CN116023230A - Method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis - Google Patents
Method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis Download PDFInfo
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Abstract
The invention discloses a method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis, which takes 1,1-difluoroethane and chlorine gas as raw materials, and prepares the 1-chloro-1,1-difluoroethane through gas phase chlorination reaction under the action of a chlorination catalyst, wherein the chlorination catalyst is selected from Lewis acid catalysts. The invention has the advantages of high single pass conversion rate, high product selectivity, low production cost, continuous reaction realization, suitability for industrialized application and the like.
Description
Technical Field
The invention relates to the field of fluoridation, in particular to a method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis in the presence of a chlorination catalyst by taking 1,1-difluoroethane and chlorine as raw materials.
Background
1-chloro-1,1-difluoroethane (1-chloro-1, 1-difluoroethane) is commonly called difluorochloroethane and freon-142 b, and is marked as HCFC-142b or R142b, is a colorless and slightly aromatic gas, is easy to dissolve in oil and is difficult to dissolve in water. R142b is an important organic intermediate, mainly used for the production of vinylidene fluoride (VDF), which in turn is used for the preparation of polyvinylidene fluoride resin (PVDF).
At present, the synthesis method of 1-chloro-1,1-difluoroethane is divided from raw materials and mainly comprises the following steps: 1, 1-trichloroethane direct fluorination process, VDC addition fluorination process and 1,1-difluoroethane photochlorination process.
(1) Direct fluorination of 1, 1-trichloroethane
1, 1-trichloroethane and hydrogen fluoride are used as raw materials, and fluoro reaction is carried out under specific conditions, wherein the reaction equation is as follows:
CH 3 CCl 3 +HF→CH 3 CFCl 2 +HCl
CH 3 CFCl 2 +HF→CH 3 CF 2 Cl+HCl
the patent CN1030746A of attochemical company discloses a method for preparing 1, 1-difluoro-1-chloroethane by liquid phase fluorination reaction by using 1, 1-trichloroethane or 1, 1-dichloro-1-fluoroethane and hydrofluoric acid as raw materials and perfluoro alkyl sulfonic acid (trifluoromethane sulfonic acid) as a catalyst, wherein the conversion rate of the raw materials 1, 1-trichloroethane is 98.5%, and the selectivity of 1, 1-difluoro-1-chloroethane is 64.4%. However, the method has the advantages that the 1, 1-trichloroethane itself trichloromethyl is very active, even in the absence of a catalyst, the fluoro reaction can occur, the reaction degree is difficult to control, the byproducts are more, and the subsequent treatment is complex. If the reaction does not use a catalyst, the required reaction temperature is higher; excess hydrogen fluoride will result in excess byproducts in the reaction product; too little hydrogen fluoride results in a reduced reaction rate and an extended reaction time.
(2) VDC addition fluoro process
The process for preparing the 1-chloro-1,1-difluoroethane by adding and fluorinating 1, 1-dichloroethylene (VDC) and hydrogen fluoride serving as raw materials under specific conditions can be divided into a one-step method and a two-step method, wherein the one-step method is to put the addition reaction and the fluorinating reaction in the same reactor to obtain a target product; the two-step method is characterized in that the reaction is divided into two stages, the first stage is to directly add VDC and hydrogen fluoride to obtain 1-fluoro-1, 1-dichloroethane, the second stage is to separate and purify the product obtained in the first stage to obtain 1-fluoro-1, 1-dichloroethane with higher purity, and the fluoro-reaction is carried out on the 1-fluoro-1, 1-difluoroethane to obtain the 1-chloro-1,1-difluoroethane, wherein the reaction equation is as follows:
CH 2 ＝CCl 2 +HF→CH 3 CCl 2 F
CH 3 CCl 2 F+HF→CH 3 CF 2 Cl+HCl
the Soviet Union fluorine chemical Co., ltd., patent CN1171837C discloses a method of using VDC and hydrogen fluoride as raw materials and SnCl 4 、CF 3 (CF 2 ) 3 The COF is used as a catalyst, and the R124b is prepared by a one-step liquid phase reaction, wherein the selectivity of the R142b reaches 95.2%, but the heat release is intense in the experimental process, and the utilization rate of the hydrogen fluoride is low.
The university of Zhejiang CN1927790A discloses that VDC and hydrogen fluoride are used as raw materials, snCl 4 The catalyst is subjected to liquid phase reaction, and the second reaction is completed in the same equipment by adopting a circulating reaction rectification modeThe method for synthesizing and separating fluorochloroethane improves the yield of HCFC-142b and the selectivity of HCFC-142b to HCF-143a, but the amplification effect of the method is remarkable, and in the industrialization process, VDC is extremely easy to generate self-polymerization and cracking reaction to generate a large amount of polymers and tar-like substances, so that the problems of reaction yield reduction, rapid reduction of catalyst activity, pipeline blockage and the like are caused.
