Method and device for producing m-halogenated alkylbenzene through continuous reaction

Abstract

The invention relates to a method and device for producing m-halogenated alkylbenzene through continuous reaction, and the method comprises the following steps: a reaction step: taking halogenated benzene and o-halogenated alkylbenzene and / or p-halogenated alkylbenzene as raw materials, and carrying out reaction in a reaction kettle under the catalysis of a catalyst; a washing step: washing the mixture obtained in the reaction step with water; a distillation step: distilling the mixture obtained in the water washing step, and refluxing the separated unreacted substances or byproducts to the reaction kettle; an adsorption step: carrying out molecular sieve adsorption on the remaining distillate after distillation in the distillation step, and separating a target product and a reaction by-product; and a refluxing step: refluxing the by-product separated by the molecular sieve into the reaction kettle. According to the method, halogenated alkylbenzene can be produced in a high-conversion-rate and environment-friendly manner.

Description

Technical Field

[0001] This invention relates to the field of halobenzene preparation, and more particularly to a method and apparatus for producing meta-haloalkylbenzenes and dihaloalkylbenzenes via a continuous reaction process. Background Technology

[0002] Chlorotoluene is an important fine chemical raw material. In recent years, the production of various new pharmaceutical, pesticide, and dye intermediates has used chlorotoluene as a starting material. These intermediates have shown very bright development prospects, and the huge development potential of the downstream market has stimulated and promoted the production and development of chlorotoluene. Among the three isomers of chlorotoluene, p-chlorotoluene is the most widely used. p-chlorotoluene can be used to prepare many important fine chemical intermediates and fine chemicals through side-chain oxidation, ring oxidation, cyanation, halogenation, and chlorination reactions. Due to its wide application, its synthesis process and purification methods are also the most mature.

[0003] However, the existing production processes for m-chlorotoluene account for less than 1% of the total, resulting in low output and limiting its production and application.

[0004] There are three main traditional methods for producing m-chlorotoluene:

[0005] (a) m-Cresol method: m-Cresol is reacted with phosphorus pentachloride to produce m-chlorotoluene. This method uses relatively expensive raw materials, resulting in higher production costs.

[0006] (b) m-Aminotoluene method: m-Aminotoluene is prepared into m-chlorotoluene through diazotization and Sandmeyer reaction. The production process is long, involving diazotization, hydrolysis and distillation. In addition, a large amount of concentrated hydrochloric acid is used in the synthesis process, and phenolic impurities are generated. Copper-containing wastewater is generated in the Sandmeyer reaction process, which causes environmental pollution and high wastewater treatment costs.

[0007] (c) o-Chlorotoluene method: o-Chlorotoluene isomerizes to m-chlorotoluene and p-chlorotoluene in the presence of a catalyst at a conversion temperature of 230–300 °C. Since the two compounds produced have the same boiling point and essentially the same properties, it is difficult to obtain high-purity m-chlorotoluene. Furthermore, the initial product of the isomerization reaction is m-chlorotoluene, with a very low content of p-chlorotoluene. As the conversion degree of o-chlorotoluene increases, m-chlorotoluene further isomerizes to p-chlorotoluene, and the selectivity of the m-chlorotoluene product decreases with increasing conversion rate, also leading to a decrease in the yield of m-chlorotoluene.

[0008] (d) Toluene chlorination method, which involves chlorinating toluene with chlorine gas. However, this method results in a low proportion of m-chlorotoluene. Furthermore, it involves multiple steps, making continuous reactions impossible, and is environmentally unfriendly.

[0009] Therefore, developing a method for synthesizing m-chlorotoluene with high conversion rate and low cost is of great significance for promoting the application of m-chlorotoluene intermediates.

[0010] Furthermore, the applications of m-chlorotoluene itself require further development and improvement. Summary of the Invention

[0011] This invention was made in view of the above-mentioned problems. Through dedicated research, the inventors have improved the existing process to develop a continuous reaction method and apparatus for preparing m-haloalkylbenzenes, which can produce haloalkylbenzenes in a high-conversion and environmentally friendly manner.

