WO2020057013A1 - Photooxidation preparation method for halo acetyl chloride - Google Patents

Abstract

Disclosed by the present invention is a photooxidation preparation method for halo acetyl chloride. A haloalkane and an oxygen source are mixed and then vaporized for photooxidation in a reactor to obtain halo acetyl chloride. The photooxidation reaction temperature is 5 to 60℃, the stay time of the material is 1 to 50s, and the molar ratio of the oxygen source to the haloalkane is 0.1 to 5:1. A quartz cold trap comprising a quartz inner shell and a quartz outer shell is arranged in the reactor, a light source is arranged inside the quartz inner shell, and a double-layer cold trap jacket is formed between the quartz inner shell and the quartz outer shell. The double-layer cold trap jacket is filled with circularly flowing filter liquor which filters out ultraviolet light generated by the light source with a wavelength band of less than 300 nm. The present invention has the advantages of simple processing, high yield, safety, environmental friendliness and continuable operation.

Description

Photo-oxidation preparation method of haloacetyl chloride Technical field

The invention relates to the field of chemical synthesis, in particular to a photooxidation preparation method of haloacetyl chloride.

Background technique

Difluoroacetyl chloride has a wide range of applications as pharmaceuticals, pesticide intermediates, reaction reagents, and especially as reagents for introducing difluoromethyl or difluoroacetyl groups into organic compounds, and its preparation methods have received increasing attention. Chinese Patent Publication No. CN102822134A reports that difluoroacetyl chloride is obtained by contacting 1-alkoxy-1,1,2,2-tetrafluoroethane as a raw material at a reaction temperature of 100 to 400 ° C to obtain difluoroacetyl chloride. The reaction temperature is high and the starting materials are not readily available. U.S. Patent No. 5,905,169 reports that 1,1-dichloro-2,2-difluoroethane (HCFC-132a) and oxygen are used as raw materials at 200 ° C and 3.10 MPa to obtain a selectivity of 15% difluoroacetyl chloride. 15 The product of% difluoroacetyl fluoride, 24% difluoroacetic acid, 13% CF ₂ HCCl ₃ and 6% phosgene, but the conversion rate of HCFC-132a is only 46%, the selectivity of difluoroacetyl chloride is low, and the reaction conditions are harsh.

The acid chloride group in monochlorodifluoroacetyl chloride is very active and can react with water, amines and alcohols to form acids, amides and lipids, respectively. It is a very important chemical intermediate, especially in Pesticide and pharmaceutical fields have a wide range of applications, and their preparation methods have also received more and more attention. Chinese Patent Publication No. CN103351292A reports that 1,1,2-trichloro-2,2-difluoroethane (HCFC-122), oxygen, and chlorine gas are heated into a reactor at 90-200 ° C for photochemical reaction. The disadvantage of the method of chlorodifluoroacetyl chloride is that 1,1,1,2,2-tetrachloro-2,2-difluoroethane is easily produced by passing chlorine gas, and it is easily decomposed by directly irradiating with a high-pressure mercury lamp. Fluoride ions corrode the glass and affect the continuous operation of the reaction. Chinese Patent Publication No. CN103524325A reports a method for converting 1,1-difluorotetrachloroethane to monochlorodifluoroacetyl chloride under the action of oxidant sulfur trioxide and catalyst chlorosulfonic acid. The disadvantage is the problem of by-products of a large amount of three liquid waste And more by-product sulfuryl chloride. U.S. Patent No. 5,545,298 reports a method for obtaining chlorodifluoroacetyl chloride by the reaction of HCFC-122 with oxygen at a high pressure mercury lamp at 100 ° C, but at the same time by-produces COCl ₂ , CO ₂ and COF ₂ as minor components.

Trifluoroacetyl chloride is also an important typical intermediate in organic chemical synthesis, and is widely used in the synthesis of fluorinated pesticides, medicines, organic intermediates and fine chemical products. Due to the electron-withdrawing effect of the CF ₃ group, compared to the non-fluorinated counterpart acetyl chloride (CH ₃ COCl), the reactivity of the carbonyl group to the nucleophile is enhanced, while the basicity of the carbonyl oxygen atom is weakened. Trifluoroacetyl chloride is mainly used to synthesize trifluoroacetic acid, trifluoroethanol or other derivatives, and is an important raw material for the synthesis of pesticides and medicines. The preparation method mainly uses 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and oxygen as raw materials to prepare trifluoroacetyl chloride through an oxidation reaction, which can be divided into the following three process routes :

(1) Gas-phase catalytic oxidation method: HCFC-123 and oxygen are passed into a reactor equipped with a catalyst for oxidation. The catalyst is selected from activated carbon or a metal-supported catalyst, and the reaction temperature is 250 to 325 ° C at normal pressure. <75%), the disadvantage is that there are many kinds of decomposition products and the catalyst life is short.

