of low chlorine atom utilization in the direct hydrolysis of p-chlorobenzaldehyde, thereby reducing environmental pollution.

[0008] This invention is achieved through the following technical solution:

[0009] A method for synthesizing 3-chloropropyne and p-chlorobenzaldehyde is provided. The method involves mixing propynyl alcohol, solvent, ionic liquid catalyst, co-catalyst DMF, and polymerization inhibitor p-tert-butylcatechol, heating the mixture, and slowly adding p-chlorobenzyl dichlorodi ...

[0010] In this invention, the chlorine atom in p-chlorobenzylidene dichloride undergoes elimination under nucleophilic conditions to generate a carbocation. Simultaneously, the hydroxyl group of propynyl alcohol complexes with the ionic liquid and attacks the benzyl group to form p-chlorobenzaldehyde and 3-chloropropyne. The nucleophilicity of the lone pair electrons on the oxygen atom of the cocatalyst DMF promotes the departure of chlorine; the polymerization inhibitor p-tert-butylcatechol can suppress free radical side reactions (such as the polymerization of 3-chloropropyne) and prevent product decomposition.

[0011] Furthermore, during vacuum distillation, the vacuum degree of 3-chloropropyne is 0.07 MPa, and the temperature is 30–45 °C; the vacuum degree of the remaining propynyl alcohol and solvent is 0.09–0.095 MPa, and the temperature is 60–90 °C; and the high vacuum of p-chlorobenzaldehyde is 0.098–0.1 MPa, and the temperature is around 105–125 °C.

[0012] The reaction mixture → first-stage vacuum distillation (around 0.07 MPa, temperature 30-45℃) → 3-chloropropyne (product) + remaining components;

[0013] Remaining components → Second-stage vacuum distillation (0.09~0.095MPa, temperature 60~90℃) → Solvent and propynyl alcohol mixture + crude p-chlorobenzaldehyde;

[0014] crude p-chlorobenzaldehyde → vacuum distillation (0.098~0.1MPa, temperature 105~125℃) → p-chlorobenzaldehyde (finished product).

[0015] Preferably, the dripping and heat preservation temperature is 80-90℃, and the mixture is kept warm and stirred for 2-4 hours.

[0016] The temperature should be 80-90℃, below the boiling point of propynyl alcohol, to prevent excessive propynyl alcohol from being carried out by the tail gas during the dropwise reaction.

[0017] Furthermore, the molar ratio of propynyl alcohol to p-chlorobenzyl dichloride is 1.1 to 1.5:1.

[0018] Preferably, the molar ratio of propynyl alcohol to p-chlorobenzyl dichloro is 1.2 to 1.3:1.

[0019] Furthermore, the mass ratio of propynyl alcohol to solvent, catalyst, co-catalyst, and polymerization inhibitor is 1:0.3-0.6:0.05-0.2:0.005-0.01:0.002.

[0020] Preferably, the mass ratio of propargyl alcohol to solvent, catalyst, co-catalyst, and polymerization inhibitor is 1:0.4-0.5:0.1-0.15:0.01:0.002.

[0021] Furthermore, the solvent is one or more of chlorobenzene, o-dichlorobenzene, and xylene.

[0022] The solvents are selected from common and readily available solvents, serving to dilute and mix the mixture evenly. They do not participate in the reaction. The boiling points of the selected solvents are higher than those of propynyl alcohol, so that they are not lost with the tail gas during the reaction. The ionic liquid of the raw material has a certain melting point. After adding the solvent, the reaction solution is mixed more evenly, and the solvent does not participate in the reaction. The generated aldehyde has a melting point of about 48°C, which facilitates the subsequent distillation of 3-chloropropyne.

[0023] Furthermore, the ionic liquid catalyst is one or more of 1-butyl-3-methylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, and 1-butyl-2,3-dimethylimidazolium bromide.

