A method for synthesizing pentafluoroiodoethane by co-conversion iodination

Abstract

The present invention belongs to the field of organic synthesis, and relates to a method for synthesizing pentafluoroiodoethane by co-conversion iodination. It is obtained by reacting carboxylic acid, pentafluoroethane and iodine in a catalyst, oxygen or a mixed gas of oxygen and an inert gas; wherein the catalyst is an AB-type bifunctional catalyst loaded on a carrier, which can not only catalyze decarboxylation iodination reaction, but also catalyze dehydrogenation iodination reaction. The single-pass conversion rate of the present invention in terms of iodine atoms reaches more than 70%, and other high-value-added iodides can be flexibly produced as by-products by changing the raw materials; not only the raw materials are cheap and safe, and the sources are convenient, but also the reaction temperature is low and the catalyst life is long; and the product separation and purification is simple, the synthesis process is safe, and it is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the field of organic chemical synthesis, and particularly relates to a method for synthesizing pentafluoroiodoethane by co-conversion iodination. Background Art

[0002] Pentafluoroiodoethane (C2F5I) is an initial polymerization agent for surfactants, a monomer for a variety of synthetic resins, a highly efficient fire extinguishing agent, and can also be used to produce fluorine-containing fine chemicals such as fluorine-containing pharmaceutical intermediates. It has broad application prospects.

[0003] At present, the main production method of C2F5I is tetrafluoroethylene fluoridation, which uses tetrafluoroethylene (TFE), iodine pentafluoride (IF5) and iodine (I2) as raw materials, and metal fluoride as catalyst. The cost of IF5 in the raw materials is high, and its purity has a great influence on the reaction. IF5 has strong irritation, corrosiveness and toxicity, and has high requirements for reaction equipment and high process risks. The tetrafluoroethylene fluoridation can also use iodine chloride (ICl) and hydrogen fluoride (HF) instead of IF5 and I2 as raw materials, but the process reaction time is too long, which is not conducive to industrial production.

[0004] In addition, C2F5I is synthesized using 1,2-diiodotetrafluoroethane (CF2ICF2I) and IF5 or HF as raw materials and oxygen-containing halogen acid salts or halogen acid salts as catalysts. This method has a long reaction time, and the price of the raw material CF2ICF2I is relatively high. It is also a highly toxic substance, and the catalyst is unstable. Improper operation can easily cause explosions.

[0005] The gas phase iodination method uses pentafluoroethane (C2HF5), I2 and / or oxygen (O2) as raw materials and catalyzes the synthesis of C2F5I at 550°C. Due to the large Gibbs free energy of the reaction, the conversion rate of iodine atoms is only about 23%, and a large amount of iodine needs to be recycled. At the same time, due to the high reaction temperature, the catalyst deactivates quickly, the production cost is high, and when the reaction temperature is below 450°C, the conversion rate of this reaction is extremely low.

[0006] The traditional C2F5I synthesis method has the problems of high raw material cost, strong corrosiveness and toxicity, and high process risk. The gas phase iodination method has low conversion rate, a large amount of iodine needs to be recycled, high reaction temperature, short catalyst life, and high production cost, which is not conducive to industrialization. Summary of the invention

[0007] In view of this, and in view of the deficiencies in the prior art, the object of the present invention is to provide a method for synthesizing pentafluoroiodoethane with safe raw materials, high iodine conversion rate, long catalyst life, low production cost and safe synthesis process.

[0008] In order to achieve the above object, the method for synthesizing pentafluoroiodoethane by co-conversion iodination provided by the present invention comprises:

[0009] A reactant stream of carboxylic acid (RCOOH), pentafluoroethane (CHF3) and elemental iodine (I2), oxygen (O2) or a mixed gas of oxygen and an inert gas; and in the presence of a catalyst, reacting the reactant stream to produce a product stream containing pentafluoroiodoethane.

