A method for preparing trichloroacetone using molecular sieve photocatalytic reaction

Abstract

This invention relates to the field of organic synthesis technology and discloses a method for preparing 1,1,3-trichloroacetone using a molecular sieve photocatalytic reaction. Specifically, it includes: activating acetone with a composite catalyst, photocatalyzing chlorine gas to form chlorine radicals, and then, in a highly active state, allowing the α-H of acetone to react with the chlorine radicals (Cl·) in the micropores of the molecular sieve to undergo a substitution reaction. The molecular sieve catalyst significantly improves the conversion rate and selectivity of the reaction, promoting the selective yield of more 1,1,3-trichloroacetone. Using the molecular sieve as a reaction medium allows the reaction liquid and chlorine gas to be adsorbed in the micropores, ensuring sufficient contact and a rapid substitution reaction, thus avoiding the impact of the gas-liquid barrier on reaction efficiency and homogeneity in traditional one-pot methods. This method offers high efficiency, high yield, and high purity in the preparation of 1,1,3-trichloroacetone, with easily controllable reaction parameters, making it suitable for scale-up industrial production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing trichloroacetone using a molecular sieve photocatalytic reaction. Background Technology

[0002] 1,1,3-Trichloroacetone is a colorless, transparent, oily liquid at room temperature and pressure. It is commonly used as an intermediate in organic synthesis and pharmaceutical chemistry, and is often used for the structural modification of drug molecules and bioactive molecules.

[0003] 1,1,3-Trichloroacetone is an important intermediate in the production of folic acid. Folic acid, an essential water-soluble B vitamin, plays a crucial role in many important physiological metabolic functions, such as nucleotide synthesis and homocysteine ​​remethylation. As a carrier of one-carbon units, folic acid is an important methyl donor in the body, participating in cell growth and tissue repair, and is an essential nutrient element for the body's growth and reproduction. Therefore, folic acid plays a vital role in rapid cell division and growth processes (such as infant development and pregnancy). Folic acid promotes the maturation of immature cells in the bone marrow into normally shaped red blood cells, thus preventing anemia. Because folic acid plays an important role in the formation of the neural tube, it is important for pregnant women to consume enough folic acid before pregnancy for normal fetal development. Folic acid deficiency during pregnancy can affect the development of the fetal nervous system. Studies have shown that adequate folic acid supplementation in early and during pregnancy can reduce the birth rate of neural tube defects and cleft lip.

[0004] Currently, industrially produced 1,1,3-trichloroacetone typically has a purity below 65%, containing numerous byproducts. This results in high levels of impurities when used in folic acid production, making it difficult to meet the purity requirements of the International Pharmacopoeia. Furthermore, the wastewater generated from low-purity 1,1,3-trichloroacetone production has a high chloride content, making wastewater treatment difficult. Therefore, high-purity 1,1,3-trichloroacetone is urgently needed for folic acid production.

[0005] According to publicly available technology, the main method for preparing 1,1,3-trichloroacetone is currently the acetone chlorination method. The hydrogen atom on the α-carbon of the acetone molecule, influenced by the carbonyl group, readily undergoes substitution reactions with halogens. Because chlorine is highly reactive, during chlorination, substitution first occurs at the methyl group (position 1) on the α-carbon to form monochloroacetone. Further chlorination, due to the electron-withdrawing effect of the Cl atom, makes the other H atoms of the methyl group at position 1 more reactive and easier to substitute, thus generating 1,1-dichloroacetone. Substitution at the other methyl group (position 3) becomes slower, resulting in less 1,3-dichloroacetone. When excess chlorine is used for further chlorination, more 1,1,1-trichloroacetone is obtained, resulting in poor selectivity for 1,1,3-trichloroacetone and ultimately low content and yield of 1,1,3-trichloroacetone.

[0006] Clearly, selectivity is a key factor in the chlorination process to prepare 1,1,3-trichloroacetone. Further chlorination of monochloroacetone predominates on 1,1-dichloroacetone, leading to a reduction in the production of 1,3-dichloroacetone. Therefore, to improve the content and yield of 1,1,3-trichloroacetone, optimizing reaction conditions and using catalysts can enhance the selectivity of the chlorination reaction of the target compound and reduce side reactions.

