A method for preparing 3,3,3-trifluoropropene

Abstract

The invention discloses a method for preparing 3,3,3-trifluoropropylene, comprising the following steps: after mixing trifluoromethane and acetylene, reacting under the catalysis of a heterogeneous catalyst to prepare 3,3,3-trifluoropropylene; the heterogeneous catalyst is a Sn-modified molecular sieve. The process route is safe and environmentally friendly, has high atomic economy, is conducive to improving process safety, and has strong industrial applicability; using Sn-modified molecular sieve as a reaction catalyst, not only the product selectivity is high, but also surprisingly, the catalyst has good long-term use stability, a service life of more than 600 hours, and the heterogeneous system catalyst is easier to separate.

Description

Technical Field

[0001] The invention relates to a synthesis method, in particular to a preparation method of 3,3,3-trifluoropropene. Background Art

[0002] 3,3,3-Trifluoropropene is a very valuable fluorine-containing intermediate with certain chemical activity. It can derive many fluorine-containing organic compounds and is the basic raw material for the production of fluorine-containing fine chemicals and polymer materials. Starting from this monomer, fluorosilicone rubber can be prepared through addition, polymerization and copolymerization reactions, which can be used in extreme environments such as aerospace and other high-tech fields. In addition, 3,3,3-trifluoropropene can also be used to develop a series of trifluoromethyl-containing compounds through various reactions, which are used in the fields of medicine, pesticides, etc. In the context of national energy conservation and emission reduction and the rapid growth of automobile and aerospace demand, the demand for 3,3,3-trifluoropropene has increased year by year, and the preparation technology of 3,3,3-trifluoropropene also needs to be more green and environmentally friendly.

[0003] There are many studies on the synthesis of 3,3,3-trifluoropropene at home and abroad. The most common preparation method is to expose halogenated hydrocarbons to hydrogen fluoride at high temperature in the presence of a solid chromium oxyfluoride catalyst, see US Patent US2889379A. Although the catalyst in this system initially has a very high reaction rate and yield, it will quickly deactivate due to the formation of carbon deposits on the catalyst surface. The deactivation rate is so fast that the economic operation of the fluorination process on an industrial scale is very difficult.

[0004] U.S. Patent No. 4465786A discloses a method for preparing 3,3,3-trifluoropropene by fluorinating 1,1,1,4-tetrachloropropane, and discloses a method for extending the life of the catalyst by adding a small amount of hexachloroethane and chlorine to the raw materials. However, hexachloroethane is easy to sublime and difficult to separate and purify, while chlorine is highly toxic, easily reacts with olefins to produce new by-products, and is extremely corrosive to the equipment.

[0005] Chinese patent CN100500626C discloses a method of injecting 1,3,3,3-tetrachloropropane liquid into superheated HF gas, using the superheated HF gas to transfer heat to 1,3,3,3-tetrachloropropane to reduce the partial pressure of 1,3,3,3-tetrachloropropane, so that 1,3,3,3-tetrachloropropane is gasified at a lower temperature, and a large amount of HF is used to dilute the polymerization reaction of olefins. The efficiency of the reactor is also reduced at the same reaction space velocity, but this method only reduces the probability of 1,3,3,3-tetrachloropropene dehydrochlorination to produce 3,3,3-trichloropropene and olefin polymerization reaction, and slows down the carbonization rate of the catalyst to a certain extent, but the life of the catalyst is not long enough, only about 400 hours, which is short in the gas phase reaction in the same field.

[0006] In summary, it is urgent to develop a new atom-economical 3,3,3-trifluoropropene production process to extend the service life of the catalyst, reduce production costs and the amount of three wastes generated, and improve process safety. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a method for preparing 3,3,3-trifluoropropene, specifically a new route for synthesizing 3,3,3-trifluoropropene using trifluoromethane and acetylene as raw materials. The process route is safe and environmentally friendly, has high atom economy, is conducive to improving process safety, and has strong industrial applicability; using Sn-modified molecular sieve as a reaction catalyst, not only the product selectivity is high, but also surprisingly, the catalyst has good long-term stability, with a service life of more than 600 hours, and the heterogeneous system catalyst is easier to separate.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing 3,3,3-trifluoropropene comprises the following steps:

[0010] After trifluoromethane and acetylene are mixed, the mixture is reacted under the catalysis of a heterogeneous catalyst to prepare 3,3,3-trifluoropropylene;

[0011] The heterogeneous catalyst is a Sn-modified molecular sieve.

[0012] In a preferred embodiment, the reaction temperature is 120-160°C, for example 130°C, 135°C, 140°C, 145°C, 150°C, etc., and the reaction pressure is 6-9 barg, for example 7 barg, 7.5 barg, 8 barg, 8.5 barg, etc.

[0013] In a preferred embodiment, the gas phase volume ratio of trifluoromethane and acetylene at the same pressure is (8-12):1, such as 8.5:1, 9:1, 10:1, 10.5:1, 11:1, etc.

[0014] In a preferred embodiment, in the heterogeneous catalyst, the loading amount of metal Sn in the molecular sieve is 1-2%, such as 1.2%, 1.4%, 1.6%, 1.8%, etc., calculated on the basis of the mass of the metal element.