(2) Liquid-phase oxidation method: Japanese patent JP198241717 reports that HCFC-123 and oxygen are passed into a reaction kettle at a temperature of 250 to 300 ° C and a pressure of up to 30 kg / cm ^2. The conversion rate of HCFC-123 is greater than 90%. The total selectivity of acyl chloride + trifluoroacetic acid is more than 90%, but the reaction conditions are harsh, the equipment is very high, and it is difficult to achieve industrialization.

(3) Photooxidation method: Chinese Patent Publication No. CN101735034A reports that oxygen and chlorine gas are passed into a stirred reactor filled with HCFC-123 liquid under light conditions to perform a liquid phase reaction to obtain trifluoroacetyl chloride, requiring a gas-liquid interface The following has a light shielding member to prevent the generated trifluoroacetyl chloride from being decomposed by mercury lamp radiation in the gas phase space, but the mercury lamp radiates to the liquid phase will still cause the trifluoroacetyl chloride to decompose and corrode the glass, and the introduction of chlorine gas will make the reaction unsafe At the same time, it brings by-products such as trifluorotrichloroethane and reduces the utilization rate of raw materials.

Summary of the Invention

The invention aims at the shortcomings of the prior art, and provides a photooxidation preparation method of halogenated acetyl chloride with simple process, high yield, safety and environmental protection, and continuous operation.

In order to achieve the above objective, the technical scheme adopted by the present invention is: a photooxidation preparation method of halogenated acetyl chloride, which is obtained by mixing and vaporizing a halogenated alkane and an oxygen source and passing it into a reactor for photooxidation to obtain the halogenated acetyl chloride. The temperature of the photo-oxidation reaction is 5 to 70 ° C, the residence time of the material is 1 to 50 s, and the molar ratio of the oxygen source to the halogenated alkane is 0.1 to 5: 1. The reactor is provided with a quartz cold trap, and the quartz cold trap It consists of a quartz inner shell and a quartz outer shell. A light source is arranged inside the quartz inner shell. A double-layer cold trap jacket is formed between the quartz inner shell and the quartz shell. The double-layer cold trap jacket is filled with circulating flow. Filter liquid, which filters out ultraviolet light in the wavelength band less than 300 nm generated by the light source.

The molecular structure of the halogenated alkane in the present invention is CF ₂ XCHCl ₂ (where X is H or F or Cl). The halogenated alkane is preferably CF ₂ HCHCl ₂ (HCFC-132a), CF ₂ ClCHCl ₂ (HCFC- 122), one of CF ₃ CHCl ₂ (HCFC-123).

The oxygen source is preferably molecular oxygen or ozone molecules.

The temperature of the photo-oxidation reaction is preferably 25-60 ° C.

The material residence time is preferably 3 to 10 s.

The molar ratio of the oxygen source to the halogenated alkane is preferably 1.2 to 3.0: 1.

The filter is preferably a copper sulfate solution or a calcium chloride solution or a mixture thereof.

The concentration of the copper sulfate solution is preferably 2.0 to 100.0 g / L, and the concentration of the calcium chloride solution is preferably 1.0 to 80.0 g / L.

The flow rate of the circulating filter is preferably 5 to 25 L / min.

The reactor described in the present invention is provided with a double-layered quartz cold trap. The quartz cold trap is composed of a quartz inner shell and a quartz outer shell. A light source is provided inside the quartz inner shell. A double-layer cold trap jacket is formed between the two layers. The double-layer cold trap jacket is filled with a circulating filtering liquid, and the filtering liquid absorbs and filters out the ultraviolet light generated by the light source in a wavelength band less than 300 nm, which effectively avoids CF rupture generates fluoride ion to corrode glass and acid chloride photolysis, improving raw material utilization. The filter liquid is continuously circulated by the external constant temperature circulation device, and also plays a role of removing the heat generated by the light source and the reaction heat. In the present invention, the light source is not limited. Generally, a conventional high-pressure mercury lamp, a medium-pressure mercury lamp, a metal halide lamp, or the like can be selected. As long as the wavelength of most of the photons emitted is concentrated in the range of 300-450 nm, it is applicable to the present invention. The power of the light source can be adjusted according to the feed flow rate of the raw materials.

