Preparation method of trifluoroiodomethane

Abstract

The invention discloses a preparation method of trifluoroiodomethane, which comprises the following steps: in an organic solvent, under the action of a catalyst, trifluoroacetic acid, elemental iodine and oxygen react to obtain trifluoroiodomethane, and the catalyst is a mixed catalyst of an amide compound and 4-dimethylaminopyridine. The method has the advantages of mild reaction conditions, high iodine atom utilization rate, small three-waste amount, suitability for industrial production and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing trifluoroiodomethane, in particular to a method for preparing trifluoroiodomethane by using trifluoroacetic acid, elemental iodine and oxygen as raw materials under the action of a catalyst. Background Art

[0002] Trifluoroiodomethane, molecular formula CF 3 I, codenamed FIC-1311, Freon1311, R-1311, has excellent environmental protection characteristics: ODP value is 0.0001, GWP value is 1, and atmospheric lifetime is 1.2 days. Trifluoroiodomethane can react with organic metal reagents and is an important fluorine-containing intermediate for introducing fluoromethyl in organic synthesis; trifluoroiodomethane as a fire extinguishing agent has a low fire extinguishing concentration and is mainly used as a substitute for halon fire extinguishing agent. It has the characteristics of high fire extinguishing efficiency and leaving no trace after fire extinguishing; trifluoroiodomethane as a semiconductor etching gas can be used in 3D NAND Flash advanced processes, and the same etching gas CF 4 , C 4 F 6 In comparison, CF 3 I has high selectivity and high aspect ratio; trifluoroiodomethane is also used as an insulation and arc extinguishing gas for electrical equipment, and is used to treat greenhouse gas SF 6 The dielectric strength is about SF 6 It is more than 1.23 times of that of other refrigerants, and will not produce toxic products after breakdown and decomposition. In addition, trifluoroiodomethane is used as a refrigerant to replace traditional Freon refrigerants CFCs, HCFCs, and HFCs. It has the characteristics of being non-flammable, oil-soluble, and having good material compatibility. It has been listed as a main component of the third generation of environmentally friendly refrigerants by the United Nations.

[0003] There are many existing synthesis routes for trifluoroiodomethane, which can be divided into three main types according to the synthesis method: trifluoroacetate thermal decomposition method, gas-solid phase catalytic synthesis method, halogen atom exchange method, etc.

[0004] Trifluoroacetate thermal decomposition method: For example, Paskovich et al. (Journal of Organic Chemistry, 1967, 32 (3): 383-388) reacted potassium trifluoroacetate or sodium trifluoroacetate in N, N-dimethylformamide (DMF) for more than 10 hours, and the yield of trifluoroiodomethane could reach 70% (the utilization rate of iodine atoms was about 35%). Chinese patent (CN108246277A) discloses a highly efficient method for synthesizing trifluoroiodomethane by reacting CF 3 COOH vapor and iodine vapor react to generate trifluoroiodomethane under the action of a catalyst; the catalyst is activated carbon or graphene as a carrier to load 1-10wt% KNO 3 and 2-7wt% RbNO 3The catalyst is used and the reaction temperature is 450-550°C. However, this type of reaction has the following two disadvantages: 1) the reaction temperature is high, there is an initiation period, and it is easy to rush the material; there are risks in industrial scale-up; 2) an equivalent amount of KI is produced, so the maximum utilization rate of iodine atoms in the reaction is only 50%.

[0005] Gas-solid phase catalytic synthesis method: For example, US Patent No. 5892136 uses trifluoromethane as raw material to synthesize trifluoroiodomethane in one step by gas phase method. During the reaction, an alkali metal catalyst with activated carbon as carrier is used. The reaction mechanism is mainly that trifluoromethane forms CF on the catalyst surface. 2 The carbene intermediate is then disproportionated to CF 3 Free radicals, then react with I 2 The reaction generates CF 3 I. This type of reaction has the following disadvantages: 1) The reaction selectivity and conversion rate are low, about 60% and 50% respectively; 2) The use of alkaline catalysts has serious deactivation problems; 3) The reaction temperature is high (550°C).

