Method for preparing dichloropropanol through glycerol chlorination

Abstract

The invention relates to the field of chemical production processes, in particular to a method for preparing dichloropropanol through glycerol chlorination. The invention relates to a method for preparing dichloropropanol by glycerol chlorination, which comprises the following steps: adding a catalyst into an adipic dialdehyde solution, introducing crude hydrogen chloride gas, and filtering after reaction to obtain feed liquid and hydrogen chloride gas; cooling the feed liquid, filtering and drying to obtain adipic acid crystals and a hydrochloric acid solution; and dissolving the adipic acid crystal in preheated glycerol, introducing hydrogen chloride gas, and reacting to obtain dichloropropanol. According to the present invention, the oxidation reduction reaction is performed on the adipaldehyde and the chlorine gas in the crude hydrogen chloride gas under the action of the catalyst, such that the chlorine gas impurity is effectively absorbed so as to reduce the probability of the side reaction of the chlorine gas and the glycerol so as to significantly improve the yield of the dichloropropanol; meanwhile, adipic acid generated by the reaction can be used as a catalyst for subsequent preparation of dichloropropanol from glycerol and hydrogen chloride gas, and a generated hydrochloric acid solution can be recycled and used for dissolving adipic dialdehyde, so that efficient utilization of resources is realized.

Description

Technical Field

[0001] The present application relates to the field of chemical production technology, and in particular to a method for preparing dichloropropanol by chlorinating glycerol. Background Art

[0002] With the adjustment and development of the automobile, energy, transportation and construction industries, the industrial demand for epoxy resin has increased greatly, which has also led to an increase in the demand for epichlorohydrin, the upstream raw material of epoxy resin. The glycerol method for preparing epichlorohydrin is an important epichlorohydrin production process, which mainly involves two basic reactions: (1) glycerol reacts with hydrogen chloride under catalysis to produce dichloropropanol; (2) dichloropropanol is cyclized with lime milk or sodium hydroxide solution to obtain epichlorohydrin.

[0003] At present, the domestic glycerin method for preparing epichlorohydrin generally uses crude hydrogen chloride, which contains chlorine impurities. Chlorine has strong oxidizing properties and will react with glycerin during the preparation process, resulting in increased glycerin consumption during the catalytic reaction of glycerin and hydrogen chloride to produce dichloropropanol, and will also reduce the quality of dichloropropanol obtained by the reaction, thereby reducing the market competitiveness of epichlorohydrin products. Summary of the invention

[0004] In order to improve the problem that chlorine impurities in crude hydrogen chloride gas will react with glycerol to produce side reactions, thereby increasing the consumption of glycerol in the process of generating dichloropropane from glycerol and hydrogen chloride, and at the same time reducing the quality of dichloropropane, the present application purifies the crude hydrogen chloride gas by using adipaldehyde to absorb the chlorine in the crude hydrogen chloride gas, so that the dichloropropane generated by glycerol and hydrogen chloride is more suitable for preparing epichlorohydrin.

[0005] The present application provides a method for preparing dichloropropanol by chlorination of glycerol, which adopts the following technical scheme: A method for preparing dichloropropane by chlorination of glycerol comprises the following steps: Step 1) dissolving adipaldehyde to obtain an adipaldehyde solution, wherein the solvent is water or a hydrochloric acid solution; Step 2) adding a catalyst to the adipaldehyde solution to obtain a first mixed solution; Step 3) introducing crude hydrogen chloride gas into the first mixed liquid, filtering after the reaction, and obtaining a feed liquid and hydrogen chloride gas; Step 4) cooling the feed liquid, filtering and drying to obtain adipic acid crystals and hydrochloric acid solution; step 5) dissolving the adipic acid crystals in the preheated glycerol to obtain a second mixed solution; Step 6) hydrogen chloride gas is introduced into the second mixed liquid to obtain dichloropropanol after reaction.

