Method for preparing chloromethyl styrene and product prepared by method

Abstract

The invention provides a method for preparing chloromethyl styrene, which comprises the following steps of: (1) reacting paraformaldehyde with hydrogen chloride in the presence of a catalyst and an optional auxiliary agent to obtain a chloromethylation reagent; (2) carrying out reaction on chloroethyl benzene and the chloromethylation reagent obtained in the step (1) to obtain chloromethyl chloroethyl benzene; (3) the chloromethyl chloroethyl benzene obtained in the step (2) is rectified and purified, a chloromethyl chloroethyl benzene product containing o-chloromethyl chloroethyl benzene, m-chloromethyl chloroethyl benzene and p-chloromethyl chloroethyl benzene is obtained through separation, and the ratio of the o-chloromethyl chloroethyl benzene to the m-chloromethyl chloroethyl benzene to the p-chloromethyl chloroethyl benzene is (0.05-50): (0.05-20): (30-99.9); and (4) in the presence of an optional solvent, carrying out elimination reaction on the chloromethyl chloroethyl benzene product obtained in the step (3) and alkali to obtain chloromethyl styrene. The chloromethyl styrene product has a low heavy halogen value, and the heavy halogen value is less than or equal to 100.

Description

Technical Field

[0001] This invention relates to a chloromethylstyrene product and its preparation method, specifically to a chloromethylstyrene product with a low heavy halogen value and its preparation method. Background Technology

[0002] Chloromethylstyrene, especially p-chloromethylstyrene (VBC), possesses high reactivity and dual functionality (vinyl and chloromethyl). It can be formed into highly reactive chloromethyl polymers through homopolymerization of a single monomer or copolymerization with other monomers. It is an important chemical raw material widely used in rubber, ion exchange membranes, rubber and plastic products, adhesives, fibers, and pesticides. Furthermore, p-chloromethylstyrene also has applications in polymer graft copolymers, organosilicon polymers, and nanomaterials.

[0003] Currently, the main synthetic route for p-chloromethylstyrene is the β-bromoethylbenzene method. This method uses β-bromoethylbenzene as a raw material, zinc chloride as a catalyst, 85% phosphoric acid and acetic acid as auxiliary agents, and HCl gas and paraformaldehyde as chloromethylating agents to perform the chloromethylation reaction, yielding the intermediate p-chloromethylbromoethylbenzene (CBB) in one step. Finally, sodium hydroxide is used to eliminate the intermediate to obtain the target product, p-chloromethylstyrene (VBC). However, this method has the following significant drawbacks: First, severe halogen exchange side reactions occur. Because the raw material β-bromoethylbenzene contains bromine atoms (Br), and the chloromethylating agent provides chlorine atoms (Cl), under Lewis acid catalysis, the two readily undergo halogen exchange reactions, generating byproducts such as bromomethylbromoethylbenzene. This not only reduces the selectivity of the main reaction but also makes the intermediate mixture complex. After elimination, these byproducts inevitably carry over to the product, resulting in bromides in the p-chloromethylstyrene product, affecting product quality. Second, the acetic acid system requires a large amount of acetic acid, and its recovery is complex. The mixed acid system formed by acetic acid with phosphoric acid, zinc chloride, etc., has high viscosity and complex composition, making recycling and reuse difficult. Its recycling cycles typically do not exceed 20 times, resulting in high acid consumption and increased production costs and environmental pressure. Third, the elimination process is inefficient. Existing elimination processes mostly use sodium hydroxide / potassium hydroxide aqueous solutions, which are oil-water two-phase reactions. Phase transfer catalysts such as polyethylene glycol (PEG) are required to promote the reaction in the forward direction, leading to slow reaction rates, low conversion and selectivity, and the potential for residual phase transfer catalysts to affect product quality. Subsequent washing and separation steps are needed to remove catalysts and inorganic salts, resulting in a longer process flow and increased wastewater generation.

[0004] Therefore, there is an urgent need in the field to develop an improved method for preparing p-chloromethylstyrene that does not involve halogen exchange, reduces equipment corrosion, simplifies the elimination process, lowers raw material costs, and facilitates product purification. Summary of the Invention

[0005] The first aspect of the present invention provides a method for preparing chloromethylstyrene, the method comprising the following steps:

[0006] (1) Paraformaldehyde and hydrogen chloride are reacted in the presence of a catalyst and optional auxiliaries to obtain a chloromethylating agent;

[0007] (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene;

[0008] (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate chloromethylchloroethylbenzene products including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9);

[0009] (4) In the presence of an optional solvent, the chloromethylchloroethylbenzene product obtained in step (3) is subjected to an elimination reaction with a base to obtain chloromethylstyrene.