[0010] The reaction of RCOOH and I2 in the reactant stream produces iodoalkane (RI), hydrogen iodide (HI) and carbon dioxide (CO2) in situ according to the following reaction formula 1:

[0011]

[0012] The CHF3 and O2 in the reactant stream react with the HI generated in situ to produce pentafluoroiodoethane (C2F5I), hydrogen fluoride (HF), carbon dioxide (CO2) and water (H2O) according to the following reaction equations 2 to 4:

[0013]

[0014]

[0015]

[0016] It should be noted that since the Gibbs free energy of the reaction between C2HF5 and HI is smaller than that of the reaction between C2HF5 and I2, reactions 2 to 4 are more likely to occur and have a higher conversion rate. At the same time, the continuous consumption of HI causes reaction 1 to continuously move to the right, and the mutual promotion between reaction 1 and reaction 2 to 4 can greatly increase the conversion rate of iodine atoms.

[0017] Furthermore, the carboxylic acid (RCOOH) is selected from: trifluoroacetic acid, pentafluoropropionic acid, acetic acid, propionic acid, cyclohexane acid and other carboxylic acids with a general formula of RCOOH and combinations thereof.

[0018] The molar ratio of the carboxylic acid, pentafluoroethane, iodine and oxygen is 1:0.5-10:0.2-2:0.1-1.

[0019] The gas phase reaction conditions are: reaction pressure 0.05-0.5 MPa, reaction temperature 300-600°C, preferably reaction temperature 350-550°C.

[0020] Furthermore, the catalyst is a bifunctional catalyst composed of at least one of an alkali metal salt or an alkaline earth metal salt and at least one of a transition metal salt supported on a carrier; wherein,

[0021] The alkali metal salt is a lithium salt, a sodium salt, a potassium salt, a rubidium salt or a cesium salt, the alkaline earth metal salt is a magnesium salt, a calcium salt, a strontium salt or a barium salt, and the transition metal salt is an iron salt, a copper salt or a zinc salt;

[0022] Furthermore, the molar ratio of the alkali metal salt or alkaline earth metal salt to the transition metal salt is 1:0.5-2;

[0023] The weight ratio of the alkali metal salt or alkaline earth metal salt and transition metal salt to the carrier is 0.05-0.35:1.

[0024] Furthermore, the carrier is chromium-based perovskite, chromium-based spinel, aluminum-based spinel, activated carbon, graphite, SiC and a combination thereof; wherein,

[0025] The chromium-based perovskite has a chemical formula of La x A 1-x CrO 3-y F 2y or Y x A 1-x CrO 3-y F 2y A compound, x is 0 to 1, y is 0 to 3, A is a metal atom selected from the group consisting of Mg, Ca, Sr, and Ba;

[0026] The chromium-based spinel has a chemical formula of BCr2O 4-z F 2z The aluminum-based spinel has a chemical formula of BAl2O 4-z F 2z A compound wherein z is 0 to 4, and B is a metal atom selected from the group consisting of Mg, Fe, Zn, Mn, Co, Cu, Ti, Cd, Ga, and Ni.

[0027] Furthermore, the contact time between the reactant stream and the catalyst is 0.1 to 120 seconds.

[0028] Furthermore, the reaction can be carried out simultaneously in the same catalyst and the same reactor, or in two series-connected reactors under different catalysts.

[0029] It can be seen from the above technical solution that, compared with the prior art, the method for synthesizing pentafluoroiodoethane by co-conversion iodination provided by the present invention has the following excellent effects:

[0030] 1. The single-pass conversion rate of the present invention in terms of iodine atoms reaches more than 70%, and other high-value-added iodides can be flexibly produced as by-products by changing the raw materials.

[0031] 2. The raw materials of the present invention are cheap, safe and convenient to source; the reaction temperature is low and the catalyst life is long; the product separation and purification are simple; the synthesis process is safe and suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 This is the GCMS detection spectrum of pentafluoroiodoethane product.

[0034] Figure 2 The graph shows the conversion rate of iodine atoms over time. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0036] The embodiment of the present invention discloses a method for synthesizing pentafluoroiodoethane by co-conversion iodination.

