Method for preparing trifluoromethane by refining chlorofluorinated methane

Abstract

The invention belongs to the field of chemical engineering, and particularly relates to a method for preparing trifluoromethane by refining chlorofluorinated methane. The method comprises the following steps: 1) carrying out contact catalytic dechlorination on crude product gas through an iron-copper catalytic system to obtain mixed gas; 2) drying the mixed gas, and performing contact catalytic reaction through a TO-MOH composite catalyst to obtain a trichloromethane product; wherein the crude product gas in the step 1) contains any one or more of CClF3, CCl2F2, CCl3F, CHClF2, CHCl2F and CH2ClF, and the crude product gas is preheated to 105 to 120 DEG C in a controlled manner. Through cooperation of two specific catalytic processes, dechlorination and fluorination can be sequentially and efficiently achieved, directional conversion from chlorofluorinated methane to trifluoromethane is effectively achieved, and by-products generated in preparation of tetrafluoromethane through chlorine catalysis are quite effectively converted and utilized.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and in particular relates to a method for refining chlorofluoromethane to prepare trifluoromethane. Background Technology

[0002] Trifluoromethane, also known as fluoroform, is an important plasma etchant used in the semiconductor industry for etching silicon dioxide and silicon nitride. Typically, trifluoromethane is prepared through the fluorination of methane. However, the fluorination reaction of methane is complex and has low controllability. Although it is not difficult to achieve and can be carried out efficiently with common chlorine catalysis or other inorganic catalysts, the reaction products usually include monofluoromethane (CH3F, methyl fluoride), difluoromethane (CH2F2, HFC-32), trifluoromethane (CHF3, fluoroform), and tetrafluoromethane (CF4, perfluoromethane). All these fluorides are valuable products, but they also act as impurities for each other. Typically, when tetrafluoromethane is used as the main target product in production, the chlorine catalytic system still contains large amounts of monofluoro, difluoro, and trifluorochlorofluoromethanes. These compounds are almost entirely mixtures of impurities, which usually cannot be used directly and effectively. Furthermore, their composition is complex, and separation is costly and difficult. As a result, most companies use specific processes to separate some easily separable and purified byproducts and then treat them as exhaust gas for further processing, resulting in a large amount of material waste. Summary of the Invention

[0003] To address the problems of numerous and varied byproducts in existing chlorine catalytic systems, the lack of effective conversion processes for these byproducts, and the waste caused by the large amount of waste requiring post-processing, this invention provides a method for refining chlorofluoromethane to prepare trifluoromethane.

[0004] The main objectives of this invention are: 1. to achieve effective conversion and utilization of byproducts from the chlorine-catalyzed preparation of tetrafluoromethane; 2. to provide a simple and efficient processing method; and 3. to ensure that the refined trifluoromethane has high purity.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for refining chlorofluoromethane to prepare trifluoromethane, the method comprising: 1) subjecting crude gas to contact catalytic dechlorination through an iron-copper catalytic system to obtain a mixed gas; 2) subjecting the mixed gas to drying and then subjecting it to contact catalytic reaction through a TO-MOH composite catalyst to obtain trichloromethane product; wherein: in step 1), the crude gas contains any one or more of CClF3, CCl2F2, CCl3F, CHClF2, CHCl2F, and CH2ClF, and the crude gas is preheated to 105-120 °C.

[0007] Preferably, the iron-copper catalytic system in step 1) is catalyzed by a porous multi-component composite catalyst; the porous multi-component composite catalyst is obtained by mixing iron-copper multi-component composite powder with iron hydroxide powder, adding a pore-forming agent, and kneading to form pores.

[0008] Preferably, the iron-copper multi-component composite powder and iron hydroxide powder are mixed in a mass ratio of 1:(0.5-0.8), and then 3-5 wt% of a pore-forming agent is added to the mixture. After ball milling and mixing in a protective atmosphere, the mixture is subjected to low-temperature heat treatment to form pores and obtain a porous multi-component composite catalyst.