[0010] A second aspect of the present invention provides a method for preparing chloromethylchloroethylbenzene, the method comprising the following steps:

[0011] (1) Paraformaldehyde and hydrogen chloride are reacted in the presence of a catalyst and optional auxiliaries to obtain a chloromethylating agent;

[0012] (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene;

[0013] (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate the chloromethylchloroethylbenzene product including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9).

[0014] A third aspect of the present invention provides a chloromethylchloroethylbenzene product prepared by the method for preparing chloromethylchloroethylbenzene described in the present invention.

[0015] A fourth aspect of the present invention provides a chloromethylstyrene product, wherein the heavy halogen value X is ≤100, preferably X ≤10, wherein the heavy halogen value X = (heavy halogen content / light halogen content) × 10 6 The heavy halogens are bromine and iodine, and the light halogens are chlorine and fluorine. Detailed Implementation

[0016] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0017] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0018] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0019] In this application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0020] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0021] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0022] In this description, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0023] Unless otherwise specified, percentages (%) or parts refer to weight percentages or parts by weight of the composition.

[0024] Unless otherwise stated herein, the sum of the contents of the components in the composition is 100%.

[0025] Unless otherwise stated herein, the sum of the parts of each component in the composition may be 100 parts by weight.

[0026] In this document, unless otherwise stated, “combination of” means a multi-component mixture of the elements, such as two, three, four, and up to the maximum possible multi-component mixture.

[0027] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0028] In this document, the terms “containing,” “comprising,” or “using” indicate that various ingredients may be used together in mixtures or compositions of this disclosure. It should be understood that the degree of “high,” “low,” etc., as used in this disclosure is well known in the art.

[0029] This invention provides a method for preparing chloromethylstyrene, the method comprising the following steps:

[0030] (1) Paraformaldehyde and hydrogen chloride are reacted in the presence of a catalyst and optional auxiliaries to obtain a chloromethylating agent;

[0031] (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene;

[0032] (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate chloromethylchloroethylbenzene products including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9);

[0033] (4) In the presence of an optional solvent, the chloromethylchloroethylbenzene product obtained in step (3) is subjected to an elimination reaction with a base to obtain chloromethylstyrene.

[0034] In this invention, "chloroethylbenzene" refers to ethylbenzene substituted with one chlorine atom. In one embodiment of this invention, the chloroethylbenzene includes α-chloroethylbenzene or β-chloroethylbenzene (i.e., 1-chloro-1-phenylethane or 1-chloro-2-phenylethane), preferably β-chloroethylbenzene.

[0035] In this invention, the reaction for preparing chloromethylstyrene from chloroethylbenzene can be divided into two stages. The first stage involves the chloromethylation of chloroethylbenzene to generate the intermediate chloromethylchloroethylbenzene, which is then purified by distillation. The second stage involves the elimination reaction of chloromethylchloroethylbenzene to obtain chloromethylstyrene. Using chloroethylbenzene instead of bromoethylbenzene as a raw material avoids other halogen impurities generated by the exchange of halogen heteroatoms such as bromine and chlorine, fundamentally preventing halogen exchange byproducts. Furthermore, chloroethylbenzene is significantly cheaper than bromoethylbenzene, reducing raw material costs at the source and offering a clear economic advantage. In existing technologies, due to the low reactivity of the chlorine atom in chloroethylbenzene, efficient chloromethylation reactions are difficult to achieve, and side reactions are prone to occur. Additionally, in the elimination reaction stage, chlorine is a difficult-to-remove group, resulting in unsatisfactory reaction rates, conversion rates, and selectivity. Therefore, bromoethylbenzene is typically used to prepare chloromethylstyrene. This invention overcomes the problem of low reactivity of chloroethylbenzene through a stepwise reaction and a specific catalyst system, successfully achieving high conversion rates and selectivity.

[0036] In the first stage of this invention, the chloromethylation of chloroethylbenzene is carried out in a stepwise manner. First, hydrogen chloride gas is introduced into a paraformaldehyde system. Under the action of a catalyst, a highly efficient chloromethylating agent is prepared. Then, chloroethylbenzene is added to generate chloromethylchloroethylbenzene. The advantage of the stepwise reaction is that it can improve reaction efficiency and selectivity, reduce side reactions, and achieve a chloroethylbenzene conversion rate of over 99.0% and a chloromethylchloroethylbenzene selectivity of over 95.0%. The chloromethylchloroethylbenzene reaction solution generated in the system at this point includes three isomers: ortho, meta, and para. Distillation purification of the chloromethylchloroethylbenzene reaction solution can obtain mixtures of ortho, meta, and para isomers in different proportions. The three isomers can be completely separated or partially separated and then eliminated separately, thereby flexibly producing target products with different isomer compositions and precisely meeting the diverse needs of downstream markets for specific proportions of chloromethylstyrene, solving the problem of single product structure in traditional methods. Advantageously, this invention can obtain para-chloromethylchloroethylbenzene with a para content >99%, which is beneficial for improving the selectivity of subsequent elimination reactions.

