A process for the high selective co-production of phthaloyl chloride and benzoyl chloride

Abstract

The present application relates to the technical field of fine chemicals synthesis, and discloses a method for high-selectivity co-production of phthaloyl chloride and benzoyl chloride. The method uses dimethylbenzene and trichlorobenzene as raw materials, and feeds them into a photochlorination reaction tower to heat the materials. Then, the reaction tower is kept in a micro-negative pressure condition to perform photochlorination reaction. After the reaction is completed, the liquid is directly fed into a reaction kettle, and phthalic acid and a catalyst are added. Finally, the reaction liquid is separated by rectification to obtain the products phthaloyl chloride and benzoyl chloride. The present application greatly improves the selectivity of dimethylbenzene photochlorination reaction, and inhibits the ring chlorination side reaction. The present application can realize flexible co-production of m-phthaloyl chloride and p-phthaloyl chloride and benzoyl chloride, and can flexibly adjust the generation ratio of phthaloyl chloride and benzoyl chloride according to the raw material supply and product demand, thereby greatly improving the production flexibility of the reaction device.

Description

Technical Field

[0001] This invention relates to the field of fine chemical synthesis technology, and in particular to a method for the highly selective co-production of phthaloyl chloride and benzoyl chloride. Background Technology

[0002] Phthaloyl chloride (terephthaloyl chloride and isophthaloyl chloride) is an important class of fine chemicals. High-purity terephthaloyl chloride and isophthaloyl chloride are important monomer raw materials for the preparation of high-performance fiber materials—aramid 1414 and aramid 1313. Benzoyl chloride is also an important fine chemical intermediate, widely used in the preparation of dyes, rubber and plastic additives, and pharmaceutical intermediates. Currently, the mainstream synthesis method of phthaloyl chloride is to use dimethylbenzene as a raw material, which undergoes a side-chain chlorination reaction to obtain di-(trichloromethyl)benzene, and then reacts with phthalic acid to obtain phthaloyl chloride; while the mainstream synthesis method of benzoyl chloride is to use toluene as a raw material, which undergoes a side-chain chlorination reaction to obtain trichlorotoluene, and then reacts with benzoic acid to obtain benzoyl chloride. Although a patent (CN105001077A) has reported the co-production of terephthaloyl chloride and benzoyl chloride through reaction using terephthalic acid and trichlorotoluene as starting materials, this method does not involve the synthesis of chlorotoluene. The ratio of terephthaloyl chloride to benzoyl chloride prepared is fixed and benzoyl chloride is the main component (the molar ratio of terephthaloyl chloride to benzoyl chloride in the product is 1:2). It is impossible to flexibly adjust the production ratio of terephthaloyl chloride and benzoyl chloride according to the supply of raw materials and product demand.

[0003] In the mainstream synthesis of phthaloyl chloride, the side-chain chlorination reaction of dimethylbenzene is a key step determining product quality. Compared with traditional processes using thionyl chloride, phosphorus trichloride, or phosphorus pentachloride as chlorinating agents, the photocatalytic side-chain chlorination process using chlorine as the chlorinating agent has advantages such as high product yield, simple operation, and less pollution, making it a more advanced side-chain chlorination process route. In the above reaction, the chlorination reaction on the aromatic ring is the main side reaction, and the resulting aromatic ring chlorinated product has a similar melting and boiling point to the side-chain chlorinated product, making it difficult to separate. To suppress the chlorination side reaction on the aromatic ring, most existing technologies use the addition of organic amines or other side reaction inhibitors to improve the selectivity of side-chain chlorination. However, the doping of these inhibitors into the reaction system greatly increases the complexity of product purification and post-processing operations. Furthermore, the inventors also found in their research on this reaction that the addition of such inhibitors leads to side effects such as a slowdown in the main reaction rate. Some technologies use segmented chlorination, segmented temperature control, and controlled light intensity to improve reaction selectivity, but this undoubtedly increases the complexity of the equipment and operation. How to improve the selectivity of side-chain chlorination simply and efficiently remains a challenge.