[0009] Preferably, the iron-copper multi-component composite powder is made by mixing iron oxide powder and metallic copper powder in a molar ratio of 1:(5-5.5), and then heat-treating it at high temperature in a protective atmosphere to obtain a block material. After crushing, the block material is placed in saturated ammonia water and ultrasonically treated until it is pulverized. Then, excess ethanol is added until the precipitate no longer increases. The precipitate is then filtered out and heat-treated in a protective atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder.

[0010] Preferably, the drying process in step 2) includes condensation treatment or desiccant treatment.

[0011] Preferably, the TO-MOH composite catalyst is a TiO2-MnO(OH)2 porous composite material.

[0012] Preferably, the TiO2-MnO(OH)2 porous composite material is prepared by the following method: titanium source and manganese hydroxide powder are mixed at a mass ratio of 1:(0.10~0.20), then a pore-forming agent is added and the mixture is ball-milled at low temperature. After ball milling, the mixture is subjected to low-temperature heat treatment to form pores and obtain a porous precursor material. The porous precursor material is then aged to obtain the TiO2-MnO(OH)2 porous composite material.

[0013] Preferably, the low-temperature heat treatment is carried out at ≤120 ℃; the aging treatment is carried out at an oxygen content ≥20% VOL until the color turns brownish-black.

[0014] Preferably, the contact catalytic reaction in step 2) is carried out under photothermal conditions, with the reaction temperature controlled at 120–280 °C, the light wavelength at 450–490 nm, and the photonic quantum density at 3.8–4.0 μmol / (m²). 2 ·s).

[0015] In this invention, a previously developed and patented TO-MOH catalyst-oriented catalysis technology is employed. In the dechlorination catalytic treatment of step 1), the iron-based ternary catalyst system of this invention is a porous Fe-Cu-Cu₂O-CuO-FeOOH multi-element composite catalyst. It is a ternary-like catalytic material specifically designed for the dechlorination and reduction of chlorofluoromethane, developed through further research and development of existing ternary catalyst systems and iron-copper alloy catalytic systems. By utilizing the ternary catalytic system to construct the specific iron-based ternary catalyst system of this invention, it improves the catalytic dechlorination effect and actual working efficiency of chlorofluoromethane in a gas-phase environment, thereby enhancing the overall refining process efficiency.

[0016] In conventional iron-copper alloy catalytic systems, it can effectively treat chlorofluoromethane in the aqueous phase. The specific reaction process includes the following sub-processes: In the formula: a+b+c=4, and b≥1.

[0017] After the above process, the iron in the actual iron-copper alloy catalytic system is gradually converted into ferrous hydroxide and / or ferrous chloride. However, the above catalytic process needs to be carried out in an aqueous system, which raises the issue that it is not suitable for the crude gas obtained from the chlorine-catalyzed preparation of carbon tetrafluoride. Tetrafluoromethane is easily decomposed in an aqueous system under the above catalytic conditions to produce impurities such as hydrogen fluoride, resulting in a significant decrease in the yield of carbon tetrafluoride. In particular, the above reaction process is not very efficient, and there is even a possibility that carbon tetrafluoride may be completely decomposed under prolonged contact catalytic reaction.

[0018] In the previously constructed Fe-Cu-FeOOH catalytic system, the gas-phase catalysis problem was solved, achieving catalysis of the gas-phase reaction system. This is because industrial ferric hydroxide contains a certain amount of amorphous components, such as the two currently recognized crystalline variants, goethite α-FeO(OH) and ferrihydrite γ-FeO(OH), which contain a variable amount of water. Therefore, ferric hydroxide, as a hydroxide, possesses the inertness to react with carbon tetrafluoride, while simultaneously possessing the ability to provide synergistic catalysis for chlorofluoromethane in the aforementioned reaction process.

[0019] Therefore, specifically, under the action of the iron-copper composite catalytic material of the present invention, the following overall reaction process will occur: In the formula: a+b+c=4, and b≥1.

