Production method of 1, 1, 2-trifluoroethylene

Abstract

The invention discloses a 1, 1, 2-trifluoroethylene production method, which comprises: (1) introducing a mixture of 1, 1, 1, 2-tetrafluoroethane, 2-chloro-1, 1, 1-trifluoroethane and N2 into a reactor, and carrying out a reaction under the action of a catalyst to obtain a reaction product, (2) introducing the reaction product into a first rectifying tower, and separating to obtain a first rectifying tower top product and a first rectifying tower kettle product; and (3) washing, drying and condensing the tower top product of the first rectifying tower to obtain nitrogen and a 1, 1, 2-trifluoroethylene product. According to the invention, the addition of 2-chloro-1, 1, 1-trifluoroethane can consume HF generated in the dehydrofluorination process of 1, 1, 1, 2-tetrafluoroethane and promote the conversion of 1, 1, 1, 2-tetrafluoroethane to 1, 1, 2-trifluoroethylene, thereby increasing the selectivity and conversion rate of the reaction, lowering the reaction temperature and reducing the energy loss.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing olefins, and in particular to a method for producing 1,1,2-trifluoroethylene. Background Art

[0002] 1,1,2-Trifluoroethylene (HFO-1123, R1123), CAS No. 359-11-5, the molecule does not contain ozone-depleting bromine and chlorine atoms, boiling point -51°C, ODP is 0, GWP 100 The value is only 0.3, and the environmental performance is excellent. HFO-1123 has a wide range of applications, such as heat pump working fluid for new energy vehicle air conditioning systems, synthetic monomers for fluorine-containing polymer materials, and key raw materials for synthesizing high value-added halogenated olefins.

[0003] The synthesis process of 1,1,2-trifluoroethylene mainly includes the following routes:

[0004] (1) Removal of hydrogen fluoride from 1,1,1,2-tetrafluoroethane (HFC-134a);

[0005] (2) Removal of hydrogen chloride from 1,1,2-trifluoro-1-chloroethane / 1,1,2-trifluoro-2-chloroethane (HCFC-133b / HCFC-133);

[0006] (3) Dechlorination reaction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113);

[0007] (4) Dechlorination reaction of 1,1,2-trifluoro-1,2-dichloroethane (HCFC-123a);

[0008] (5) Fluorine-chlorine exchange reaction of 1,1,2-trichloroethylene (TCE).

[0009] Among them, using HFC-134a as raw material and dehydrofluorinating to prepare HFO-1123 is an economically feasible route.

[0010] For example, CN103288589A discloses a method for producing trifluoroethylene and hydrogen fluoride, which uses 1,1,1,3-tetrafluoroethane as the main raw material to produce trifluoroethylene and hydrogen fluoride through dehydrofluorination. Specifically, in the presence of diluent gas CO2, γ-Al2O3 is used as a catalyst, and the reaction is carried out at 400°C, with an HFC-134a conversion rate of 30% and a selectivity of 98.8%.

[0011] For example, CN108368011A discloses a method for producing hydrofluoroolefins, which includes converting 1,1,1,2-tetrafluoroethane into HFO-1123 by contacting it with a metal catalyst in the presence of water vapor. The invention uses water vapor as a diluent gas, but the HF produced by the cracking of water vapor and HFC-134a forms hydrofluoric acid, which will corrode the equipment and have an adverse effect on the catalyst.

[0012] For example, US5856593A reported that aluminum fluoride was used as a catalyst for preparing trifluoroethylene from HFC-134a. In the presence of diluent gas nitrogen, the reaction was carried out at 600°C, and the initial conversion rate of HFC-134a could reach 34%. However, the catalyst was quickly deactivated. After 190 minutes of reaction, the conversion rate of HFC-134a dropped to 5.8%.

[0013] For example, CN104710273A discloses a method for preparing trifluoroethylene by a gas phase method, which uses 1,1,1,2-tetrafluoroethane as a raw material, and produces trifluoroethylene by dehydrofluorination in a one-step gas phase reaction at 380°C to 500°C under the action of a fluorination cracking catalyst. When the reaction temperature is 500°C, the conversion rate of 1,1,1,2-tetrafluoroethane reaches a maximum of 65.1%, but the selectivity of the product trifluoroethylene is only 96.3%. Summary of the invention

[0014] The present invention aims at the deficiencies of the prior art and provides a method for producing 1,1,2-trifluoroethylene with high yield, good selectivity and low cost.

