Environmentally friendly tetrachloroethylene and preparation method thereof

Abstract

The invention discloses an environmentally friendly tetrachloroethylene and a preparation method thereof, and relates to the technical field of tetrachloroethylene purification. Modified aluminum oxide is prepared by modification using potassium hydroxide and / or potassium carbonate, and the modified aluminum oxide statically adsorbs tetrachloroethylene to well adsorb impurities in the tetrachloroethylene. After the static adsorption, filtering or vacuum distillation is performed according to the absorbance to complete the purification process. The purification method provided by the invention is easy to operate, and the impurities in the tetrachloroethylene can be better removed by improving the adsorbent, so that the absorbance of the prepared tetrachloroethylene meets the requirements.

Description

Technical Field

[0001] The invention relates to the technical field of tetrachloroethylene purification, and in particular to environmentally friendly tetrachloroethylene and a preparation method thereof. Background Art

[0002] As an ozone-depleting substance, the use of carbon tetrachloride is strictly restricted. It is only used for non-ozone-depleting raw materials and special purposes, and is not suitable as an extraction agent for laboratory testing. With the advancement and implementation of the new national standard HJ 637-2018 "Infrared spectrophotometric method for the determination of petroleum and animal and vegetable oils in water quality", environmentally friendly perchloroethylene needs to be used to replace carbon tetrachloride.

[0003] Environmentally friendly tetrachloroethylene is usually used with an infrared oil tester or infrared spectrometer to detect the environmental water quality. -1 The infrared spectrum absorbance at 2960cm is no more than 0.34. -1 The infrared spectrum absorbance at 3030cm is no more than 0.07. -1 The infrared spectrum absorbance at is no more than 0.00. These three conditions must be met at the same time to be called environmentally friendly grade tetrachloroethylene.

[0004] In order to meet the requirements of environmentally friendly tetrachloroethylene, the purity of tetrachloroethylene needs to be improved. Currently reported methods for purifying tetrachloroethylene are as follows: (1) dehydration of color-changing silica gel, filtration of aluminum silicate fiber cotton (burned at above 600°C), and distillation. After the above process, the purity of tetrachloroethylene at 2930, 2960, and 3030 cm -1 The absorbances at the locations are less than 0, 0.0321, and 0.3147, respectively. (2) Soak industrial tetrachloroethylene in 13X molecular sieve for 3 hours, pass through an injection activated carbon column, and then pass through a magnesium silicate column to obtain the product. (3) Soak industrial tetrachloroethylene in 0.01-0.2% inorganic alkali for 24 hours, shake it 3 times in the middle, and reflux and distill it under nitrogen protection. (4) Wash industrial tetrachloroethylene with potassium carbonate solution, wash with pure water, add solid potassium carbonate and stir, dehydrate the molecular sieve, and distill it. (5) Adsorption on activated carbon, adsorption on silicon-magnesium type adsorbent, adsorption on 5A molecular sieve or 13X molecular sieve, filter, and distill with zeolite and calcium hydride. In addition to the above purification methods, there are also methods such as alkali washing + water washing + adsorption treatment, and direct adsorption treatment. Generally speaking, the methods used mainly include extraction (washing), adsorption, distillation, and a combination of these methods.

[0005] However, the current preparation methods of environmentally friendly tetrachloroethylene generally have the following problems: the purification process is complicated, and the purity and stability of the product need to be improved.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide an environmentally friendly tetrachloroethylene and a preparation method thereof, aiming to purify and obtain the environmentally friendly tetrachloroethylene through a simplified process.

[0008] The present invention is achieved in that:

[0009] In a first aspect, the present invention provides a method for preparing environmentally friendly tetrachloroethylene, comprising: using modified alumina to statically adsorb tetrachloroethylene so that the adsorbed tetrachloroethylene has a peak at 2930 cm -1 The absorbance at is less than 0.4;

[0010] After the static adsorption is completed, at least one of filtration or vacuum distillation is selected for purification according to the absorbance of the tetrachloroethylene;

[0011] Wherein, the modifier used in the preparation process of modified alumina is selected from at least one of potassium hydroxide and potassium carbonate.

[0012] In an optional embodiment, the preparation process of modified alumina includes: mixing a modifier and water to obtain an alkaline solution, mixing activated alumina and the alkaline solution and soaking them for 12 hours to 36 hours, then separating the solid and the liquid, and washing, drying and calcining the obtained solid material.

[0013] In an optional embodiment, the concentration of the alkaline solution is 0.05 Kg / L-0.15 Kg / L, and the mass ratio of activated alumina to the alkaline solution is 1:(0.8-1.2).

[0014] In an optional embodiment, the solid material is washed with water, dried at 100° C.-150° C. for 1 h-5 h, and then calcined at 300° C.-500° C. for 4 h-5 h.