[0020] However, this process actually requires a long contact time of 30-40 minutes for catalytic dechlorination. In actual industrial production, the inconsistency in efficiency before and after dechlorination leads to low actual output and even directly affects the production and operation process. Therefore, this invention integrates the advantages of existing ternary catalytic systems, using a Fe-Cu-Cu2O-CuO quasi-ternary system constructed with Fe, Cu2O, and CuO as the main components. Cuprous oxide and copper oxide promote the reduction of chlorofluoromethane by iron to achieve dechlorination efficiency. This process is similar to the process of copper ternary system catalyzing silicon and chloromethane. Copper and copper oxide have oxidizing and reducing properties, respectively. One catalyzes and initiates the reaction, while the other consumes reaction byproducts to inhibit some byproduct reactions and promote the forward reaction. A similar mechanism exists in this invention. Cuprous oxide has both oxidizing and reducing properties. In the process of this invention, it cannot achieve both catalytic and promoting effects, but it has a significant effect on consuming excess oxygen and chlorine, and promotes the construction of high specific surface area iron-copper multi-component composite powder. In the specific preparation process of iron-copper multi-component composite powder, this invention uses a redox method, with copper as a reducing agent to reduce iron oxide. Firstly, the Cu(I) / Cu(II) oxides are fully combined with Fe(O). Then, through dissolution and re-precipitation, copper-ammonia complexation is used to achieve copper-iron encapsulation. Finally, in the heat treatment, ammonia and water are removed to obtain the desired product. Figure 1 The catalyst morphology shown and its TEM characterization results indicate that it has a structure with elemental iron as the main component as the core layer and Cu(I) / Cu(II) oxide active quantum dots on the surface. It also has good bonding stability and can maintain effective coordination in the subsequent ball milling granulation process, achieving effective coordination between iron and the two copper oxides.

[0021] The resulting iron-copper multi-component composite powder, together with industrial iron hydroxide, forms a porous Fe-Cu-Cu2O-CuO-FeOOH multi-component composite catalyst, which can reduce the contact reaction time in step 1) by more than half, and can effectively achieve catalytic dechlorination in only 15 to 20 minutes, greatly improving the efficiency of catalytic dechlorination.

[0022] After achieving efficient dechlorination, this invention further incorporates a self-developed TO-MOH catalyst for targeted catalysis. Specifically, under photoelectron (hv) excitation, titanium dioxide can be excited to form valence band holes. It can perform single-electron oxidation of methane to form methane in a cationic radical state. (also as (The same applies below), and has the following process: The formed cationic free radical methane The activity of fluorination with electrophilic fluorinating agents, the resulting Cation radicals (a=0, 1, 2, or 3, b=1, 2, 3, or 4, and a+b=4) further undergo deprotonation reactions with water molecules or nitrogen molecules in the environment to form hydrated hydrogen ions (…). ) or protonated dinitrate ( ), with hydrated hydrogen ions ( ) and protonated dinitrogen ( For example, it would look like this: The reaction that forms Free radicals possess extremely strong fluorination activity; they interact with electrophilic fluorinating agents such as common HF and F2, thus enabling fluorination. Fluorination of free radicals is shown below: In the formula, W is composed of common electrophilic fluorinating agent elements such as H or F, that is, WF constitutes electrophilic fluorinating agents such as HF and F2.

[0023] Titanium dioxide photoexcites electrons or complex ions of titanium peroxide complexes Then, with the hydrogen ions produced in the second stage The interaction forms a complex, where the complexed ions' composite product depends on the actual composition; for example, in the technical solution of this invention, it is formed as water, while photoexcited electrons... With hydrogen ions They interact to form hydrogen atoms The hydrogen atoms formed and This further forms the complex HW, completing the reaction cycle.

[0024] However, as mentioned in the aforementioned research, this process has significant limitations. Under the photocatalytic conditions of titanium dioxide alone, the products are mostly mixtures of CF2H2 and CF3H compounds, failing to effectively and precisely convert trifluoromethane. Although extending the reaction contact time can improve the yield of trifluoromethane to some extent, it is still insufficient to achieve a complete trifluoromethane yield. In response, researchers discovered that while titanium dioxide can generate photoexcitation current under photocatalytic conditions, and manganese dioxide possesses the ability to oxidize and dehydrogenate organic matter under the influence of current, this combination alone is insufficient to effectively achieve the directional conversion of trifluoromethane. Instead, it produces a small amount of tetrafluoromethane impurities, indicating poor controllability of its oxidation capacity.