[0006] Halogen atom exchange method: For example, Naumann et al. (Journal of Fluorine Chemistry, 1994, 67(1):91–93.) first used BrCF 3 Preparation of ZnBrCF from zinc powder 3 , the yield can reach 60%; then in DMF solvent, ZnBrCF 3 The final yield of this step can reach 70% by reacting with iodine chloride to prepare trifluoroiodomethane. This type of reaction has a low yield, a large amount of byproducts and three wastes, and the solid waste is difficult to recycle, which is not suitable for large-scale industrial production.

[0007] The existing methods for preparing trifluoroiodomethane may produce an equivalent amount of iodine salt (with elemental iodine as the iodine source) as a by-product; or have high reaction temperature and easy material impact; or have low reaction selectivity and conversion rate; or have serious catalyst deactivation. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method for preparing trifluoroiodomethane with mild reaction conditions, high iodine utilization rate, small amount of three wastes and suitable for industrial production.

[0009] The present invention is achieved through the following technical solutions:

[0010] In an organic solvent, under the action of a catalyst, trifluoroacetic acid, elemental iodine and oxygen react to obtain trifluoroiodomethane, wherein the catalyst is a mixed catalyst of an amide compound and 4-dimethylaminopyridine.

[0011] The reaction formula of the present invention is as follows:

[0012]

[0013] The organic solvent is an aprotic solvent. Preferably, the organic solvent is selected from at least one of nitrobenzene, chloroform or N,N-dimethylformamide.

[0014] The catalyst of the present invention is a mixed catalyst of an amide compound and 4-dimethylaminopyridine. Under the action of 4-dimethylaminopyridine, the amide compound first reacts with iodine to form an iodinated amide compound; the iodinated amide then reacts with trifluoroacetic acid to form trifluoroacetyl hypoiodous acid, and is converted back into an amide compound, thereby realizing a catalytic cycle. Preferably, the amide compound is selected from at least one of formamide, acetamide or propionamide.

[0015] In the reaction of the present invention, the specific reaction mechanism is: (1) the amide compound reacts with elemental iodine under the action of 4-dimethylaminopyridine (DMAP) to generate iodinated amide compounds; (2) the iodinated amide compounds react with trifluoroacetic acid to generate trifluoroacetyl hypoiodous acid (TFAI) and amide compounds, and the iodinated amide compounds are converted back into amide compounds, thereby realizing a catalytic cycle; (3) trifluoroacetyl hypoiodous acid (TFAI) generates carbon dioxide and trifluoroiodomethane. During the reaction, the 4-dimethylaminopyridine can form a hydrogen bond with the amide compound, thereby increasing the nucleophilic ability of the amide compound and accelerating the generation of the process substance iodinated amide compound; the HI produced by the reaction is oxidized to elemental iodine by oxygen in real time, thereby realizing efficient utilization of iodine. Preferably, the amide compound is selected from at least one of formamide, acetamide or propionamide. Specifically, the chemical formula of the amide compound is RONH 2 , wherein R is methyl, ethyl or propyl. The specific reaction process of the present invention is shown in the following reaction formula:

[0016]

[0017] The molar ratio of the amide compound to 4-dimethylaminopyridine in the catalyst is (1-10):(0.5-5), preferably (5-8):(3-5).

[0018] According to the above-mentioned method for preparing trifluoroiodomethane, the molar ratio of trifluoroacetic acid, elemental iodine and oxygen is (1.0-1.5):1:(0.25-1.0); preferably, the molar ratio of trifluoroacetic acid, elemental iodine and oxygen is (1.1-1.3):1:(0.5-0.8).

[0019] Furthermore, the molar ratio of the catalyst to elemental iodine is (0.015-0.15):1; preferably (0.08-0.13):1.

[0020] The method for preparing trifluoroiodomethane of the present invention has a reaction temperature of 50-120° C. and a reaction time of 2-12 hours; preferably, the reaction temperature is 70-100° C. and the reaction time is 5-8 hours.

[0021] The preparation method of heptafluoroisobutyronitrile of the present invention specifically comprises the following steps:

[0022] A1. Add an organic solvent, trifluoroacetic acid, elemental iodine, oxygen and a catalyst into a reactor and react at a reaction temperature of 70 to 100° C. for 5 to 8 hours;

[0023] A2. Cool the reaction system to 10-35°C and liquefy and collect the generated trifluoroiodomethane product.