[0004] In summary, the existing technology has not yet provided a method for the co-production of phthaloyl chloride and benzoyl chloride based on a highly selective aromatic ring side chain chlorination process. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a simple, flexible, and highly selective method for the co-production of phthaloyl chloride and benzoyl chloride.

[0006] This invention is achieved through the following technical solution:

[0007] A method for the highly selective co-production of phthaloyl chloride and benzoyl chloride includes the following steps:

[0008] (1) Using dimethylbenzene and trichlorotoluene as raw materials, they are transported to the photochlorination reaction tower in a certain ratio. The materials are heated to the set temperature under the protection of dry nitrogen atmosphere. Then, the vacuum device is started to keep the reaction tower under a slight negative pressure. The light source is turned on and a mixture of dry chlorine and dry nitrogen is blown in from the bottom of the reaction tower. The content of raw material dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene is monitored during the photochlorination reaction.

[0009] (2) After the photochlorination reaction is completed, dry nitrogen gas is introduced into the reaction tower to purge the residual chlorine and hydrogen chloride. Then, the liquid is directly transported to the reaction vessel without separation, and phthalic acid and catalyst are added to the reaction vessel. The reaction is started after the temperature is raised to the set temperature.

[0010] (3) After the reaction is completed, the reaction liquid is separated by distillation to obtain high-purity products benzoyl chloride and benzoyl chloride.

[0011] Through long-term research on the photochlorination reaction of aromatic ring side chains, the inventors have creatively discovered that the hydrogen chloride generated in the reaction, when dissolved in the reaction system, accelerates the heterolytic cleavage of chlorine molecular bonds, thereby eliminating the side reaction of chlorination on the aromatic ring. During the photochlorination process, maintaining a negative pressure inside the reactor and continuously introducing nitrogen gas while chlorinating significantly reduces the concentration of hydrogen chloride in the reaction system, allowing the generated hydrogen chloride to be rapidly removed from the reactor, thus suppressing the side reaction of chlorination on the aromatic ring. The continuous introduction of nitrogen gas along with chlorine gas also dilutes the chlorine gas, improving its dispersibility in the reactants and avoiding the possibility of excessively high local chlorine concentrations inducing side reactions.

[0012] Furthermore, the inventors have creatively discovered that the introduction of trichlorotoluene, as an excellent solvent for the photochlorination reaction of dimethylbenzene, reduces the concentration of dimethylbenzene in the overall reaction system through dilution, significantly improving the selectivity of side-chain chlorination in the initial stage of the reaction. Once the side-chain methyl group undergoes chlorination, the electron-withdrawing effect of the benzyl chloride can reduce the electron cloud density on the benzene ring, further reducing the possibility of electrophilic chlorination side reactions on the ring. Using the above-mentioned technical method, the selectivity of the photochlorination reaction of dimethylbenzene can reach over 98.5%. In the subsequent acyl chloride reaction, trichlorotoluene is directly converted into benzoyl chloride and phthaloyl chloride as a reactant, avoiding the complex steps of solvent recovery and recycling, and allowing for free adjustment of the production ratio of phthaloyl chloride and benzoyl chloride by adjusting the ratio with dimethylbenzene, significantly improving the production flexibility of the reaction apparatus.

[0013] A more preferred technical solution of the present invention is as follows:

[0014] In step (1), the dimethylbenzene is m-dimethylbenzene or p-dimethylbenzene, and the mass ratio of dimethylbenzene to trichlorotoluene is 0.2-5:1.

[0015] In a further preferred embodiment, the material is heated to 120℃-160℃ for photochlorination reaction, and the negative pressure inside the reaction tower is controlled at 10-100Pa during the reaction process.

[0016] More preferably, the dry chlorine and dry nitrogen are mixed in a volume flow ratio of 0.1:1 to 10:1.

[0017] More preferably, the light source is an LED light source with a wavelength of 300nm-500nm and an illuminance of 30000Lux-60000Lux.