[0025] Further research revealed that Mn(IV) compound MnO(OH)2, existing in a special form, possesses a unique catalytic oxidative dehydrogenation ability for difluoromethane.

[0026] Compared to pure manganese dioxide, MnO(OH)₂ compounds contain valence band vacancies. When forming a specific complex with titanium dioxide, it exhibits catalytic dehydrogenation ability only for difluoromethane. Using electro-excitation to simulate the microcurrent conditions under the light irradiation specified in this invention, a single-current excitation catalytic experiment was conducted on the MnO(OH)2 compound. The experiment showed that its conversion rate exhibited the following relationship:

[0027] It exhibits extremely high catalytic oxidative dehydrogenation activity for difluoromethane, and for trifluoromethane, tetrafluoromethane was basically undetectable, indicating that under the experimental conditions, it has virtually no catalytic oxidative dehydrogenation activity for trifluoromethane.

[0028] By combining the above two steps, the technical solution of the present invention can effectively achieve directional catalytic refining of chlorofluoromethane mixtures and realize the recovery and reuse of chlorofluoromethane.

[0029] The beneficial effects of this invention are as follows: by combining two specific catalytic processes, this invention can achieve dechlorination and fluorination sequentially and efficiently, and effectively realize the directional conversion of chlorofluoromethane to trifluoromethane, and make very effective conversion and utilization of the by-products of chlorine catalytic preparation of tetrafluoromethane. Attached Figure Description

[0030] Figure 1 This is a SEM characterization image of the iron-copper multi-element composite powder prepared according to the present invention. Detailed Implementation Plan

[0031] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or obtainable by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0033] Unless otherwise specified, the TO-MOH catalyst used in this invention is prepared by the following process: titanium dioxide powder and manganese hydroxide powder are mixed at a mass ratio of 1:0.15, and then ammonium bicarbonate is added at 4% of the mass of the mixed powder as a pore-forming agent. The mixture is ball-milled at 20 °C. After ball milling, the mixture is heat-treated at 80 °C to form pores and obtain a porous precursor material. The porous precursor material is then placed in air and aged until the color turns brownish-black and no longer darkens to obtain the TiO2-MnO(OH)2 porous composite material. In this embodiment, the aging time is 48 h.

[0034] Example 1: Preparation of porous multi-component composite catalyst (Fe-Cu-Cu2O-CuO-FeOOH): a) Iron oxide powder and copper powder were mixed at a molar ratio of 1:5.5 and heat-treated at 900 °C for 3 h in a vacuum atmosphere to obtain a block material. The block material was crushed into small blocks with a particle size ≤1 cm. The small blocks were ultrasonically treated in saturated ammonia water for 30 min until they were completely pulverized. Then, 3 times the volume of anhydrous ethanol was added and allowed to stand for 30 min until the precipitate no longer increased. The precipitate was filtered out and heat-treated at 90 °C for 2 h in a nitrogen atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder; b) The iron-copper multi-component composite powder obtained in step a) was mixed with iron hydroxide powder at a mass ratio of 1:0.6. Then, ammonium bicarbonate was added at 4% of the mass of the mixed powder as a pore-forming agent. After mixing, the mixture was ball-milled at 20 °C. After being formed into a block material in a mold, it was heat-treated at 70 °C for 2 h. The porous catalytic material obtained by h was subjected to low-temperature ball milling at ≤60 ℃ and passed through a 60-mesh sieve to obtain a porous multi-component composite catalyst.

[0035] Example 2: Preparation of porous multi-component composite catalyst (Fe-Cu-Cu2O-CuO-FeOOH): a) Iron oxide powder and copper powder were mixed in a molar ratio of 1:5 and heat-treated at 900 °C for 3 h in a vacuum atmosphere to obtain a block material. The block material was crushed into small blocks with a particle size ≤1 cm. The small blocks were ultrasonically treated in saturated ammonia water for 30 min until they were completely pulverized. Then, 3 times the volume of anhydrous ethanol was added and allowed to stand for 30 min until the precipitate no longer increased. The precipitate was filtered out and heat-treated at 90 °C for 2 h in a nitrogen atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder; b) The iron-copper multi-component composite powder obtained in step a) was mixed with iron hydroxide powder in a mass ratio of 1:0.6. Then, ammonium bicarbonate was added as a pore-forming agent at 4% of the mass of the mixed powder. After mixing, the mixture was ball-milled at 20 °C. After being formed into a block material in a mold, it was heat-treated at 70 °C for 2 h. The porous catalytic material obtained by h was subjected to low-temperature ball milling at ≤60 ℃ and passed through a 60-mesh sieve to obtain a porous multi-component composite catalyst.