[0015] In an optional embodiment, during the static adsorption process, the mass ratio of the tetrachloroethylene raw material and the modified alumina is controlled to be (8-12):1;

[0016] Preferably, the tetrachloroethylene raw material is at 2930 cm -1 The absorbance at is less than 0.9;

[0017] Preferably, static adsorption is carried out under closed conditions, and the adsorption time is controlled to be 2 days to 5 days.

[0018] In an optional embodiment, when the tetrachloroethylene after static adsorption satisfies the following conditions at the same time, fine filtration is performed: at 2930 cm -1 The absorbance at 2960 cm-1 is A1≤0.335. -1 The absorbance at 3030cm is A2≤0.045. -1 The absorbance at A3≤0;

[0019] When the tetrachloroethylene after static adsorption does not meet the above conditions at the same time, vacuum distillation is performed.

[0020] In an optional embodiment, during the precision filtration, a filter membrane with a pore size of 0.1 μm-0.3 μm is used for filtration;

[0021] Preferably, the filter membrane is a polytetrafluoroethylene filter membrane.

[0022] In an optional embodiment, the distillation temperature of the vacuum distillation is 70°C-80°C, and the vacuum degree is greater than or equal to 0.09 MPa;

[0023] Preferably, each batch of distillation is 400Kg-600Kg, and the output per hour is 10L-15L.

[0024] In an optional embodiment, after filtering or vacuum distillation, the method further comprises mixing the product having absorbance meeting the requirements with a stabilizer;

[0025] The stabilizer is a monocomponent or a dicomponent, the monocomponent is trichlorophenol, and the addition amount of the monocomponent is 15ppm-25ppm; the dicomponent is a mixture of trichlorophenol and epichlorohydrin, the addition amount of trichlorophenol is 12ppm-17ppm, and the addition amount of epichlorohydrin is 3ppm-8ppm;

[0026] Preferably, after mixing with the stabilizer, purging with an inert gas is performed.

[0027] In a second aspect, the present invention provides an environmentally friendly grade tetrachloroethylene prepared by the preparation method of any one of the aforementioned embodiments.

[0028] The invention has the following beneficial effects: modified aluminum oxide is prepared by modifying potassium hydroxide and / or potassium carbonate, and the modified aluminum oxide can well adsorb impurities in tetrachloroethylene by static adsorption of tetrachloroethylene, and the purification process can be completed by filtering or vacuum distillation according to absorbance after static adsorption. The purification method provided by the invention is easy to operate, and the impurities in tetrachloroethylene can be better removed by improving the adsorbent, so that the absorbance of the prepared tetrachloroethylene meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1A process flow chart of a preparation method is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0032] Because environmentally friendly tetrachloroethylene is unstable, it needs to be stabilized by adding stabilizers. The use requirements of stabilizers must meet the following requirements: the absorption value of itself and the stabilizer at a specific infrared wave number cannot exceed the index, so as not to affect the use. -1 、2960cm -1、 3030cm -1 Infrared absorption is generally caused by specific functional groups absorbing energy. There are two reasons for the high absorbance of raw materials: (1) the absorption of infrared spectra by impurities in the raw materials at specific wave numbers; (2) the absorption of infrared spectra by stabilizers in the raw materials at specific wave numbers.

[0033] Therefore, the preparation process of environmentally friendly grade products is divided into two aspects: (1) testing a suitable purification method to prepare a product that meets the infrared absorption requirements; (2) finding a suitable stabilizer that can not only play a good role in stabilizing the product but also has no strong infrared absorption.

[0034] The present invention provides a method for preparing environmentally friendly tetrachloroethylene. Figure 1 , including the following steps:

[0035] S1. Preparation of modified alumina

[0036] The inventor creatively uses a specific modifier to modify the activated alumina, so that the prepared modified alumina can well adsorb impurities in tetrachloroethylene and improve the purification effect. The specific modifier is selected from at least one of potassium hydroxide and potassium carbonate, and can be any one or two of the above.

[0037] In some embodiments, the preparation process of modified alumina includes: mixing a modifier and water to obtain an alkaline solution, mixing the activated alumina and the alkaline solution and soaking for 12 hours to 36 hours, then separating the solid and the liquid, and washing, drying and calcining the obtained solid material. During the soaking process, the alkaline solution affects the pores of the activated alumina and can change the pore structure, so that the modified alumina can be more suitable for adsorbing impurities in tetrachloroethylene.

[0038] Specifically, the activated alumina is a commercially available material, has a spherical morphology, and a particle size of 3-5 mm. The activated alumina can be immersed in the alkaline solution for 12 hours, 15 hours, 18 hours, 20 hours, 25 hours, 30 hours, 36 hours, etc. The solid-liquid separation method is not limited, and the alkali solution can be filtered out using a conventional sieve.

[0039] Furthermore, the concentration of the alkaline solution is 0.05Kg / L-0.15Kg / L, and the mass ratio of activated alumina to the alkaline solution is 1:(0.8-1.2). By adjusting the concentration and dosage of the alkaline solution, the modification effect is better, and the obtained modified alumina can more fully absorb impurities in tetrachloroethylene.