[0018] In a further preferred embodiment, the bottom of the photochlorination reaction tower is equipped with an aeration device made of corrosion-resistant material, through which a dry atmosphere is blown into the reaction tower.

[0019] Further preferred, the reaction is considered to have reached its termination condition when the total mass content of dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the feed liquid of the total reaction material system (excluding trichlorotoluene) is less than 0.5%.

[0020] In step (2), the phthalic acid is isophthalic acid or terephthalic acid, and the amount of phthalic acid added is 1.005-1.05 times the theoretical amount (based on the actual amount of phthaloyl chloride and benzoyl chloride in the reaction solution).

[0021] More preferably, the catalyst is one or more of ferric chloride, zinc chloride, and aluminum chloride, and the amount of catalyst added is 0.1%-0.5% of the mass of phthalic acid; the reaction is carried out after heating to 100℃-140℃.

[0022] In a further preferred embodiment, the mixed gas of hydrogen chloride and chlorine discharged from the condenser at the top of the photochlorination reaction tower is thoroughly washed in an absorption tank containing a saturated sodium chloride solution, and the remaining chlorine gas is dried and then recycled back into the chlorination reaction tower to continue participating in the reaction.

[0023] The beneficial effects of this invention are mainly reflected in:

[0024] Photochlorination is a one-stage chlorination process that does not require the addition of any initiators, catalysts, auxiliaries, or inhibitors. It does not require a multi-stage reaction process and has a high tolerance for reaction conditions such as light intensity and chlorination temperature. While performing highly selective chlorination of aromatic ring side chains, it significantly reduces the complexity of reaction operation and subsequent separation and purification.

[0025] It can achieve flexible co-production of terephthaloyl chloride and benzoyl chloride, and the production ratio of terephthaloyl chloride and benzoyl chloride can be flexibly adjusted according to the supply of raw materials and product demand, which greatly improves the production flexibility of the reaction unit. Attached Figure Description

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] Figure 1 This is a gas chromatogram of the photochlorination reaction products in Example 1;

[0028] Figure 2 This is a gas chromatogram of the photochlorination reaction products in Example 4;

[0029] Figure 3 This is a gas chromatogram of the photochlorination reaction products in Example 6;

[0030] Figure 4 This is a gas chromatogram of the photochlorination reaction product in Example 10. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to embodiments, so that those skilled in the art can implement it based on the description. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] Example 1: A method for highly selective co-production of terephthaloyl chloride and benzoyl chloride, comprising the following steps:

[0033] (1) Weigh 200g of p-dimethylbenzene and 1000g of trichlorotoluene, mix them and add them to a tower-type photochlorination reactor with a reflux condenser. Heat the material to 140°C under a dry nitrogen atmosphere. Then start the vacuum pump to maintain a slight negative pressure of 40Pa in the reaction tower. Turn on the LED light source, adjust the wavelength of the light source to 300nm and the light intensity to 40000Lux. Then blow in a mixture of dry chlorine and dry nitrogen through the corrosion-resistant aeration device at the bottom of the reaction tower. The volume flow ratio of chlorine to nitrogen is 0.1:1. During the photochlorination reaction, the content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the reaction material is monitored and analyzed by gas chromatography. After 4 hours of reaction, the gas chromatography analysis results show that the total content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) is less than 0.3% (area normalization method). Stop the chlorine gas and turn off the LED light source.

[0034] (2) Continue to purge the reaction tower with dry nitrogen to remove any remaining chlorine and hydrogen chloride. Samples were taken from the reactants and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) was as high as 99.04%, and the content of benzene ring chlorination byproducts and other byproducts was less than 0.6% (area normalization method; detailed analysis results are attached). Figure 1 The reaction mixture was transferred entirely to a 5L reactor without separation. 749g of terephthalic acid and 1.12g of ferric chloride were added to the reactor. The mixture was heated to 105℃ and reacted for 3 hours. Samples were then taken for analysis. Gas chromatography analysis showed that the total residue of p-bis(trichloromethyl)benzene and trichlorotoluene in the total reactants was less than 0.3% (area normalization method). The reaction was then terminated.