[0036] Example 3: Preparation of porous multi-component composite catalyst (Fe-Cu-Cu2O-CuO-FeOOH): a) Iron oxide powder and copper powder were mixed in a molar ratio of 1:5 and heat-treated at 900 °C for 3 h in a vacuum atmosphere to obtain a block material. The block material was crushed into small blocks with a particle size ≤1 cm. The small blocks were ultrasonically treated in saturated ammonia water for 30 min until they were completely pulverized. Then, 3 times the volume of anhydrous ethanol was added and allowed to stand for 30 min until the precipitate no longer increased. The precipitate was filtered out and heat-treated at 90 °C for 2 h in a nitrogen atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder; b) The iron-copper multi-component composite powder obtained in step a) was mixed with iron hydroxide powder in a mass ratio of 1:0.8. Then, ammonium bicarbonate was added as a pore-forming agent at 4% of the mass of the mixed powder. After mixing, the mixture was ball-milled at 20 °C. After being formed into a block material in a mold, it was heat-treated at 70 °C for 2 h. The porous catalytic material obtained by h was subjected to low-temperature ball milling at ≤60 ℃ and passed through a 60-mesh sieve to obtain a porous multi-component composite catalyst.

[0037] Comparative Example 1: Preparation of a porous multi-component composite catalyst (Fe-Cu-Cu2O-CuO-FeOOH): a) Iron powder, cuprous oxide, and copper oxide powder were ball-milled in a molar ratio of 4:5:1, then pressed into block material. The block material was crushed into small blocks with a particle size ≤1 cm. The small blocks were ultrasonically treated in saturated ammonia water for 30 min until completely pulverized. Then, 3 times the volume of anhydrous ethanol was added, and the mixture was allowed to stand for 30 min until the precipitate no longer increased. The precipitate was then filtered out and heat-treated at 90 °C for 2 h in a nitrogen atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder; b) The iron-copper multi-component composite powder obtained in step a) was mixed with iron hydroxide powder in a mass ratio of 1:0.6. Then, ammonium bicarbonate was added at 4% of the mass of the mixed powder as a pore-forming agent. After mixing, the mixture was ball-milled at 20 °C. The mixture was then molded into block material in a mold and heat-treated at 70 °C for 2 h to obtain a porous catalyst material. The catalyst was subjected to low-temperature ball milling at ℃ and passed through a 60-mesh sieve to obtain a porous multi-component composite catalyst.

[0038] The iron-copper multi-component composite powders prepared in Example 1 and Comparative Example 1 were characterized by SEM. The characterization results showed that the iron-copper multi-component composite powder prepared in Example 1 had a relatively uniform particle size, while the iron-copper multi-component composite powder prepared in Comparative Example 1 had a significantly non-uniform particle size, ranging from 0.5 to 2 μm. In terms of specific surface area, the specific surface area of ​​the iron-copper multi-component composite powder prepared in Example 1 was approximately 11.2 m2 / g, while that of the iron-copper multi-component composite powder prepared in Comparative Example 1 was approximately 6.9 m2 / g. It can be seen that the preparation effect of simple mixing is obviously poor, and the distribution of copper oxide on the surface is uneven.

