Aqueous phase synthesis method for trans-1,2-dichloroethylene

Abstract

The present invention belongs to the technical field of organic compound preparation and relates to a method for synthesizing trans-1,2-dichloroethylene in an aqueous phase. The present invention introduces acetylene, chlorine and a hydrochloric acid solution containing a PdCl2 catalyst into a microreactor for catalytic reaction to generate trans-1,2-dichloroethylene. The present invention adopts a microreactor with a PdCl2 catalyst and a heart-shaped channel module. The heart-shaped module microreactor is conducive to increasing the dissolution rate of acetylene in water, matching the acetylene chlorination reaction rate under the action of the PdCl2 catalyst, and greatly improving the yield of trans-1,2-dichloroethylene per unit reactor volume. However, the aqueous phase acetylene chlorination reaction carried out in a traditional kettle reactor has a high acetylene concentration in the gas phase due to the low dissolution rate of acetylene in water, which easily causes a violent chlorination reaction with chlorine, resulting in loss of control of the reaction equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of organic compound preparation, and in particular to an aqueous phase synthesis method of trans-1,2-dichloroethylene. Background Art

[0002] Trans-1,2-dichloroethylene has zero ozone depletion potential and zero global warming potential, and shares properties similar to other halogenated hydrocarbons. It has been actively developed in recent years as a high-value, environmentally friendly cleaning agent. It is currently widely used in cleaning, degreasing, and degreasing precision components such as electronic devices, chips, and medical equipment. It can also be used as a solvent for paints, resins, rubber, and cellulose acetate, and in dry cleaning agents, pesticides, fungicides, anesthetics, cryogenic extractants, and refrigerants.

[0003] There are two main methods for producing trans-1,2-dichloroethylene that have been reported. One is to use acetylene and chlorine as raw materials and selectively add chlorine to produce it; the other is to use chlorinated hydrocarbons such as trichloroethane as raw materials and remove HCl through a cracking reaction. Among them, the reaction using acetylene and chlorine as raw materials has the advantages of cheap raw materials and high atom economy, which has attracted more attention. However, this reaction has two disadvantages. One is that trans-1,2-dichloroethylene can easily react with chlorine to produce tetrachloroethane, resulting in extremely low selectivity for trans-1,2-dichloroethylene. The other is that the heat release of the reaction is very large (△H = -137.3kJ / mol), and the adiabatic temperature rise of the reaction system reaches 2000 degrees, which makes the system prone to temperature runaway and explosion hazards.

[0004] To solve this problem, scholars have adopted two technical solutions. One is the indirect reaction technology, that is, acetylene does not directly contact chlorine in the reactor for reaction. Instead, a high-valent CuCl2 solution is used as a solvent. Acetylene reacts with CuCl2 in one reactor to produce trans-1,2-dichloroethylene and CuCl. The CuCl solution is then transferred to another reactor and reacted with chlorine to produce CuCl2. During the entire process, acetylene does not directly contact chlorine, which avoids strong heating and temperature fluctuations, such as CN200910264425.2 and CN202110182625.4. However, this process needs to be carried out in two reactors, and the concentration and flow rate of the CuCl2 mother liquor during the reaction need to be precisely controlled, making the reaction control scheme extremely complicated. The other is the direct reaction technology, which dilutes acetylene and chlorine in a large amount of halogenated solvents such as tetrachloroethane, and then undergoes a selective chlorination reaction under the action of an alkaline earth metal chloride catalyst such as MgCl2, such as CN110054546B. However, the tetrachloroethane solvent in this process undergoes a chlorination reaction with the raw chlorine to produce byproducts such as pentachloroethane and hexachloroethane. This not only consumes the raw chlorine and reaction solvent, but also brings certain difficulties to product separation. In addition, acetylene and chlorine need to be diluted in a large amount of tetrachloroethane solvent, resulting in a low yield of the target product per unit volume of the reactor and poor economic benefits. Therefore, the industry urgently needs to develop a catalytic reaction process technology for the reaction of acetylene and chlorine in an aqueous solvent to produce trans-1,2-dichloroethylene. On the one hand, this can ensure the safe and efficient production of the target product, and on the other hand, it can avoid the use of organic solvents and reduce the burden of subsequent product separation. Summary of the Invention

[0005] The purpose of the present invention is to provide a novel microchannel catalytic reaction technology, which enables acetylene and chlorine to react in a water solvent in one step to highly selectively obtain trans-1,2-dichloroethylene, thereby solving the technical bottleneck of low production efficiency in the process.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides an aqueous phase synthesis method of trans-1,2-dichloroethylene, comprising the following steps:

[0008] Acetylene, chlorine and a hydrochloric acid solution containing a PdCl2 catalyst are introduced into a microreactor for catalytic reaction to generate trans-1,2-dichloroethylene.