[0007] Patent document CN116283525B discloses a method for preparing 1,1,3-trichloropropanone. Using acetone as a raw material, 1,1,3-trichloropropanone is prepared by reacting it with the chlorinating agent N-chlorosuccinimide under the catalysis of 1-methylpyrazole. The reaction time is 9-12 hours, and the purity of 1,1,3-trichloropropanone is above 79.2%, with a yield above 62.0%. While the yield and purity of 1,1,3-trichloropropanone are improved by using a catalyst, a significant amount of 1,1,1-trichloropropanone byproducts are still generated.

[0008] Patent document CN107602364B discloses a method for preparing 1,1,3-trichloroacetone by chlorination of acetone. Using triethylamine as a catalyst and an alcohol compound as a solvent, this method significantly improves the selectivity of chlorination of 1,1-dichloroacetone, increases the formation of 1,1,3-trichloroacetone, and inhibits its formation. However, this method uses gas chromatography to monitor the reaction process in both the first and second chlorination stages, increasing the difficulty and complexity of control.

[0009] Ideally, obtaining more 1,3-dichloroacetone during the second-stage chlorination of acetone would significantly increase the final content and yield of 1,1,3-trichloroacetone. Patent document CN100494147C discloses a method for preparing 1,3-dichloroacetone, in which monochloroacetone is chlorinated under strong acid and water conditions using a platinum catalyst, yielding acetone and 1,3-dichloroacetone as products. This method avoids the formation of 1,1-dichloroacetone and exhibits high selectivity; however, the catalyst cost is too high, making industrial-scale production difficult.

[0010] The existing method for preparing 1,1,3-trichloroacetone is a one-pot process, where chlorine gas is directly introduced into a stirred acetone solution for reaction. This method is difficult to control and inevitably forms various chlorinated ketone byproducts such as 1,1,1-trichloroacetone, 1,1,3,3-tetrachloroacetone, and 1,1,1,3-tetrachloroacetone. Simply using a catalyst to improve the chlorination selectivity has extremely limited effect, resulting in low yield and low purity of 1,1,3-trichloroacetone. Summary of the Invention

[0011] To address the problems of low purity, low yield, low preparation efficiency, and difficulty in stable control during batch production of 1,1,3-trichloroacetone, this invention proposes a method for preparing trichloroacetone using a molecular sieve photocatalytic reaction. By enhancing the activity of acetone and chlorine, and using the micropores of the molecular sieve as the catalytic reaction channel, the hydrogen atoms of the two methyl groups of acetone and the chlorine radical (Cl·) are simultaneously substituted, thereby improving the selectivity of 1,1,3-trichloroacetone preparation, increasing reaction efficiency and yield, and significantly reducing the generation of byproducts.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A method for preparing trichloroacetone using a molecular sieve photocatalytic reaction mainly includes the following steps:

[0014] S1. Acetone and the composite catalyst are added to the reactor at a mass ratio of 100:(1-1.5), the stirring speed is adjusted to 50-80 rpm, and the mixture is stirred and activated for 15-20 min to obtain a pre-activated product; the composite catalyst is a combination of sodium ethoxide, N,N-dimethylacetamide and triethanolamine;

[0015] S2. Open the delivery valve to guide the pre-activated material from step S1 to the vertical reaction tower containing the molecular sieve. It will naturally seep down, and the pre-activated material will be completely adsorbed by the molecular sieve, which has a pore size of 6-10 angstroms. Chlorine gas, treated with ultraviolet light activation, will be introduced into the bottom of the vertical reaction tower at a flow rate of 0.20-0.25 mol / min. The total amount of chlorine gas introduced will be 2.5-3.0 times the molar amount of the pre-activated material (only acetone is considered). The chlorine gas will gradually rise from the bottom of the vertical reaction tower, chlorinating the pre-activated material step-by-step through the micropores of the molecular sieve.

[0016] S3. After the aeration is completed, continue the reaction for 0.5-1h, check the density of the reaction liquid in each section, and after it meets the standard, vacuum desorption is performed, and trichloroacetone is collected in the receiving tank at the bottom of the vertical reaction tower.

