Synthesis method of vinyl chloride and polyvinyl chloride

Abstract

The invention belongs to the field of chemical production, and relates to a method for synthesizing vinyl chloride and polyvinyl chloride, in particular to a method for synthesizing vinyl chloride and polyvinyl chloride through acetylene dichloroethane liquid phase catalysis. The synthesis method of vinyl chloride comprises the following step: acetylene and dichloroethane are subjected to a liquid-phase catalytic reaction in the presence of a catalyst, wherein the catalyst is pyridine hydrochloride and / or pyridine derivative hydrochloride. The pyridine hydrochloride and / or pyridine derivative hydrochloride are / is used as the catalyst for liquid-phase catalytic synthesis of vinyl chloride from acetylene dichloroethane, the catalytic performance is stable, the content of vinyl chloride in a gas-phase component can be effectively increased, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the field of chemical production, and relates to a method for synthesizing vinyl chloride and polyvinyl chloride, and in particular to a method for synthesizing vinyl chloride and polyvinyl chloride by using acetylene dichloroethane in liquid phase catalysis. Background Art

[0002] Polyvinyl chloride (PVC) is one of the world's five most common resins, which is formed by the polymerization of vinyl chloride monomer. Due to its good processing performance, low manufacturing cost, corrosion resistance, insulation and other good characteristics, PVC is widely used in various fields such as industry, construction, electrical, decoration, packaging and daily life.

[0003] The ethylene method and the calcium carbide method are traditional production processes for synthesizing vinyl chloride. The ethylene method is to first chlorinate or oxychlorinate ethylene to synthesize ethylene dichloride, and then crack ethylene dichloride to obtain vinyl chloride and hydrogen chloride. The advantages of the ethylene method are that chlorine can be fully utilized, the "three wastes" can be treated without being discharged, the production process is simple, easy to control and suitable for large-scale production, and the product has strong adaptability, but the process is long, the investment is large, external heating is required, and ethylene dichloride will crack to produce hydrogen chloride as a by-product. The calcium carbide method is to synthesize vinyl chloride from acetylene and hydrogen chloride under the action of mercuric chloride catalyst. The advantages of the calcium carbide method are that the process and equipment are relatively simple, the investment is low, and the yield is high, but hydrogen chloride is required as a raw material, the energy consumption is large, and the catalyst mercury salt is highly toxic, which will cause great pollution to the environment.

[0004] In view of the defects of the ethylene method and the calcium carbide method, Zhongke Yigong (Shanghai) Chemical Technology Co., Ltd. has developed a new process for the solid-phase mercury-free catalytic synthesis of vinyl chloride from acetylene and dichloroethane ("Jiang Zhong Method"), which uses acetylene and dichloroethane as raw materials to couple to obtain vinyl chloride in one step. The "Jiang Zhong Method" can achieve both energy balance and material balance. Specifically, the reaction of acetylene and dichloroethane to produce vinyl chloride is a slightly exothermic reaction, the elimination reaction of dichloroethane is an endothermic reaction, and the addition reaction of acetylene is an exothermic reaction. The two are coupled, so that the reaction heat of the endothermic reaction and the exothermic reaction is self-balanced in the same reactor, thereby achieving energy balance. One molecule of acetylene and one molecule of dichloroethane are catalytically reformed to obtain two molecules of vinyl chloride, and all the raw materials are converted into products without by-products, thereby achieving material balance. Compared with the ethylene method, the "Jiang Zhong Method" has a small equipment investment, only a simple fixed bed, and mild reaction conditions. Compared with the calcium carbide method, the "Jiang Zhong Method" does not require the use of hydrogen chloride and mercuric chloride catalysts, which not only saves hydrogen energy, but also solves the problem of mercury pollution. However, since the "Jiang Zhong method" currently requires the use of fixed-bed catalysts, there are defects such as catalyst deactivation due to carbon deposition, difficulty in controlling bed temperature rise, and large amounts of dust and time-consuming catalyst loading. Therefore, there is an urgent need to optimize and improve the process, and the technology of liquid-phase catalytic synthesis of vinyl chloride by acetylene dichloroethane was born.