[0024] The A2 step further comprises: cooling the reaction system to 10-35° C., opening the gas phase valve on the reactor, and collecting the trifluoroiodomethane mixed gas (including non-condensable gas) with an air bag; then connecting the air bag to a gas condensing device, liquefying and collecting the trifluoroiodomethane liquid, and discharging the non-condensable gas, wherein the non-condensable gas is the by-product trifluoromethane.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses trifluoroacetic acid and elemental iodine as raw materials to prepare trifluoroiodomethane through a one-step reaction without producing an equivalent amount of iodine salt. The process is simple, the utilization rate of iodine atoms in a single-pass reaction is high, the reaction conditions are mild, and it is suitable for industrial production.

[0027] 2. The raw materials, solvents and catalysts used are conventional reagents, which are easily available in the market and are low in price, and the process has cost advantages. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0029] Example 1

[0030] A1. Add or pass nitrobenzene (300 mL), elemental iodine (76.2 g, 0.3 mol), trifluoroacetic acid (37.6 g, 0.33 mol), formamide (0.68 g, 0.015 mol), 4-dimethylaminopyridine (1.1 g, 0.009 mol) and oxygen (4.8 g, 0.15 mol) into a 2 L autoclave equipped with a mechanical stirrer, a temperature control system and a gas phase discharge system. After the addition is complete, heat to 85 ° C and react for 7.0 h;

[0031] A2. After the reaction is completed, the temperature is lowered to 25°C, the gas phase outlet is connected to an air bag, the gas phase valve on the reactor is opened, and the trifluoroiodomethane mixed gas (including non-condensable gas) is collected with an air bag; then the air bag is connected to a gas condensation device to collect trifluoroiodomethane liquid and discharge non-condensable gas.

[0032] A total of 51.7 g of crude trifluoroiodomethane was obtained with a purity of 95.2%, a yield of 83.7% (based on elemental iodine), and an iodine atom utilization rate of 83.7%.

[0033] Example 2

[0034] A1. Add or pass N,N-dimethylformamide (300 mL), elemental iodine (76.2 g, 0.3 mol), trifluoroacetic acid (44.5 g, 0.39 mol), acetamide (1.42 g, 0.024 mol), 4-dimethylaminopyridine (1.83 g, 0.015 mol) and oxygen (7.7 g, 0.24 mol) into a 2 L autoclave equipped with a mechanical stirrer, a temperature control system and a gas phase discharge system. After the addition is complete, heat to 100 ° C and react for 8.0 hours;

[0035] A2. After the reaction is completed, the temperature is lowered to 25°C, the gas phase outlet is connected to an air bag, the gas phase valve on the reactor is opened, and the trifluoroiodomethane mixed gas (including non-condensable gas) is collected with an air bag; then the air bag is connected to a gas condensation device to collect trifluoroiodomethane liquid and discharge non-condensable gas.

[0036] A total of 52.6 g of crude trifluoroiodomethane was obtained with a purity of 95.7%, a yield of 85.6% (based on elemental iodine), and an iodine atom utilization rate of 85.6%.

[0037] Example 3

[0038] A1. Add or pass chloroform (300 mL), elemental iodine (76.2 g, 0.3 mol), trifluoroacetic acid (41.0 g, 0.36 mol), propionamide (1.31 g, 0.018 mol), 4-dimethylaminopyridine (1.46 g, 0.012 mol) and oxygen (5.8 g, 0.18 mol) into a 2 L autoclave equipped with a mechanical stirrer, a temperature control system and a gas phase discharge system. After the addition is complete, heat to 70 ° C and react for 5.0 h;

[0039] A2. After the reaction is completed, the temperature is lowered to 25°C, the gas phase outlet is connected to an air bag, the gas phase valve on the reactor is opened, and the trifluoroiodomethane mixed gas (including non-condensable gas) is collected with an air bag; then the air bag is connected to a gas condensation device to collect trifluoroiodomethane liquid and discharge non-condensable gas.