[0035] (3) The above reaction solution was subjected to a single vacuum distillation, and 676g of benzoyl chloride (purity 99.41%) and 1195g of terephthaloyl chloride (purity 99.72%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to terephthaloyl chloride (by mass) was 0.56:1.

[0036] The quantitative analysis methods for the photochlorination reaction raw materials, intermediates, products, and impurities involved in the above embodiments are as follows:

[0037] Gas chromatograph: Agilent 7820A; Detector: Flame Ionization Detector (FID); Column: HP-5 (30m × 0.32mm × 0.25μm); Detector temperature: 300℃; Vaporization chamber temperature: 300℃; Combustion gas (hydrogen) flow rate: 30mL / min; Combustion gas (air) flow rate: 300mL / min; Carrier gas (nitrogen) flow rate: 25mL / min; Split ratio: 50:1; Injection volume: 1μL; Solvent for sample preparation: dichloromethane.

[0038] Programmed temperature conditions: Initial column temperature 100℃, hold for 2 min; increase temperature to 300℃ at a rate of 8℃ / min, hold for 5 min.

[0039] Under the above chromatographic conditions, the retention time of the peak of p-di(trichloromethyl)benzene was 12.4 min-12.5 min.

[0040] Example 2: A method for highly selective co-production of terephthaloyl chloride and benzoyl chloride, comprising the following steps:

[0041] (1) Weigh 1000g of p-dimethylbenzene and 200g of trichlorotoluene, mix them and add them to a tower-type photochlorination reactor with a reflux condenser. Heat the material to 125°C under a dry nitrogen atmosphere. Then start the vacuum pump to maintain a slight negative pressure of 50Pa in the reaction tower. Turn on the LED light source, adjust the wavelength of the light source to 360nm and the light intensity to 30000Lux. Then blow in a mixture of dry chlorine and dry nitrogen through the corrosion-resistant aeration device at the bottom of the reaction tower. The volume flow ratio of chlorine to nitrogen is 0.5:1. During the photochlorination reaction, the content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the reaction material is monitored and analyzed by gas chromatography. After 12 hours of reaction, the gas chromatography analysis results show that the total content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) is less than 0.5% (area normalization method). Stop the chlorine gas and turn off the LED light source.

[0042] (2) Continue to purge the residual chlorine and hydrogen chloride into the reaction tower with dry nitrogen. Take a sample from the reactants and analyze the reaction liquid using gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) is 98.79% (area normalization method). Transfer the entire reaction liquid to a 5L reactor without separation, and add 1667g of terephthalic acid and 3.33g of aluminum trichloride to the reactor. Heat to 115℃ and react for 6.5 hours. Take a sample for analysis. The chromatographic analysis results show that the total residue of p-bis(trichloromethyl)benzene and trichlorotoluene in the total reactants is less than 0.2% (area normalization method). End the reaction.

[0043] (3) The above reaction solution was subjected to a single vacuum distillation, and 125g of benzoyl chloride (purity 99.47%) and 3640g of terephthaloyl chloride (purity 99.61%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to terephthaloyl chloride was 0.03:1.

[0044] In the above embodiments, the quantitative analysis methods for the photochlorination reaction raw materials, intermediates, products and impurities are the same as in Example 1.

[0045] Example 3: A method for highly selective co-production of terephthaloyl chloride and benzoyl chloride, comprising the following steps:

[0046] (1) Weigh 600g of p-dimethylbenzene and 600g of trichlorotoluene, mix them and add them to a tower-type photochlorination reactor with a reflux condenser. Heat the material to 130°C under a dry nitrogen atmosphere. Then start the vacuum pump to maintain a slight negative pressure of 80Pa in the reaction tower. Turn on the LED light source, adjust the wavelength of the light source to 420nm and the light intensity to 40000Lux. Then blow in a mixture of dry chlorine and dry nitrogen through the corrosion-resistant aeration device at the bottom of the reaction tower. The volume flow ratio of chlorine to nitrogen is 0.5:1. During the photochlorination reaction, the content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the reaction material is monitored and analyzed by gas chromatography. After 7 hours of reaction, the gas chromatography analysis results show that the total content of p-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) is less than 0.3% (area normalization method). Stop the chlorine gas and turn off the LED light source.