[0005] CN113582809A discloses a method for eliminating hydrogen chloride from organic chlorinated substances, wherein the method uses polar organic solvents and metal compounds as catalytic solutions, wherein the polar organic solvents include but are not limited to amides, ketones, and weakly alkaline organic solvents, and then acetylene and ethylene dichloride are introduced into the catalytic solution to react and obtain vinyl chloride. The method has a good acetylene conversion rate in synthesizing vinyl chloride, but since the organic solvents and metal compounds in the catalytic solution used are easy to react with ethylene dichloride or acetylene to produce polymers or complexes, the catalyst has poor stability and is prone to pipe blockage.

[0006] CN115155655A discloses a method for synthesizing vinyl chloride by acetylene dichloroethane liquid phase catalysis, which comprises reacting acetylene and dichloroethane under the condition of a non-metallic liquid phase catalyst to obtain a gas phase product containing vinyl chloride. The non-metallic liquid phase catalyst comprises a weakly basic organic compound hydrochloride and an organic solvent, the weakly basic organic compound hydrochloride is selected from one or more of imidazole compound hydrochloride and its derivatives, benzimidazole compound hydrochloride and its derivatives, and the organic solvent is a non-protonic polar solvent. The liquid phase catalytic technology uses a non-metallic catalyst, and there is no phenomenon of side reactions between metal compounds and reaction materials. However, since the weakly basic catalyst used is unstable in the reaction system, this will result in a short life of the catalytic solution and the catalytic activity of the liquid phase catalyst will decrease as the operating time increases. Summary of the invention

[0007] The first purpose of the present invention is to solve the defects of the existing liquid phase method for synthesizing vinyl chloride, such as poor catalyst stability and low vinyl chloride content in the gas phase component after long-term operation, and to provide a liquid phase catalytic synthesis method for vinyl chloride with more stable catalytic performance and higher vinyl chloride content in the gas phase component.

[0008] Specifically, the synthesis method of vinyl chloride provided by the present invention comprises subjecting acetylene and ethylene dichloride to a liquid phase catalytic reaction in the presence of a catalyst, wherein the catalyst is pyridine hydrochloride and / or pyridine derivative hydrochloride.

[0009] The second object of the present invention is to provide a method for synthesizing polyvinyl chloride, which comprises synthesizing vinyl chloride by the above method, and then subjecting the obtained vinyl chloride and optional comonomers to polymerization reaction.

[0010] The key to the present invention is to use pyridine hydrochloride and / or pyridine derivative hydrochloride as a liquid phase catalyst, which has the following beneficial effects compared with the prior art:

[0011] (1) The catalyst provided by the present invention has more stable performance, is less likely to cause coking and deterioration, and the content of vinyl chloride in the gas phase component is significantly increased.

[0012] (2) The present invention uses pyridine hydrochloride and / or pyridine derivative hydrochloride as a catalyst, which can effectively prevent the decomposition of dichloroethane to produce hydrogen chloride. Therefore, there is no hydrogen chloride in the product gas, which can reduce the treatment process of waste acid and simplify the production process.

[0013] (3) Pyridine hydrochloride and pyridine derivative hydrochloride are both water-soluble compounds, and the target product is in the gas phase and can be easily separated from the catalyst. Furthermore, when lipophilic organic polymers (impurities) are produced in the catalyst solution, the water solubility of pyridine hydrochloride and pyridine derivative hydrochloride can easily separate the catalyst and impurity components, and the catalyst solution can be easily regenerated. DETAILED DESCRIPTION

[0014] The synthesis method of vinyl chloride provided by the invention comprises the steps of subjecting acetylene and ethylene dichloride to a liquid phase catalytic reaction in the presence of a catalyst to obtain a product containing vinyl chloride.

[0015] In the present invention, the catalyst is pyridine hydrochloride and / or pyridine derivative hydrochloride. Specifically, the catalyst can be selected from pyridine hydrochloride or pyridine derivative hydrochloride alone, or a mixture of pyridine hydrochloride and pyridine derivative hydrochloride. After in-depth and extensive research, the inventors of the present invention found that pyridine hydrochloride and / or pyridine derivative hydrochloride can not only effectively catalyze the reaction of acetylene and dichloroethane to generate vinyl chloride, and the content of vinyl chloride in the gas phase component can reach a very high level, but also pyridine hydrochloride and / or pyridine derivative hydrochloride can stably exist in the acetylene dichloroethane liquid phase reaction system, and are not prone to coking and deterioration problems, and can achieve efficient catalysis for a long time.