[0017] Preferably, the composite catalyst is a composition of sodium ethoxide, N,N-dimethylacetamide, and triethanolamine in a mass ratio of 2:3:5. The alkaline composite catalyst facilitates the activation of the α-H atom of acetone, making it easier to remove hydrogen atoms.

[0018] Preferably, the upper part of the vertical reaction tower is provided with an exhaust port, which is connected to an external negative pressure absorption tank. The hydrogen chloride gas generated by the replacement and a small amount of unreacted chlorine gas are introduced into the absorption tank through the exhaust port to form water absorption liquid and fix the emissions.

[0019] Preferably, the molecular sieve is a titanium-silicon molecular sieve with a pore size of 6-10 angstroms; the titanium-silicon molecular sieve is composed of microspheres with a diameter of 1-2 mm. The molecular sieve has a high specific surface area and a uniform microporous structure, providing a large number of active sites, thereby increasing the activity of the reactants. The titanium-silicon molecular sieve attracts chlorine molecules, making it easier for them to undergo a substitution reaction with acetone.

[0020] Preferably, the molar ratio of the pre-activated material (acetone only) to the chlorine gas introduced at the bottom of the column is 1:2.8. If the amount of chlorine gas used is too low, more dichloroacetone byproducts will be produced. If the amount of chlorine gas used is increased, deep chlorination products (such as 1,1,3,3-tetrachloroacetone, 1,1,1,3-tetrachloroacetone) will be formed, resulting in more impurities.

[0021] Preferably, the pressure of chlorine gas introduced at the bottom of the column is controlled at 0.01-0.05 MPa. By finely adjusting the flow rate and pressure of chlorine gas, the rising speed of chlorine gas from the bottom to the top of the column is controlled, thereby controlling the reaction progress.

[0022] Preferably, the wavelength of the ultraviolet light source in step S2 is 365-450nm; particularly preferably, ultraviolet light with a wavelength of 404.7nm generated by a high-pressure mercury lamp is used, with an optical power of 0.5-1.0kW. After being treated by the ultraviolet light source, the chlorine gas enters the bottom of the tower, and the ultraviolet light irradiation time of the chlorine gas is controlled at 8-10s.

[0023] Preferably, the vertical reaction tower is provided with three temperature control zones in sequence from bottom to top; the temperature control zones are controlled by jackets and built-in circulating cooling pipes; the temperature control of the first zone is 5-15℃, the temperature control of the second zone is 20-30℃, and the temperature control of the third zone is 45-50℃.

[0024] Further preferably, the density of the reaction solution is measured by sampling at the first, second, and third stages of the vertical reaction tower, serving as a basis for controlling the reaction progress. The preferred standard density of the reaction solution is 1.43-1.48 g / mL. Once the reaction density at each stage reaches the standard, vacuum desorption is initiated, and the crude acetone chlorination solution is collected in the receiving tank at the bottom of the vertical reaction tower.

[0025] The traditional method for preparing 1,1,3-trichloroacetone involves a one-pot process where chlorine gas is introduced into acetone. When an α-H on a methyl group of acetone is replaced by chlorine, the α-H at that site becomes more active and easier to be replaced, resulting in the production of 1,1-dichloroacetone, which in turn affects the selectivity of 1,1,3-trichloroacetone.

[0026] Unlike the one-pot method for preparing 1,1,3-trichloroacetone, this invention uses a composite catalyst to lower the activation energy of the hydrogen atoms on the methyl group of acetone, thereby increasing its activity and making it more readily involved in chemical reactions. Simultaneously, chlorine gas homolytically splits into two chlorine radicals (Cl·) under photocatalysis. These radicals selectively undergo substitution reactions with hydrogen atoms on the methyl group that have lower bond energies. The molecular sieve disperses the acetone, fully exposing its active sites and allowing it to rapidly react with the chlorine radicals (Cl·). This results in the simultaneous substitution of hydrogen atoms on both methyl groups of acetone by the chlorine radicals (Cl·), leading to the selective production of more 1,3-dichloroacetone. When excess chlorine gas is encountered, the reaction rate is controlled, and all 1,3-dichloroacetone is converted to 1,1,3-trichloroacetone.