[0040] Specifically, the concentration of the alkaline solution can be 0.05Kg / L, 0.08Kg / L, 0.10Kg / L, 0.12Kg / L, 0.15Kg / L, etc., and the mass ratio of activated alumina and alkaline solution can be 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, etc.

[0041] Furthermore, the solid material can be washed in any manner, and can be washed with water for multiple times. After washing with water, it is dried at 100°C-150°C for 1h-5h to remove surface moisture; then, it is calcined at 300°C-500°C for 4h-5h to change the pore structure of the modified alumina and affect the crystal structure of the inner surface of the pores. After calcination, it is cooled to room temperature for standby use.

[0042] Specifically, the amount of water used for washing is determined according to the mass of the solid material. 35 kg of activated alumina corresponds to 36 L to 72 L of water, which can fully remove the alkali solution and dust on the surface. The drying temperature can be 100 ° C, 110 ° C, 120 ° C, 130 ° C, 140 ° C, 150 ° C, etc., and the drying time can be 1 h, 3 h, 5 h, etc. The calcination temperature can be 300 ° C, 350 ° C, 400 ° C, 450 ° C, 500 ° C, etc., and the calcination time can be 4.0 h, 4.5 h, 5.0 h, etc.

[0043] S2, static adsorption

[0044] The modified alumina was used to statically adsorb tetrachloroethylene so that the adsorbed tetrachloroethylene was -1 The absorbance A1 at the point is less than 0.4. If the absorbance A1 ≥ 0.4, the static adsorption is continued and the static adsorption time is extended.

[0045] Specifically, the tetrachloroethylene raw material used in static adsorption is industrial grade or AR grade raw material, and the absorbance of the raw material can be detected at 2930cm -1 The absorbance <0.9 meets the raw material requirements.

[0046] In some embodiments, the mass ratio of the tetrachloroethylene raw material to the modified alumina is controlled to be (8-12):1, and the amount of the modified alumina should not be too large or too small. If the amount of the modified alumina is too small, the adsorption effect cannot be guaranteed, so that the tetrachloroethylene after static adsorption cannot meet the absorbance requirements; if the amount of the modified alumina is too large, the process cost will increase, which is not conducive to the subsequent separation. Specifically, the mass ratio of the tetrachloroethylene raw material to the modified alumina can be 8:1, 9:1, 10:1, 11:1, 12:1, etc.

[0047] In some embodiments, static adsorption is carried out under closed conditions, and the adsorption time is controlled to be 2-5 days. The specific adsorption time is obtained according to the absorbance after adsorption, and detection can be performed at intervals. After the absorbance meets the requirements, the next stage is entered. Specifically, the adsorption operation container can be operated in the original packaging barrel, and after adding the modified alumina, the barrel mouth is sealed and placed for 2-5 days.

[0048] It should be noted that when sampling for absorbance detection, you can use a 0.22-micron polytetrafluoroethylene filter membrane to filter and then detect, or you can let it stand for more than 12 hours (in this case, you can directly sample tetrachloroethylene to avoid interference from modified alumina) and directly sample and detect without filtering.

[0049] It should be noted that after the adsorption is completed, the used modified alumina can be placed in a distillation kettle for heating and distillation to recover the tetrachloroethylene adsorbed by the alumina until there is no distillate, and then calcined at 400°C for 4 hours, cooled to room temperature, and then modified according to the modification and activation method of S1 before being reused.

[0050] S3, filtration or vacuum distillation

[0051] After the static adsorption is completed, at least one of filtration or vacuum distillation is selected for purification according to the absorbance of tetrachloroethylene. When the absorbance meets the absorbance requirement of environmental-grade tetrachloroethylene, the product can be directly filtered to obtain the product. If the absorbance does not meet the absorbance requirement of environmental-grade tetrachloroethylene, it can be further purified by vacuum distillation.

[0052] In some embodiments, the tetrachloroethylene after static adsorption is finely filtered when the following conditions are met at the same time: -1 The absorbance at 2960 cm-1 is A1≤0.335. -1 The absorbance at 3030cm is A2≤0.045. -1 The absorbance at A3 is ≤ 0. When A1, A2 and A3 meet the above requirements at the same time, there is no need for distillation, and the aluminum oxide powder can be directly removed by precision filtration.

[0053] It should be noted that in the actual use of infrared oil tester, at the three spectral bands of environmental grade tetrachloroethylene detection (2930cm -1 、2960cm -1 、3030cm -1 ) is used to characterize the oil in water extracted by tetrachloroethylene. It is generally believed that: 2930cm -1 The infrared absorption at 2960cm is caused by the stretching vibration of the CH bond in the CH2 group. -1 The infrared absorption at 3030cm is caused by the stretching vibration of the CH bond in the CH3 group. -1 The infrared absorption at is caused by the stretching vibration of the CH bond in the aromatic ring.