[0016] In the present invention, the structure of the pyridine hydrochloride is shown in formula (1). The structure of the pyridine derivative hydrochloride is shown in formula (2).

[0017]

[0018] In formula (2), R1 and R2 are each independently H or a C1-C5 alkyl group, and at least one of them is a C1-C5 alkyl group. The C1-C5 alkyl group may be, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. From the perspective of raw material availability, the pyridine derivative hydrochloride is preferably selected from at least one of 2-methylpyridine hydrochloride (having a structure shown in formula (3)), 3-methylpyridine hydrochloride (having a structure shown in formula (4)), 4-methylpyridine hydrochloride (having a structure shown in formula (5)), 2,4-dimethylpyridine hydrochloride (having a structure shown in formula (6)), 2,5-dimethylpyridine hydrochloride (having a structure shown in formula (7)), 2,6-dimethylpyridine hydrochloride (having a structure shown in formula (8)), 2-ethylpyridine hydrochloride (having a structure shown in formula (9)), 3-ethylpyridine hydrochloride (having a structure shown in formula (10)) and 4-ethylpyridine hydrochloride (having a structure shown in formula (11)).

[0019]

[0020] The present invention has no particular limitation on the ratio of acetylene to ethylene dichloride, but in order to achieve the best ratio and improve the conversion rate of acetylene and the purity of vinyl chloride, preferably, the molar ratio of acetylene to ethylene dichloride is 1:(0.8-1.2), specifically 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2 or any value therebetween. In addition, the acetylene can be made from petroleum or raw coal as raw materials, and the specific process is well known to those skilled in the art and will not be described in detail herein.

[0021] The present invention has no particular limitation on the liquid phase catalytic reaction method, and acetylene, ethylene dichloride and the catalyst can be placed in a reaction container at the same time in any manner for reaction. In a preferred embodiment, the liquid phase catalytic reaction method includes the following steps: S1, heating and melting pyridine hydrochloride and / or pyridine derivative hydrochloride to obtain a liquid catalyst; S2, contacting acetylene, ethylene dichloride and the liquid catalyst to react to obtain a gas phase component containing vinyl chloride.

[0022] In the reaction process of the above-mentioned liquid phase catalytic reaction, in step S1, the temperature of the heating and melting can be any temperature that can transform the pyridine hydrochloride and the pyridine derivative hydrochloride from solid to liquid, preferably 120-220°C, such as 120°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 220°C or any value therebetween. In addition, the temperature of the heating and melting in step S1 is preferably consistent with the temperature of the contact reaction in step S2, so that the contact reaction can proceed more smoothly.

[0023] In the reaction process of the above-mentioned liquid phase catalytic reaction, in step S2, the contact reaction can be an intermittent reaction or a continuous reaction. Specifically, the intermittent reaction method can include mixing acetylene, ethylene dichloride and a catalyst solution and reacting them under specific conditions, collecting gas during the reaction, and the gas is the gas phase component containing vinyl chloride, and the liquid phase product remaining after the reaction is completed is the catalyst solution, which can be recycled. In the intermittent reaction process, the reaction conditions preferably include a temperature of 140-200°C, such as 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or any value therebetween; a pressure of 0-0.1MPa, such as 0, 0.01MPa, 0.02MPa, 0.03MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa or any value therebetween; and the reaction is terminated when the volume content of vinyl chloride in the gas phase component detected by sampling reaches more than 80% (such as 80%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, 99.5%, 99.8%, 100% or any value therebetween). The continuous reaction method may include continuously passing acetylene and ethylene dichloride into the catalyst solution for reaction to obtain a gas phase component containing vinyl chloride and a catalyst solution. In the continuous reaction process, the contact reaction conditions preferably include a temperature of 140 to 200°C, such as 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or any value therebetween; a pressure of 0 to 0.1MPa, such as 0, 0.03MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.1MPa or any value therebetween; and by controlling the reaction temperature and residence time, the volume content of vinyl chloride in the crude product gas phase component reaches more than 80%, such as 80%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, 99.5%, 99.8%, 100% or any value therebetween. In the present invention, pressure refers to gauge pressure. It should be noted that in the actual production process, the entire process is generally controlled by temperature, pressure and the content of vinyl chloride in the gas phase component to make the content of vinyl chloride in the gas phase component reach the target value. However, in the early stage of evaluating the performance of the catalyst, the entire process is generally controlled by temperature, pressure and raw material space velocity, with the content of vinyl chloride in the gas phase component as the final consideration target.