[0037] In step (1) of the present invention, the catalysts that can be used for the chloromethylation of chloroethylbenzene include, but are not limited to, metal chlorides. In one specific embodiment of the present invention, the catalyst includes at least one metal chloride selected from the group consisting of ferric chloride, aluminum chloride, zinc chloride, tin chloride, and titanium tetrachloride. Preferably, the catalyst includes aluminum chloride, zinc chloride, or titanium tetrachloride; more preferably, the catalyst includes aluminum chloride or zinc chloride. In one specific embodiment of the present invention, the molar ratio of the catalyst to chloroethylbenzene is (0.1-5):1, preferably (1-3):1.

[0038] The chloromethylation of chloroethylbenzene is carried out under conditions of an auxiliary agent. The auxiliary agent is added to make the reaction system acidic; the auxiliary agent includes, but is not limited to, organic acids and inorganic acids. Acetic acid is not used in the acidic system of this invention. In one specific embodiment of this invention, the auxiliary agent includes at least one acid selected from the group consisting of phosphoric acid, formic acid, hydrochloric acid, and sulfuric acid. Preferably, the auxiliary agent includes phosphoric acid or formic acid. In one specific embodiment of this invention, the molar ratio of the auxiliary agent to chloroethylbenzene is (1-10):1, preferably (1-5):1.

[0039] Because of its simple catalyst composition, the acetic acid-free catalytic system of this invention can be efficiently recycled and reused through dehydration treatment, significantly reducing the consumption of catalyst and additives and reducing the discharge of waste gas, wastewater, and solid waste. Dehydration can be carried out by any method known in the art, including but not limited to negative pressure water carrying and dehydration by dehydrating agents, wherein the dehydrating agents include but are not limited to acetyl chloride, acetic anhydride, etc. After dehydration treatment, the water content of the acid layer is controlled at 2.0%-20%, preferably 3.0%-15.0%. The acid layer after dehydration treatment can be recycled and reused, for example, by adding a certain amount of paraformaldehyde and passing hydrogen chloride gas through it again.

[0040] In one specific embodiment of the present invention, the molar ratio of paraformaldehyde, catalyst, auxiliary agent, hydrogen chloride and chloroethylbenzene is (1-10):(0.1-5):(1-10):(1-10):1, preferably (3-5):(1-3):(1-5):(3-5):1. In one specific embodiment of the present invention, the reaction temperature of steps (1) and (2) is controlled at 0-100°C, preferably 20-60°C; the reaction pressure is atmospheric pressure.

[0041] In one preferred embodiment of the present invention, the catalyst is aluminum chloride, and the auxiliary agent is phosphoric acid. In yet another preferred embodiment of the present invention, the catalyst is zinc chloride, and the auxiliary agent is phosphoric acid. In yet another preferred embodiment of the present invention, the catalyst is titanium tetrachloride, and the auxiliary agent is phosphoric acid. In yet another preferred embodiment of the present invention, the catalyst is zinc chloride, and the auxiliary agent is formic acid.

[0042] In step (2) of this invention, chloroethylbenzene reacts with the chloromethylating reagent obtained in step (1) to obtain chloromethylchloroethylbenzene. The chloromethylchloroethylbenzene reaction solution obtained in step (2) includes three isomers: ortho, meta, and para.