[0027] In particular, by chlorination substitution in the micropores of the molecular sieve, the gas-liquid barrier affecting mass transfer is overcome, the reaction efficiency is greatly improved, and continuous, efficient and stable preparation of 1,1,3-trichloroacetone is achieved. The selectivity of the reaction is improved, the reaction progress is easy to control, and the obtained 1,1,3-trichloroacetone has high yield and high purity.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention utilizes a composite catalyst to activate acetone and photocatalyze chlorine gas to form chlorine free radicals (Cl·). In a highly active state, the α-H of acetone comes into contact with the chlorine free radicals (Cl·) to undergo a rapid substitution reaction, which promotes the simultaneous substitution of the α-H of the two methyl groups of acetone by the chlorine free radicals (Cl·), thereby selectively yielding more 1,1,3-trichloroacetone.

[0030] 2. This invention utilizes the micropores of molecular sieves to catalyze substitution reactions. Molecular sieve catalysts significantly improve reaction conversion and selectivity. As a reaction medium, the molecular sieve allows the reaction liquid and chlorine gas to be adsorbed within the micropores, ensuring sufficient contact and rapid substitution reactions. This avoids the gas-liquid barrier in traditional one-pot methods that negatively impacts reaction efficiency and homogeneity.

[0031] 3. The preparation method of the present invention has high preparation efficiency, high yield and high purity of 1,1,3-trichloroacetone, and the reaction progress parameters are easy to control, making it suitable for large-scale industrial production. Attached Figure Description

[0032] Figure 1 This is a simplified process flow diagram of the preparation of trichloroacetone using a molecular sieve photocatalytic reaction according to the present invention. In the diagram, 1-reaction vessel; 2-vertical reaction tower; 3-absorption tank; 4-liquid chlorine storage tank; 5-ultraviolet light source; 6-receiving tank. Detailed Implementation

[0033] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] As attached Figure 1 A simplified process flow diagram of the preparation of trichloroacetone using molecular sieve photocatalytic reaction is shown below. The process is as follows: acetone and composite catalyst are pre-mixed and activated in a reaction vessel (1) to obtain a pre-activated product; according to the reaction amount, the pre-activated product is transported to a vertical reaction tower (2), which is equipped with molecular sieves to adsorb the pre-activated product; after the liquid chlorine storage tank (4) is buffered and depressurized, chlorine gas is treated by ultraviolet light source (5) and enters the bottom of the tower; chlorine gas rises gradually from the bottom of the vertical reaction tower and chlorinates the pre-activated product step by step in the micropores of the molecular sieve; the hydrogen chloride gas generated by the substitution and a small amount of unreacted chlorine gas are introduced into the absorption tank (3) through the exhaust port to form a water absorption liquid and fix the discharge; the qualified reaction liquid after the substitution reaction is completed is desorbed by vacuum suction and trichloroacetone is collected in the receiving tank (6) at the bottom of the vertical reaction tower.

[0036] The specific implementation plan is as follows:

[0037] S1. 580.8g of acetone and the composite catalyst were added to the reactor at a mass ratio of 100:1.2. The stirring speed was adjusted to 50rpm and the mixture was stirred and activated for 20min to obtain a pre-activated product. The composite catalyst was a pre-mixed composition of sodium ethoxide, N,N-dimethylacetamide and triethanolamine in a mass ratio of 2:3:5.

[0038] S2. Open the delivery valve to guide the pre-activated material from step S1 to the vertical reaction tower containing the molecular sieve. It will naturally seep down and be completely adsorbed by the molecular sieve. The vertical reaction tower is set with three temperature control zones from bottom to top. The temperature control zones are controlled by a jacket and an internal circulating cooling pipe. The temperature control zone is 10℃ for the first zone, 25℃ for the second zone, and 50℃ for the third zone. The molecular sieve is a titanium-silicon microsphere molecular sieve with a pore size of 6-10 angstroms and a diameter of 1-2 mm.