[0024] The method for synthesizing vinyl chloride provided by the present invention preferably further comprises separating and purifying the gas phase component containing vinyl chloride to obtain vinyl chloride and unreacted acetylene, in which case not only vinyl chloride with higher purity can be obtained, but also unreacted acetylene can be recovered. Unreacted acetylene can preferably be recycled.

[0025] The method for synthesizing polyvinyl chloride provided by the present invention comprises synthesizing vinyl chloride by the above method, and then subjecting the obtained vinyl chloride and optional comonomer to polymerization reaction. Whether to add the comonomer needs to be selected according to the target product. For example, when homopolymer polyvinyl chloride is required, there is no need to use the comonomer; when copolymer polyvinyl chloride is required, the comonomer needs to be added, and the comonomer can be, for example, a styrene monomer and / or an acrylic monomer. Among them, the styrene monomer can be, for example, at least one of styrene, methyl styrene and dimethyl styrene. The acrylic monomer can be, for example, at least one of acrylic acid, methacrylic acid, methyl acrylate and methyl methacrylate. In addition, the main improvement of the method for synthesizing polyvinyl chloride provided by the present invention is that a new method is used to synthesize the vinyl chloride monomer, and the polymerization reaction process and conditions can be conventionally selected in the art, which can be known to those skilled in the art and will not be elaborated here.

[0026] The present invention will be described in detail below through examples.

[0027] The raw materials and conditions not mentioned in the following examples and comparative examples are conventionally selected, and all examples and comparative examples are consistent.

[0028] Example 1

[0029] S1, heating and melting 2-methylpyridine hydrochloride at 120° C. to obtain a liquid catalyst;

[0030] S2. After mixing acetylene and ethylene dichloride, continuously introduce them into a reaction tower filled with a liquid catalyst for reaction, controlling the molar ratio of acetylene to ethylene dichloride to be 1.0:0.8, the reaction temperature to be 140°C, the reaction pressure to be 0.03MPa, and the acetylene space velocity to be 10h -1 The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 86.5%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 84.7%.

[0031] Example 2

[0032] S1, heating and melting 4-ethylpyridine hydrochloride at 150° C. to obtain a liquid catalyst;

[0033] S2. After mixing acetylene and ethylene dichloride, continuously introduce them into a reaction tower filled with a liquid catalyst for reaction, controlling the molar ratio of acetylene to ethylene dichloride to be 1.0:1.0, the reaction temperature to be 150°C, the reaction pressure to be 0 MPa, and the acetylene space velocity to be 20 h -1 The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 85.0%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 82.6%.

[0034] Example 3

[0035] S1. heating and melting pyridine hydrochloride at 140° C. to obtain a liquid catalyst;

[0036] S2. Acetylene and ethylene dichloride are respectively introduced into a reaction tower containing a liquid catalyst for reaction, and the molar ratio of acetylene to ethylene dichloride is controlled to be 1.0:0.9, the reaction temperature is 160° C., the reaction pressure is 0.06 MPa, and the acetylene space velocity is 40 h -1 The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 92.3%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 89.8%.

[0037] Example 4

[0038] S1, heating and melting 4-methylpyridine hydrochloride at 170° C. to obtain a liquid catalyst;

[0039] S2. After mixing acetylene and ethylene dichloride, continuously introduce them into a reaction tower filled with a liquid catalyst for reaction, controlling the molar ratio of acetylene to ethylene dichloride to be 1.0:1.0, the reaction temperature to be 170°C, the reaction pressure to be 0.08MPa, and the acetylene space velocity to be 60h -1 The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 88.0%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 85.4%.

[0040] Example 5

[0041] S1, heating and melting 2-ethylpyridine hydrochloride at 190° C. to obtain a liquid catalyst;

[0042] S2. Acetylene and ethylene dichloride are respectively introduced into a reaction tower containing a liquid catalyst for reaction, and the molar ratio of acetylene to ethylene dichloride is controlled to be 1.0:1.1, the reaction temperature is 190° C., the reaction pressure is 0.1 MPa, and the acetylene space velocity is 80 h -1The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 90.2%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 87.0%.