[0037] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0038] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0039] Example 1

[0040] Liquid pentafluoropropionic acid at a flow rate of 10.0 ml / h and solid I2 at a flow rate of 15.0 g / h were mixed and sent to the evaporator. After evaporation into gaseous state, they were mixed with C2HF5 at a flow rate of 22.0 sccm and O2 at a flow rate of 6.0 sccm. 0.6 Ca 0.4 The fixed bed reactor of CrO2F2 catalyst has a reaction temperature of 400℃ and a contact time of 10s between the reactant flow and the catalyst. The gas after the reaction is deiodinated, deacidified and dried before being detected by gas chromatograph. The actual content of the product is calculated by the external standard method, and the conversion rate and selectivity are determined by material balance in and out of the reactor. The changes in conversion rate and selectivity over time are also investigated.

[0041] Experimental results: The gases after the reaction mainly include unreacted iodine, hydrogen fluoride, water, pentafluoroiodoethane, trifluoroiodomethane, unreacted pentafluoroethane and carbon dioxide. The boiling points of the products vary greatly. According to the boiling points and acidity and alkalinity of the products, a product with a purity of more than 99% can be obtained through conventional unit operations such as cooling, liquid separation, absorption, drying and distillation. The product is pentafluoroiodoethane as detected by GCMS (see Figure 1 ), unreacted iodine and pentafluoroethane can be recycled. The single-pass conversion rate of iodine atoms is 81.4%, the selectivity of C2F5I is 84.6%, and the selectivity of trifluoroiodomethane is 15.4%. Since the reaction temperature of this technology is greatly reduced, the life of the catalyst is extended at a lower temperature. In this implementation case, the catalyst life is more than 300h (see Figure 2 ).

[0042] Example 2

[0043] Liquid trifluoroacetic acid at a flow rate of 5.0 ml / h and solid I2 at a flow rate of 15.0 g / h are mixed and sent to an evaporator. After evaporation into gas, they are mixed with CHF3 at a flow rate of 45.0 sccm and O2 at a flow rate of 6.0 sccm, and passed into a fixed bed reactor filled with 30 ml of Na2CO3-FeCl2 / ZnCr2O3F2 catalyst. The reaction temperature is 400°C, and the contact time between the reactant stream and the catalyst is 20 s. The gas after the reaction is deiodinated, deacidified, dried, and then detected by a gas chromatograph. The actual content of the product is calculated by the external standard method, and the conversion rate and selectivity are determined by the material balance in and out of the reactor.

[0044] Experimental results: The single-pass conversion rate based on iodine atoms was 85.3%, the selectivity of C2F5I was 79.6%, and the selectivity of trifluoroiodomethane was 20.4%.

[0045] Example 3

[0046] Liquid cyclopentane acid at a flow rate of 10.0 ml / h and solid I2 at a flow rate of 15.0 g / h are mixed and sent to an evaporator. After evaporation into gas, they are mixed with CHF3 at a flow rate of 67.0 sccm and O2 at a flow rate of 11.0 sccm, and passed into a fixed bed reactor filled with 45 ml of RbNO3-ZnCl2 / MgAl2O3F2 catalyst. The reaction temperature is 350°C, and the contact time between the reactant stream and the catalyst is 30 s. The gas after the reaction is deiodinated, deacidified, dried, and then detected by a gas chromatograph. The actual content of the product is calculated by the external standard method, and the conversion rate and selectivity are determined by the material balance in and out of the reactor.

[0047] Experimental results: The single-pass conversion rate based on iodine atoms was 70.7%, the selectivity of C2F5I was 75.4%, the selectivity of trifluoroiodomethane was 8.9%, and the selectivity of iodinated cycloalkanes was 15.7%.