[0015] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for producing 1,1,2-trifluoroethylene, comprising the following steps:

[0016] (1) introducing a mixture of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane (HCFC-133a) and N2 into a reactor, reacting under the action of a catalyst to obtain a reaction product, wherein the catalyst comprises a carrier and an active component, wherein the active component comprises Cr as a main component and one selected from Zn, Ni, Co, La, Mg, Fe and Ce as an auxiliary component, wherein the molar ratio of the carrier to Cr is 1 to 20:1, and the molar ratio of the carrier to the auxiliary component is 10 to 30:1;

[0017] (2) the reaction product obtained in step (1) is introduced into a first distillation tower for separation to obtain a first distillation tower top product and a first distillation tower bottom product;

[0018] (3) The top product of the first distillation tower obtained in step (2) is washed with water, dried, and condensed to obtain nitrogen and 1,1,2-trifluoroethylene products.

[0019] As a preferred embodiment of the present invention, the reaction temperature in step (1) is 250-500°C, the pressure is 0.1-3 MPa, and the space velocity is 300-2000 h -1 The molar ratio of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and N2 is 1:0.01-5:1-20.

[0020] As a preferred embodiment of the present invention, the reaction temperature in step (1) is 300-480°C, the pressure is 0.1-1.5 MPa, and the air velocity is 300-1000 h -1 The molar ratio of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and N2 is 1:0.05-2:10-20.

[0021] As a preferred embodiment of the present invention, the carrier is at least one of Al2O3, TiO2, CeO2, MoO3, MgO, and ZnO.

[0022] As a preferred embodiment of the present invention, the catalyst is prepared by precipitation method and equal volume impregnation method.

[0023] As a preferred embodiment of the present invention, the bottom product of the first distillation tower obtained in step (2) is distilled to obtain HF and a material containing 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane, and the material containing 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane is circulated to the reactor.

[0024] As a preferred embodiment of the present invention, the nitrogen obtained in step (3) is circulated to the reactor.

[0025] As a preferred embodiment of the present invention, the catalyst is activated before the reaction, and the activation gas used is a mixture of HF and N2.

[0026] In the process of chemical synthesis, in order to improve the efficiency and selectivity of a specific reaction path, an effective strategy is to introduce a synergist or promoter into the reaction system. In the present invention, by adding HCFC-133a synergist to the reaction system using HFC-134a as raw material, the reaction performance is significantly improved.

[0027] Specifically, HFC-134a undergoes a dehydrofluorination reaction to generate 1,1,2-trifluoroethylene and HF, and the reaction conditions are relatively harsh. At this time, HCFC-133a is introduced as a synergist. Its uniqueness lies in that HCFC-133a can react with HF generated during the dehydrofluorination process of HFC-134a to generate HFC-134a itself and hydrogen chloride. This reaction not only effectively consumes HF in the system and reduces its concentration, thereby promoting the conversion of HFC-134a to 1,1,2-trifluoroethylene, but also realizes the recycling of raw materials by generating additional HFC-134a, thereby improving the economy and sustainability of the overall reaction. The reaction principle of the present invention is as follows:

[0028] Dehydrofluorination reaction of HFC-134a: CF3CH2F → CF2=CHF + HF (a)

[0029] Reaction of HCFC-133a with HF: CF3CH2Cl + HF → CF3CH2F + HCl (b)

[0030] Through the coupling effect of reaction (b), reaction (a) is made easier to proceed, thus forming an efficient catalytic cycle system. The synergistic effect of these two reactions not only reduces the temperature conditions required for the reaction and reduces energy consumption, but also significantly improves the yield and reaction efficiency of the target product 1,1,2-trifluoroethylene. This strategy of promoting complex chemical reactions by introducing synergists has broad application prospects and research value in the field of chemical synthesis.

[0031] The boiling points of some substances in the present invention are as follows:

[0032] name Abbreviation Molecular weight Boiling point / ℃ 1,1,1,2-Tetrafluoroethane HFC-134a 102 -26.5 2-Chloro-1,1,1-trifluoroethane HCFC-133a 118 6.9 1,1,2-Trifluoroethylene HFO-1123 82 -51 Nitrogen <![CDATA[N2]]> 28 -196 Hydrogen fluoride HF 20 19.5 Hydrogen chloride HCl 36.5 -85

[0033] As can be seen from the table, the boiling points of various substances vary greatly, which can improve separation efficiency, reduce energy consumption, and increase product purity, which is beneficial to subsequent separation.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The process is simple and the cost is low. The addition of the synergist HCFC-133a in the present invention reduces the reaction temperature and reduces the energy loss. At the same time, the temperature reduction reduces the types and quantities of by-products, improves the selectivity of the product, and reduces the difficulty of subsequent separation and purification. The synergist HCFC-133a can react with HF generated in the process of dehydrofluorination of HFC-134a to generate HFC-134a itself and hydrogen chloride, which not only effectively consumes HF in the system and reduces its concentration, thereby promoting the conversion of HFC-134a to 1,1,2-trifluoroethylene, but also realizes the recycling of raw materials by generating additional HFC-134a, thereby improving the economy and sustainability of the overall reaction.

