A method for synthesizing trifluoroiodomethane by decarboxylation and decarbonylation iodination

Abstract

The invention belongs to the field of organic synthesis, and relates to a method for synthesizing trifluoroiodomethane by decarboxylation, decarbonylation, and iodination. The method is obtained by reacting carboxylic acid, trifluoroacetyl halide, and iodine element in a catalyst, oxygen, or in the absence of oxygen; wherein the catalyst is at least one of an alkali metal salt, an alkaline earth metal salt, or a transition metal salt, and may also be an AB-type bifunctional catalyst loaded on a carrier, which can not only catalyze decarboxylation iodination reaction, but also catalyze decarbonylation iodination reaction. The single-pass conversion rate of the present invention in terms of iodine atoms reaches more than 85%, 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 convenient to source, 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 trifluoroiodomethane by decarboxylation and decarbonylation iodination. Background Art

[0002] Trifluoroiodomethane (CF 3 I) is a new type of clean and efficient gas fire extinguishing agent, environmentally friendly semiconductor etching agent, insulating gas, refrigerant, foaming agent, trifluoromethylation agent, etc., and has broad application prospects.

[0003] Currently, CF 3 The main production method is to use iodine (I 2 ) is the gas phase iodination method with iodine source, due to I 2 The cost of iodine atoms accounts for more than 90% of the raw material cost, so the conversion rate in terms of iodine atoms is the most important factor in evaluating CF 3 I is the main indicator of the advancedness of the production method. Based on the different trifluoromethyl sources, the gas phase iodination method mainly includes:

[0004] Trifluoroacetyl halide (CF 3 COX, X=F, Cl, Br), hydrogen (H 2 ) and I 2 As raw material, palladium as catalyst, firstly 2 and I 2 Synthesize hydrogen iodide (HI) and then react with CF 3 Synthesis of CF by COX reaction 3 I.

[0005] The Gibbs free energy of this reaction is very high, the reaction conditions are harsh, the environment must be anhydrous, and the conversion rate is low, resulting in a very low conversion rate of iodine atoms in this method. At the same time, the use of precious metal catalysts is costly. 2 and I 2 Change to HI, and CF 3 Synthesis of CF by COX reaction 3 However, anhydrous HI gas is difficult to purify, expensive, unstable, and easily decomposed under heating conditions.

[0006] With trifluoroacetic acid (CF 3 COOH) and I 2 As raw material, decarboxylation iodination is used to synthesize CF under the action of catalyst 3 I, while an equal amount of HI is produced as a by-product, the yield of which is only about 35% in terms of iodine atoms. In the future, an HI oxidation device will be added to recover I 2 , increasing equipment investment.

[0007] Trifluoromethane (CHF 3 ), I2 and / or oxygen (O 2 ) as raw materials, catalytic synthesis of CF at 550 °C 3 I, Due to the large Gibbs free energy of the reaction, the conversion rate of iodine atoms is only about 26%, 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.

[0008] The conversion rate of traditional gas-phase iodine method based on iodine atoms generally does not exceed 40%, and a large amount of iodine needs to be recycled, which increases energy consumption and waste of raw materials. In addition, some methods are difficult to recycle iodine, have high reaction temperatures, short catalyst life, or use precious metal catalysts, which have high production costs and are not conducive to industrialization. Summary of the invention

[0009] In view of this, in view of the deficiencies in the prior art, the object of the present invention is to provide a method for synthesizing trifluoroiodomethane with high iodine conversion rate, long catalyst life and low production cost.

[0010] In order to achieve the above object, the method for synthesizing trifluoroiodomethane by decarboxylation and decarbonylation iodination provided by the present invention comprises:

[0011] Carboxylic acid (RCOOH), trifluoroacetyl halide (CF 3 COX, X = F, Cl, Br, I) and iodine (I 2 ) a reactant stream of a mixed gas; and in the presence of a catalyst, in an oxygen or oxygen-free environment, reacting the reactant stream to produce a product stream comprising trifluoroiodomethane.

