Purification method of octafluorocyclobutane

Abstract

This invention discloses a method for purifying octafluorocyclobutane, comprising adsorption, oxidation, and distillation of octafluorocyclobutane feed gas. The oxidation process involves further oxidizing the adsorbed feed gas using an oxidation column. The oxidation column includes a support loaded with an oxidant, the support having a porous structure and providing passageways for the feed gas to flow in the direction of flow. This method yields a product with a purity greater than 99.999%, and offers advantages such as high safety, low equipment investment, low energy consumption, low cost, simple operation, and high product purity.

Description

Technical Field

[0001] This invention relates to the fields of fluorochemicals and electronic industrial gases, and in particular to a method for purifying octafluorocyclobutane. Background Technology

[0002] Octafluorocyclobutane is stable, non-toxic, has zero ozone depletion potential (ODP), and possesses excellent insulating properties. In recent years, it has been widely used in high-voltage insulation, cleaning and etching, and plasma treatment technologies. High-purity octafluorocyclobutane (≥5N) is mainly used as an etchant and cleaning agent for large-scale integrated circuits. In integrated circuit etchant applications, even trace amounts of impurities can increase the defect rate in manufacturing high-density integrated circuits. With the trend towards higher performance, smaller size, higher winding density, and finer circuit patterns in electronic or electrical equipment, the purity requirements for octafluorocyclobutane are becoming increasingly stringent in achieving high-precision circuit patterns.

[0003] Currently, the main purification methods for octafluorocyclobutane are distillation and adsorption. Octafluorocyclobutane contains many types of impurities, often including impurities with boiling points close to or azeotropic to octafluorocyclobutane, and isomers, which are difficult to remove through distillation. While commonly used adsorption methods such as molecular sieves, activated carbon, and carbon molecular sieves have very low adsorption capacity for some of the numerous impurities in octafluorocyclobutane, making it difficult to meet purification requirements. Therefore, neither distillation nor adsorption can effectively remove fluorocarbon impurities from octafluorocyclobutane to obtain a product with a purity of 99.999% or higher.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for purifying octafluorocyclobutane, which uses a combination of adsorption-oxidation-distillation to obtain a product with a purity greater than 99.999%. This method has the advantages of high safety, low equipment investment, low energy consumption, low cost, simple process operation, and high product purity.

[0006] To achieve the above objectives, embodiments of the present invention provide a method for purifying octafluorocyclobutane, comprising adsorption, oxidation, and distillation of octafluorocyclobutane feed gas. The oxidation involves further oxidizing the adsorbed feed gas by passing it through an oxidation column. The oxidation column includes a support loaded with an oxidant, the support having a porous structure, and the support having a passageway for the feed gas to flow in the direction of feed gas flow. Here, the flow direction refers to a feasible flow path from an upstream point to a downstream point.

[0007] In one or more embodiments of the present invention, in order to enhance the oxidative activity during the oxidation process and fully utilize the activity and efficiency of oxygen free radicals, the support is also fully activated and pretreated. The pretreatment involves placing 4.5–5 kg of freshly ground graphite powder with a particle size of 1–10 micrometers into a reactor, sequentially adding hydrofluoric acid (2.0%–2.5% by weight of graphite), nitric acid (0.2%–0.32%), and hydrochloric acid (0.20%–0.24%), and then mixing them. After mixing, 5–10 times the volume of pure water is added and the mixture is stirred thoroughly. The reactor temperature is then raised to 86–90°C, and the reaction is carried out for 3–4 hours, with stirring every hour for 4–6 minutes each time. The support is then immersed in the reactor and impregnated under heat and pressure with carbon dioxide to 1–3 MPa for 2–3 hours, followed by drying. Here, the high dissociation of H+ provided by hydrochloric acid… + "In this environment, a suitable "H" environment is provided for the activation of the carrier. + "In addition to an acidic environment, the carrier is activated using graphite micropowder as a medium in appropriate concentrations of hydrofluoric acid and nitric acid in a low-concentration active slurry form. At the same time, the small amount of hydrofluoric acid also slightly corrodes the surface of the carrier, thereby providing more active centers. Meanwhile, the activated and adsorbed graphite microstructures can also become new centers."