[0054] Furthermore, during the precision filtration process, a filter membrane with a pore size of 0.1 μm-0.3 μm is used for filtration to fully remove the small amount of aluminum oxide remaining in tetrachloroethylene. Specifically, the pore size of the filter membrane used for precision filtration can be 0.1 μm, 0.2 μm, 0.3 μm, etc. The material of the filter membrane can be polytetrafluoroethylene filter membrane, PP, PE, etc. cannot be used, and no plastic devices must be contacted during the filtration process.

[0055] When the tetrachloroethylene after static adsorption does not meet the above conditions at the same time, vacuum distillation is carried out. That is to say, when A1, A2 and A3 cannot meet the above requirements at the same time, vacuum distillation is required for further purification. Vacuum distillation can be heated by steam. The distillation temperature of vacuum distillation is 70℃-80℃, and the vacuum degree is greater than or equal to 0.09MPa. The distillation process is preferably carried out slowly under high vacuum to prevent the temperature of the liquid in the kettle from being too high. In actual operation, each batch of distillation can be controlled to be 400Kg-600Kg, and the discharge per hour can be 10L-15L to ensure the purification effect. After the discharge, the condenser with good cooling capacity is used for cooling to avoid losses.

[0056] Specifically, the distillation temperature of the vacuum distillation can be 70° C., 75° C., 80° C., etc. The amount of each batch of distillation can be 400 Kg, 500 Kg, 600 Kg, etc., and the output per hour can be 10 L, 13 L, 15 L, etc.

[0057] S4. Add stabilizer

[0058] Environmentally friendly tetrachloroethylene is easily affected by oxygen and moisture in the air due to its product characteristics, and is easily decomposed under light conditions. Therefore, it is necessary to add stabilizers to improve its storage stability while ensuring that the packaging is strictly sealed. After filtration or vacuum distillation, the product with absorbance that meets the requirements is mixed with the stabilizer, and the stability of environmentally friendly tetrachloroethylene is improved by adding stabilizers. In the presence or irradiation of air, water and light, tetrachloroethylene containing stabilizers has no obvious corrosive effect on commonly used metal materials even when heated to 140°C. Tetrachloroethylene without stabilizers gradually hydrolyzes into trichloroacetic acid and hydrogen chloride when in contact with water for a long time under the action of light.

[0059] The inventors have optimized the types of stabilizers, and the stabilizers can be either mono-component or di-component.

[0060] When a monocomponent stabilizer is used, trichlorophenol can be used, and the addition amount of the monocomponent is 15ppm-25ppm, such as 15ppm, 18ppm, 20ppm, 23ppm, 25ppm, etc.

[0061] When a binary stabilizer is used, the stabilizer is a mixture of trichlorophenol and epichlorohydrin, the amount of trichlorophenol added is 12ppm-17ppm, and the amount of epichlorohydrin added is 3ppm-8ppm. By optimizing the type of stabilizer, the stability of environmentally friendly tetrachloroethylene is improved and the shelf life of the product is increased. Specifically, the amount of trichlorophenol added can be 12ppm, 15ppm, 17ppm, etc., and the amount of epichlorohydrin added can be 3ppm, 5ppm, 8ppm, etc.

[0062] It is advisable to select the monocomponent or dicomponent provided in the embodiments of the present invention. If the stabilizer is not selected properly, it may cause the absorbance at these spectral bands to increase, thereby failing to meet the use requirements. It is necessary to avoid the presence of CH2 groups, CH3 groups, and CH bonds in aromatic rings in the stabilizer that affect the absorbance value.

[0063] It should be noted that the stabilizer can be added by directly mixing with the corresponding amount of environmentally friendly tetrachloroethylene. In order to further improve the uniformity of dispersion, the stabilizer can be first dissolved in an appropriate amount of tetrachloroethylene and then mixed with the remaining amount of tetrachloroethylene. Specifically, the stabilizer is dissolved in an appropriate amount of tetrachloroethylene to prepare a 5000ppm solution, and then this solution is added to the finished product that has passed the absorbance test. The specific operation is as follows: (1) 500mL of tetrachloroethylene is loaded into a 500mL brown glass bottle, 4g of trichlorophenol is added, stirred to dissolve completely, filtered, and the stabilizer content is about 5000ppm. (2) 500mL of tetrachloroethylene is loaded into a 500mL brown glass bottle, 3g of trichlorophenol and 1g of epichlorohydrin are added, stirred to dissolve completely, filtered, and the stabilizer content is about 5000ppm. (3) Add 400 mL of the above stabilizer solution (the solution in step (1) or step (2)) to every 100 L (162 kg) of the finished tetrachloroethylene product that has passed the absorbance test, and package it after it is evenly dispersed.

[0064] In some embodiments, after mixing with the stabilizer, the product is purged with an inert gas to remove dissolved oxygen in the product, and then the product is stored in a sealed container away from light. The type of inert gas is not limited, and it can be high-purity nitrogen, argon, etc., and the purging time can be 10 min-20 min.