[0024] Ionic liquids possess the properties of Lewis acids, enabling them to accept electrons from chloride ions to form negatively charged protons, promoting the formation of p-chlorobenzyl dichlorocarbocations and complexing with propynyl alcohol; moreover, they have lower oxidizing power than conventional inorganic Lewis acids, preventing excessive oxidation of p-chlorobenzaldehyde.

[0025] Preferably, the ionic liquid catalyst is 1-butyl-3-methylimidazolium chloride or 1-butyl-3-methylimidazolium bromide.

[0026] Furthermore, the ionic liquid catalyst remaining at the bottom of the distillation vessel can be reused in the next batch of synthesis.

[0027] The remaining ionic liquid catalyst from distillation can be reused 5-12 times, achieving recycling and reducing waste.

[0028] The beneficial effects of this invention are:

[0029] This invention features a clean process using low-toxicity solvents and catalysts, employing p-chlorobenzylene dichloride to avoid the use of hazardous chlorinating agents such as thionyl chloride, phosphorus chloride, and carbonyl chloride, thus reducing health risks to operators. The ionic liquid exhibits high biodegradability, and the reaction proceeds in an acidic environment where Cl- directly participates in substitution, completely converting p-chlorobenzylene dichloride into p-chlorobenzaldehyde, avoiding persistent organic pollutants (POPs) residues. The solvent is recyclable within the system, achieving zero emissions. The catalyst retains >95% activity after 5-12 cycles, reducing waste generation and meeting the requirements of green chemistry and sustainable development. Economically, co-production reduces raw material consumption, simultaneously preparing p-chlorobenzaldehyde during the synthesis of 3-chloropropyne, as the same reaction step produces two products concurrently, improving atom utilization. The efficient use and recycling of the catalyst lowers production costs. Optimized separation processes yield not only high-purity p-chlorobenzaldehyde and 3-chloropropyne but also high yields of both, making them more valuable for industrial applications.

[0030] This invention solves the problems of using toxic and hazardous chlorinating agents in the production of 3-chloropropyne in the prior art, and generating a large amount of toxic waste acid gas or low-value-added by-products; it also solves the problem of low utilization rate of chlorine atoms in the direct hydrolysis of p-chlorobenzaldehyde, while reducing environmental pollution; compared with the mainstream industrial production processes of existing 3-chloropropyne and p-chlorobenzaldehyde, waste acid gas emissions are reduced by more than 75%.

[0031] The synthesis method of this invention achieves zero emissions of toxic chlorinating agent waste gas through green solvents, efficient ionic liquid catalysis, and co-production design; the utilization rate of chlorine atoms is significantly improved compared with the traditional hydrolysis method; all by-products are utilized in a closed loop (propynyl alcohol recycling, solvent recovery, and catalyst reuse), achieving the triple goals of efficient resource utilization, environmentally friendly emissions, and significantly improved economic benefits. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the present invention.

[0033] Figure 2 This is a yield table of 3-chloropropyne and p-chlorobenzaldehyde corresponding to different ionic liquid catalysts in Example 2 of this invention. Detailed Implementation

[0034] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0035] The test materials used in the various embodiments of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0036] Example 1:

[0037] Add 184.8g of propynyl alcohol, 56g of chlorobenzene, 9.3g of 1-butyl-3-methylimidazolium chloride, 1.8g of DMF, and 0.37g of p-tert-butylcatechol to a 1000ml reaction flask. Stir and heat to 80℃, then slowly add 586.5g of p-chlorobenzyl dichloro. After the addition is complete, keep the temperature at 80℃ and stir until the p-chlorobenzyl dichloro reacts completely.

[0038] The products in this scheme have significantly different boiling points: 3-chloropropyne 58℃, propynyl alcohol 114.5℃, solvent 130–180℃, and p-aldehyde 213℃, making distillation relatively easy. The reaction mixture is distilled off to remove 3-chloropropyne under a vacuum of 0.07 MPa and a temperature of 30–45℃; the solvent and remaining propynyl alcohol mixture is distilled off at 0.09 MPa and a temperature of 60–80℃; and finally, p-chlorobenzaldehyde is distilled off at 0.1 MPa and a temperature of 105–125℃.