In the present invention, a halogenated alkane having a molecular structure general formula of CF ₂ XCHCl ₂ (where X is H or F or Cl) is mixed with an oxygen source and vaporized, and then passed into a reactor equipped with a built-in cold trap light source, which is excited by light emitted from the light source. The oxidation reaction yields a product of hydrogen chloride and structural formula CF ₂ XCOCl (where X is H or F or Cl). The reactions involved in the present invention are as follows:

CF ₂ HCHCl ₂ + 1 / 2O ₂ → CF ₂ HCOCl + HCl

CF ₂ ClCHCl ₂ + 1 / 2O ₂ → CF ₂ ClCOCl + HCl

CF ₃ CHCl ₂ + 1 / 2O ₂ → CF ₃ COCl + HCl

CF ₂ HCHCl ₂ + 1 / 3O ₃ → CF ₂ HCOCl + HCl

CF ₂ ClCHCl ₂ + 1 / 3O ₃ → CF ₂ ClCOCl + HCl

CF ₃ CHCl ₂ + 1 / 3O ₃ → CF ₃ COCl + HCl

Compared with the prior art, the present invention has the following advantages:

1. The process is simple, the reaction conditions are mild, no catalyst is used, and continuous preparation is achieved;

2. The reaction efficiency is high. The present invention filters out ultraviolet light in a wavelength band less than 300 nm through a filtering solution, effectively avoids acid chloride photolysis, improves raw material utilization rate, the conversion rate of haloalkanes is above 96.6%, and the selectivity of the target product is high. Above 99.5%;

3. Safety and environmental protection. The present invention filters the ultraviolet light generated by the light source with a wavelength less than 300 nm through a filter liquid to prevent fluorine ions from dissociating the halogenated alkanes from corroding the glass, and also removes the heat generated by the light source and the reaction heat. The reaction continued to run for one month without significant corrosion of the reactor and its components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a reactor according to the present invention.

As shown in the figure: 1 is a mixer, 2 is a reactor, 3 is a quartz cold trap, 4 is a light source, and 5, 6, 7, and 8 are pipelines.

detailed description

The process of the present invention is shown in FIG. 1. The halogenated alkane feedstock and the oxygen source are passed into the mixer 1 for mixing and vaporization, and then enter the reactor 2 through the pipeline 5 for reaction. The reactor outlet pipeline 6 obtains products containing CF ₂ XCOCl and HCl. The filter liquid is driven into the quartz cold trap 3 through a pipeline 7 to filter out ultraviolet light of a wavelength less than 300 nm emitted by the lamp source 4 while taking away the reaction heat, and finally entering the external constant temperature circulation device through a pipeline 8.

The present invention is further described in detail through the following examples, but the present invention is not limited to the examples.

Example 1

In a quartz cold trap, a copper sulfate solution having a concentration of 35.0 g / L was continuously circulated at a flow rate of 11 L / min as a filter liquid, and ultraviolet light with a wavelength less than 300 nm was filtered. Oxygen and HCFC-123 are driven into the mixer at a molar ratio of 1.5: 1, mixed and vaporized, and then passed to the reactor for photooxidation. The reaction temperature is 40 ° C, the residence time is 3s, and the power of the metal halide lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The outlet of the reactor was sampled and analyzed. The conversion rate of HCFC-123 was 97.1%, and the selectivity of trifluoroacetyl chloride was 99.6%.

Example 2

In a quartz cold trap, a copper sulfate solution having a concentration of 20.0 g / L was continuously circulated as a filter liquid at a flow rate of 10 L / min, and ultraviolet light with a wavelength less than 300 nm was filtered. Ozone and HCFC-123 are driven into the mixer at a molar ratio of 1.5: 1, mixed and vaporized, and then passed to the reactor for photooxidation. The reaction temperature is 30 ° C, the residence time is 3s, and the power of the high-pressure mercury lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The reactor outlet was sampled and analyzed. The conversion of HCFC-123 was 98.3%, and the selectivity of trifluoroacetyl chloride was 99.9%.

Example 3

In a quartz cold trap, a copper sulfate solution with a concentration of 50.0 g / L was continuously circulated at a flow rate of 22 L / min as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Oxygen and HCFC-132a are driven into the mixer at a molar ratio of 2.5: 1, mixed and vaporized, and then passed to the reactor for photooxidation. The reaction temperature is 50 ° C, the residence time is 6s, and the power of the medium pressure mercury lamp is 500W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The outlet of the reactor was sampled and analyzed. The conversion of HCFC-132a was 96.6%, and the selectivity of difluoroacetyl chloride was 99.5%.

Example 4

Calcium chloride solution having a concentration of 20.0 g / L was continuously circulated into the quartz cold trap at a flow rate of 25 L / min as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Ozone and HCFC-132a are driven into the mixer at a molar ratio of 2.0: 1, mixed and vaporized, and then passed into the reactor for photooxidation. The reaction temperature is 60 ° C, the residence time is 4s, and the power of the metal halide lamp is 800W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The outlet of the reactor was sampled and analyzed. The conversion of HCFC-132a was 97.5%, and the selectivity of difluoroacetyl chloride was 99.8%.