[0065] The embodiment of the present invention provides an environmentally friendly grade tetrachloroethylene, which is prepared by the above-mentioned preparation method, has low preparation cost, low absorbance A1, A2 and A3, and good product stability.

[0066] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0067] Example 1

[0068] This embodiment provides a method for preparing environmentally friendly tetrachloroethylene, comprising the following steps:

[0069] (1) Provide raw materials

[0070] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: at 2930cm -1 The infrared absorbance at 2960 cm-1 is 0.968. -1 The infrared absorbance at 3030cm is 1.161. -1 The infrared absorbance at is 0.142.

[0071] (2) Preparation of modified alumina AA-b

[0072] Add 10g KOH to 100g pure water, stir to dissolve, and cool to room temperature. Add 100g activated alumina and leave overnight. Take out the alumina, wash it with 200g pure water, dry it at 120℃ for 2 hours, and then burn it at 400℃ for 5 hours.

[0073] (3) Static adsorption and vacuum distillation

[0074] Take 80g of modified alumina AA-b and add it to 500mL of tetrachloroethylene (about 850g) and leave it for 3 days. Take the supernatant and add it to a 1L flask, install a vacuum distillation device, oil bath 85℃, vacuum degree 0.095MPa, extract 10mL, keep 50mL at the bottom, and get about 400mL of positive fraction.

[0075] (4) Add stabilizer

[0076] The tetrachloroethylene obtained in step (3) was mixed with trichlorophenol and epichlorohydrin, with the amount of trichlorophenol added being 15ppm and the amount of epichlorohydrin added being 5ppm. The infrared absorbance value was detected, and the result showed that: 2930cm -1 The infrared absorbance at 0.311 and 2960 cm -1 The infrared absorbance at 0.035 and 3030 cm -1 The infrared absorbance at is < 0. Store in a sealed container away from light.

[0077] Example 2

[0078] This embodiment provides a method for preparing environmentally friendly tetrachloroethylene, comprising the following steps:

[0079] (1) Provide raw materials

[0080] The raw material is industrial-grade tetrachloroethylene produced by Ningbo Juhua Chemical Technology Co., Ltd., 300Kg / barrel*2. The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.876 and 2960 cm -1 The infrared absorbance at 1.129 and 3030 cm -1 The infrared absorbance at is 0.165.

[0081] (2) Preparation of modified alumina AA-b

[0082] Add 10 kg of KOH to 100 kg of pure water, stir to dissolve, and cool to room temperature. Add 100 kg of activated alumina, leave overnight without stirring. Pour the alumina into a sieve to filter out the alkali solution, wash with 100 kg of pure water, dry at 120°C for 2 hours, and then burn at 400°C for 5 hours.

[0083] (3) Static adsorption and vacuum distillation

[0084] Take 60Kg of modified alumina AA-b and add it to the above tetrachloroethylene (add 30Kg of modified alumina AA-b to each barrel, the same below), and leave it for 5 days. Filter the supernatant and pump it into a 500L enamel distillation kettle, steam heat, vacuum distill, control the internal temperature to about 80-90℃, vacuum degree to 0.090-0.095MPa, and distillation speed to about 15L / h. The amount of head and bottom is 58Kg, and the amount of positive distillate is 498Kg (yield 83%).

[0085] (4) Add stabilizer

[0086] The tetrachloroethylene obtained in step (3) is mixed with trichlorophenol and epichlorohydrin, with the amount of trichlorophenol added being 15ppm and the amount of epichlorohydrin added being 5ppm. The positive fraction meets the environmental protection grade requirements, and the test results are: 2930cm -1 The infrared absorbance at 0.331 and 2960 cm -1 The infrared absorbance at 0.016 and 3030 cm -1 The infrared absorbance at is <0.

[0087] Example 3

[0088] This embodiment provides a method for preparing environmentally friendly tetrachloroethylene, comprising the following steps:

[0089] (1) Provide raw materials

[0090] The raw material is industrial-grade tetrachloroethylene produced by Ningbo Juhua Chemical Technology Co., Ltd., 300Kg / barrel*2. The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.967 and 2960 cm -1 The infrared absorbance at 1.201 and 3030 cm -1 The infrared absorbance at is 0.155.

[0091] (2) Preparation of modified alumina AA-b

[0092] Add 10 kg of anhydrous K2CO3 to 100 kg of pure water, stir to dissolve, and cool to room temperature. Add 100 kg of activated alumina, leave overnight without stirring. Pour the alumina into a sieve to filter out the alkali solution, wash with 100 kg of pure water, dry at 120°C for 2 hours, and then burn at 400°C for 5 hours.

[0093] (3) Static adsorption and vacuum distillation

[0094] Take 60 kg of modified alumina AA-b and add it to the above tetrachloroethylene, and leave it for 5 days. Filter the supernatant and pump it into a 500 L enamel distillation kettle, steam-heat it, and perform vacuum distillation. Control the internal temperature to about 80-90 ° C, the vacuum degree to 0.090-0.095 MPa, and the distillation rate to about 15 L / h. The amount of the head and bottom fraction is 46 kg, and the amount of the positive fraction is 512 kg (yield 85.3%).