[0048] Example 4

[0049] Liquid acetic acid at a flow rate of 7.0 ml / h and solid I2 at a flow rate of 15.0 g / h are mixed and sent to an evaporator. After evaporation into gas, they are mixed with CHF3 at a flow rate of 90.0 sccm and O2 at a flow rate of 11.0 sccm, and passed into a fixed bed reactor filled with 45 ml Mg(NO3)2-CuCl / activated carbon catalyst. The reaction temperature is 450°C, and the contact time between the reactant stream and the catalyst is 60 s. The gas after the reaction is deiodinated, deacidified, dried, and then detected by a gas chromatograph. The actual content of the product is calculated by the external standard method, and the conversion rate and selectivity are determined by the material balance in and out of the reactor.

[0050] Experimental results: the single-pass conversion rate based on iodine atoms was 76.8%, the selectivity of C2F5I was 47.2%, the selectivity of trifluoroiodomethane was 15.2%, and the selectivity of methyl iodide was 37.6%.

[0051] Example 5

[0052] Liquid propionic acid at a flow rate of 9.0 ml / h and solid I2 at a flow rate of 15.0 g / h are mixed and sent to an evaporator. After evaporation into gas, they are mixed with CHF3 at a flow rate of 67.0 sccm and O2 at a flow rate of 22.0 sccm, and passed into a fixed bed reactor containing 45 ml of Ba(NO3)2-FeCl3 / SiC catalyst. The reaction temperature is 500°C, and the contact time between the reactant stream and the catalyst is 90 s. The gas after the reaction is deiodinated, deacidified, dried, and then detected by a gas chromatograph. The actual content of the product is calculated by the external standard method, and the conversion rate and selectivity are determined by the material balance in and out of the reactor.

[0053] Experimental results: The single-pass conversion rate based on iodine atoms was 79.2%, the selectivity of C2F5I was 48.9%, the selectivity of trifluoroiodomethane was 20.2%, and the selectivity of ethyl iodide was 30.9%.

[0054] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synthesizing pentafluoroethane by co-conversion iodination, characterized in that: The method is obtained by reacting carboxylic acid, pentafluoroethane and iodine in a gas phase in a catalyst, oxygen or a mixed gas of oxygen and an inert gas; wherein, The catalyst is an AB type bifunctional catalyst supported on a carrier; wherein, The molar ratio of A to B is 1:(0.5~2), and the weight ratio of AB to the carrier is (0.05~0.35):1; And, A is an alkali metal salt or an alkaline earth metal salt; B is a transition metal salt; The carrier is at least one of chromium-based perovskite, chromium-based spinel, and aluminum-based spinel; wherein, The chromium-based perovskite has a chemical formula of La x A 1-x CrO 3-y F 2y or Y x A 1-x CrO 3-y F 2y A is a metal atom, which is at least one of Mg, Ca, Sr and Ba. The chromium-based spinel has a chemical formula of BCr2O 4-z F 2z The aluminum-based spinel has a chemical formula of BAl2O 4- z F 2z A compound of, z is 0-4; B is a metal atom, at least one of Mg, Fe, Zn, Mn, Co, Cu, Ti, Cd, Ga, Ni; The carboxylic acid has a general structural formula of RCOOH, and is at least one selected from trifluoroacetic acid, pentafluoropropionic acid, acetic acid, propionic acid, and cyclohexane acid; Moreover, the molar ratio of the carboxylic acid, pentafluoroethane, iodine and oxygen is: 1: (0.5-10): (0.2-2): (0.1-1).

2. The method for synthesizing pentafluoroiodoethane by co-conversion iodination according to claim 1, characterized in that: The alkali metal salt is a lithium salt, a sodium salt, a potassium salt, a rubidium salt or a cesium salt, the alkaline earth metal salt is a magnesium salt, a calcium salt, a strontium salt or a barium salt, and the transition metal salt is an iron salt, a copper salt or a zinc salt.

3. The method for synthesizing pentafluoroiodoethane by co-conversion iodination according to claim 1, characterized in that: The gas phase reaction conditions are: reaction pressure of 0.05-0.5 MPa, reaction temperature of 300°C-600°C.

4. The method for synthesizing pentafluoroiodoethane by co-conversion iodination according to claim 3, characterized in that: The gas phase reaction temperature is 350° C. to 550° C., and the catalytic reaction contact time is 0.1 to 120 seconds.

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