(3) 1,1-difluoroethane photochlorination process
The process is carried out by taking 1,1-difluoroethane and chlorine as raw materials, and carrying out gas-phase or liquid-phase chlorination reaction in a photochlorination reactor under ultraviolet illumination to obtain 1-chloro-1, 1-difluoroethane. According to the existence of spraying facilities in the photochlorination reactor, the wet photochlorination and the dry photochlorination are carried out according to the free radical process, and the reaction is catalyzed by heat, light and free radical initiation, belonging to exothermic reaction, and the equation is as follows:
CH 3 CHF 2 +Cl 2 →CH 3 CF 2 Cl+HCl
patent CN106431819A of Shandong Huaan new material limited company discloses a method for preparing difluoro chloroethane by taking difluoroethane and chlorine as raw materials and carrying out steps of vaporization, multistage photochlorination reaction, water alkali washing, compression, dehydration, rectification and the like. The method is a wet photochlorination reaction under ultraviolet light, the heat released by the reaction is taken away by internal spray water, the generated hydrogen chloride gas is also absorbed by water washing in a photochlorination tower, and the content of hydrochloric acid in a byproduct sodium hypochlorite solution generated by subsequent alkali washing is low, but the method has large amplification effect of a reactor and low production efficiency.
At present, in actual industrial production, a VDC (direct-current) addition fluoro method and a1, 1-difluoroethane photochlorination method are mainly adopted for preparing the difluorochloroethane, but the price of VDC raw materials is always at a higher level, the amplification effect of a photochlorination reactor is obvious, the risk of material leakage caused by damage of a light pipe is easy to occur, and the production scale is limited.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis, which has the advantages of high single pass conversion, high product selectivity and low production cost, can realize continuous reaction, and is suitable for industrial application.
The invention aims at realizing the following technical scheme:
a process for the vapor phase catalytic production of 1-chloro-1,1-difluoroethane, said process comprising: the 1-chloro-1,1-difluoroethane is prepared by taking 1,1-difluoroethane and chlorine as raw materials through gas-phase chlorination reaction under the action of a chlorination catalyst, wherein the chlorination catalyst is selected from Lewis acid catalysts, and the reaction equation is as follows:
CH 3 CHF 2 +Cl 2 →CH 3 CF 2 Cl+HCl
the reaction of 1,1-difluoroethane and chlorine is easier to carry out, and under the action of a high-activity catalyst, the reaction condition is not reasonably controlled, so that excessive reaction is easy to form byproducts, and the prior art usually adopts photocatalysis.
The Lewis acid catalyst comprises a carrier and an active component, wherein the active component is at least one of zinc chloride, magnesium chloride or calcium chloride, and the active component accounts for 10-30% of the total mass of the Lewis acid catalyst. Preferably, the active component is zinc chloride and accounts for 15-20% of the total mass of the Lewis acid catalyst.
The Lewis acid catalyst package carrier and the active component are provided by the invention, wherein the carrier is at least one of active carbon, alumina or aluminum fluoride. Preferably, the carrier is activated carbon.
The reaction temperature of the gas-phase chlorination reaction is 200-300 ℃, the reaction pressure is 0-0.05 MPa, and the molar ratio of chlorine to 1,1-difluoroethane is 0.33-5:1, preferably 1-3:1.
The reaction of 1,1-difluoroethane and chlorine belongs to exothermic reaction, but the reaction can be smoothly carried out only by heating the reactants with certain activation energy, and the heating temperature is too low to enable the reactants to reach an activation state; if the heating temperature is too high, side reactions are deepened, resulting in low yield of the target product. Thus, the reaction temperature of the present invention is controlled to 200 to 300℃and preferably 250 to 300 ℃.
The material molar ratio of 1,1-difluoroethane and chlorine has less influence on the reaction, the chlorine ratio is increased, and the conversion rate of 1,1-difluoroethane is increased. Therefore, the molar ratio of the chlorine to the 1,1-difluoroethane is 0.33-5:1, and the preferable ratio is 1-3:1 in order to reduce the separation difficulty of the chlorine in the later stage.
The chloridizing catalyst is subjected to activation treatment, and the activation treatment step comprises the following steps:
A1. and (3) roasting: roasting in nitrogen atmosphere at 300-350 deg.c for 2-5 hr;
A2. and (3) an activation step: introducing chlorine, maintaining at 150-200 deg.c for 0.5-2 hr, heating to 200-300 deg.c, and activating for 0.5-2 hr to obtain the activated chloridizing catalyst.