[0009] Preferably, the concentration of the hydrochloric acid solution is 0.1 to 1.0 mol / L, and the concentration of the PdCl2 catalyst in the hydrochloric acid solution is 0.01 to 0.1 mol / L.

[0010] Preferably, the molar ratio of acetylene to chlorine is 0.5 to 2:1.

[0011] Preferably, the volume flow ratio of the acetylene to the hydrochloric acid solution containing the PdCl2 catalyst is 10 to 100:1.

[0012] Preferably, the temperature of the catalytic reaction is 80-120°C.

[0013] Preferably, the microreactor is a microreactor with a heart-shaped channel module.

[0014] The technical solution of the present invention has the following advantages:

[0015] The present invention provides an aqueous-phase synthesis process for trans-1,2-dichloroethylene in a microreactor, eliminating the use of organic solvents such as tetrachloroethane and achieving the production of trans-1,2-dichloroethylene through the continuous reaction of acetylene and chlorine in an aqueous solvent. The process is simple, utilizes readily available and inexpensive raw materials, and offers low production costs. Furthermore, the process eliminates the discharge of three wastes and is safe to operate, making it a clean production process. Furthermore, since the raw materials used are acetylene and chlorine, the reaction exhibits high atom economy, facilitating its industrial application.

[0016] 2. The present invention provides an aqueous-phase synthesis process for trans-1,2-dichloroethylene in a microreactor, which utilizes a PdCl2 catalyst and a microreactor with a heart-shaped channel module. The heart-shaped module microreactor is advantageous in increasing the dissolution rate of acetylene in water, matching the rate of the acetylene chlorination reaction under the action of the PdCl2 catalyst, and greatly improving the yield of trans-1,2-dichloroethylene per unit reactor volume. In contrast, the aqueous-phase acetylene chlorination reaction conducted in a traditional kettle reactor has a high concentration of acetylene in the gas phase due to the low dissolution rate of acetylene in water. This can easily cause a violent chlorination reaction with chlorine, leading to loss of control of the reaction equipment.

[0017] 3. The present invention provides an aqueous phase synthesis process for trans-1,2-dichloroethylene in a microreactor. The microreactor using a heart-shaped channel module has a high heat transfer coefficient and heat transfer area, greatly reducing the reactor volume and replacing the process of conducting chemical reactions in traditional kettle reactors.

[0018] 4. The present invention provides an aqueous phase synthesis process for trans-1,2-dichloroethylene in a microreactor. The target product, trans-1,2-dichloroethylene, is insoluble in aqueous solution and can be easily separated from the reaction system.

[0019] 5. The present invention provides an aqueous phase synthesis process for trans-1,2-dichloroethylene in a microreactor, wherein the acetylene conversion rate is stable between 65% and 88%, and the product selectivity is stable between 83% and 93%, indicating good reaction stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process flow of the aqueous phase synthesis method of the present invention. DETAILED DESCRIPTION

[0021] The present invention provides an aqueous phase synthesis method of trans-1,2-dichloroethylene, comprising the following steps:

[0022] Acetylene, chlorine and a hydrochloric acid solution containing a PdCl2 catalyst are introduced into a microreactor for catalytic reaction to generate trans-1,2-dichloroethylene.

[0023] In the present invention, the concentration of the hydrochloric acid solution is 0.1 to 1.0 mol / L, preferably 0.3 to 0.8 mol / L, and more preferably 0.5 to 0.6 mol / L; the concentration of the PdCl2 catalyst in the hydrochloric acid solution is 0.01 to 0.1 mol / L, preferably 0.2 to 0.8 mol / L, and more preferably 0.5 to 0.6 mol / L.

[0024] In the present invention, the molar ratio of acetylene to chlorine is 0.5 to 2:1, preferably 0.8 to 1.5:1, and more preferably 1 to 1.2:1.

[0025] In the present invention, the volume flow ratio of acetylene to the hydrochloric acid solution containing the PdCl2 catalyst is 10 to 100:1, preferably 20 to 80:1, and more preferably 40 to 60:1.

[0026] In the present invention, the temperature of the catalytic reaction is 80-120°C, preferably 90-110°C, and more preferably 100-105°C.

[0027] In the present invention, the microreactor is a microreactor with a heart-shaped channel module, and the two gas raw materials, acetylene and chlorine, are connected to the reactor via a T-shaped channel.

[0028] In the present invention, in the microreactor, acetylene is first introduced into the solution, and then chlorine is introduced after the solution is evenly mixed.

[0029] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Examples 1 to 13

[0031] S1: A hydrochloric acid solution containing PdCl2 of a certain concentration is introduced into the reactor of the heart-shaped module;

[0032] S2: heating the reaction system;

[0033] S3: A certain flow rate of acetylene and chlorine is continuously introduced into the reactor, and the trans-1,2-dichloroethylene product can be collected at the reactor outlet.