[0015] In a preferred embodiment, the heterogeneous catalyst is selected from one or more of Sn-Beta-12.5 molecular sieve, Sn-Y-30 molecular sieve, Sn-ZSM-5 molecular sieve.

[0016] The Sn-modified molecular sieve preparation method is, for example, placing the corresponding hydrogen-type molecular sieve in an acidic solution for reflux treatment for a period of time, filtering, cleaning, and drying to obtain a dealuminated molecular sieve. Then, an inorganic salt solution of metal Sn is slowly added dropwise to the dealuminated molecular sieve, and after rapid grinding, it is transferred to a muffle furnace for high-temperature calcination to obtain a Sn-modified molecular sieve.

[0017] The acidic solution is, for example, one or more of 0.5-2 mol / L nitric acid, oxalic acid, hydrochloric acid, and sulfuric acid solutions. The treatment conditions of the acidic solution are, for example, treatment at 60-70° C. for 12-36 hours.

[0018] The inorganic salt of metal Sn is, for example, one or more of tin tetrachloride, tin nitrate, and tin acetate. The amount of the inorganic salt of metal Sn added is 1-2% of the mass of the dealuminated molecular sieve, calculated on the mass of the metal element.

[0019] The high temperature calcination conditions are, for example, calcination at 500-700° C. for 3-5 hours.

[0020] The above preparation method is not a limiting method for obtaining Sn-modified molecular sieves. For example, you can directly purchase commercial products of related catalysts, or prepare them by referring to other methods disclosed in the prior art.

[0021] In a preferred embodiment, the feed amount of trifluoromethane is 100-300 mL / (mL) relative to the volume space velocity of the heterogeneous catalyst. cat .h), for example 130mL / (mL cat .h)、150mL / (mL cat .h)、190mL / (mL cat .h)、210mL / (mL cat .h)、260mL / (mL cat .h).

[0022] The beneficial effects of the present invention are:

[0023] 1) The reaction route is safe and environmentally friendly, with high atom economy, basically no three wastes are produced, and the pressure of environmental protection treatment is relatively small;

[0024] 2) The entire reaction process is carried out in the presence of a heterogeneous catalyst, the reaction products are easy to separate, which is beneficial to improving product quality, and the product selectivity is high, and the unreacted raw materials can be recycled to improve the overall reaction yield;

[0025] 3) Sn-modified molecular sieves can not only activate the CH bond of trifluoromethane, catalyze the reaction and improve product selectivity, but also have a long catalyst life and significant economic benefits;

[0026] 4) This method can realize the continuous production of 3,3,3-trifluoropropene and is suitable for industrial scale-up. DETAILED DESCRIPTION

[0027] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0028] In the following examples of the present invention, the preparation method of Sn-Beta-12.5 molecular sieve is as follows:

[0029] Take 50g of H-Beta-12.5 molecular sieve, put it into 600mL, 1mol / L HNO3 solution, and reflux it at 70℃ for 24h; after the reaction is completed, filter to obtain the solid and wash it with water until the filtrate is neutral. Dry the solid in an oven at 100℃ for 12h to obtain the dealuminated molecular sieve DeAl-Beta-12.5. Take 1.2g SnCl4·5H2O and dissolve it in 5g anhydrous ethanol, add it dropwise to 40g of the dealuminated molecular sieve, grind it quickly and evenly, and transfer it to a muffle furnace and calcine it at 700℃ for 5h. After the solid is pressed into tablets and crushed, it is sieved to a particle size of 40-60 mesh to obtain a Sn-Beta-12.5 molecular sieve with a Sn loading of 1%.

[0030] Other heterogeneous catalysts are prepared in a similar manner to the above steps, the only difference being that the selection and dosage of the metal inorganic salt are adjusted to meet the design requirements.

[0031] H-Beta-12.5 molecular sieve, HY-30 molecular sieve, and H-ZSM-5 molecular sieve were all purchased from UOP.

[0032] Unless otherwise specified, other raw materials and reagents were purchased from conventional commercial sources.

[0033] The components involved in the reactions of the following examples were analyzed by gas chromatography, the analysis instrument was Shimadzu GC-2010 gas chromatograph, and the chromatographic analysis conditions are shown in Table 1:

[0034] Table 1. Gas chromatography analysis conditions

[0035] Carrier gas High purity nitrogen Hydrogen flow 40mL / min Oxygen flow 400mL / min Make-up gas flow 30mL / min Injection mode Constant current Vaporization chamber temperature 280℃ Split Ratio 50 / 1 Injection volume 0.2μL Column flow rate 1mL / min Detector temperature 300℃

[0036] Column temperature: two-step temperature program, initial temperature 50°C, hold for 2 minutes, then increase to 80°C at a rate of 5°C / min; then increase to 280°C at a rate of 15°C / min, hold for 10 minutes.