[0043] In step (3) of this invention, the chloromethylchloroethylbenzene reaction solution obtained in step (2) is purified by distillation. Since the thermal stability of the intermediate chloromethylchloroethylbenzene is much better than that of the bromine-containing intermediate, no side reactions such as halogen exchange, decomposition, or polymerization will occur under the high temperature conditions required for distillation. Different proportions of ortho, meta, and para isomers can be stably obtained through distillation. The distillation purification step in step (2) can be carried out using distillation equipment commonly used in the art, such as a vacuum distillation column. The distillation is carried out under the following conditions: the absolute pressure of the system is 20-10000 Pa, preferably 50-5000 Pa, where absolute pressure refers to the pressure of the fluid (gas or liquid) with absolute vacuum (or ideal vacuum) as the reference zero point; the number of trays is 10-60, preferably 20-40; and the reflux ratio is controlled at 1-50, preferably 2-30. The ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene in the chloromethylchloroethylbenzene product obtained by distillation purification is (0.05-50):(0.05-20):(30-99.9). By adjusting the number of trays, reflux ratio, and absolute pressure, chloromethylchloroethylbenzene products containing the above-mentioned composition of three isomers can be obtained. For example, increasing the number of trays and reflux ratio can improve the purity of the para-isomer, while decreasing the absolute pressure can reduce the risk of thermal decomposition. Due to the small difference in boiling points among the three isomers, in actual distillation, only the middle and later fractions can yield high-purity para-chloromethylchloroethylbenzene.

[0044] In the second stage of this invention, chloromethyl styrene is prepared by an elimination reaction of chloromethyl chloroethylbenzene with a base. Specifically, the elimination process of chloromethyl chloroethylbenzene includes mixing chloromethyl chloroethylbenzene with a solvent until homogeneous; and adding a base to the mixture under certain temperature and pressure to carry out the elimination reaction.

[0045] In step (4) of the present invention, a solvent may or may not be used. When a solvent is used, the solvent includes, but is not limited to, cyclohexane, ethylcyclohexane, methylcyclohexane, tetrahydrofuran, tert-butanol, methanol, ethanol, ethylene glycol, n-propanol, isopropanol, toluene, benzene, chlorobenzene, etc. In one specific embodiment, the solvent includes at least one solvent selected from the group consisting of cyclohexane, ethylcyclohexane, methylcyclohexane, tetrahydrofuran, tert-butanol, methanol, ethanol, ethylene glycol, n-propanol, isopropanol, toluene, benzene, and chlorobenzene. In one specific embodiment of the present invention, the molar ratio of the solvent to chloromethylchloroethylbenzene is (1-5):1, preferably (1-3):1.

[0046] In step (4) of this invention, the reaction temperature of the elimination reaction is 25-80°C, preferably 25-50°C; the reaction pressure can be atmospheric pressure. The bases that can be used in the elimination reaction include, but are not limited to, organic or inorganic bases. In one specific embodiment, the base includes at least one base selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide. The molar ratio of the base to chloromethylchloroethylbenzene is (1-5):1, preferably (1-2):1. This invention employs a solid-liquid two-phase system comprising a solvent and a base, completely abandoning the traditional aqueous / organic / solid three-phase system, avoiding the use of phase transfer catalysts, simplifying the post-processing procedure, avoiding catalyst residue, and significantly improving the conversion rate and selectivity of the elimination reaction.

[0047] In this invention, the method further includes step (5): adding a polymerization inhibitor to the chloromethylstyrene obtained in step (4) and performing distillation, wherein the polymerization inhibitor comprises at least one polymerization inhibitor selected from the group consisting of 2,4-dinitrophenol, tert-butylcatechol, p-hydroxyanisole, and 2,6-di-tert-butyl-p-cresol. The distillation is performed under vacuum at an absolute pressure of 20-5000 Pa, preferably 50-2000 Pa. In one specific embodiment, the polymerization inhibitor comprises one or more polymerization inhibitors selected from the group consisting of 2,4-dinitrophenol, tert-butylcatechol, p-hydroxyanisole, and 2,6-di-tert-butyl-p-cresol. In one specific embodiment, the amount of polymerization inhibitor used is 1000-10000 ppm of the chloromethylstyrene content, preferably 5000-10000 ppm.

[0048] The present invention also provides a method for preparing chloromethylchloroethylbenzene, the method comprising the following steps:

[0049] (1) In the presence of a catalyst and an auxiliary agent, paraformaldehyde and hydrogen chloride are reacted to obtain a chloromethylating agent;

[0050] (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene;

[0051] (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate the chloromethylchloroethylbenzene product including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9).

[0052] Because chloromethylchloroethylbenzene has a much higher thermal stability than chloromethylbromoethylbenzene, it will not undergo side reactions such as halogen exchange, decomposition, or polymerization under the high-temperature conditions required for distillation. Subsequent distillation can stably obtain mixtures of ortho, meta, and para isomers in different proportions. The separated isomers can be eliminated individually, allowing for flexible production of target products with different isomer compositions, precisely meeting the diverse downstream market demand for specific proportions of chloromethylstyrene.