[0047] (2) Continue to purge the residual chlorine and hydrogen chloride into the reaction tower with dry nitrogen. Take samples from the reactants and analyze the reaction liquid using gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) is 98.93%, and the content of benzene ring chlorination byproducts and other impurities is less than 0.6% (area normalization method). The reaction liquid does not need to be separated and is completely transferred to a 5L reactor. Add 1214g of terephthalic acid and 3.04g of ferric chloride to the reactor, heat to 125℃ and react for 4.5 hours. Take samples for analysis. The chromatographic analysis results show that the total residue of p-bis(trichloromethyl)benzene and trichlorotoluene in the total reactants is less than 0.3% (area normalization method). The reaction is then terminated.

[0048] (3) The above reaction solution was subjected to a single vacuum distillation, and 395g of benzoyl chloride (purity 99.52%) and 2410g of terephthaloyl chloride (purity 99.63%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to terephthaloyl chloride was 0.16:1.

[0049] In the above embodiments, the quantitative analysis methods for the photochlorination reaction raw materials, intermediates, products and impurities are the same as in Example 1.

[0050] Example 4: A method for highly selective co-production of isophthaloyl chloride and benzoyl chloride, comprising the following steps:

[0051] (1) Weigh 800g of m-dimethylbenzene and 800g of trichlorotoluene, mix them and add them to a tower-type photochlorination reactor with a reflux condenser. Heat the material to 130°C under a dry nitrogen atmosphere. Then start the vacuum pump to maintain a slight negative pressure of 70Pa in the reaction tower. Turn on the LED light source, adjust the wavelength of the light source to 450nm and the light intensity to 45000Lux. Then blow in a mixture of dry chlorine and dry nitrogen through the corrosion-resistant aeration device at the bottom of the reaction tower. The volume flow ratio of chlorine to nitrogen is 0.5:1. During the photochlorination reaction, the content of intermediate dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the reaction material is monitored and analyzed by gas chromatography. After 9.5 hours of reaction, the gas chromatography analysis results show that the total content of m-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) is less than 0.4% (area normalization method). Stop the chlorine gas and turn off the LED light source.

[0052] (2) Continue to purge the reaction tower with dry nitrogen to remove any remaining chlorine and hydrogen chloride. Take samples from the reactants and analyze the reaction mixture using gas chromatography. The purity of m-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) was 98.73% (area normalization method; detailed analysis results are attached). Figure 2 The reaction mixture was transferred entirely to a 5L reactor without separation. A mixture of 1610g isophthalic acid, 2.42g ferric chloride, and 2.42g aluminum chloride was added to the reactor. The mixture was heated to 120℃ and reacted for 5 hours. Samples were then taken for analysis. Chromatographic analysis showed that the total residue of intermediate di(trichloromethyl)benzene and trichlorotoluene in the total reaction mixture was less than 0.3% (area normalization method). The reaction was then terminated.

[0053] (3) The above reaction solution was subjected to a single vacuum distillation, and 520g of benzoyl chloride (purity 99.76%) and 3210g of isophthaloyl chloride (purity 99.72%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to isophthaloyl chloride was 0.16:1.

[0054] In the above embodiments, the quantitative analysis methods for the photochlorination reaction raw materials, intermediates, products and impurities are the same as in Example 1.

[0055] Under the above chromatographic conditions, the retention time of m-di(trichloromethyl)benzene was 11.9 min.