Example 5

A quartz cold trap was continuously circulated at a flow rate of 15 L / min, and a mixed solution of calcium chloride with a concentration of 2.5 g / L and copper sulfate with a concentration of 15.0 g / L was used as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Ozone and HCFC-122 are driven into the mixer at a molar ratio of 3.0: 1, mixed and vaporized, and then passed into the reactor for photooxidation. The reaction temperature is 35 ° C, the residence time is 5s, and the power of the high-pressure mercury lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The reactor outlet was sampled and analyzed. The conversion of HCFC-122 was 97.5%, and the selectivity of monochlorodifluoroacetyl chloride was 99.9%.

Example 6

A quartz cold trap was continuously circulated at a flow rate of 20 L / min, and a mixed solution of calcium chloride with a concentration of 12.0 g / L and copper sulfate with a concentration of 8.0 g / L was used as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Oxygen and HCFC-122 are driven into the mixer at a molar ratio of 1.2: 1, mixed and vaporized, and then passed to the reactor for photooxidation. The reaction temperature is 45 ° C, the residence time is 5s, and the power of the metal halide lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The reactor outlet was sampled and analyzed. The conversion rate of HCFC-122 was 96.6%, and the selectivity of monochlorodifluoroacetyl chloride was 99.9%.

Example 7

Calcium chloride solution having a concentration of 10.0 g / L was continuously circulated into the quartz cold trap at a flow rate of 8 L / min as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Oxygen and HCFC-122 are driven into the mixer at a molar ratio of 1.5: 1 and mixed. After vaporization, they are passed into the reactor for photo-oxidation. The reaction temperature is 25 ° C, the residence time is 10s, and the power of the metal halide lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The outlet of the reactor was sampled and analyzed. The conversion of HCFC-122 was 97.6%, and the selectivity of monochlorodifluoroacetyl chloride was 99.6%.

Example 8

Calcium chloride solution having a concentration of 60.0 g / L was continuously circulated into the quartz cold trap at a flow rate of 20 L / min as a filter liquid to filter out ultraviolet light with a wavelength less than 300 nm. Oxygen and HCFC-122 are driven into the mixer at a molar ratio of 2: 1, mixed and vaporized, and then passed to the reactor for photooxidation. The reaction temperature is 45 ° C, the residence time is 5s, and the power of the metal halide lamp is 700W. The reaction continued to run for one month without significant corrosion of the reactor and its components. The reactor outlet was sampled and analyzed. The conversion of HCFC-122 was 96.9%, and the selectivity of monochlorodifluoroacetyl chloride was 99.7%.

Claims (9)

A photooxidation preparation method of halogenated acetyl chloride, which is obtained by mixing and vaporizing a halogenated alkane with an oxygen source, and then passing it into a reactor for photooxidation to obtain a halogenated acetyl chloride. The temperature of the photooxidation reaction is 5 to 70 ° C. The time is 1 to 50 seconds, and the molar ratio of the oxygen source to the halogenated alkane is 0.1 to 5: 1. It is characterized in that the reactor is provided with a quartz cold trap, which is composed of a quartz inner shell and a quartz outer shell. A light source is arranged inside the quartz inner shell, and a double-layer cold trap jacket is formed between the quartz inner shell and the quartz shell, and the double-layer cold trap jacket is filled with a circulating filter liquid, and the filter liquid The ultraviolet light generated by the light source in a wavelength band of less than 300 nm is filtered out. The production method of claim 1 photooxidation haloacetyl chloride claim, wherein said halogenated alkane as a _{CF 2 HCHCl 2, CF 2 ClCHCl} 2, CF 3 CHCl 2 in. The method according to claim 1, wherein the oxygen source is molecular oxygen or ozone molecules. The method for preparing a photo-oxidation of haloacetyl chloride according to claim 1, wherein the temperature of the photo-oxidation reaction is 25-60 ° C. The photooxidation preparation method of haloacetyl chloride according to claim 1, characterized in that the residence time of the material is 3 to 10 s. The method according to claim 1, wherein a molar ratio of the oxygen source to the halogenated alkane is 1.2 to 3.0: 1. The method according to claim 4, wherein the filter liquid is a copper sulfate solution or a calcium chloride solution or a mixture thereof. The method according to claim 8, wherein the concentration of the copper sulfate solution is 2.0 to 100.0 g / L, and the concentration of the calcium chloride solution is 1.0 to 80.0 g / L. The method for preparing a photo-oxidation of haloacetyl chloride according to claim 1, wherein a flow rate of the circulating filtering solution is 5 to 25 L / min.

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