[0053] The present invention also provides a chloromethylstyrene product, wherein the heavy halogen value X of the chloromethylstyrene product is ≤100, preferably X≤10, wherein the heavy halogen value X = (heavy halogen content / light halogen content) × 10 6 The heavy halogens are bromine and iodine, and the light halogens are chlorine and fluorine. Preferably, the chloromethylstyrene product is prepared by the method described in this invention. The chloromethylstyrene product prepared by this invention does not contain other halogen impurities and has the advantage of high product purity. Furthermore, as an important chemical intermediate, its extremely low heavy halogen value ensures consistent reaction rates and stability in subsequent synthesis of other products.

[0054] Compared with the prior art, the present invention has at least the following beneficial effects:

[0055] 1. This invention uses chloroethylbenzene instead of bromoethylbenzene as a raw material to prepare chloromethylchloroethylbenzene products, avoiding other halogen impurities generated by the exchange of heteroatoms of halogens such as bromine and chlorine, fundamentally avoiding the occurrence of halogen exchange byproducts, resulting in high product purity and relatively consistent reactivity in polymer synthesis and modification applications, making it easy to control the stability and uniformity of polymer properties; at the same time, the price of chloroethylbenzene is much lower than that of bromoethylbenzene, reducing raw material costs from the source, resulting in significant economic advantages.

[0056] 2. This invention uses an acetic acid-free catalytic system with a simple catalyst composition. It can be efficiently recovered and reused through dehydration treatment, which significantly reduces the unit consumption of catalyst and auxiliary agents.

[0057] 3. The intermediate chloromethylchloroethylbenzene exhibits significantly better thermal stability than bromine-containing intermediates, and does not undergo side reactions such as halogen exchange, decomposition, or polymerization under the high-temperature conditions required for distillation. Different proportions of ortho, meta, and para isomers can be stably obtained through distillation, and these isomers can be eliminated individually. This allows for flexible production of target products with varying isomer compositions, precisely meeting the diverse downstream market demands for specific proportions of chloromethylstyrene and solving the problem of limited product structure associated with traditional methods.

[0058] 4. The reaction conditions of this system are mild and the reaction rate is fast, which increases the conversion rate of chloromethylchloroethylbenzene to over 97% and the selectivity to over 95%.

[0059] Unless otherwise specified, all raw materials used in this application are commercially available or prepared according to conventional methods in the art. Unless otherwise defined or specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods disclosed herein. Other aspects of this disclosure will be apparent to those skilled in the art from the content of this disclosure.

[0060] Example

[0061] The present disclosure is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure. Experimental methods in the following embodiments, unless specific conditions are specified, are generally determined according to national standards. If no corresponding national standard exists, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed. Unless otherwise stated, all parts are parts by weight, all percentages are weight percentages, and the molecular weight of the polymer is a number-average molecular weight.

[0062] Raw material sources and preparation

[0063] Paraformaldehyde, purity ≥95%, degree of polymerization n=10, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0064] Zinc chloride, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0065] Ferric chloride, purity ≥99%, purchased from Aladdin Reagent Co., Ltd.

[0066] Aluminum chloride, purity ≥99%, purchased from Aladdin Reagent Co., Ltd.

[0067] Tin chloride, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0068] Titanium tetrachloride, purity ≥99%, purchased from Aladdin Reagent Co., Ltd.

[0069] Phosphoric acid, 85% purity, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0070] Formic acid, purity ≥88%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0071] Hydrochloric acid, purity 36-38%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0072] Sulfuric acid, 95-98% purity, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0073] Acetic acid, purity ≥99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0074] Hydrogen chloride, purity ≥99.9%, purchased from Shanghai Zhenqi Chemical Reagent Co., Ltd.

[0075] β-Chloroethylbenzene, 99% purity, purchased from Aladdin Reagent Co., Ltd.

[0076] α-Chloroethylbenzene, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0077] tert-Butanol, purity ≥99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0078] Sodium tert-butoxide, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0079] Ethanol, purity ≥99.7%, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0080] Sodium ethoxide, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0081] Tetrahydrofuran, purity ≥99%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0082] Potassium tert-butoxide, purity ≥98%, purchased from Aladdin Reagent Co., Ltd.

[0083] Toluene, purity ≥99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0084] Sodium hydroxide, purity ≥96%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0085] Cyclohexane, purity ≥99.5%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0086] Isopropanol, purity ≥99.7%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0087] Potassium hydroxide, purity ≥85%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0088] Main instruments for the experiment

[0089]

[0090] Gas chromatography test conditions

[0091]

[0092] Ion chromatography test conditions

[0093]

[0094] Methods for calculating conversion rate, selectivity, yield, and purity:

[0095] In this embodiment, the content of each component was quantitatively analyzed by gas chromatography with internal standard method. The mass fraction (wt%) of each component was calculated based on the gas chromatography data processing.