[0006] By adopting the above technical solution, under the action of the catalyst, adipaldehyde can undergo an oxidation-reduction reaction with chlorine in the crude hydrogen chloride gas, thereby effectively absorbing and removing chlorine impurities in the crude hydrogen chloride gas, thereby reducing the probability of side reactions and generation of by-products in the subsequent reaction between chlorine impurities and glycerol, reducing the consumption of glycerol, and increasing the yield of the generated dichloropropanol; Adipaldehyde reacts with chlorine to generate adipic acid and hydrochloric acid. Adipic acid crystals can be precipitated after the mixed solution of adipic acid and hydrochloric acid is cooled. The adipic acid crystals obtained after filtration can be used as a catalyst for the reaction of glycerol and hydrogen chloride gas to generate dichloropropanol in a subsequent step, thereby realizing the recycling of resources and saving production costs. Meanwhile, the hydrochloric acid solution remaining after filtering the adipic acid crystals can be recovered for dissolving adipic acid and continuously used for absorbing and removing chlorine in crude hydrogen chloride, thereby further realizing the recycling of resources and saving production costs.

[0007] The present application effectively absorbs chlorine impurities through the redox reaction of adipaldehyde with chlorine in crude hydrogen chloride gas under the action of a catalyst, thereby reducing the probability of side reactions between chlorine and glycerol, thereby significantly improving the yield of dichloropropane; at the same time, the adipic acid generated by the reaction of adipaldehyde with chlorine can be recycled and used as a catalyst for the subsequent preparation of dichloropropane from glycerol and hydrogen chloride gas, and the generated hydrochloric acid solution can be recycled and used as a solvent for dissolving adipaldehyde, thereby achieving efficient utilization of resources.

[0008] Preferably, the catalyst comprises at least one of tungsten oxide and molybdenum oxide.

[0009] Preferably, the catalyst is tungsten oxide.

[0010] By adopting the above technical solution, both tungsten oxide and molybdenum oxide have variable oxidation states, and the change of such oxidation states enables both to act as electron donors or acceptors in redox reactions; in the catalytic process, tungsten oxide and molybdenum oxide can accept or release electrons, promote electron transfer between reactants, and thus accelerate the redox reaction; at the same time, the surfaces of tungsten oxide and molybdenum oxide have a large number of active sites, which can adsorb and activate adipaldehyde molecules and chlorine molecules, reduce the activation energy of the reaction, and promote the reaction; In the reaction process of adipaldehyde and chlorine, tungsten oxide shows higher stability and has a more significant catalytic effect on the reaction of adipaldehyde and chlorine than molybdenum oxide. Therefore, tungsten oxide is preferred.

[0011] Preferably, the mass ratio of the adipaldehyde solution to tungsten oxide is 100:3-6.

[0012] By adopting the above technical solution, when the content of tungsten oxide is low, the active sites on the surface of tungsten oxide may not be sufficient to fully catalyze the redox reaction of adipaldehyde and chlorine, resulting in a decrease in the reaction rate; due to the low catalytic efficiency, the reaction of adipaldehyde and chlorine may be incomplete, resulting in the failure to effectively remove chlorine impurities; when the content of tungsten oxide is high, the catalytic effect of tungsten oxide on the reaction of adipaldehyde and chlorine is difficult to continue to improve, and for cost considerations, there is no need to continue to increase the content of tungsten oxide; for this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of adipaldehyde solution and tungsten oxide in this application is preferably the above.

[0013] Preferably, the catalyst is a mixture of tungsten oxide and molybdenum oxide.

[0014] By adopting the above technical scheme, tungsten oxide and molybdenum oxide have different electronic structures and oxidation state change capabilities. When the two are mixed, an electron transfer channel can be formed to promote the flow of electrons on the catalyst surface, thereby accelerating the redox reaction. The complementarity of this electronic structure further improves the activity of the catalyst and reduces the activation energy of the reaction. Since tungsten and molybdenum have similar atomic radii, tungsten oxide and molybdenum oxide can form an infinitely miscible solid solution. The mutual doping and vacancy filling between tungsten atoms and molybdenum atoms in the solid solution significantly improve the structural stability of the catalyst.

[0015] Preferably, the weight ratio of tungsten oxide to molybdenum oxide is 10:2-3.