[0008] In one or more embodiments of the present invention, the oxidation conditions are: a temperature of 20°C to 60°C and a pressure of 0.05-0.3 MPa.

[0009] In one or more embodiments of the present invention, the oxidant includes potassium permanganate or potassium dichromate.

[0010] In one or more embodiments of the present invention, the oxidant is loaded onto the surface of the porous structure of the carrier.

[0011] In one or more embodiments of the present invention, the adhesion depth of the oxidant on the carrier surface is no greater than 0.8 mm.

[0012] In one or more embodiments of the present invention, the loading amount of oxidant on the carrier surface is obtained by spraying an aqueous oxidant solution. The concentration of the aqueous oxidant solution is 0.0001-0.0005 g / ml. During operation, the volume ratio of the sprayed aqueous oxidant solution to the inlet gas volume is 1:(5-10).

[0013] In one or more embodiments of the present invention, the carrier is zeolite, porous alumina, porous magnesium oxide, or porous ceramic.

[0014] In one or more embodiments of the present invention, the specific surface area of ​​the carrier is 1-5 m². 2 / g. In this scheme, the micropores formed by the traditional porous structure exist to provide active centers, not for the adsorption of oxidants or airflow. One or more active centers may be formed at the edge of the micropores, providing higher activation energy, which can be achieved through the pretreatment process.

[0015] In one or more embodiments of the present invention, the carrier has a mesh shape formed by a woven body.

[0016] In one or more embodiments of the present invention, the braided body is a porous structure with at least micropores on its surface.

[0017] Compared with the prior art, the method according to the embodiments of the present invention uses adsorption to remove most of the components such as water, oxygen, and carbon dioxide;

[0018] The method employs oxidation, which essentially completely removes various fluorocarbon olefin impurities that are difficult to remove from octafluorocyclobutane, greatly reducing the cooling and heating requirements of subsequent distillation, resulting in low energy consumption and good economic efficiency.

[0019] The method involves two-stage distillation to remove low-boiling-point light components and high-boiling-point heavy components, especially fluorocarbon alkane impurities, thereby improving the purity of the product and obtaining octafluorocyclobutane with a purity greater than 99.999%.

[0020] This method employs a combined adsorption-oxidation-distillation process. By selecting highly selective adsorbents, oxidants with suitable oxidation capabilities, and optimal distillation parameters, it removes difficult-to-remove fluorocarbon impurities while significantly reducing the cooling and heating required during purification. The process is simple to operate, yields high output, has a large production capacity, requires minimal equipment investment, has a simple structure, is suitable for industrial production, and achieves a purity of over 99.999%. Attached Figure Description

[0021] Figure 1 This is a flowchart according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a partial morphology of a carrier according to an embodiment of the present invention;

[0023] Figure 3 This is a partially enlarged view of a carrier according to an embodiment of the present invention;

[0024] Figure 4 This is another enlarged view of a carrier according to an embodiment of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0026] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0027] like Figures 1 to 4 The present invention describes a method for purifying octafluorocyclobutane according to a preferred embodiment.

[0028] Example 1

[0029] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 20°C and a pressure of 0.05 MPa. The oxidation column includes a support loaded with the oxidant potassium permanganate, and has a specific surface area of ​​1 m². 2 The support is a porous ceramic carrier with a density of 0.0001 g / ml, and the carrier forms a passage for the feed gas to flow in the direction of feed gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, with the concentration of the oxidant aqueous solution being 0.0001 g / ml, and the volume ratio of the sprayed oxidant aqueous solution to the feed gas intake being 1:5.