[0039] After being buffered and depressurized, the liquid chlorine storage tank is used to activate the chlorine gas with ultraviolet light. The ultraviolet light source is a high-pressure mercury lamp that generates ultraviolet light with a wavelength of 404.7 nm and a light power of 1.0 kW. The illumination time is controlled at 8 s. The gas flow rate is 0.22 mol / min and the pressure is controlled at 0.03 MPa. The total amount of chlorine gas is measured as 2.8 times the molar amount of acetone. The chlorine gas rises gradually from the bottom of the vertical reaction tower and undergoes stepwise chlorination with the pre-activated material in the micropores of the molecular sieve. The gas flow is completed after about 127 minutes.

[0040] S3. Continue the reaction for 30 minutes, and check the density of each stage of the reaction solution. The density of the first stage reaction solution is 1.48 g / mL, the density of the second stage reaction solution is 1.48 g / mL, and the density of the third stage reaction solution is 1.47 g / mL. The reaction solution density meets the standard. Vacuum suction desorption is performed, and the solution is collected in the receiving tank at the bottom of the vertical reaction tower to obtain 1552 g of 1,1,3-trichloroacetone with a purity of 72.4%, with a yield of 69.6%.

[0041] Example 2

[0042] The specific implementation plan is as follows:

[0043] S1. 580.8g of acetone and the composite catalyst were added to the reactor at a mass ratio of 100:1.5. The stirring speed was adjusted to 50rpm and the mixture was stirred and activated for 20min to obtain a pre-activated product. The composite catalyst was a pre-mixed composition of sodium ethoxide, N,N-dimethylacetamide and triethanolamine in a mass ratio of 2:3:5.

[0044] S2. Open the delivery valve to guide the pre-activated material from step S1 to the vertical reaction tower containing the molecular sieve. It will naturally seep down and be completely adsorbed by the molecular sieve. The vertical reaction tower is set with three temperature control zones from bottom to top. The temperature control zones are controlled by jackets and built-in circulating cooling pipes. The temperature control zone is 5℃ for the first zone, 20℃ for the second zone, and 45℃ for the third zone. The molecular sieve is a microsphere zeolite molecular sieve with a pore size of 7-10 angstroms and a diameter of 1-2 mm.

[0045] After being buffered and depressurized, the liquid chlorine storage tank is used to activate the chlorine gas with ultraviolet light. The ultraviolet light source is a high-pressure mercury lamp that generates ultraviolet light with a wavelength of 404.7 nm and a light power of 1.0 kW. The illumination time is controlled at 10 s. The gas flow rate is 0.25 mol / min and the pressure is controlled at 0.05 MPa. The total amount of chlorine gas is measured as 3.0 times the molar amount of acetone. The chlorine gas rises gradually from the bottom of the vertical reaction tower and undergoes stepwise chlorination with the pre-activated material in the micropores of the molecular sieve. The gas flow is completed after about 120 minutes.

[0046] S3. Continue the reaction for 60 minutes, and check the density of each stage of the reaction solution. The density of the first stage reaction solution is 1.46 g / mL, the density of the second stage reaction solution is 1.47 g / mL, and the density of the third stage reaction solution is 1.44 g / mL. The reaction solution density meets the standard. Vacuum suction desorption is performed, and the solution is collected in the receiving tank at the bottom of the vertical reaction tower, yielding 1568 g of 1,1,3-trichloroacetone with a purity of 69.2%, and a yield of 67.2%.

[0047] Comparative Example 1

[0048] The process described in Example 1 was used, except that no composite catalyst was added to the acetone. 1576g of 1,1,3-trichloroacetone with a purity of 63.2% was obtained, with a yield of 61.7%.

[0049] Comparative Example 2

[0050] The process described in Example 1 was used, except that sodium ethoxide was replaced with N,N-dimethylacetamide as the composite catalyst added to the acetone. 1580g of 1,1,3-trichloroacetone with a purity of 66.7% was obtained, with a yield of 65.3%.