[0016] By adopting the above technical scheme, when the content of molybdenum oxide in the mixture is low, the molybdenum oxide introduced into the catalyst is not sufficient to form an electron transfer channel with tungsten oxide, thereby promoting the flow of electrons on the surface of the catalyst, and the improvement of the catalytic effect of the catalyst is not obvious; when the content of molybdenum oxide in the mixture is high, since the catalytic effect of tungsten oxide on the reaction of adipaldehyde and chlorine is more significant than that of molybdenum oxide, excessive molybdenum oxide content will lead to a relative decrease in the content of tungsten oxide, which will in turn lead to a decrease in the catalytic effect of the mixture of tungsten oxide and molybdenum oxide; for this reason, the applicant finally determined after a lot of research and experimental verification that the weight ratio of tungsten oxide and molybdenum oxide in this application is preferably as mentioned above.

[0017] Preferably, in step 5), in the second mixed solution, the mass ratio of the preheated glycerol to the adipic acid crystals is 100:4-5.

[0018] By adopting the above technical solution, when the content of adipic acid crystals is low, adipic acid may not be sufficient to provide sufficient active sites to catalyze the reaction of glycerol and hydrogen chloride, thereby reducing the reaction rate; at the same time, adipic acid crystals may also play a role in regulating the reaction path in the reaction system. A low content may cause the adipic acid crystals to be unable to effectively inhibit the occurrence of side reactions, resulting in a decrease in the selectivity of the target product dichloropropanol and an increase in the generation of other by-products; When the content of adipic acid crystals is too high, the catalytic effect of adipic acid on the reaction of glycerol and hydrogen chloride is difficult to further improve. For cost considerations, there is no need to continue to add the content of adipic acid crystals. For this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of preheated glycerol and adipic acid crystals described in this application is preferably the above.

[0019] Preferably, in step 6), carboxyferrocene is further added to the second mixed solution, and the weight ratio of the preheated glycerol to carboxyferrocene is 100:0.3-0.5.

[0020] By adopting the above technical solution, the carboxyl group in carboxyferrocene can interact with the hydroxyl group in the glycerol molecule and the hydrogen ion in the hydrogen chloride molecule, thereby reducing the activation energy of the reaction; at the same time, the iron ion can act as an electron donor to participate in the electron transfer process, promote the breaking of the carbon-hydrogen bond in the glycerol molecule, and form a carbon cation intermediate, so that the addition of carboxyferrocene can further promote the reaction of glycerol and hydrogen chloride gas; When the content of carboxyferrocene is low, the carboxyferrocene introduced into the reaction system reduces the activation energy of the reaction, and the effect of promoting the breaking of the carbon-hydrogen bonds in the glycerol molecules is not obvious; when the content of carboxyferrocene is high, the effect of carboxyferrocene in promoting the reaction of glycerol and hydrogen chloride gas is difficult to further improve. For cost considerations, there is no need to continue to increase the content of carboxyferrocene; for this reason, the applicant finally determined after a lot of research and experimental verification that the weight ratio of glycerol and carboxyferrocene in this application is preferably as mentioned above.

[0021] Preferably, in step 4), the cooling temperature of the feed liquid is 25-30°C.

[0022] By adopting the above technical scheme, when the cooling temperature is low, the rate of change of the solubility of adipic acid in water with temperature change is small, and it is difficult to continue to precipitate adipic acid crystals; when the cooling temperature is high, the rate of change of the solubility of adipic acid in water with temperature change is large, and stopping cooling will cause a large amount of adipic acid to still be dissolved in the solution and cannot be effectively precipitated, thereby causing a waste of raw materials; for this reason, the applicant finally determined after a lot of research and experimental verification that the cooling temperature of the feed liquid in this application is preferably the above.

[0023] Preferably, in step 5), the preheating temperature of the preheated glycerol is 55-65°C.