[0040] A total of 51.4 g of crude trifluoroiodomethane was obtained with a purity of 94.3%, a yield of 82.5% (based on elemental iodine), and an iodine atom utilization rate of 82.5%.

[0041] Comparative Example 1

[0042] A1. Add or pass nitrobenzene (300 mL), elemental iodine (76.2 g, 0.3 mol), trifluoroacetic acid (37.6 g, 0.33 mol), formamide (0.68 g, 0.015 mol) and oxygen (4.8 g, 0.15 mol) into a 2 L autoclave equipped with a mechanical stirrer, a temperature control system and a gas phase discharge system. After the addition, heat to 85 ° C and react for 7.0 h;

[0043] A2. After the reaction is completed, the temperature is lowered to 25°C, the gas phase outlet is connected to an air bag, the gas phase valve on the reactor is opened, and the trifluoroiodomethane mixed gas (including non-condensable gas) is collected with an air bag; then the air bag is connected to a gas condensation device to collect trifluoroiodomethane liquid and discharge non-condensable gas.

[0044] A total of 47.0 g of crude trifluoroiodomethane was obtained with a purity of 93.5%, a yield of 74.7% (based on elemental iodine), and an iodine atom utilization rate of 74.7%.

[0045] Comparative Example 2

[0046] A1. Add or pass nitrobenzene (300 mL), elemental iodine (76.2 g, 0.3 mol), trifluoroacetic acid (37.6 g, 0.33 mol), formamide (0.68 g, 0.015 mol), 4-dimethylaminopyridine (1.1 g, 0.009 mol), and oxygen (4.8 g, 0.15 mol) into a 2 L autoclave equipped with a mechanical stirrer, a temperature control system, and a gas phase discharge system. After the addition is complete, heat to 85 ° C and react for 7.0 h;

[0047] A2. After the reaction is completed, the temperature is lowered to 25°C, the gas phase outlet is connected to an air bag, the gas phase valve on the reactor is opened, and the trifluoroiodomethane mixed gas (including non-condensable gas) is collected with an air bag; then the air bag is connected to a gas condensation device to collect trifluoroiodomethane liquid and discharge non-condensable gas.

[0048] A total of 10.3 g of crude trifluoroiodomethane was obtained with a purity of 92.6%, a yield of 16.2% (based on elemental iodine), and an iodine atom utilization rate of 16.2%.

Claims

1. A method for preparing trifluoroiodomethane, Features: In an organic solvent, under the action of a catalyst, trifluoroacetic acid, elemental iodine and oxygen react to obtain trifluoroiodomethane, wherein the catalyst is a mixed catalyst of an amide compound and 4-dimethylaminopyridine.

2. The method for preparing trifluoroiodomethane according to claim 1, Features: The organic solvent is an aprotic solvent.

3. The method for preparing trifluoroiodomethane according to claim 2, Features: The aprotic solvent is selected from at least one of nitrobenzene, chloroform or N,N-dimethylformamide.

4. The method for preparing trifluoroiodomethane according to claim 1, Features: The amide compound is selected from at least one of formamide, acetamide or propionamide.

5. The method for preparing trifluoroiodomethane according to claim 1, Features: The molar ratio of the amide compound to 4-dimethylaminopyridine in the catalyst is (1-10): (0.5-5).

6. The method for preparing trifluoroiodomethane according to claim 1, Features: The reaction temperature is 50-120° C., and the reaction time is 2-12 hours.

7. The method for preparing trifluoroiodomethane according to claim 1, Features: The molar ratio of trifluoroacetic acid, elemental iodine and oxygen is (1.0-1.5):1:(0.25-1.0).

8. The method for preparing trifluoroiodomethane according to claim 1, Features: The molar ratio of the catalyst to elemental iodine is (0.015-0.15):

1.

9. The method for preparing trifluoroiodomethane according to claim 1, Features: The preparation method comprises the following steps: A1. Add or introduce an organic solvent, trifluoroacetic acid, elemental iodine, oxygen and a catalyst into a reactor and react at a reaction temperature of 70 to 100° C. for 2 to 8 hours; A2. Cool down to 10-35℃, liquefy and collect the generated trifluoroiodomethane product.

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