[0096] Chloromethylation step:

[0097] The raw material (chloroethylbenzene) has a mass of m1 and a purity of C. r0 After settling and stratification, the oil layer mass is m2, and the mass fraction of the feedstock in the oil layer is C. r The mass fraction of the target product (chloromethylchloroethylbenzene) is C. p The relative molecular mass of the raw material is M. r The relative molecular mass of the target product is M. p ,but

[0098] Haloethylbenzene conversion rate =

[0099] Chloromethyl haloethylbenzene selectivity =

[0100] Purity: determined by normalized content by gas chromatography.

[0101] Purification steps:

[0102] The feedstock for distillation is m3, of which the content of para-chloromethylchloroethylbenzene is C. p0 The mass of the bottom fraction of the distillation column is m4, and its content of para-chloromethylchloroethylbenzene is C. p1 ,but

[0103] para-chloromethyl haloethylbenzene separation yield =

[0104] Elimination reaction steps:

[0105] The raw material (para-chloromethylchloroethylbenzene) has a mass of m5 and a purity of C. p2 After the reaction was completed and the layers were separated by post-treatment, the oil reservoir mass was m6, and the mass fraction of the feedstock in the oil reservoir was C. p3 The target product (p-chloromethylstyrene) has a mass fraction of C. q The relative molecular mass of the raw material is M. p The relative molecular mass of the target product is M. q ,but

[0106] Haloethylbenzene conversion rate =

[0107] Chloromethyl haloethylbenzene selectivity =

[0108] Purity: determined by normalized content by gas chromatography.

[0109] Methods for testing and calculating the heavy halogen value:

[0110] The halogen content in the product was determined using ion chromatography, and the heavy halogen value of the product was calculated using the following formula:

[0111] Heavy halogen value = (heavy halogen content / light halogen content) × 10 6 The heavy halogens are bromine and iodine, and the light halogens are chlorine and fluorine.

[0112] Example 1

[0113] 1) Chloromethylation

[0114] 252.8 g of paraformaldehyde, 278.2 g of zinc chloride, and 691.5 g of phosphoric acid (85%) were sequentially added to a 2000 ml reactor equipped with a stirrer and thermometer, and stirred until homogeneous. The temperature was controlled at 35℃, and 291.9 g of hydrogen chloride gas was slowly introduced, yielding 1514.4 g of chloromethylated acid layer reagent. 284.8 g of β-chloroethylbenzene was added dropwise using a constant-pressure dropping funnel. After the addition was complete, the mixture was kept at 35℃ for 4 hours, yielding 1799.2 g of the collected material. The molar ratio of β-chloroethylbenzene, paraformaldehyde, catalyst, auxiliary agent, and hydrogen chloride was 1:4:1:3:4. The resulting reaction solution was allowed to stand and separate into layers, yielding an oil layer of 372.1 g. The oil layer content was analyzed by gas chromatography (GC), as shown in Tables 1 and 2 below. The calculated conversion rate of β-chloroethylbenzene was 99.12%, and the selectivity of chloromethylchloroethylbenzene was 95.82%.

[0115] Table 1

[0116]

[0117] Table 2

[0118]

[0119] 2) Purification of chloromethylchloroethylbenzene

[0120] The 372.1 g of chloromethylchloroethylbenzene obtained in the above steps was fed into a distillation unit for separation and purification. The distillation column had a theoretical number of 30 trays, with feed introduced at the 15th tray. The operating reflux ratio was 24, the system absolute pressure was maintained at 1 kPa, and the reboiler temperature was controlled at 140℃. The composition of the top and bottom fractions was analyzed by gas chromatography (GC), as shown in Table 3 below. The top fraction was 254.44 g, and the bottom fraction was 117.66 g. Based on the total amount of para-isomers in the feed, the yield of para-chloromethylchloroethylbenzene was 50.94%.