[0030] like Figure 2-4 As shown, the carrier 01 has a mesh-like structure formed by a braided body 011 (the formed mesh 010 serves as a flow channel for the raw material gas), and the braided body is a porous structure with micropores on at least its surface. Furthermore, the surface of the braided body may also be distributed with... Figure 3 The small groove structure 012 shown has a depth that defines the adhesion depth of the oxidant, which is 0.5 mm.

[0031] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.999% after purification.

[0032] Example 2

[0033] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 30°C and a pressure of 0.1 MPa. The oxidation column includes a support loaded with the oxidant potassium permanganate, and has a specific surface area of ​​2 m². 2 / g of zeolite, and the carrier forms a passage for the feed gas to flow in the direction of feed gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, the concentration of the oxidant aqueous solution is 0.0002g / ml, and the volume ratio of the spray volume of the oxidant aqueous solution to the feed gas intake volume is 1:6.

[0034] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.999% after purification.

[0035] Example 3

[0036] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 40°C and a pressure of 0.15 MPa. The oxidation column includes a support loaded with the oxidant potassium permanganate, and has a specific surface area of ​​3 m². 2 / g porous alumina, and the carrier forms a passage for the raw gas to flow in the direction of the raw gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, the concentration of the oxidant aqueous solution is 0.0003g / ml, and the volume ratio of the spray volume of the oxidant aqueous solution to the volume of the raw gas is 1:7.

[0037] like Figure 2-4 As shown, the carrier 01 has a mesh-like structure formed by a braided body 011 (the formed mesh 010 serves as a flow channel for the raw material gas), and the braided body is a porous structure with micropores on at least its surface. Furthermore, the surface of the braided body may also be distributed with... Figure 4 The structure shown has alternating small protrusions 014 and gaps 013. The height difference between the small protrusions 014 and gaps 013 limits the adhesion depth of the oxidant, and the height difference between the two is 0.8 mm.

[0038] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.999% after purification.

[0039] Example 4

[0040] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 50°C and a pressure of 0.2 MPa. The oxidation column includes a support loaded with potassium dichromate as an oxidant, and has a specific surface area of ​​4 m². 2 / g porous magnesium oxide, and the carrier forms a passage for the raw gas to flow in the direction of the raw gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, the concentration of the oxidant aqueous solution is 0.0004g / ml, and the volume ratio of the spray volume of the oxidant aqueous solution to the volume of the raw gas is 1:9.

[0041] The carrier is formed by the accumulation of particles with a diameter of 3-5 mm.

[0042] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.999% after purification.

[0043] Example 5

[0044] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 60°C and a pressure of 0.3 MPa. The oxidation column includes a support loaded with potassium dichromate as an oxidant, and has a specific surface area of ​​5 m². 2 The support is a porous ceramic carrier with a flow path for the feed gas in the direction of feed gas flow. The oxidant loading on the support is achieved by spraying an oxidant solution with a concentration of 0.0005 g / ml. The volume ratio of the sprayed oxidant solution to the feed gas inlet is 1:10.

[0045] The carrier is formed by the stacking of 3-5 cm columnar materials.

[0046] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.999% after purification.

[0047] Example 6

[0048] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 20°C and a pressure of 0.05 MPa. The oxidation column includes a support loaded with the oxidant potassium permanganate, and has a specific surface area of ​​1 m². 2 The support is a porous ceramic carrier with a density of 0.0001 g / ml, and the carrier forms a passage for the feed gas to flow in the direction of feed gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, with the concentration of the oxidant aqueous solution being 0.0001 g / ml, and the volume ratio of the sprayed oxidant aqueous solution to the feed gas intake being 1:5.

[0049] like Figure 2-4 As shown, the carrier 01 has a mesh-like structure formed by a braided body 011 (the formed mesh 010 serves as a flow channel for the raw material gas), and the braided body is a porous structure with micropores on at least its surface. Furthermore, the surface of the braided body may also be distributed with... Figure 3 The small groove structure 012 shown has a depth that defines the adhesion depth of the oxidant, which is 0.5 mm, and is pretreated.