The mixed raw material gas of the 1,1-difluoroethane and the chlorine gas and the activated chlorination catalyst undergo gas-phase chlorination reaction, and the airspeed of the mixed raw material gas is 240h -1 ～720h -1 。
The space velocity selection of the 1,1-difluoroethane and the chlorine on the catalyst has larger influence on the reaction, and the contact time of the material and the catalyst is too short, so that the conversion rate of the 1,1-difluoroethane is low; the contact time of the material and the catalyst is too long, so that deep chlorination reaction is easy to occur, and byproducts are increased. Therefore, the space velocity of the reaction materials on the catalyst is 240 to 720 hours -1 Preferably 360 to 720 hours -1 。
The gas-phase chlorination reaction crude product is subjected to water alkali washing, compression, dehydration and rectification to obtain a high-purity 1-chloro-1,1-difluoroethane product. The 1,1-difluoroethane separated in the rectification operation can be used as a raw material for recycling.
Under the chlorination catalyst and the reaction conditions, the raw material single-pass conversion rate is high, the product selectivity is high, and excessive reaction is not easy to cause to form excessive chlorination byproducts.
Detailed Description
The invention will be further illustrated with reference to the following specific examples, without limiting the invention to these specific embodiments. It will be appreciated by those skilled in the art that the invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Preparation example 1
20mL of catalyst is filled in a Yingkang material reaction tube with the inner diameter of 19mm and the length of 800mm, the catalyst carrier is activated carbon, the active component is zinc chloride, the zinc chloride accounts for 15% of the total mass, the reaction tube is heated to 300 ℃, nitrogen is introduced for roasting for 2 hours, then the temperature is reduced to 200 ℃, chlorine is introduced into the reaction tube at the feed flow of 11.4g/h for catalyst activation, the temperature is raised to 300 ℃ after half an hour of activation, and the activation is continued for half an hour, so that the activated chlorination catalyst is obtained and is marked as Cat1.
Preparation example 2
The procedure of this preparation example was identical to that of preparation example 1, except that: the active components are respectively calcium chloride, magnesium chloride, copper chloride and nickel chloride, and the obtained catalysts are respectively referred to as Cat2, cat3, cat4 and Cat5.
Preparation example 3
20mL of catalyst is filled in a Yingkang material reaction tube with the inner diameter of 19mm and the length of 800mm, the catalyst carrier is alumina, the active component is zinc chloride, the zinc chloride accounts for 15% of the total mass, the reaction tube is heated to 300 ℃, nitrogen is introduced for roasting for 2 hours, then the temperature is reduced to 200 ℃, chlorine is introduced into the reaction tube at the feed flow of 11.4g/h for catalyst activation, the temperature is raised to 300 ℃ after half an hour of activation, and the activation is continued for half an hour, so that the activated chloridized catalyst is obtained and is marked as Cat6.
Preparation example 4
The procedure of this preparation example was identical to that of preparation example 3, except that: the support was aluminum fluoride and the resulting catalysts were designated Cat7, respectively.
Example 1
According to the chlorine gas feeding flow rate of 11.4g/h and the 1,1-difluoroethane feeding flow rate of 10.6g/h, mixing, introducing into a fixed bed reactor (filled with Cat 1), controlling the reaction temperature at 300 ℃, controlling the molar ratio of chlorine gas and 1,1-difluoroethane to be 1:1, and controlling the airspeed to be 360h -1 The reaction product was subjected to sampling analysis from the outlet sampling port of the reactor through a water-alkali washing device, a compression device, a drying and dehydrating device and a rectifying device in this order, and the conversion rate of 1,1-difluoroethane and the selectivity of 1-chloro-1,1-difluoroethane were as shown in the following table 1.