[0012] The continuous reaction method for preparing m-haloalkylbenzenes of the present invention includes:

[0013] The reaction procedure involves using halobenzenes, as well as ortho-haloalkylbenzenes and / or p-haloalkylbenzenes as raw materials, and carrying out the reaction in a reaction vessel under the catalysis of a catalyst.

[0014] The water washing step involves washing the mixture obtained from the reaction step with water.

[0015] The distillation step involves distilling the mixture obtained from the water washing step, and refluxing the separated unreacted substances or byproducts back into the reaction vessel.

[0016] The adsorption step involves molecular sieve adsorption of the distillate remaining after distillation in the distillation step to separate the target product and reaction byproducts.

[0017] The reflux step involves returning the byproducts separated by the molecular sieve back to the reactor.

[0018] In the haloalkylbenzene of the present invention, the alkyl group on the benzene ring is an alkyl group with 1 to 3 carbon atoms, and the halosubstituent on the benzene ring is Cl, Br, or I.

[0019] Preferably, the alkyl group is methyl and the halogen substituent is Cl. In this case, the starting material is chlorobenzene, o-chlorotoluene, and / or p-chlorotoluene, and the product is m-chlorotoluene.

[0020] The method of this invention improves the utilization rate of raw materials by producing m-chlorotoluene through continuous reaction and by returning all byproducts to the reactor.

[0021] This invention enables continuous reaction, yielding high-purity reaction products, and is environmentally friendly.

[0022] According to the method of the present invention, the catalyst is a Lewis acid catalyst, preferably one or more of BF3, SbF5, and AlCl3.

[0023] According to the aforementioned method, the mass ratio of the catalyst added to the raw material is 1-3%, preferably 2%.

[0024] Within this quality range, the yield can be increased and the residual catalyst can be easily removed.

[0025] According to the aforementioned method, the reaction temperature in the reaction step is 100–140°C.

[0026] According to the aforementioned method, the mass ratio of o-chlorotoluene and / or p-chlorotoluene to chlorobenzene added in the reaction step is 1-7:1-3, the catalytic reaction temperature is 100-140°C, and the catalytic reaction time is 1-4 hours.

[0027] According to the method of the present invention, the molar ratio of chlorotoluene to chlorobenzene is 3:2; the catalytic reaction temperature is 125-130°C; and the catalytic reaction time is 2 hours.

[0028] According to the method of the present invention, the water-washed oil layer is distilled to obtain a mixture of o-chlorotoluene and m-chlorotoluene, wherein the molecular sieve is ZMS-5 and the silicon-to-aluminum ratio is 350-500.

[0029] According to the method of the present invention, the adsorption step further includes a step of eluting the substances adsorbed on the molecular sieve by a desorbing agent.

[0030] The present invention also provides a continuous reaction apparatus for the continuous reaction method of the present invention, comprising, in sequence:

[0031] A reaction apparatus for providing the environment and temperature required for the reaction of raw materials, wherein halobenzenes, ortho-halotoluenes and / or para-halotoluenes are used as raw materials and the reaction is carried out in the presence of a catalyst in the reaction apparatus.

[0032] A water washing device is used to wash the mixture obtained from the reaction apparatus with water.

[0033] A distillation apparatus for distilling a mixture obtained from a water washing apparatus, wherein unreacted substances or byproducts separated by distillation are returned to the reaction apparatus;

[0034] An adsorption device is used to perform molecular sieve adsorption on the distillate remaining after distillation in the distillation device to separate the target product and reaction byproducts.

[0035] The reflux device returns the byproducts separated by the molecular sieve back to the reactor.

[0036] According to the apparatus of the present invention, the raw materials are chlorobenzene, o-chlorotoluene and / or p-chlorotoluene, and the product is m-chlorotoluene.

[0037] Preferably, the molecular sieve used in the device of the present invention is ZMS-5, and the silicon-to-aluminum ratio is 350-500.