[0050] The pretreatment of the carrier can be carried out by taking 4.5 kg of freshly ground graphite powder with a particle size of 10 micrometers and putting it into the reactor. Then, add hydrofluoric acid (2.0% by weight of graphite), nitric acid (0.3%), and hydrochloric acid (0.20%) in sequence. After mixing, add 8 volumes of pure water and stir thoroughly. Then raise the temperature of the reactor to 86°C and react for 4 hours. During the reaction, stir once every 1 hour for 4 minutes each time. Then, immerse the carrier in the reactor and impregnate it with carbon dioxide at a pressure of 3 MPa for 2 hours under heat preservation conditions. Finally, take it out and dry it.

[0051] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.99999% after purification.

[0052] Example 7

[0053] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at a temperature of 30°C and a pressure of 0.1 MPa. The oxidation column includes a support loaded with the oxidant potassium permanganate, and has a specific surface area of ​​2 m². 2 / g of zeolite, and the carrier forms a passage for the feed gas to flow in the direction of feed gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, the concentration of the oxidant aqueous solution is 0.0002g / ml, and the volume ratio of the spray volume of the oxidant aqueous solution to the feed gas intake volume is 1:6.

[0054] The pretreatment of the carrier can be carried out by taking 5 kg of freshly ground graphite powder with a particle size of 1 micrometer and putting it into the reactor. Then, add hydrofluoric acid (2.5% by weight of graphite), nitric acid (0.32%), and hydrochloric acid (0.22%) in sequence. After mixing, add 10 times the volume of pure water and stir thoroughly. Then raise the temperature of the reactor to 88°C and react for 3.4 hours. Stir once every 1 hour during the reaction, and each stirring time is 5 minutes. Then, immerse the carrier in the reactor and impregnate it with carbon dioxide at a pressure of 2 MPa for 3 hours under heat preservation conditions. Finally, take it out and dry it.

[0055] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 consecutive samplings. The average value was taken to obtain a product with a purity of over 99.99996% after purification.

[0056] Example 8

[0057] The purification method for octafluorocyclobutane in this embodiment includes adsorption, oxidation, and distillation of the octafluorocyclobutane feed gas. The oxidation process involves passing the adsorbed feed gas through an oxidation column at 0°C and 0.15 MPa. The oxidation column includes a support loaded with potassium permanganate as an oxidant, and has a specific surface area of ​​3 m². 2 / g porous alumina, and the carrier forms a passage for the raw gas to flow in the direction of the raw gas flow. The oxidant loading on the carrier is achieved by spraying an oxidant solution, the concentration of the oxidant aqueous solution is 0.0003 / ml, and the volume ratio of the spray volume of the oxidant aqueous solution to the volume of the raw gas is 1:7.

[0058] like Figure 2-4 As shown, the carrier 01 has a mesh-like structure formed by a braided body 011 (the formed mesh 010 serves as a flow channel for the raw material gas), and the braided body is a porous structure with micropores on at least its surface. Furthermore, the surface of the braided body may also be distributed with... Figure 4 The structure shown is characterized by alternating small protrusions 014 and gaps 013. The height difference between the small protrusions 014 and gaps 013 defines the adhesion depth of the oxidant. The height difference between the two is 0.8 mm, and the structure has been pretreated.

[0059] The pretreatment of the carrier can be carried out by taking 4.75 kg of freshly ground graphite powder with a particle size of 5 micrometers and putting it into the reactor. Then, add hydrofluoric acid (2.25% by weight of graphite), nitric acid (0.2%), and hydrochloric acid (0.24%) in sequence. After mixing, add 5 times the volume of pure water and stir thoroughly. Then raise the temperature of the reactor to 90°C and react for 3 hours. During the reaction, stir once every 1 hour for 6 minutes each time. Then, immerse the carrier in the reactor and impregnate it under the heat and pressure of carbon dioxide to 1 MPa for 2.5 hours. After that, take it out and dry it.

[0060] The purity of the sample obtained in this embodiment was tested by intermittent sampling of 10 ml, with an interval of 1 hour between each sampling, for a total of 10 samplings. The average value was taken to obtain a product with a purity of over 99.99999% after purification.