[0012] RCOOH and I in the reactant stream 2 The reaction of the following reaction formula 1 produces iodoalkane (RI), hydrogen iodide (HI) and carbon dioxide (CO 2 ):

[0013]

[0014] CF in the reactant stream 3 COX reacts with the in situ generated HI to produce trifluoroiodomethane (CF) according to the following reaction formula 2 3 I), hydrogen halides (HX) and carbon monoxide (CO):

[0015]

[0016] It should be noted that both reaction equations 1 and 2 are easy to occur and have a high conversion rate. At the same time, the continuous consumption of HI causes reaction equation 1 to continuously move to the right. The mutual promotion of reaction equations 1 and 2 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, trifluoroacetyl halide and iodine gas is 1:0.5-10:0.2-2.

[0019] The gas phase reaction conditions are: reaction pressure 0.05-0.5 MPa, reaction temperature 200-600° C., preferably reaction temperature 300-550° C.

[0020] Furthermore, the catalyst is at least one of an alkali metal salt, an alkaline earth metal salt or a transition metal salt, and catalyzes both decarboxylation and decarbonylation iodination reactions; 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] In addition, the catalyst may include a carrier, and the carrier is chromium-based perovskite, chromium-based spinel, aluminum-based spinel, activated carbon, graphite, SiC, and a combination thereof; wherein,

[0023] 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;

[0024] The chromium-based spinel has a chemical formula of BCr 2 O 4-z F 2z The aluminum-based spinel has a chemical formula of BAl 2 O 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.

[0025] Furthermore, the weight ratio of the alkali metal salt or alkaline earth metal salt or transition metal salt to the carrier is 0.05-0.35:1.

[0026] Furthermore, the contact time between the reactant stream and the catalyst is 0.1 to 120 seconds.

[0027] 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.

[0028] It can be seen from the above technical solution that, compared with the prior art, the method for synthesizing trifluoroiodomethane by decarboxylation and decarbonylation iodination provided by the present invention has the following excellent effects:

[0029] 1. The single-pass conversion rate of the present invention in terms of iodine atoms reaches more than 85%, and other high-value-added iodides can be flexibly produced as by-products by changing the raw materials.

[0030] 2. The raw materials of the present invention are cheap 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

[0031] 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.

[0032] Figure 1 This is the GCMS detection spectrum of trifluoroiodomethane product.

[0033] Figure 2 The graph shows the conversion rate of iodine atoms over time. DETAILED DESCRIPTION

[0034] 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.

[0035] The embodiment of the invention discloses a method for synthesizing trifluoroiodomethane by decarboxylation and decarbonylation iodination.

[0036] 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 limiting 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.

[0037] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0038] Example 1

[0039] Liquid trifluoroacetic acid at a flow rate of 5.0 ml / h and solid I at a flow rate of 15.0 g / h 2 The mixture was sent to the evaporator, evaporated into gaseous state and mixed with CF at a flow rate of 22.0 sccm. 3 COCl mixture, and pass into 30 ml KF / La 0.6 Ca 0.4 CrO 2 F 2 The catalyst is fixed-bed reactor, the reaction temperature is 300°C, the contact time between the reactant flow and the catalyst is 10s, 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, the conversion rate and selectivity are determined by the material balance in and out of the reactor, and the changes in the conversion rate and selectivity with time are investigated.

[0040] Experimental results: The gas after the reaction mainly includes unreacted iodine, pentafluoroiodoethane, trifluoroiodomethane, unreacted CF 3 COCl, carbon dioxide, hydrogen chloride and carbon monoxide, the boiling points of the products vary greatly. According to the boiling points and acidity and alkalinity of the products, the 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 GCMS test shows that it is trifluoroiodomethane (see Figure 1 ), unreacted iodine and CF 3 COCl can be recycled. The single-pass conversion rate based on iodine atoms is 92.0%, and CF 3 The selectivity of I is 97.6%, and the selectivity of pentafluoroiodoethane is 2.4%. Since the reaction temperature of this technology is greatly reduced, the life of the catalyst is extended at a lower temperature. In this embodiment, the catalyst life is more than 300h (see Figure 2 ).