[0095] (4) Add stabilizer

[0096] The tetrachloroethylene obtained in step (3) is mixed with trichlorophenol and epichlorohydrin, with the amount of trichlorophenol added being 15ppm and the amount of epichlorohydrin added being 5ppm. The positive fraction meets the environmental protection grade requirements, and the test results are: 2930cm -1 The infrared absorbance at 0.323 and 2960 cm -1 The infrared absorbance at 0.020 and 3030 cm -1 The infrared absorbance at is <0.

[0097] Stability test 1

[0098] The raw material is AR grade tetrachloroethylene. The infrared absorbance value was tested and the result was 2930cm -1 The infrared absorbance at 0.708 and 2960 cm -1 The infrared absorbance at 0.686 and 3030 cm -1 The infrared absorbance at is 0.084.

[0099] Static adsorption: Take 90g of modified alumina AA-b (prepared in Example 1) and add it to 500mL of tetrachloroethylene and leave it for 2 days. Vacuum distillation: Take the supernatant and add it to a 1L flask, install a vacuum distillation device, oil bath 85℃, vacuum degree 0.095MPa, extract 15ml, keep 45ml, and get about 390mL of positive fraction. Add stabilizer: trichlorophenol 20ppm. Detect the infrared absorbance value, the result is: 2930cm -1 The infrared absorbance at 0.311 and 2960 cm -1 The infrared absorbance at 0.029 and 3030 cm -1 The infrared absorbance at is <0.

[0100] The finished product was placed in a glass conical flask, tightly covered with a glass stopper, and subjected to a stability test under uninterrupted light. The results are shown in Table 1 below.

[0101] Table 1 Stability test results

[0102] Serial number <![CDATA[2930cm -1 ]]> <![CDATA[2960cm -1 ]]> <![CDATA[3030cm -1 ]]> 1 0.315 0.026 ＜0 3 days of light exposure 2 0.312 0.034 ＜0 7 days of light exposure 3 0.313 0.030 ＜0 17 days of exposure 4 0.316 0.029 ＜0 22 days of light exposure 5 0.314 0.032 ＜0 26 days of light exposure 6 0.318 0.027 ＜0 31 days of exposure

[0103] Stability test 2

[0104] The raw material is industrial grade tetrachloroethylene. The infrared absorbance value was tested and the result was 2930cm -1 The infrared absorbance at 0.754 and 2960 cm -1 The infrared absorbance at 0.663 and 3030 cm -1 The infrared absorbance at is 0.066.

[0105] Static adsorption: Take 90g of modified alumina AA-b (prepared in Example 1) and add it to 500mL of tetrachloroethylene and leave it for 3 days. Vacuum distillation: Take 786g of the supernatant and add it to a 1L flask. Install a vacuum distillation device, oil bath at 85°C, vacuum degree 0.095MPa, extract 60g, keep 75g, and get about 624g of the positive fraction. Add stabilizer: 15ppm trichlorophenol, 5ppm epichlorohydrin. Detect the infrared absorbance value, the result is 2930cm -1 The infrared absorbance at 0.310 and 2960 cm -1 The infrared absorbance at 0.031 and 3030 cm -1 The infrared absorbance at is <0.

[0106] The finished product was placed in a glass conical flask, covered with a glass stopper, and subjected to a stability test under uninterrupted light. The results are shown in Table 2.

[0107] Table 2 Stability test results

[0108] Serial number <![CDATA[2930cm -1 ]]> <![CDATA[2960cm -1 ]]> <![CDATA[3030cm -1 ]]> 1 0.313 0.034 ＜0 4 days of light exposure 2 0.311 0.028 ＜0 14 days of light exposure 3 0.322 0.035 ＜0 19 days of exposure 4 0.318 0.036 ＜0 23 days of light exposure 5 0.310 0.029 ＜0 28 days of light exposure 6 0.317 0.040 ＜0 32 days of light exposure

[0109] Comparative Example 1

[0110] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: at 2930cm -1 The infrared absorbance at 2960 cm-1 is 0.968. -1 The infrared absorbance at 3030cm is 1.161. -1 The infrared absorbance at is 0.142.

[0111] 500mL of tetrachloroethylene was washed twice with 100mL of 5% Na2CO3 solution, dried with anhydrous Na2CO3, dried with 3A molecular sieve overnight, filtered to remove the molecular sieve, and vacuum distilled in an oil bath at 85°C and a vacuum degree of 0.095MPa. 10mL of the head was removed and 55mL of the bottom was retained. About 400mL of the positive fraction was obtained. The infrared absorbance value was tested and the result was 2930cm -1 The infrared absorbance at 0.343 and 2960 cm -1 The infrared absorbance at 0.501 and 3030 cm -1 The infrared absorbance at is 0.100.