[0038] In this invention, p-chlorotoluene and / or o-chlorotoluene and chlorobenzene are used as raw materials, and a catalytic isomerization reaction is carried out to obtain m-chlorotoluene. The selectivity and conversion rate are high. Through continuous reaction, the conversion rate of p-chlorotoluene and o-chlorotoluene to m-chlorotoluene is as high as 99% or more, and the selectivity of m-chlorotoluene is higher than 90%. The apparatus of this invention can provide an efficient and low-cost method for manufacturing m-chlorotoluene.

[0039] According to another aspect of the present invention, a method for the industrial production of dihaloalkylbenzenes is also provided, the method comprising: a step of preparing m-haloalkylbenzenes according to the present invention, and a step of reacting the prepared m-haloalkylbenzenes with a halogen element in the presence of a catalyst.

[0040] The catalyst is a composite catalyst of a metal compound and a sulfur-containing compound.

[0041] Preferably, the m-haloalkylbenzene is m-chlorotoluene, and the halogen element is chlorine gas.

[0042] The preferred mass ratio of the metal compound to the sulfur-containing compound is 1:0.1 to 10.

[0043] According to this method, the reaction temperature is preferably 0–80°C, and more preferably 30–50°C.

[0044] In the method described, the reaction solution is purified by alkali washing followed by distillation.

[0045] Existing processes for preparing dichlorotoluene mostly use p-chlorotoluene and o-chlorotoluene. The method of producing dichlorotoluene from o-chlorotoluene will simultaneously produce four dichlorotoluene isomers. Among them, the boiling point difference between 2,5-dichlorotoluene and 2,4-dichlorotoluene is within 1°C, making it difficult to obtain high-purity 2,5-dichlorotoluene by distillation.

[0046] In addition, there are few existing processes for preparing m-chlorotoluene, and therefore very few processes that use m-chlorotoluene as a raw material to produce dichlorotoluene.

[0047] The inventors used the prepared m-chlorotoluene as a reactant and employed a compound catalyst, unexpectedly discovering that the selectivity of the main product 2,5-dichlorotoluene was greater than 70%, the content of the byproduct trichlorotoluene was less than 0.5%, and the reaction conversion rate of m-chlorotoluene was greater than 95%, which meets the standards for industrial application.

[0048] Preferably, the metal oxide is a metal compound of aluminum, iron, nickel, titanium, copper, zirconium, or antimony, and the sulfur-containing substance is sulfur, disulfide chloride, or an organic sulfur-containing compound, more preferably an organic sulfur-containing heterocyclic compound.

[0049] The amount of the compound catalyst is preferably 0.05% to 1% relative to the mass of m-chlorotoluene. According to the present invention, a method and apparatus for producing m-halotoluene, especially m-chlorotoluene, with high raw material utilization and high product purity can be improved.

[0050] The continuous reaction apparatus of the present invention can obtain high-purity target products by separating products and by-products through two different methods, namely distillation and molecular sieve separation, after the reaction. It also has high material conversion rate and low environmental pollution.

[0051] Furthermore, the process for producing 2,5-dichlorotoluene using m-haloalkylbenzenes, especially m-chlorotoluene, as raw materials provided by this invention can solve the problem of difficult separation of products in previous 2,5-dichlorotoluene preparation processes. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the reaction apparatus for the continuous production of meta-haloalkylbenzenes according to the present invention;

[0053] Figure 2 This is a schematic diagram of a batch reaction apparatus;

[0054] Figure 3 This is a schematic diagram of a reaction apparatus for further reacting m-chlorotoluene produced by this invention to obtain dichlorotoluene. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the embodiments described are only some representative embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0056] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0057] In this invention, halobenzenes are, for example, iodobenzene, chlorobenzene, bromobenzene, and fluorobenzene; ortho-haloalkylbenzenes are, for example, alkyl groups with 1 to 3 carbon atoms, such as methyl, ethyl, propyl, and isopropyl; and halosubstituents are such as fluorine, chlorine, bromine, and iodine, such as ortho-iodotoluene, ortho-chlorotoluene, or ortho-bromotoluene, or ortho-fluorotoluene, or ortho-chloroethylbenzene. Meta-halotoluenes are, for example, ortho-iodotoluene, ortho-chlorotoluene, or ortho-bromotoluene, or ortho-fluorotoluene, or ortho-chloroethylbenzene. Preferably, ortho-chlorotoluene is generated by reacting p-chlorotoluene and / or ortho-chlorotoluene with chlorobenzene.