[0061] In operation, apart from the oxidation process where this invention is innovative, other corrections can be made using other conventional solutions in the field, and of course, solutions including but not limited to the following can also be used: Figure 1As shown, the crude octafluorocyclobutane (raw gas) enters the adsorption column (the adsorbent is one or more of molecular sieves, activated carbon, silica gel, and alumina) in gaseous form through a heat exchanger at a temperature of 20℃~60℃ and a pressure of 0.05-0.3MPa. Adsorption removes most of the water, oxygen, carbon dioxide, and other components. After gas-phase adsorption, it is directly discharged into the oxidation column (the oxidant is potassium permanganate, and the support is porous alumina) at a temperature of 20℃~60℃ and a pressure of 0.05-0.3MPa. Oxidation removes olefin impurities from the fluorocarbons. The oxidized octafluorocyclobutane gas then enters the distillation column, i.e., the light-duty removal column. Lightweight material removal is carried out in T01, with a bottom temperature of 15℃~50℃ and a pressure of 0.1~0.6MPa. The top temperature is 10~45℃ lower than the bottom temperature, and the pressure is 0.08~0.6MPa. The low-boiling-point substance collected from the top of the column directly enters the low-boiling-point impurity tank, while the bottom material enters the heavy weight removal column T02 for heavy weight removal. The bottom temperature of the heavy weight removal column T02 is 5℃~45℃, and the pressure is 0.08~0.5MPa. The top temperature is 0~40℃ lower than the bottom temperature, and the pressure is 0.05~0.45MPa. The high-boiling-point substance discharged from the bottom of the column directly enters the high-boiling-point impurity tank, and the top of the column is purified by distillation to obtain a product with a purity of over 99.999%.

[0062] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for purifying octafluorocyclobutane, comprising adsorption and distillation of octafluorocyclobutane feed gas, characterized in that, The process also includes oxidizing the feed gas after adsorption. This oxidation involves passing the adsorbed feed gas through an oxidation column. The oxidation column includes a support loaded with an oxidant. The oxidant loading on the support surface is obtained by spraying an aqueous solution. The support has a porous structure and provides pathways for the feed gas to flow in the direction of flow. The support is pretreated. The pretreatment involves placing 4.5–5 kg of freshly ground graphite powder with a particle size of 1–10 micrometers into the reactor, and then adding substances sequentially according to the weight of the graphite... A mixture of 2.0%–2.5% hydrofluoric acid, 0.2%–0.32% nitric acid, and 0.20%–0.24% hydrochloric acid is added, followed by the addition of 5–10 times the volume of pure water and thorough stirring. The reactor temperature is then raised to 86–90°C, and the reaction is carried out for 3–4 hours, with stirring every hour for 4–6 minutes each time. The carrier is then immersed in the reactor and impregnated under carbon dioxide pressure (1–3 MPa) for 2–3 hours under insulated conditions. Afterward, it is removed and dried. The specific surface area of ​​the carrier is 1–5 m². 2 / g, the carrier has a mesh morphology formed by a woven body, the woven body being a porous structure with micropores on at least its surface.

2. The method for purifying octafluorocyclobutane as described in claim 1, characterized in that, The oxidation conditions are: temperature of 20℃~60℃ and pressure of 0.05-0.3 MPa.

3. The method for purifying octafluorocyclobutane as described in claim 1 or 2, characterized in that, The oxidant includes potassium permanganate or potassium dichromate.

4. The purification method for octafluorocyclobutane as described in claim 3, characterized in that, The oxidant is loaded onto the surface of the porous structure of the support.

5. The purification method for octafluorocyclobutane as described in claim 3, characterized in that, The oxidant adheres to a depth of no more than 0.8 mm on the carrier surface.

6. The purification method for octafluorocyclobutane as described in claim 1, characterized in that, The carrier is zeolite, porous alumina, porous magnesium oxide, or porous ceramic.

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