Examples 2 to 3
The operation of this embodiment is identical to that of embodiment 1, except that: the reaction temperatures were controlled at 275℃and 250℃respectively, and the reaction results are shown in Table 1 below:
TABLE 1
| Examples | Reaction temperature/. Degree.C | Conversion of 1,1-difluoroethane | R142b Selectivity |
| Example 1 | 300 | 95.0％ | 93.5％ |
| Example 2 | 275 | 91.3％ | 94.0％ |
| Example 3 | 250 | 86.2％ | 94.2％ |
Examples 4 to 5
The operation of this embodiment is identical to that of embodiment 1, except that: the ratio of chlorine to 1,1-difluoroethane is controlled at 0.33:1 and 3:1 respectively, and the reaction results are shown in the following table 2:
TABLE 2
| Examples | Chlorine gas and 1,1-difluoroethane ratio | Conversion of 1,1-difluoroethane | R142b Selectivity |
| Example 1 | 1:1 | 95.0％ | 93.5％ |
| Example 4 | 0.33:1 | 50.3％ | 93.3％ |
| Example 5 | 3:1 | 97.8％ | 87.2％ |
Examples 6 to 7
The operation of this embodiment is identical to that of embodiment 1, except that: chlorine feed rate 7.5g/h, 1-difluoroethane feed rate 6.9g/h, space velocity 240h -1 The method comprises the steps of carrying out a first treatment on the surface of the Chlorine feed rate 22.7g/h, 1-difluoroethane feed rate 21.1g/h, space velocity 720h -1 The reaction results are shown in table 3 below:
TABLE 3 Table 3
| Examples | Airspeed/h -1 | Conversion of 1,1-difluoroethane | R142b Selectivity |
| Example 1 | 360 | 95.0％ | 93.5％ |
| Example 6 | 240 | 75.1％ | 93.3％ |
| Example 7 | 720 | 95.5％ | 84.9％ |
Examples 8 to 11
The operation of this embodiment is identical to that of embodiment 1, except that: the catalysts were Cat2, cat3, cat6, cat7, respectively, and the reaction results are shown in Table 4 below:
TABLE 4 Table 4
| Examples | Catalyst | Conversion of 1,1-difluoroethane | R142b Selectivity |
| Example 1 | Cat1 | 95.0％ | 93.5％ |
| Example 8 | Cat2 | 90.1％ | 93.3％ |
| Example 9 | Cat3 | 94.5％ | 91.3％ |
| Example 10 | Cat6 | 40.2％ | 90.2％ |
| Example 11 | Cat7 | 93.2％ | 32.2％ |
Comparative examples 1 to 2
According to chlorine feed streamThe amount of the catalyst is 11.4g/h, the feeding flow rate of the 1,1-difluoroethane is 10.6g/h, the catalyst is mixed and then is introduced into a fixed bed reactor (Cat 4 and Cat5 are respectively filled), the reaction temperature is controlled at 300 ℃, the molar ratio of chlorine to 1,1-difluoroethane is 1:1, and the space velocity is 360h -1 The reaction product sequentially passes through a water alkali washing device, a compression device, a drying dehydration device and a rectification device, and is sampled and analyzed from a sampling port at the outlet of the reactor, wherein the conversion rate of 1,1-difluoroethane and the selectivity of 1-chloro-1,1-difluoroethane are shown in the following table 5:
TABLE 5
| Examples | Catalyst | Conversion of 1,1-difluoroethane | R142b Selectivity |
| Comparative example 1 | Cat4 | 82.5％ | 74.8％ |
| Comparative example 2 | Cat5 | 50.3％ | 65.5％ |
Claims (7)
1. A method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis, which is characterized in that: the 1-chloro-1,1-difluoroethane is prepared by taking 1,1-difluoroethane and chlorine as raw materials through gas-phase chlorination reaction under the action of a chlorination catalyst, wherein the chlorination catalyst is selected from Lewis acid catalysts.
2. The process for the vapor phase catalytic preparation of 1-chloro-1,1-difluoroethane according to claim 1, wherein: the Lewis acid catalyst comprises a carrier and an active component, wherein the active component is at least one of zinc chloride, calcium chloride or magnesium chloride, and the active component accounts for 10-30% of the total mass of the Lewis acid catalyst; the carrier is at least one of active carbon, alumina or aluminum fluoride.
3. The process for the vapor phase catalytic preparation of 1-chloro-1,1-difluoroethane according to claim 2, wherein: the active component is zinc chloride and accounts for 15-20% of the total mass of the Lewis acid catalyst; the carrier is activated carbon.
4. The process for the vapor phase catalytic preparation of 1-chloro-1,1-difluoroethane according to claim 1, wherein: the reaction temperature of the gas-phase chlorination reaction is 200-300 ℃, the reaction pressure is 0-0.05 MPa, and the molar ratio of chlorine to 1,1-difluoroethane is 0.33-5:1.
5. The process for the vapor phase catalytic preparation of 1-chloro-1,1-difluoroethane according to claim 1, wherein: the chloridizing catalyst is activated, and the activating treatment step comprises the following steps:
A1. and (3) roasting: roasting in nitrogen atmosphere at 300-350 deg.c for 2-5 hr;
A2. and (3) an activation step: introducing chlorine, maintaining at 150-200 deg.c for 0.5-2 hr, heating to 200-300 deg.c, and activating for 0.5-2 hr to obtain the activated chloridizing catalyst.
6. The method for the vapor phase catalytic production of 1-chloro-1,1-difluoroethane according to claim 5, wherein: the mixed raw material gas of 1,1-difluoroethane and chlorine gas and the activated chlorination catalyst undergo gas-phase chlorination reaction, and the mixed raw material gasIs 240h -1 ～720h -1 。
7. The method for the vapor phase catalytic production of 1-chloro-1,1-difluoroethane according to claim 6, wherein: the gas-phase chlorination reaction crude product is subjected to water alkali washing, compression, dehydration and rectification to obtain a high-purity 1-chloro-1,1-difluoroethane product.
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