[0058] In this invention, the Lewis acid can be a common Lewis acid, such as aluminum trichloride, boron trifluoride, antimony trichloride, and ferric bromide. Other common Lewis acids can also be used.

[0059] Examples 1-2: Continuous Reaction Device

[0060] according to Figure 1 The reaction apparatus is assembled as shown. p-chlorotoluene, o-chlorotoluene, chlorotoluene, and Lewis acids are added to the reactor as catalysts according to the proportions in Table 1. The reactor is heated to 100–140°C for continuous reaction. The reaction liquid in the water washing device is 50% of the mass of the reaction liquid passing through the water washing device. After water-oil separation, the water layer is separated to a wastewater treatment device, and the oil layer enters a distillation tower to obtain a mixture of p-chlorotoluene and m-chlorotoluene.

[0061] The mixture obtained from distillation was purified by molecular sieve adsorption to obtain m-chlorotoluene. The molecular sieve used for adsorption was ZMS-5, with a silica-to-alumina ratio of 350-500. The molecular sieve was reused after desorption with a desorbent.

[0062] After the reaction was completed, the content of intermediate chlorotoluene and impurities in the reaction solution were analyzed by gas chromatography. The results are shown in Table 1.

[0063] Comparative Examples 1-2: Batch Reactor

[0064] Figure 2 This is a schematic diagram of a reaction apparatus that does not reflux by-products. Figure 2 The apparatus shown is equipped with reaction equipment. Experiments were conducted using the same feed amounts and reaction conditions as in Examples 1-2. The results are also shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, according to the continuous reaction method of the present invention, by separating the product in real time and returning the unreacted raw materials to the reactor, the reaction conversion rate is greatly improved and the occurrence of side reactions is reduced.

[0068] The inventors speculate that this is because, during the reaction of p-chlorotoluene with chlorobenzene, byproducts such as o-chlorotoluene and chloroxylene are refluxed back into the reactor and reacted again, potentially generating the target product. This significantly improves the reaction conversion rate and reduces material waste.

[0069] Since o-chlorotoluene typically has low reactivity, timely separation of the reaction products through continuous reaction can significantly improve the conversion rate of o-chlorotoluene and the yield of m-chlorotoluene.

[0070] In this embodiment, the reaction temperature is set to 125-130°C, but it can also be 100-140°C.

[0071] Subsequent Reactions in Examples 3-6

[0072] The catalyst was prepared according to the proportions shown in Table 2 below for subsequent experiments.

[0073] Table 2

[0074]

[0075] Reference Figure 3 The diagram illustrates a continuous reaction apparatus where the m-chlorotoluene produced in Examples 1 and 2 is chlorinated in the presence of a catalyst to produce 2,5-dichlorotoluene. The yields of 2,5-dichlorotoluene obtained by reacting according to the conditions in Table 3 are shown in the table below.

[0076] Table 3

[0077]

[0078] This invention enables the preparation of high-purity m-chlorotoluene. Using this prepared m-chlorotoluene as a reactant, the resulting target product, 2,5-dichlorotoluene, has a significantly different boiling point from other dichlorotoluenes, allowing for the acquisition of high-purity 2,5-dichlorotoluene through distillation. Compared to existing technologies, this reduces separation and purification costs and improves production efficiency.

[0079] The embodiments of the present invention describe the preferred reaction temperature and time based on the inventor's experiments. However, the temperature and time can be adjusted according to actual needs, reactant activity, and expected reaction yield. The type and amount of catalyst can also be adjusted according to actual needs.

[0080] In addition, the apparatus in this embodiment is equipped with a distillation column; however, two to three distillation columns can be installed as needed to further separate and purify the reaction products and byproducts. Similarly, the water washing step can be repeated two to three times.

[0081] In addition, in the embodiments of the present invention, as the most preferred embodiment, the subsequent reaction is described using a continuous reaction as an example, but obviously the subsequent reaction can also be a batch reaction.