[0056] Example 5: A method for highly selective co-production of isophthaloyl chloride and benzoyl chloride, comprising the following steps:

[0057] (1) Weigh 400g of m-dimethylbenzene and 800g of trichlorotoluene, mix them and add them to a tower-type photochlorination reactor with a reflux condenser. Heat the material to 130°C under a dry nitrogen atmosphere. Then start the vacuum pump to maintain a slight negative pressure of 60Pa in the reaction tower. Turn on the LED light source, adjust the wavelength of the light source to 380nm and the light intensity to 35000Lux. Then blow in a mixture of dry chlorine and dry nitrogen through the corrosion-resistant aeration device at the bottom of the reaction tower. The volume flow ratio of chlorine to nitrogen is 0.5:1. During the photochlorination reaction, the content of intermediate dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the reaction material is monitored and analyzed by gas chromatography. After 5.5 hours of reaction, the gas chromatography analysis results show that the total content of m-dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) is less than 0.3% (area normalization method). Stop the chlorine gas and turn off the LED light source.

[0058] (2) Continue to purge the residual chlorine and hydrogen chloride into the reaction tower with dry nitrogen. Take a sample from the reactants and analyze the reaction liquid using gas chromatography. The purity of m-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) is 98.92% (area normalization method). Transfer the entire reaction liquid to a 5L reactor without separation, and add a mixture of 991g isophthalic acid, 1.98g ferric chloride, and 1.98g aluminum trichloride to the reactor. Heat to 115℃ and react for 3.5 hours. Take a sample for analysis. The chromatographic analysis results show that the total residue of m-bis(trichloromethyl)benzene and trichlorotoluene in the total reactants is less than 0.2% (area normalization method). End the reaction.

[0059] (3) The above reaction solution was subjected to vacuum distillation, and 515g of benzoyl chloride (purity 99.87%) and 1780g of isophthaloyl chloride (purity 99.81%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to isophthaloyl chloride was 0.29:1.

[0060] In the above embodiments, the quantitative analysis methods for the photochlorination reaction raw materials, intermediates, products and impurities are the same as in Example 1.

[0061] Example 6 (Comparative Example 1):

[0062] 1000g of p-dimethylbenzene was directly weighed and added to a tower-type photochlorination reactor equipped with a reflux condenser. The reaction was carried out under the same photochlorination conditions as in Example 1. During the reaction, the content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the reactants was monitored and analyzed by gas chromatography. After 10.7 hours of reaction, the gas chromatography analysis results showed that the total content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the total reactants (excluding trichlorotoluene) was less than 0.4% (area normalization method). The chlorine gas supply was then stopped and the LED light source was turned off.

[0063] Dry nitrogen gas was continuously introduced into the reaction tower to purge any remaining chlorine and hydrogen chloride. Samples were taken from the reactants and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants was 89.28%, and the content of benzene ring chlorination byproducts and other byproducts was greater than 8% (area normalization method; detailed analysis results are attached). Figure 3 ).

[0064] Example 7 (Comparative Example 2):

[0065] 200g of p-dimethylbenzene and 1000g of trichlorotoluene were weighed and mixed, then added to a tower-type photochlorination reactor equipped with a reflux condenser. The material was heated to 140℃ under a dry nitrogen atmosphere. The LED light source was turned on, with the wavelength adjusted to 300nm and the light intensity to 40000Lux. Dry chlorine gas was bubbled into the reactor through a corrosion-resistant aeration device at the bottom of the tower to initiate the reaction. During the reaction, the reactor was kept at atmospheric pressure, and only chlorine gas was introduced; no nitrogen gas was bubbled in. Gas chromatography was used to monitor and analyze the content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the reactants. After 4.5 hours of reaction, the gas chromatography analysis showed that the total content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the total reactants (excluding trichlorotoluene) was less than 0.4% (area normalization method). The chlorine gas supply was then stopped, and the LED light source was turned off.

[0066] Dry nitrogen gas was introduced into the reaction tower to purge any residual chlorine and hydrogen chloride. Samples were taken from the reaction mixture and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reaction mixture (excluding trichlorotoluene) was only 80.85% (area normalization method), and the color of the reaction mixture was significantly darker than that in Examples 1-3.