[0039] Example 1 of Catalysis Application: A method for refining chlorofluoromethane to prepare trifluoromethane, the method comprising: 1) filling a reaction tube with a porous multi-component composite catalyst, then passing a crude gas preheated to 110 °C through an iron-copper composite catalyst material, controlling the temperature of the iron-copper composite catalyst material to 90 °C and the contact time between the crude gas and the iron-copper composite catalyst material to 15 min, to perform a contact catalytic dechlorination reaction to obtain a mixed gas; the crude gas is obtained from the byproduct of chlorination catalysis to prepare tetrafluoromethane, after separating and collecting tetrafluoromethane, and contains any one or more of CClF3, CCl2F2, CCl3F, CHClF2, CHCl2F, and CH2ClF; 2) filling the reaction tubes of a tubular reactor with a TO-MOH composite catalyst, preheating to a reaction temperature of 200 °C, and symmetrically placing 480 nm semiconductor laser sources above and below the reaction tubes, controlling the semiconductor laser sources at a frequency of 4.0 nm. The reaction tube is irradiated with a photon density of μmol / (m2·s); 3) The mixed gas is condensed to obtain a dry precursor gas, which is mixed with a fluorine-nitrogen mixture as the reaction gas. The molar ratio of the dry precursor gas to fluorine is controlled at 1:2. In the fluorine-nitrogen mixture, fluorine and nitrogen are mixed in a volume ratio of 1:9. The laser irradiation is maintained, and the reaction gas is controlled to pass through a tubular reactor and catalytically fluorinate with the TO-MOH composite catalyst. The flow rate of the reaction gas is controlled to carry out the catalytic fluorination reaction. The flow rate of the reaction gas is 0.3 RV / min (RV is the reaction tube volume), and trifluoromethane reaction product is obtained.

[0040] Specifically, catalytic experiments were conducted on the porous multi-component composite catalysts prepared in Examples 1-3 and Comparative Example 1, and the trifluoromethane content in the feed gas and reaction products was characterized, and the trifluoromethane conversion rate was calculated.

[0041] The yield of trifluoromethane is calculated based on the maximum theoretical conversion amount of the reaction products from the CClF3, CCl2F2, CCl3F, CHClF2, CH2F2, CHCl2F, CH2ClF, CH3F, and CH4 in the feed gas. The unconverted amount is calculated based on the actual remaining CClF3, CCl2F2, CCl3F, CHClF2, CH2F2, CHCl2F, CH2ClF, CH3F, and CH4. The conversion rate is calculated as (maximum theoretical conversion amount - unconverted amount) / maximum theoretical conversion amount × 100%.

[0042] The results of the catalytic test are shown in the table below. The experimental results in the table above clearly show that the technical solution of the present invention can very effectively and efficiently achieve the directional conversion of by-products prepared by chlorine catalysis, and achieve very effective refining treatment.

[0043] Example 2 of Catalysis Application: A method for refining chlorofluoromethane to prepare trifluoromethane, the method comprising: 1) filling a reaction tube with the porous multi-component composite catalyst prepared in Example 1, and then passing crude gas preheated to 110 °C through an iron-copper composite catalyst material, controlling the temperature of the iron-copper composite catalyst material to 90 °C and the contact time between the crude gas and the iron-copper composite catalyst material to 15 min, to carry out a contact catalytic dechlorination reaction to obtain a mixed gas; the crude gas is obtained from the byproduct of chlorination catalysis to prepare tetrafluoromethane, after separating and collecting tetrafluoromethane, and contains any one or more of CClF3, CCl2F2, CCl3F, CHClF2, CHCl2F, and CH2ClF; 2) filling the reaction tube of a tubular reactor with a TO-MOH composite catalyst, preheating to a reaction temperature of 220 °C, and symmetrically setting a 450 nm semiconductor laser source above and below the reaction tube, controlling the semiconductor laser source at 3.8 nm... The reaction tube is irradiated with a photon density of μmol / (m2·s); 3) The mixed gas is condensed to obtain a dry precursor gas, which is mixed with a fluorine-nitrogen mixture as the reaction gas. The molar ratio of the dry precursor gas to fluorine is controlled at 1:2. In the fluorine-nitrogen mixture, fluorine and nitrogen are mixed in a volume ratio of 1:9. The laser irradiation is maintained, and the reaction gas is controlled to pass through a tubular reactor and catalytically fluorinate with the TO-MOH composite catalyst. The flow rate of the reaction gas is controlled to carry out the catalytic fluorination reaction. The flow rate of the reaction gas is 0.3 RV / min (RV is the reaction tube volume), and trifluoromethane reaction product is obtained.