[0043] Example 6

[0044] S1. Heat and melt 2,6-dimethylpyridine hydrochloride at 220° C. to obtain a liquid catalyst;

[0045] S2. Acetylene and ethylene dichloride are respectively introduced into a reaction tower containing a liquid catalyst for reaction, and the molar ratio of acetylene to ethylene dichloride is controlled to be 1.0:1.2, the reaction temperature is 200°C, the reaction pressure is 0.07MPa, and the acetylene space velocity is 100h -1 The crude product gas obtained by the reaction is discharged from the top of the tower, and the crude product gas is separated to obtain vinyl chloride. When it is just running, the volume content of vinyl chloride in the crude product is 87.6%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product is 84.3%.

[0046] Comparative Example 1

[0047] Vinyl chloride was synthesized according to the method of Example 1, except that 2-methylpyridine hydrochloride was replaced by the same molar amount of imidazole hydrochloride, and the other conditions were the same as those of Example 1 to obtain vinyl chloride. When the operation was just started, the volume content of vinyl chloride in the crude product was 54.8%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product was 37.4%.

[0048] Comparative Example 2

[0049] Vinyl chloride was synthesized according to the method of Example 1, except that 2-methylpyridine hydrochloride was replaced by the same molar amount of N-methylbenzimidazole hydrochloride, and the other conditions were the same as those of Example 1 to obtain vinyl chloride. When it was just started, the volume content of vinyl chloride in the crude product was 61.3%; after continuous operation for 1500 hours, the volume content of vinyl chloride in the crude product was 40.8%.

[0050] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for synthesizing vinyl chloride, characterized in that: The method comprises the steps of subjecting acetylene and ethylene dichloride to a liquid phase catalytic reaction in the presence of a catalyst, wherein the catalyst is pyridine hydrochloride and / or pyridine derivative hydrochloride.

2. The method for synthesizing vinyl chloride according to claim 1, characterized in that: The pyridine derivative hydrochloride is selected from at least one of 2-methylpyridine hydrochloride, 3-methylpyridine hydrochloride, 4-methylpyridine hydrochloride, 2,4-dimethylpyridine hydrochloride, 2,5-dimethylpyridine hydrochloride, 2,6-dimethylpyridine hydrochloride, 2-ethylpyridine hydrochloride, 3-ethylpyridine hydrochloride and 4-ethylpyridine hydrochloride.

3. The method for synthesizing vinyl chloride according to claim 1, characterized in that: The molar ratio of acetylene to ethylene dichloride is 1:(0.8-1.2).

4. The method for synthesizing vinyl chloride according to any one of claims 1 to 3, characterized in that: The liquid phase catalytic reaction method comprises the following steps: S1. heating and melting pyridine hydrochloride and / or pyridine derivative hydrochloride to obtain a liquid catalyst; S2. Contacting acetylene, ethylene dichloride and a liquid catalyst to react, to obtain a gas phase component containing vinyl chloride.

5. The method for synthesizing vinyl chloride according to claim 4, characterized in that: The heating and melting temperature is 120-220°C.

6. The method for synthesizing vinyl chloride according to claim 4, characterized in that: The contact reaction is a batch reaction or a continuous reaction.

7. The method for synthesizing vinyl chloride according to claim 6, characterized in that: The conditions of the intermittent reaction include a temperature of 140-200° C., a pressure of 0-0.1 MPa, and the reaction is terminated when the volume content of vinyl chloride in the gas phase component detected by sampling reaches more than 80%.

8. The method for synthesizing vinyl chloride according to claim 6, characterized in that: The continuous reaction conditions include a temperature of 140-200° C. and a pressure of 0-0.1 MPa. The volume content of vinyl chloride in the gas phase component reaches more than 80% by controlling the reaction temperature and residence time.

9. The method for synthesizing vinyl chloride according to claim 4, characterized in that: The method also includes separating and purifying the gas phase components to obtain vinyl chloride and unreacted acetylene, and the unreacted acetylene is recycled.

10. A method for synthesizing polyvinyl chloride, characterized in that: The method comprises synthesizing vinyl chloride by the method described in any one of claims 1 to 9, and then subjecting the obtained vinyl chloride and optional comonomer to polymerization reaction.

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