[0112] Comparative Example 2

[0113] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: at 2930cm -1 The infrared absorbance at 2960 cm-1 is 0.968. -1 The infrared absorbance at 3030cm is 1.161. -1 The infrared absorbance at is 0.142.

[0114] 500mL of tetrachloroethylene was washed 3 times with 7% KOH solution, 3 times with pure water, dried with anhydrous Na2CO3, dried with 3A molecular sieve overnight, filtered to remove the molecular sieve, vacuum distilled, oil bath 85℃, vacuum degree 0.095MPa, 15mL was extracted, 40mL was retained, and about 400mL of the positive fraction was obtained. The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.331 and 2960 cm -1 The infrared absorbance at 0.466 and 3030 cm -1 The infrared absorbance at is 0.097.

[0115] Comparative Example 3

[0116] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: at 2930cm -1 The infrared absorbance at 2960 cm-1 is 0.968. -1 The infrared absorbance at 3030cm is 1.161. -1 The infrared absorbance at is 0.142.

[0117] Add 25g activated carbon to 500mL tetrachloroethylene, stir for 1h, and filter. Add activated MgSiO2 adsorbent to the filtrate, stir for 1h, and filter. Add activated 13X molecular sieve to the filtrate, stir for 1h, and filter. Dry the filtrate with 3A molecular sieve overnight and filter with 0.1um PTFE membrane.

[0118] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.468 and 2960 cm -1 The infrared absorbance at 0.557 and 3030 cm -1 The infrared absorbance at is 0.108.

[0119] Comparative Example 4

[0120] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0121] 500mL of tetrachloroethylene was added with 10g of KOH and 50g of newly activated 3A molecular sieves and allowed to stand for 1 day, then filtered. 1g of KOH and 1.5g of CaH2 were added to the filtrate, and distilled under normal pressure at 125°C in an oil bath, 10mL of the head was removed, 50mL of the bottom was retained, and about 420mL of the positive fraction was obtained.

[0122] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.342 and 2960 cm -1 The infrared absorbance at 0.069 and 3030 cm -1 The infrared absorbance at is 0.051.

[0123] Comparative Example 5

[0124] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1 The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0125] Modified molecular sieve 4A-a preparation: Add 8g KOH to 100g pure water, stir to dissolve, and cool to room temperature. Add 100g 4A molecular sieve and leave overnight. Take out the 4A molecular sieve, wash it with 200g pure water, dry it at 120℃ for 2 hours, and then calcine it at 400℃ for 5 hours.

[0126] Add 80g 4A-a to 500mL tetrachloroethylene, let stand for 3 days, and filter. Add 2g 4A-a and 2g CaH2 to the filtrate, and distill under normal pressure, oil bath at 125℃, extract 10mL, keep 40mL, and obtain about 400mL of the positive fraction.

[0127] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.328 and 2960 cm -1 The infrared absorbance at 0.426 and 3030 cm -1 The infrared absorbance at is 0.089.

[0128] Comparative Example 6

[0129] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0130] Modified activated carbon is prepared as AC-C: Add 8g KOH to 100g pure water, stir to dissolve, and cool to room temperature. Add 100g activated carbon and leave overnight. Take out the activated carbon, wash it with 200g pure water, and dry it at 120℃.

[0131] Add 30g AC-C to 500mL tetrachloroethylene, let stand for 3 days, and filter. Add 2g modified alumina AA-b and 2g CaH2 to the filtrate, and distill at atmospheric pressure, oil bath at 125℃, extract 10mL, keep 40mL, and obtain about 410mL of the positive fraction.

[0132] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.321 and 2960 cm -1 The infrared absorbance at 0.037 and 3030 cm -1 The infrared absorbance at is 0.011.

[0133] Comparative Example 7

[0134] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1 The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0135] Preparation of modified alumina AA-a: Add 8g KOH to 100g pure water, stir to dissolve, and cool to room temperature. Add 100g activated alumina and leave overnight. Take out the activated alumina, wash it with 200g pure water, dry it at 120℃, and calcine it at 500℃ for 4h.

[0136] Add 80g AA-a to 500mL tetrachloroethylene, let stand for 5 days, and filter. Add 2g modified alumina AA-a and 2g CaH2 to the filtrate, and distill at normal pressure, oil bath 125℃, extract 10mL, keep 40mL, and get about 400mL of positive fraction.

[0137] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.317 and 2960 cm -1 The infrared absorbance at 0.037 and 3030 cm -1 The infrared absorbance at is 0.018.

[0138] Comparative Example 8

[0139] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1 The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0140] 500mL of tetrachloroethylene was added with 80g of modified alumina AA-b, left for 4 days, and filtered. The filtrate was distilled under normal pressure, in an oil bath at 125°C, 10mL was extracted, 40mL was retained as the bottom, and about 400mL of the positive fraction was obtained.

[0141] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.312 and 2960 cm -1 The infrared absorbance at 0.033 and 3030 cm -1 The infrared absorbance at is 0.011.