[0082] Those skilled in the art will understand that all substitutions and additions made without departing from the technical concept of the present invention are included within the scope of the present invention.

Claims

1. A method for continuously producing meta-haloalkylbenzene, comprising: a reaction step, in which a halobenzene, and, an ortho-haloalkylbenzene and / or a para-haloalkylbenzene are used as raw materials, and a catalyst is used to catalyze the reaction in a reactor; a water washing step, in which the mixture obtained in the reaction step is washed with water; a distillation step, in which the mixture obtained in the water washing step is distilled, and the unreacted substances or by-products separated in the distillation are refluxed into the reactor; an adsorption step, in which the distillate remaining after the distillation in the distillation step is subjected to molecular sieve adsorption to separate the target product and the reaction by-products; and a reflux step, in which the by-products separated by the molecular sieve are refluxed into the reactor. The raw materials are chlorobenzene, ortho-chlorotoluene and para-chlorotoluene, respectively. The catalyst is a Lewis acid catalyst, preferably one or more of BF3, SbF5 and AlCl3, and the catalyst is preferably added in an amount of 1-3% by mass, preferably 1-2%, relative to the raw materials. In the reaction step, the molar ratio of the ortho-chlorotoluene and / or para-chlorotoluene to chlorobenzene is 1-7:1-3, and the reaction temperature is 100-140°C, preferably the molar ratio of the chlorotoluene to chlorobenzene is 3:2, and the reaction temperature is 125-130°C. The molecular sieve is ZMS-5, and the silica-alumina ratio is 350-500.

6. An apparatus for the method of any one of claims 1-5, comprising, in sequence: a reaction device, in which a halobenzene, and, an ortho-haloalkylbenzene and / or a para-haloalkylbenzene are used as raw materials, and a catalyst is used to catalyze the reaction; a water washing device, which is used to wash the mixture obtained in the reaction device; a distillation device, which is used to distill the mixture obtained in the water washing device, and the unreacted substances or by-products separated in the distillation are refluxed into the reaction device; an adsorption device, which is used to subject the distillate remaining after the distillation in the distillation device to molecular sieve adsorption to separate the target product and the reaction by-products; and a reflux device, which is used to reflux the by-products separated by the molecular sieve into the reactor.

2. The method of claim 1, wherein, The raw materials are chlorobenzene, ortho-chlorotoluene and / or para-chlorotoluene, and the product is meta-chlorotoluene, and the molecular sieve is preferably ZMS-5, and the silica-alumina ratio is 350-500.

3. The method of claim 1, wherein, 8. A method for industrial production of dihaloalkylbenzene, comprising: a step of preparing meta-haloalkylbenzene by the method of claims 1-5, and a step of reacting the prepared meta-haloalkylbenzene with a halogen element in the presence of a catalyst, wherein the catalyst is a complex catalyst of a metal compound and a sulfur-containing compound.

4. The method of claim 2, wherein, 9. The method of claim 8, wherein the meta-haloalkylbenzene is meta-chlorotoluene, and the halogen element is chlorine.

5. The method of claim 2, wherein, 10. The method of claim 9, wherein the mass ratio of the metal compound to the sulfur-containing compound is 1:0.1-10.

11. The method of claim 9, wherein the reaction temperature is 0-80°C, preferably 30-50°C. In the method, the reaction solution is purified by a method of distillation after alkaline washing. ​ ​ ​ ​ 7. The apparatus of claim 6, wherein, ​ ​ ​ ​ ​ ​ ​ 12. The method of claim 9, wherein, ​ 13. The method of claim 9, wherein, The metal oxides are metal compounds of aluminum, iron, nickel, titanium, copper, zirconium, antimony, the sulfur-containing substances are sulfur, disulfide chloride, organic sulfur-containing compounds, preferably organic sulfur-containing heterocyclic compounds.

14. The process as claimed in claim 13, wherein the amount of the complex catalyst is in the range of 0.05% to 1% by mass with respect to the mass of m-chlorotoluene.

Images