[0039] During the reaction, 56.4 g of crude 3-chloropropyne with a purity of 91.2% was collected at the tail gas outlet; 179.8 g of 3-chloropropyne with a purity of 99.3% was obtained by vacuum distillation of the reaction solution; and 416.4 g of p-chlorobenzaldehyde with a purity of 99.4% was obtained by distillation. The overall yield of 3-chloropropyne was 93.6%, and the yield of p-chlorobenzaldehyde was 98.2%.

[0040] Example 2:

[0041] The operating steps and feed amounts in this embodiment are the same as in Example 1, except that the ionic liquid catalyst is replaced with 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, or a combination thereof. Yield results for 3-chloropropyne and p-chlorobenzaldehyde are also provided. Figure 2 As shown.

[0042] Example 3:

[0043] The remaining catalyst from the distillation in Example 1 was reused. 184.8 g of propynyl alcohol, 56 g of chlorobenzene, 1.8 g of DMF, and 0.37 g of p-tert-butylcatechol were added to a 1000 ml reaction flask. The mixture was stirred and heated to 80°C, and 586.5 g of p-chlorobenzyl dichlorochloride was slowly added dropwise. After the addition was complete, the mixture was kept at the same temperature and stirred until the p-chlorobenzyl dichlorochloride had completely reacted. 53.8 g of crude 3-chloropropyne was collected, with a purity of 92.4%. 179.1 g of 3-chloropropyne with a purity of 99.5% was obtained by vacuum distillation of the reaction solution; 418.5 g of p-chlorobenzaldehyde with a purity of 99.3% was also obtained by distillation. The overall yield of 3-chloropropyne was 92.7%, and the yield of p-chlorobenzaldehyde was 98.6%.

[0044] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A process for the synthesis of 3-chloropropyne co-product p-chlorobenzaldehyde, characterized by: The propargyl alcohol, solvent and ionic liquid catalyst, co-catalyst DMF and polymerization inhibitor p-t-butyl pyrocatechol are mixed and heated, and p-chlorobenzylidene dichloride is slowly added dropwise thereto, the dropping and holding temperature is 80-90℃, holding and stirring for 2-4h; the ionic liquid catalyst is one or more of 1-butyl-3-methylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium bromide and 1-butyl-2,3-dimethylimidazolium bromide; the generated 3-chloropropargyl alcohol is collected at the tail gas port after holding and stirring, and after the reaction is completed, the temperature is lowered, 3-chloropropargyl alcohol, residual propargyl alcohol and solvent, and p-chlorobenzaldehyde are successively distilled out by reducing pressure in a rectifying column; the ionic liquid catalyst remaining at the bottom of the rectifying column can be used for the next batch of synthesis; the solvent is one or more of chlorobenzene, o-dichlorobenzene and xylene.

2. The process for the synthesis of 3-chloropropyne co-product p-chlorobenzaldehyde according to claim 1, characterized by the fact that: When the 3-chloropropargyl alcohol is distilled under reduced pressure, the vacuum degree is 0.07MPa, and the temperature is 30-45℃; the vacuum degree of the residual propargyl alcohol and solvent is 0.09-0.095MPa, and the temperature is 60-90℃; the vacuum degree of the p-chlorobenzaldehyde is 0.098-0.1MPa, and the temperature is 105-125℃.

3. The process for the synthesis of 3-chloropropyne co-product p-chlorobenzaldehyde according to claim 1, characterized by the fact that: The molar ratio of propargyl alcohol to p-chlorobenzylidene dichloride is 1.1-1.5:

1.

4. The process for the synthesis of 3-chloropropyne co-product p-chlorobenzaldehyde according to claim 1, characterized by the fact that: The mass ratio of propargyl alcohol to solvent, catalyst, co-catalyst, polymerization inhibitor is 1:0.3-0.6:0.05-0.2:0.005-0.01:0.002.

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