[0044] The trifluoromethane content in the feed gas and reaction products was characterized, and the conversion rate of trifluoromethane was calculated.

[0045] The yield of trifluoromethane is calculated based on the maximum theoretical conversion amount of the reaction products from the CClF3, CCl2F2, CCl3F, CHClF2, CH2F2, CHCl2F, CH2ClF, CH3F, and CH4 in the feed gas. The unconverted amount is calculated based on the actual remaining CClF3, CCl2F2, CCl3F, CHClF2, CH2F2, CHCl2F, CH2ClF, CH3F, and CH4. The conversion rate is calculated as (maximum theoretical conversion amount - unconverted amount) / maximum theoretical conversion amount × 100%.

[0046] Characterization calculations show that the CHF3 content of the reaction product in this embodiment is 93.9%, and the CHF3 conversion rate is 98.8%.

Claims

1. A process for the refining of chlorofluorinated methane to trifluoromethane, characterized in that, The method includes: 1) dechlorinating the crude gas through a copper-iron catalytic system to obtain a mixed gas; 2) after drying, the mixed gas undergoes a contact catalytic reaction with a TO-MOH composite catalyst to obtain chloroform product; wherein: in step 1), the crude gas contains any one or more of CClF3, CCl2F2, CCl3F, CHClF2, CHCl2F, and CH2ClF, and the crude gas is preheated to 105-120℃.

2. A process for the refining of chlorofluorinated methane to trifluoromethane according to claim 1, characterized in that, Step 1) The iron-copper catalytic system is catalyzed by a porous multi-component composite catalyst; the porous multi-component composite catalyst is obtained by mixing iron-copper multi-component composite powder with iron hydroxide powder, adding a pore-forming agent, and kneading to form pores.

3. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 2, characterized in that, The iron-copper multi-component composite powder and iron hydroxide powder are mixed in a mass ratio of 1:(0.5-0.8). After mixing, 3-5 wt% of the total mass of the mixture is added to form a pore-forming agent. The mixture is then ball-milled and kneaded in a protective atmosphere, followed by low-temperature heat treatment to form pores, thus obtaining a porous multi-component composite catalyst.

4. A method for preparing trifluoromethane by refining chlorofluoromethane according to claim 2 or 3, characterized in that, The iron-copper multi-component composite powder is made by mixing iron oxide powder and metallic copper powder in a molar ratio of 1:(5-5.5), and then heat-treating it at high temperature in a protective atmosphere to obtain a block material. After crushing, the block material is placed in saturated ammonia water and ultrasonically treated until it is pulverized. Then, excess ethanol is added until the precipitate no longer increases. The precipitate is then filtered out and heat-treated in a protective atmosphere to remove the water of crystallization, thus obtaining the iron-copper multi-component composite powder.

5. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 1, characterized in that, Step 2) The drying process includes condensation treatment or desiccant treatment.

6. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 1, characterized in that, The TO-MOH composite catalyst is a TiO2-MnO(OH)2 porous composite material.

7. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 6, characterized in that, The TiO2-MnO(OH)2 porous composite material is prepared by the following method: titanium source and manganese hydroxide powder are mixed at a mass ratio of 1: (0.10~0.20), then a pore-forming agent is added and the mixture is ball-milled at low temperature. After ball milling, the mixture is subjected to low-temperature heat treatment to form pores and obtain a porous precursor material. The porous precursor material is then aged to obtain the TiO2-MnO(OH)2 porous composite material.

8. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 7, characterized in that, The low-temperature heat treatment is carried out at ≤120 ℃; the aging treatment is carried out at an oxygen content ≥20% VOL until the color turns brownish-black.

9. The method for preparing trifluoromethane by refining chlorofluoromethane according to claim 1, characterized in that, Step 2) the catalytic reaction is carried out under photo-thermal conditions, the reaction temperature is controlled to be 120-280 ℃, the light wavelength is 450-490 nm, and the light quantum density is 3.8-4.0 μmol / (m 2 ·s).

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