[0142] Comparative Example 9

[0143] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1 The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0144] The modified molecular sieve is 5A-a, preparation method: add 8g KOH to 100g pure water, stir to dissolve, cool to room temperature. Add 100g 5A molecular sieve and leave overnight. Take out the 5A molecular sieve, wash with 200g pure water, dry at 120℃, and calcine at 500℃ for 4h.

[0145] Add 80g 5A-a to 500mL tetrachloroethylene, let stand for 2 days, add 30g modified alumina AA-b, let stand for 2 days, filter. Add 2g CaH2 to the filtrate, distill at normal pressure, oil bath 125℃, extract 10mL, keep 35mL, and get about 390mL of positive fraction.

[0146] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.310 and 2960 cm -1 The infrared absorbance at 0.028 and 3030 cm -1 The infrared absorbance at is 0.007.

[0147] Comparative Example 10

[0148] The raw material is AR grade tetrachloroethylene. The infrared absorbance value is tested and the result is: 2930cm -1 The infrared absorbance at 0.968 and 2960 cm -1 The infrared absorbance at 1.161 and 3030 cm -1 The infrared absorbance at is 0.142.

[0149] 500mL of tetrachloroethylene was washed 3 times with 7% K2CO3 solution, 2 times with pure water, dried overnight with 3A molecular sieve and anhydrous K2CO3, filtered to remove the desiccant. 2g of anhydrous K2CO3 and 2g of CaH2 were added to the filtrate, and distilled at normal pressure, oil bath at 125℃, 10mL was extracted, 40mL was retained, and about 410mL of the positive fraction was obtained.

[0150] The infrared absorbance value was tested and the result was: 2930cm -1 The infrared absorbance at 0.335 and 2960 cm -1 The infrared absorbance at 0.453 and 3030 cm -1 The infrared absorbance at is 0.094.

[0151] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing environmentally friendly tetrachloroethylene, characterized in that: include: The modified alumina was used to statically adsorb tetrachloroethylene so that the adsorbed tetrachloroethylene was -1 The absorbance at is less than 0.4; After the static adsorption is completed, at least one of filtration or vacuum distillation is selected for purification according to the absorbance of the tetrachloroethylene; The modifier used in the preparation process of the modified alumina is selected from at least one of potassium hydroxide and potassium carbonate; the preparation process of the modified alumina comprises: mixing the modifier with water to obtain an alkaline solution, mixing the activated alumina and the alkaline solution and soaking them for 12 hours to 36 hours, then separating the solid from the liquid, and washing, drying and burning the obtained solid material; When the tetrachloroethylene after static adsorption meets the following conditions at the same time, fine filtration is performed: at 2930cm -1 The absorbance at 2960 cm-1 is A1≤0.

335. -1 The absorbance at 3030cm is A2≤0.

045. -1 The absorbance at A3 is ≤ 0; when the tetrachloroethylene after static adsorption does not meet the above conditions at the same time, vacuum distillation is performed; During the precision filtration, a filter membrane with a pore size of 0.1 μm-0.3 μm is used for filtration; After filtering or vacuum distillation, the process also includes mixing the product having absorbance meeting the requirements with a stabilizer; Wherein, the stabilizer is a monocomponent or a dicomponent, the monocomponent is trichlorophenol, and the addition amount of the monocomponent is 15ppm-25ppm; the dicomponent is a mixture of trichlorophenol and epichlorohydrin, the addition amount of trichlorophenol is 12ppm-17ppm, and the addition amount of epichlorohydrin is 3ppm-8ppm.

2. The preparation method according to claim 1, characterized in that: The concentration of the alkaline solution is 0.05 Kg / L-0.15 Kg / L, and the mass ratio of the activated alumina to the alkaline solution is 1:(0.8-1.2).

3. The preparation method according to claim 1, characterized in that: After washing the solid material with water, the solid material is dried at 100° C.-150° C. for 1 h-5 h, and then calcined at 300° C.-500° C. for 4 h-5 h.

4. The preparation method according to claim 1, characterized in that: During the static adsorption process, the mass ratio of the tetrachloroethylene raw material to the modified alumina is controlled to be (8-12):

1.

5. The preparation method according to claim 4, characterized in that: The tetrachloroethylene raw material is at 2930cm -1 The absorbance at is less than 0.

9.

6. The preparation method according to claim 4, characterized in that: Static adsorption is carried out under closed conditions, and the adsorption time is controlled to be 2 days to 5 days.

7. The preparation method according to claim 1, characterized in that: The filter membrane is a polytetrafluoroethylene filter membrane.

8. The preparation method according to claim 1, characterized in that: The distillation temperature of the vacuum distillation is 70° C.-80° C., and the vacuum degree is greater than or equal to 0.09 MPa.

9. The preparation method according to claim 8, characterized in that: Each batch of distillation is 400Kg-600Kg, and the output per hour is 10L-15L.

10. The preparation method according to claim 1, characterized in that: After mixing with the stabilizer, purging with an inert gas is performed.

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