[0067] Example 8 (Comparative Example 3):

[0068] 200g of p-dimethylbenzene and 1000g of trichlorotoluene were weighed and mixed, then added to a tower-type photochlorination reactor equipped with a reflux condenser. The material was heated to 140℃ under a dry nitrogen atmosphere. The LED light source was turned on, with the wavelength adjusted to 300nm and the light intensity to 40000Lux. A mixture of dry chlorine and dry nitrogen was introduced through a corrosion-resistant aeration device at the bottom of the reaction tower to initiate the reaction. The volumetric flow rate ratio of chlorine to nitrogen was 0.1:1, and the reaction tower was kept at atmospheric pressure. Gas chromatography was used to monitor and analyze the content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the reaction material. After 4.8 hours of reaction, the gas chromatography analysis showed that the total content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) was less than 0.4% (area normalization method). The chlorine supply was then stopped, and the LED light source was turned off.

[0069] Dry nitrogen gas was continuously introduced into the reaction tower to purge any remaining chlorine and hydrogen chloride. Samples were taken from the reactants and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) was 87.37% (area normalization method).

[0070] Example 9 (Comparative Example 4):

[0071] 200g of p-dimethylbenzene and 1000g of trichlorotoluene were weighed and mixed, then added to a tower-type photochlorination reactor equipped with a reflux condenser. The material was heated to 140℃ under a dry nitrogen atmosphere. A vacuum pump was then activated to maintain a slight negative pressure of 40Pa inside the reaction tower. The LED light source was turned on, with the wavelength adjusted to 300nm and the light intensity to 40000Lux. Dry chlorine gas was bubbled in only through a corrosion-resistant aeration device at the bottom of the reaction tower. Gas chromatography was used to monitor and analyze the content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the reaction material. After 5 hours of reaction, gas chromatography analysis showed that the total content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) was less than 0.2% (area normalization method). The chlorine gas flow was then stopped, and the LED light source was turned off.

[0072] Dry nitrogen gas was continuously introduced into the reaction tower to purge any remaining chlorine and hydrogen chloride. Samples were taken from the reactants and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) was 84.32% (area normalization method).

[0073] Example 10 (Comparative Example 5):

[0074] 200g of p-dimethylbenzene and 1000g of trichlorotoluene were weighed and mixed, then added to a tower-type photochlorination reactor equipped with a reflux condenser. The material was heated to 140°C under a dry nitrogen atmosphere. The LED light source was turned on, with the wavelength adjusted to 300nm and the light intensity to 40,000 Lux. A mixture of dry chlorine and dry hydrogen chloride gas was bubbled into the reactor through an aeration device made of corrosion-resistant material at the bottom of the reactor. The volumetric flow rate ratio of chlorine to hydrogen chloride was 2:1, and the reactor was kept at atmospheric pressure. Gas chromatography was used to monitor and analyze the content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the reaction material during the photochlorination reaction. After 5 hours of reaction, the gas chromatography analysis showed that the total content of p-dimethylbenzene and the intermediate product 1-5-chlorodimethylbenzene in the total reaction material (excluding trichlorotoluene) was less than 0.4% (area normalization method). The chlorine gas flow was then stopped, and the LED light source was turned off.

[0075] Dry nitrogen gas was introduced into the reaction tower to purge any residual chlorine and hydrogen chloride. Samples were taken from the reactants and analyzed by gas chromatography. The purity of p-bis(trichloromethyl)benzene in the total reactants (excluding trichlorotoluene) was only 76.07% (area normalization method; detailed analysis results are attached). Figure 4 Furthermore, the color of the reactants is significantly darker compared to Examples 1-3.

[0076] Example 11 (Comparative Example 6):

[0077] Take 500g of trichlorotoluene and add it to a 1L reactor. Add 221g of terephthalic acid and 1.05g of ferric chloride to the reactor. Heat the mixture to 120℃ and react for 1.2 hours. Take a sample for analysis. The chromatographic analysis results show that the total residual amount of trichlorotoluene in the total reactants is less than 0.2% (area normalization method). The reaction is then terminated.