[0036] 2. The catalyst has high activity. The precursor of the catalyst of the present invention is prepared by impregnating Zn, Ni, Co, La, Mg, Fe, Ce and other metals with chromium / oxide, which modulates the Lewis acidity of the catalyst and improves the dispersion of the active components, thereby improving the activity and selectivity of the catalyst. The conversion rate of 1,1,1,2-tetrafluoroethane is above 65.8%, and can reach up to 72.2%. The selectivity of 1,1,2-trifluoroethylene is above 99.0%, and can reach up to 99.6%.

[0037] 3. Green and environmentally friendly, the unreacted 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane and diluent gas nitrogen can be recycled to the reactor, effectively improving resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a process flow chart of the present invention.

[0039] In the figure: 1 represents a reactor, 2 represents a first distillation tower, 3 represents a second distillation tower, 4 represents a water washing tower, 5 represents a dryer, and 6 represents a condenser. DETAILED DESCRIPTION

[0040] The process of the present invention is as follows Figure 1As shown, a mixture of 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane and a diluent gas N2 are introduced into a reactor 1 for reaction to obtain a product mixture containing 1,1,2-trifluoroethylene; the product mixture is introduced into a first distillation tower 2 for separation, and a mixture containing 1,1,2-trifluoroethylene, nitrogen and hydrogen chloride is obtained at the top of the tower, and a mixture containing 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and hydrogen fluoride is obtained at the bottom of the tower; the mixture obtained at the bottom of the first distillation tower 2 is introduced into a second distillation tower 3 for further separation, and HF is obtained at the bottom of the second distillation tower 3, and 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and hydrogen fluoride are obtained at the top of the tower. The material containing unreacted 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane is returned to the reactor 1 for a cyclic reaction; the mixture containing 1,1,2-trifluoroethylene, nitrogen and hydrogen chloride obtained at the top of the first distillation tower 2 is passed into a water washing tower 4 for washing to remove hydrogen chloride, and the hydrochloric acid obtained at the bottom of the water washing tower 4 is disposed of separately, and the top material containing 1,1,2-trifluoroethylene and nitrogen after the hydrogen chloride is removed is passed into a dryer 5 for drying and dehydration; then the dried and dehydrated material is passed into a condenser 6 for condensation to obtain products 1,1,2-trifluoroethylene and nitrogen, and the nitrogen is recycled to the reactor 1.

[0041] The technical scheme of the present invention is described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] a. Catalyst preparation

[0044] Dissolve Al2O3 and chromium chloride in water. 3+ :Cr 3+ The molar ratio was 2:1 to prepare a mixed solution, to which urea (Al 3+ Cr 3+ 4 times the total molar amount), heated to 40 ° C with stirring, added with ammonia water to adjust the pH value to about 8.5, aged for 2 h, raised the temperature to 80 ° C, continued to age for 10 h, cooled and filtered, the obtained colloidal precipitate was washed to neutrality, and dried at 120 ° C to obtain a Cr / Al2O3 precursor.

[0045] Zinc nitrate (the molar ratio of Al2O3 to Zn is 10:1) is dissolved in water to prepare an impregnation solution, and the impregnation solution is evenly impregnated on the Cr / Al2O3 precursor by an equal volume impregnation method. The precursor is then dried at 50°C, pressed into shape, and calcined at 450°C in a muffle furnace for 8 hours to prepare a Cr-Zn / Al2O3 catalyst.

[0046] b. Catalyst pretreatment

[0047] The prepared Cr-Zn / Al2O3 catalyst was loaded into a fixed bed reactor, and N2 was introduced at a flow rate of 500 mL / min. The temperature was raised to 250°C for drying and purging for 4 h, and then the temperature was raised to 350°C at a heating rate of 1°C / min. Then, N2 was switched to 10% HF / N2 gas for fluorination for 10 h to obtain a fluorinated Cr-Zn / Al2O3 catalyst.

[0048] c. Dehydrofluorination of 1,1,1,2-tetrafluoroethane

[0049] A mixed raw gas with a molar ratio of 1,1,1,2-tetrafluoroethane: 2-chloro-1,1,1-trifluoroethane: N2 = 1:0.05:10 was introduced into the catalyst bed, wherein the catalyst bed temperature was 300°C, and the catalyst was heated at 0.1 MPa, 300 h -1 The reaction was carried out at a space velocity of . The product mixture coming out of the reactor was separated by a distillation tower separation unit to obtain the product 1,1,2-trifluoroethylene. The conversion rate of the raw material at the reactor outlet and the selectivity of the product were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 65.8%, and the selectivity of 1,1,2-trifluoroethylene was 99.6%.