[0121] Table 3

[0122]

[0123] 3) Elimination and distillation

[0124] 116g of the bottom fraction, containing 99.60% p-chloromethylchloroethylbenzene and 103.9g of cyclohexane, was sequentially added to a 500mL reactor. The reaction was carried out at 40°C under normal pressure. 38.2g of sodium hydroxide was added to maintain the reactor temperature at 45°C, and the reaction was stopped after 2 hours. The molar ratio of p-chloromethylchloroethylbenzene:catalyst:solvent was 1:1.5:2. After the reaction, water was added to dissolve the solids in the system, and 10% hydrochloric acid was added to adjust the pH to 7. The system was allowed to stand and separate into layers, yielding 96.8g of upper oil. Gas chromatography (GC) analysis showed that the oil layer contained 10.14% p-chloromethylchloroethylbenzene, 83.05% p-chloromethylstyrene, and 6.81% other byproducts. The calculated conversion rate of p-chloromethylchloroethylbenzene was 91.50%, and the selectivity for p-chloromethylstyrene was 94.21%. The oil layer was subjected to solvent extraction and distillation. 0.010 g of the polymerization inhibitor tert-butylcatechol was added to the organic phase. Distillation was carried out in a 35-plate column at an absolute pressure of 1 kPa, with a reflux ratio of 10. 72.8 g of p-chloromethylstyrene was obtained after distillation. A sample was taken and analyzed by gas chromatography for area percentage normalization, confirming a purity of 99.65% for p-chloromethylstyrene. Ion chromatography analysis was used to determine the halogen content, and the halogen values ​​in the p-chloromethylstyrene product are shown in Table 4 below. The calculated heavy halogen value X of the p-chloromethylstyrene product was 3.50, which meets the product quality requirements.

[0125] Table 4

[0126]

[0127] Example 2

[0128] Example 2 used the same reaction apparatus as Example 1, and was carried out according to the steps and conditions of Example 1, except that the raw material β-chloroethylbenzene in the chloromethylation reaction step was replaced with α-chloroethylbenzene. Reaction results: α-chloroethylbenzene conversion rate 96.85%, chloromethylchloroethylbenzene selectivity 94.70%, final product p-chloromethylstyrene purity 99.52%, and heavy halogen value X=4.20.

[0129] Example 3-12

[0130] Examples 3-12 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, except that the molar ratios of chloroethylbenzene, paraformaldehyde, catalyst, auxiliaries, and hydrogen chloride gas in the chloromethylation reaction step were changed. The specific conditions and reaction results are shown in Table 5 below:

[0131] Table 5

[0132]

[0133] As can be seen from the data in Table 5, when the molar ratio of paraformaldehyde, catalyst, auxiliaries, hydrogen chloride, and chloroethylbenzene is in the range of (1-10):(0.1-5):(1-10):(1-10):1, both high conversion rate and high selectivity can be obtained simultaneously. Preferably, the molar ratio of paraformaldehyde, catalyst, auxiliaries, hydrogen chloride, and chloroethylbenzene is in the range of (3-5):(1-3):(1-5):(3-5):1, which yields the best and most stable overall benefits.

[0134] Examples 13-22

[0135] Examples 13-22 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, only changing the types of catalysts and auxiliaries. The types of catalysts and auxiliaries used and the reaction effects are shown in Table 6:

[0136] Table 6

[0137]

[0138] As can be seen from the data in Table 6, the acetic acid-free catalytic system of the present invention not only has better or equivalent reaction performance than the acetic acid-containing system, but more importantly, it solves the inherent recycling problem of the acetic acid-containing system, thus achieving significant progress in the overall process economy and environmental protection.

[0139] Examples 23-24

[0140] Examples 23-24 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, except that the number of trays, reflux ratio, and absolute pressure of the distillation column in the purification step were changed. The distillation conditions and reaction results are shown in Table 7 below:

[0141] Table 7

[0142]

[0143] As can be seen from the data in Table 7, by adjusting the distillation conditions, such as the number of trays, reflux ratio, and system absolute pressure, the chloromethylchloroethylbenzene isomer can be effectively separated and a high-purity para product can be obtained.

[0144] Examples 25-33

[0145] Examples 25-33 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, only changing the solvent and alkali used in the elimination reaction. The reaction conditions and reaction results are shown in Table 8 below:

[0146] Table 8

[0147]

[0148] The elimination reaction system provided by this invention, particularly the combination of solvents such as tert-butanol, ethanol, and tetrahydrofuran with organic bases such as sodium tert-butoxide and sodium ethoxide, achieves excellent overall results under mild reaction conditions. The conversion rate of chloromethylchloroethylbenzene and the selectivity for chloromethylstyrene are significantly higher than those of traditional heterogeneous systems represented by cyclohexane-sodium hydroxide, and far superior to aqueous systems requiring phase transfer catalysts. Furthermore, the heavy halogen values ​​of the products obtained from all the preferred systems of this invention are significantly lower than those of traditional aqueous processes, fully demonstrating its significant advancements in improving reaction efficiency, simplifying post-processing, and ensuring product purity.