[0078] (3) The above reaction solution was subjected to vacuum distillation, and 315g of benzoyl chloride (purity 99.57%) and 224g of terephthaloyl chloride (purity 99.61%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to terephthaloyl chloride was 1.41.

[0079] Example 12 (Comparative Example 7):

[0080] Take 1000g of trichlorotoluene and add it to a 2.5L reactor. Add 442g of terephthalic acid and 1.77g of ferric chloride to the reactor. Heat the mixture to 120℃ and react for 3 hours. Take a sample for analysis. The chromatographic analysis results show that the total residual amount of trichlorotoluene in the total reactants is less than 0.3% (area normalization method). The reaction is then terminated.

[0081] (3) The above reaction solution was subjected to vacuum distillation, and 640g of benzoyl chloride (purity 99.52%) and 465g of terephthaloyl chloride (purity 99.71%) were obtained by controlling an appropriate reflux ratio. The yield ratio of benzoyl chloride to terephthaloyl chloride was 1.44.

[0082] The preferred embodiments of the present invention have been described in the above examples. It is obvious that many variations can be made within the inventive concept of the present invention. It should be noted that any changes made within the inventive concept of the present invention will fall within the protection scope of the present invention.

Claims

1. A method for the highly selective co-production of phthaloyl chloride and benzoyl chloride, characterized by comprising the following steps: (1) Using dimethylbenzene and trichlorotoluene as raw materials, they are transported to the photochlorination reaction tower. The materials are heated under the protection of dry nitrogen atmosphere. Then, the vacuum device is started to maintain a slight negative pressure in the reaction tower. The light source is turned on and a mixture of dry chlorine and dry nitrogen is blown in from the bottom of the reaction tower. The content of raw material dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene is monitored during the photochlorination reaction. The dimethylbenzene is either m-dimethylbenzene or p-dimethylbenzene, and the mass ratio of dimethylbenzene to trichlorotoluene is 0.2-5:1; dry chlorine and dry nitrogen are mixed in a volume flow ratio of 0.1:1-10:

1. (2) After the photochlorination reaction is completed, dry nitrogen gas is introduced into the reaction tower to purge it. Then the liquid is directly transported to the reaction vessel, and phthalic acid and catalyst are added to the reaction vessel. The reaction is then heated. (3) After the reaction is completed, the reaction liquid is separated by distillation to obtain benzoyl chloride and benzoyl chloride products.

2. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (1), the material is heated to 120℃-160℃ for photochlorination reaction.

3. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (1), the light source is an LED light source with a wavelength of 300nm-500nm and an illumination intensity of 30000Lux-60000Lux.

4. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (1), a corrosion-resistant aeration device is installed at the bottom of the photochlorination reaction tower, and a dry atmosphere is blown into the reaction tower through the aeration device.

5. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (1), the reaction is considered to have reached the termination condition when the total mass content of dimethylbenzene and intermediate product 1-5-chlorodimethylbenzene in the total reactant system is less than 0.5%.

6. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (2), the phthalic acid is isophthalic acid or terephthalic acid, and the amount of phthalic acid added is 1.005-1.05 times the theoretical amount.

7. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (2), the catalyst is one or more of ferric chloride, zinc chloride, and aluminum chloride, and the amount of catalyst added is 0.1%-0.5% of the mass of phthalic acid; the reaction is carried out after the temperature is raised to 100℃-140℃.

8. The method for highly selective co-production of phthaloyl chloride and benzoyl chloride as described in claim 1, characterized in that: In step (2), the mixed gas of hydrogen chloride and chlorine discharged from the top condenser of the photochlorination reaction tower after purging enters the absorption tank containing saturated sodium chloride solution for thorough washing. The remaining chlorine gas is dried and then recycled back into the chlorination reaction tower to continue participating in the reaction.

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