[0041] Example 2

[0042] Liquid trifluoroacetic acid at a flow rate of 5.0 ml / h and solid I at a flow rate of 15.0 g / h 2 The mixture was sent to the evaporator, evaporated into gas and mixed with CF at a flow rate of 45.0 sccm. 3 COF and 6.0 sccm O 2 Mix and pass 30ml RbNO 3 / ZnCr 2 O 3 F 2The fixed bed reactor of the catalyst has a reaction temperature of 350°C and a contact time of 20 seconds between the reactant flow and the catalyst. The gas after the reaction is deiodinated, deacidified and dried before being tested by a gas chromatograph. The actual content of the product is calculated using the external standard method, and the conversion rate and selectivity are determined by balancing the materials entering and leaving the reactor.

[0043] Experimental results: The single-pass conversion rate of iodine atoms was 86.3%, CF 3 The selectivity of I was 97.2%, and the selectivity of pentafluoroiodoethane was 2.8%.

[0044] Example 3

[0045] The flow rate of 10.0 ml / h of liquid cyclopentane acid and 15.0 g / h of solid I 2 The mixture was sent to the evaporator, evaporated into gas and mixed with CF at a flow rate of 67.0 sccm. 3 COCl mixture, and 45 ml of Mg(NO 3 ) 2 / The fixed bed reactor with activated carbon catalyst has a reaction temperature of 350°C and a contact time of 30 seconds between the reactant stream and the catalyst. The gas after the reaction is deiodinated, deacidified and dried before being tested 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 balance of materials entering and leaving the reactor.

[0046] Experimental results: The single-pass conversion rate of iodine atoms was 91.5%, CF 3 The selectivity of I was 59.6%, and the selectivity of pentafluoroiodoethane was 40.4%.

[0047] Example 4

[0048] The flow rate of liquid pentafluoropropionic acid was 10.0 ml / h and the solid I was 15.0 g / h. 2 The mixture was sent to the evaporator, evaporated into gas and mixed with CF at a flow rate of 67.0 sccm. 3 COF mixture, and 45 ml of FeCl 2 In a fixed bed reactor with SiC catalyst, the reaction temperature is 400°C, the contact time between the reactant flow and the catalyst is 90s, the gas after the reaction is deiodinated, deacidified and dried before being 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 balance of materials entering and leaving the reactor.

[0049] Experimental results: The single-pass conversion rate of iodine atoms was 88.6%, CF 3 The selectivity of I was 63.2%, and the selectivity of pentafluoroiodoethane was 36.8%.

[0050] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 trifluoroiodomethane by decarboxylation and decarbonylation iodination, characterized in that: The method is obtained by reacting carboxylic acid, trifluoroacetyl halide and iodine in a catalyst, oxygen or in the absence of oxygen in a gas phase; wherein, The catalyst is at least one of an alkali metal salt or a transition metal salt; The general structural formula of the trifluoroacetyl halide is CF3COX, where X=F, Cl, Br, I; The carboxylic acid has a general structural formula of RCOOH and is at least selected from trifluoroacetic acid and pentafluoropropionic acid; Furthermore, the molar ratio of the carboxylic acid, trifluoroacetyl halide and iodine is: 1: (0.5-10): (0.2-2); The alkali metal salt is a lithium salt, a sodium salt, a potassium salt, a rubidium salt or a cesium salt, and the transition metal salt is an iron salt; The gas phase reaction conditions are: reaction pressure of 0.05-0.5 MPa, reaction temperature of 200°C-600°C; The catalyst is supported on a carrier; and the weight ratio of the catalyst to the carrier is 0.05 to 0.35:1; The carrier is at least one of chromium-based perovskite and chromium-based spinel; wherein, The chromium-based perovskite has a chemical formula of La 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 A compound in which z is 0 to 4 and B is a metal atom Zn.

2. The method for synthesizing trifluoroiodomethane by decarboxylation and decarbonylation iodination according to claim 1, characterized in that: The gas phase reaction temperature is 300° C. to 550° C., and the catalytic reaction contact time is 0.1 to 120 seconds.

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