[0149] The above description is merely a preferred embodiment of this disclosure and is not intended to limit the scope of the substantive technical content of this disclosure. The substantive technical content of this disclosure is broadly defined within the scope of the claims of this application. Any technical entity or method completed by others that is completely identical to or an equivalent modification of the claims of this application shall be deemed to be covered within the scope of the claims.

[0150] All documents mentioned in this disclosure are incorporated herein by reference as if each document were individually incorporated herein by reference. Furthermore, it should be understood that after reading the foregoing contents of this disclosure, those skilled in the art can make various alterations or modifications to this disclosure, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing chloromethylstyrene, the method comprising the following steps: (1) Paraformaldehyde and hydrogen chloride are reacted in the presence of a catalyst and optional auxiliaries to obtain a chloromethylating agent; (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene; (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate chloromethylchloroethylbenzene products including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9); (4) In the presence of an optional solvent, the chloromethylchloroethylbenzene product obtained in step (3) is subjected to an elimination reaction with a base to obtain chloromethylstyrene.

2. The method as described in claim 1, characterized in that, In step (1), the catalyst comprises at least one compound selected from the group consisting of ferric chloride, aluminum chloride, zinc chloride, tin chloride, and titanium tetrachloride, and / or The adjuvant includes at least one acid selected from the group consisting of phosphoric acid, formic acid, hydrochloric acid, and sulfuric acid, and / or The molar ratio of the paraformaldehyde, catalyst, auxiliaries, hydrogen chloride, and chloroethylbenzene is (1-10):(0.1-5):(1-10):(1-10):1, preferably (3-5):(1-3):(1-5):(3-5):1; and / or The reaction temperature is controlled between 0-100℃, preferably 20-60℃.

3. The method as described in claim 1 or 2, characterized in that, In step (2), the molar ratio of chloroethylbenzene to paraformaldehyde in step (1) is 1:(1-10), preferably 1:(3-5).

4. The method as described in claim 1 or 2, characterized in that, In step (3), the distillation purification is carried out using a vacuum distillation column, and the distillation conditions are: absolute pressure of the system 20-10000Pa, preferably 50-5000Pa; number of trays 10-60, preferably 20-40; reflux ratio controlled at 1-50, preferably 1-30.

5. The method as described in claim 1 or 2, characterized in that, A solvent is present in step (4), said solvent comprising at least one solvent selected from the group consisting of cyclohexane, ethylcyclohexane, methylcyclohexane, tetrahydrofuran, tert-butanol, methanol, ethanol, ethylene glycol, n-propanol, isopropanol, toluene, benzene, and chlorobenzene; and / or The molar ratio of the solvent to chloromethylchloroethylbenzene is (1-5):1, preferably (1-3):1; and / or The base comprises at least one base selected from the group consisting of: sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide; and / or The molar ratio of the alkali to chloromethylchloroethylbenzene is (1-5):1, preferably (1-2):1; and / or The reaction temperature in step (4) is 25-80℃, preferably 25-50℃.

6. The method as described in claim 1 or 2, characterized in that, The method further includes step (5): adding a polymerization inhibitor to the chloromethylstyrene obtained in step (4) and distilling the mixture, wherein the polymerization inhibitor includes at least one polymerization inhibitor selected from the group consisting of 2,4-dinitrophenol, tert-butylcatechol, p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol.

7. A method for preparing chloromethylchloroethylbenzene, the method comprising the following steps: (1) Paraformaldehyde and hydrogen chloride are reacted in the presence of a catalyst and optional auxiliaries to obtain a chloromethylating agent; (2) Chloroethylbenzene is reacted with the chloromethylating agent obtained in step (1) to obtain chloromethylchloroethylbenzene; (3) The chloromethylchloroethylbenzene obtained in step (2) is purified by distillation to separate the chloromethylchloroethylbenzene product including o-chloromethylchloroethylbenzene, m-chloromethylchloroethylbenzene and p-chloromethylchloroethylbenzene, wherein the ratio of o-chloromethylchloroethylbenzene: m-chloromethylchloroethylbenzene: p-chloromethylchloroethylbenzene is (0.05-50):(0.05-20):(30-99.9).

8. A chloromethylchloroethylbenzene product, wherein the chloromethylchloroethylbenzene product is prepared by the method of claim 7.

9. A chloromethylstyrene product, wherein the heavy halogen value X of the chloromethylstyrene product is ≤100, preferably X≤10, wherein the heavy halogen value X = (heavy halogen content / light halogen content) × 10 6 The heavy halogens are bromine and iodine, and the light halogens are chlorine and fluorine.

10. The chloromethylstyrene product according to claim 9, wherein the chloromethylstyrene product is prepared by the method according to any one of claims 1-6.

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