[0051] Comparative Example 3

[0052] The process scheme of Example 1 was adopted, except that the molecular sieve was replaced with a large-pore zeolite molecular sieve with a pore size of 50-100 angstroms; 1633g of 1,1,3-trichloroacetone with a purity of 57.7% was obtained, with a yield of 58.4%.

[0053] Comparative Example 4

[0054] The process described in Example 1 was used, except that chlorine was not used for photocatalytic activation. 1583g of 1,1,3-trichloroacetone with a purity of 64.0% was obtained, with a yield of 62.8%.

[0055] The purity and yield of 1,1,3-trichloroacetone obtained in each example and comparative example are shown in Table 1.

[0056] Table 1:

[0057] Implementation Plan 1,1,3-Trichloroacetone content (%) Yield of 1,1,3-trichloroacetone (%) Example 1 72.4 69.6 Example 2 69.2 67.2 Comparative Example 1 63.2 61.7 Comparative Example 2 66.7 65.3 Comparative Example 3 57.7 58.4 Comparative Example 4 64.0 62.8

[0058] The basic principles, main features, and advantages of this invention have been described above. In particular, the efficient dispersion of acetone by the molecular sieve when the pore size is close to that of an acetone molecule increases the probability that both methyl groups of acetone will be simultaneously substituted with chlorine, greatly enhancing the selectivity for obtaining 1,1,3-trichloroacetone. As in Comparative Example 3, when a larger pore size molecular sieve is used, the dispersion of acetone is limited due to the larger pore size, resulting in a significant decrease in the yield of 1,1,3-trichloroacetone and a decline in selectivity.

[0059] Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing trichloroacetone using a molecular sieve photocatalytic reaction, characterized in that, The main steps include the following: S1. Acetone and the composite catalyst are added to the reactor at a mass ratio of 100:(1-1.5), the stirring speed is adjusted to 50-80 rpm, and the mixture is stirred and activated for 15-20 min to obtain a pre-activated product; the composite catalyst is a combination of sodium ethoxide, N,N-dimethylacetamide and triethanolamine; S2. Open the delivery valve to guide the pre-activated material from step S1 to the vertical reaction tower containing the molecular sieve. It will naturally seep down, and the pre-activated material will be completely adsorbed by the molecular sieve, which has a pore size of 6-10 angstroms. Chlorine gas, treated with ultraviolet light activation, will be introduced into the bottom of the vertical reaction tower at a flow rate of 0.20-0.25 mol / min. The total amount of chlorine gas introduced will be 2.5-3.0 times the molar amount of acetone in the pre-activated material. The chlorine gas will gradually rise from the bottom of the vertical reaction tower, chlorinating the pre-activated material step-by-step through the micropores of the molecular sieve. S3. After the aeration is completed, continue the reaction for 0.5-1h. Check the density of the reaction liquid in each section. After the density meets the standard, vacuum desorption is performed, and 1,1,3-trichloroacetone is collected in the receiving tank at the bottom of the vertical reaction tower.

2. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The composite catalyst is a composition of sodium ethoxide, N,N-dimethylacetamide, and triethanolamine in a mass ratio of 2:3:

5.

3. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The molecular sieve is a titanium-silicon molecular sieve with a pore size of 6-10 angstroms; the titanium-silicon molecular sieve is a microsphere with a diameter of 1-2 mm.

4. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The vertical reaction tower is equipped with an exhaust port at the top, which is connected to an external negative pressure absorption tank. The hydrogen chloride gas generated during the replacement and a small amount of unreacted chlorine gas are introduced into the absorption tank through the exhaust port to form a water absorption liquid.

5. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The pressure of chlorine gas introduced into the bottom of the vertical reaction tower is controlled at 0.01-0.05 MPa.

6. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The wavelength of the ultraviolet light source mentioned in step S2 is 365-450nm.

7. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, The vertical reaction tower is provided with three temperature control zones in sequence from bottom to top: the first zone is 5-15℃, the second zone is 20-30℃, and the third zone is 45-50℃.

8. The method for preparing trichloroacetone using a molecular sieve photocatalytic reaction according to claim 1, characterized in that, In step S3, the density of the reaction solution is measured. The standard density of the reaction solution is 1.43-1.48 g / mL.

Images