[0034] The flow rates of acetylene, chlorine gas and solution, the concentrations of PdCl2 and hydrochloric acid, and the reaction temperature for each implementation are shown in Table 1.

[0035] Table 1. Process operating conditions of each embodiment

[0036]

[0037]

[0038] Comparative Example 1

[0039] The difference between Comparative Example 1 and Example 4 is that no catalyst is added in Comparative Example 1.

[0040] Comparative Examples 2 to 4

[0041] The difference between Comparative Examples 2 to 4 and Example 4 is that the catalysts are different. The specific catalysts of each comparative example are shown in Table 2.

[0042] Table 2. Catalyst types of each comparative example

[0043]

[0044]

[0045] Comparative Example 5

[0046] The difference between Comparative Example 5 and Example 4 is that the reaction temperature in Comparative Example 5 is 60°C.

[0047] Comparative Examples 6-7

[0048] The difference between Comparative Examples 6 and 7 and Example 4 is that the types of organic solvents are different. The organic solvents of each comparative example are shown in Table 3.

[0049] Table 3. Organic solvents of each comparative example

[0050] Types of organic solvents Comparative Example 6 Tetrachloroethane Comparative Example 7 Pentachloroethane

[0051] Test example

[0052] The liquid products and gaseous products of each embodiment and comparative example were collected, wherein the mixed gas after the reaction was directly fed into an online gas chromatograph for quantitative analysis through a quantitative loop. The gas chromatograph was equipped with an FID detector and a plot-Q capillary column. The liquid product was qualitatively analyzed for product composition on a gas chromatography-mass spectrometer (GC-MS), and then each product was quantitatively analyzed on a gas chromatograph to calculate the selectivity of each product. The chromatographic column used was an HP-5ms, 30m×0.25mm×0.25μm capillary column. The calculation method is that n(inlet acetylene) = n(outlet acetylene) + n(trans-1,2-dichloroethylene) + n(cis-1,2-dichloroethylene) + n(vinylidene chloride) + n(1-chloroethylene) + n(trichloroethylene) + n(high-boiling-point chlorinated hydrocarbons), where n refers to the amount of substance (the same below), and the high-boiling-point chlorinated hydrocarbons are tetrachloroethane, pentachloroethane, hexachloroethane, etc. generated by the reaction. The composition of the products was analyzed and the conversion rate of acetylene and the selectivity of the main products were calculated. The calculation formulas for the acetylene conversion rate and product selectivity are as follows. The data results are recorded in Tables 4 and 5.

[0053]

[0054]

[0055] Table 4. Acetylene conversion of each embodiment and comparative example

[0056]

[0057] Table 5. Product selectivity of each embodiment and comparative example

[0058]

[0059]

[0060] According to the comparison of Examples 1 to 13, the amount of acetylene and chlorine introduced, the liquid flow rate and concentration, and the reaction temperature all affect the conversion rate of acetylene and the yield of trans-1,2-dichloroethylene.

[0061] The acetylene conversion rates of Comparative Examples 2 to 4 were all less than 10%, and the selectivities of trans-1,2-dichloroethylene were all less than 5%, while the acetylene conversion rates of Examples 1 to 13 were between 65% and 88%, and the selectivities of trans-1,2-dichloroethylene were all over 85%, indicating that when no catalyst is used or when other catalysts such as magnesium chloride, calcium chloride, and titanium chloride are used, the target product trans-1,2-dichloroethylene cannot be obtained with high conversion and high selectivity.

[0062] The acetylene conversion rate of Comparative Example 5 is less than 10%, while the acetylene conversion rates of Examples 1 to 13 are between 65% and 88%, indicating that when the reaction temperature is too low, the raw materials cannot be effectively converted.

[0063] The selectivity of trans-1,2-dichloroethylene in Comparative Examples 6 to 7 was less than 5%, while the selectivity of trans-1,2-dichloroethylene in Examples 1 to 13 was more than 85%, indicating that trans-dichloroethylene could not be obtained with high selectivity when an organic substance such as tetrachloroethane or pentachloroethane was used as a solvent.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for synthesizing trans-1,2-dichloroethylene in an aqueous phase, characterized in that: The following steps are included: Acetylene, chlorine gas and hydrochloric acid solution containing PdCl2 catalyst are introduced into a microreactor for catalytic reaction to generate trans-1,2-dichloroethylene; The concentration of the hydrochloric acid solution is 0.1-1.0 mol / L, and the concentration of the PdCl2 catalyst in the hydrochloric acid solution is 0.01-0.1 mol / L; The molar ratio of acetylene to chlorine is 0.5 to 2:1; The volume flow ratio of the acetylene and the hydrochloric acid solution containing the PdCl2 catalyst is 10-100:1; The temperature of the catalytic reaction is 80-120°C.

2. The method according to claim 1, characterized in that The microreactor is a microreactor with a heart-shaped channel module.

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