[0050] Example 2

[0051] This example is carried out according to the same steps as Example 1, except that the composition of the prepared catalyst is different, and the specific composition of the catalyst is shown in Table 1; the reaction conditions and parameters of 1,1,1,2-tetrafluoroethane dehydrofluorination are also different, and the specific reaction conditions and parameters are shown in Table 2.

[0052] The conversion rate of the raw materials and the selectivity of the products at the reactor outlet were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 67.1%, and the selectivity of 1,1,2-trifluoroethylene was 99.4%.

[0053] Example 3

[0054] This example is carried out according to the same steps as Example 1, except that the composition of the prepared catalyst is different, and the specific composition of the catalyst is shown in Table 1; the reaction conditions and parameters of 1,1,1,2-tetrafluoroethane dehydrofluorination are also different, and the specific reaction conditions and parameters are shown in Table 2.

[0055] The conversion rate of the raw materials and the selectivity of the products at the reactor outlet were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 68.9%, and the selectivity of 1,1,2-trifluoroethylene was 99.1%.

[0056] Example 4

[0057] This example is carried out according to the same steps as Example 1, except that the composition of the prepared catalyst is different, and the specific composition of the catalyst is shown in Table 1; the reaction conditions and parameters of 1,1,1,2-tetrafluoroethane dehydrofluorination are also different, and the specific reaction conditions and parameters are shown in Table 2.

[0058] The conversion rate of the raw materials and the selectivity of the products at the reactor outlet were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 70.4%, and the selectivity of 1,1,2-trifluoroethylene was 99.5%.

[0059] Example 5

[0060] This example is carried out according to the same steps as Example 1, except that the composition of the prepared catalyst is different, and the specific composition of the catalyst is shown in Table 1; the reaction conditions and parameters of 1,1,1,2-tetrafluoroethane dehydrofluorination are also different, and the specific reaction conditions and parameters are shown in Table 2.

[0061] The conversion rate of the raw materials and the selectivity of the products at the reactor outlet were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 72.2%, and the selectivity of 1,1,2-trifluoroethylene was 99.3%.

[0062] Example 6

[0063] This example is carried out according to the same steps as Example 1, except that the composition of the prepared catalyst is different, and the specific composition of the catalyst is shown in Table 1; the reaction conditions and parameters of 1,1,1,2-tetrafluoroethane dehydrofluorination are also different, and the specific reaction conditions and parameters are shown in Table 2.

[0064] The conversion rate of the raw materials and the selectivity of the products at the reactor outlet were analyzed by gas chromatography. The conversion rate of 1,1,1,2-tetrafluoroethane was 69.8%, and the selectivity of 1,1,2-trifluoroethylene was 99.0%.

[0065] Table 1 Catalyst compositions of Examples 1 to 6

[0066]

[0067]

[0068] Table 2 Reaction conditions parameters of Examples 1 to 6

[0069]

Claims

1. A method for producing 1,1,2-trifluoroethylene, characterized in that: The following steps are involved: (1) introducing a mixture of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and N2 into a reactor and reacting under the action of a catalyst to obtain a reaction product, wherein the catalyst comprises a carrier and an active component, wherein the active component has Cr as a main component and one selected from Zn, Ni, Co, La, Mg, Fe and Ce as an auxiliary component, wherein the molar ratio of the carrier to Cr is 1 to 20:1, and the molar ratio of the carrier to the auxiliary component is 10 to 30:1; (2) the reaction product obtained in step (1) is introduced into a first distillation tower for separation to obtain a first distillation tower top product and a first distillation tower bottom product; (3) The top product of the first distillation tower obtained in step (2) is washed with water, dried, and condensed to obtain nitrogen and 1,1,2-trifluoroethylene products.

2. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The reaction temperature in step (1) is 250-500°C, the pressure is 0.1-3 MPa, and the space velocity is 300-2000 h -1 The molar ratio of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and N2 is 1:0.01-5:1-20.

3. The method for producing 1,1,2-trifluoroethylene according to claim 2, characterized in that: The reaction temperature in step (1) is 300-480°C, the pressure is 0.1-1.5 MPa, and the air velocity is 300-1000 h -1 The molar ratio of 1,1,1,2-tetrafluoroethane, 2-chloro-1,1,1-trifluoroethane and N2 is 1:0.05-2:10-20.

4. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The carrier is at least one of Al2O3, TiO2, CeO2, MoO3, MgO and ZnO.

5. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The catalyst is prepared by precipitation method and equal volume impregnation method.

6. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The bottom product of the first distillation tower obtained in step (2) is distilled to obtain HF and a material containing 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane, and the material containing 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane is circulated to the reactor.

7. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The nitrogen obtained in step (3) is circulated to the reactor.

8. The method for producing 1,1,2-trifluoroethylene according to claim 1, characterized in that: The catalyst is activated before the reaction, and the activation gas used is a mixture of HF and N2.

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