[0037] [Example 1]

[0038] 2L / h of trifluoromethane and 200mL / h of acetylene were fully mixed, preheated to 100°C, and continuously introduced into a tubular reactor filled with 20mL of Sn-Beta-12.5 molecular sieve (Sn loading 1%). The temperature in the reactor was controlled at 120°C and the pressure was controlled at 9barg to prepare 3,3,3-trifluoropropene.

[0039] After 620 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 68%, the product selectivity was 98.5%, and the reaction effect was basically the same as that in the initial stage.

[0040] [Example 2]

[0041] 6L / h of trifluoromethane and 500mL / h of acetylene were fully mixed, preheated to 100°C and continuously introduced into a tubular reactor filled with 40mL of Sn-Y-30 molecular sieve (loading amount 1.2%). The temperature in the reactor was controlled at 140°C and the pressure was controlled at 7barg to prepare 3,3,3-trifluoropropene.

[0042] After 650 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 74% and the product selectivity was 99.1%, and the reaction effect was basically the same as that in the initial stage.

[0043] [Example 3]

[0044] 5L / h of trifluoromethane and 550mL / h of acetylene were fully mixed, preheated to 120°C, and continuously introduced into a tubular reactor filled with 25mL Sn-ZSM-5 molecular sieve (loading amount 1.5%). The temperature in the reactor was controlled at 160°C and the pressure was 8barg to prepare 3,3,3-trifluoropropene.

[0045] After 720 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 76% and the product selectivity was 97.3%, and the reaction effect was basically the same as that in the initial stage.

[0046] [Example 4]

[0047] 9 L / h of trifluoromethane and 1125 mL / h of acetylene were fully mixed, preheated to 100 ° C, and continuously introduced into a tubular reactor filled with 30 mL of Sn-Beta-12.5 molecular sieve (loading amount 2%). The temperature in the reactor was controlled at 125 ° C and the pressure was 6 barg to prepare 3,3,3-trifluoropropene.

[0048] After 690 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 65%, the product selectivity was 99.5%, and the reaction effect was basically the same as that in the initial stage.

[0049] [Comparative Example 1]

[0050] 3,3,3-trifluoropropene was prepared in substantially the same manner as in Example 1, except that the Sn-Beta-12.5 molecular sieve (Sn loading 1%) was replaced with the H-Beta-12.5 molecular sieve.

[0051] After 24 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 51% and the product selectivity was 92.3%.

[0052] After 400 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 22.1% and the product selectivity was 67.8%.

[0053] [Comparative Example 2]

[0054] 3,3,3-Trifluoropropene was prepared in substantially the same manner as in Example 1, except that Sn-Beta-12.5 molecular sieve (Sn loading 1%) was replaced with SnO2.

[0055] After 10 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was only 18.6% and the product selectivity was 44.6%.

[0056] [Comparative Example 3]

[0057] 3,3,3-trifluoropropene was prepared in substantially the same manner as in Example 1, except that the Sn-Beta-12.5 molecular sieve (Sn loading 1%) was replaced with the Zr-Beta-12.5 molecular sieve (Zr loading 1%).

[0058] After the reaction was continued for 24 hours, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 45.3% and the product selectivity was 96.1%.

[0059] After 300 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 26.3% and the product selectivity was 91.3%.

[0060] [Comparative Example 4]

[0061] 3,3,3-trifluoropropene was prepared in substantially the same manner as in Example 1, except that the Sn-Beta-12.5 molecular sieve (Sn loading 1%) was replaced with the Ti-Beta-12.5 molecular sieve (Ti loading 1%).

[0062] After 24 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 49.6% and the product selectivity was 94.6%.

[0063] After 300 hours of continuous reaction, gas chromatography-mass spectrometry analysis of the reaction gas revealed that the reaction conversion rate was 29.7% and the product selectivity was 90.4%.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing 3,3,3-trifluoropropene, characterized in that: The following steps are involved: After trifluoromethane and acetylene are mixed, the mixture is reacted under the catalysis of a heterogeneous catalyst to prepare 3,3,3-trifluoropropylene; The heterogeneous catalyst is a Sn-modified molecular sieve.

2. The method for preparing 3,3,3-trifluoropropene according to claim 1, characterized in that: The reaction temperature is 120-160°C and the reaction pressure is 6-9 barg.

3. The method for preparing 3,3,3-trifluoropropene according to claim 2, characterized in that: The gas phase volume ratio of trifluoromethane and acetylene at the same pressure is (8-12):

1.

4. The method for preparing 3,3,3-trifluoropropene according to any one of claims 1 to 3, characterized in that: In the heterogeneous catalyst, the loading amount of metal Sn in the molecular sieve is 1-2%, calculated by the mass of the metal element.

5. The method for preparing 3,3,3-trifluoropropene according to any one of claims 1 to 3, characterized in that: The heterogeneous catalyst is selected from one or more of Sn-Beta-12.5 molecular sieve, Sn-Y-30 molecular sieve, Sn-ZSM-5 molecular sieve.

6. The method for preparing 3,3,3-trifluoropropene according to any one of claims 1 to 3, characterized in that: The feed amount of trifluoromethane is 100-300 mL / (mL) relative to the volume space velocity of the heterogeneous catalyst. cat .h).