[0024] By adopting the above technical scheme, when the preheating temperature is low, the solubility of adipic acid crystals in glycerol is limited, and the insufficient content of adipic acid crystals dissolved in glycerol will lead to a reduction in the catalytic effect of adipic acid on the reaction between glycerol and hydrogen chloride gas; when the preheating temperature is high, the temperature of glycerol is sufficient to allow the adipic acid crystals to fully dissolve, and for cost considerations, there is no need to continue to increase the preheating temperature of glycerol; for this reason, the applicant finally determined after a lot of research and experimental verification that the preheating temperature of glycerol in this application is preferably the above.

[0025] In summary, this application has the following beneficial effects: 1. The present application effectively absorbs chlorine impurities through the redox reaction of adipaldehyde with chlorine in crude hydrogen chloride gas under the action of a catalyst, thereby reducing the probability of side reactions between chlorine and glycerol, thereby significantly improving the yield of dichloropropanol; adipic acid generated by the reaction of adipaldehyde with chlorine can be used as a catalyst for the subsequent preparation of dichloropropanol from glycerol and hydrogen chloride gas, and the generated hydrochloric acid solution can be recycled as a solvent for dissolving adipaldehyde, thereby achieving efficient utilization of resources; 2. The present application adds tungsten oxide and molybdenum oxide to synergistically promote the electron transfer between adipaldehyde and chlorine, accelerate the redox reaction, and absorb the chlorine impurities in the crude hydrogen chloride gas, making the hydrogen chloride gas more suitable for the preparation of dichloropropanol; 3. The present application interacts with the carboxyl group in carboxyferrocene with the hydroxyl group in the glycerol molecule and the hydrogen ion in the hydrogen chloride molecule. The iron ion participates in the electron transfer process as an electron donor, promotes the breaking of the carbon-hydrogen bond in the glycerol molecule, and further promotes the reaction of glycerol and hydrogen chloride gas. DETAILED DESCRIPTION

[0026] The raw materials in this application include the following parts: Adipaldehyde: a commercially available product with CAS number 1072-21-5 is used; Crude hydrogen chloride: using the by-product hydrogen chloride gas discharged from the chlorinated paraffin unit; Adipic acid: a commercially available product with CAS No. 124-04-9 was used; Glycerol: a commercial product with CAS number 56-81-5 was used; Tungsten oxide: a commercially available product with CAS number 12036-22-5; Molybdenum oxide: a commercially available product with CAS number 18868-43-4; Carboxyferrocene: a commercially available product with CAS number 1293-87-4; The present application is further described in detail below in conjunction with embodiments and comparative examples.

[0027] Example 1 A method for preparing dichloropropane by chlorination of glycerol comprises the following steps: Step 1) Weigh 20 kg of adipaldehyde and dissolve it in 80 kg of hydrochloric acid solution (water or hydrochloric acid solution can be used), use a circulating pump to fully circulate and dissolve, and obtain an adipaldehyde solution, the operating temperature is 80° C., and the pressure is 8 kPaG; Step 2) adding 6 kg of catalyst (tungsten oxide) to the adipaldehyde solution to obtain a first mixed solution; Step 3) The crude hydrogen chloride gas from the paraffin chloride device is introduced into the first mixed liquid, and the tungsten oxide is filtered out after reacting for 3 hours. The reaction temperature is 100° C. and the pressure is 0.4 mPaG to obtain a feed liquid and hydrogen chloride gas; Step 4) cooling the feed liquid to 25° C. and filtering and drying to obtain adipic acid crystals and hydrochloric acid solution; Step 5) Weigh 5 kg of the adipic acid crystals obtained in step 4) and dissolve them in 100 kg of glycerol, the preheating temperature of the glycerol is 60° C., to obtain a second mixed solution; Step 6) The hydrogen chloride gas obtained in step 3) is introduced into the second mixed solution, and dichloropropanol is obtained after reacting for 4 hours.

[0028] Example 2 Example 2 Based on the preparation method of Example 1, in step 2), the catalyst is replaced by tungsten oxide with molybdenum oxide, and the other conditions remain unchanged.

[0029] Comparative Example 1 A method for preparing dichloropropane by chlorination of glycerol comprises the following steps: Step 1) Weigh 5 kg of adipic acid and dissolve it in 100 kg of glycerol (preheated at 60° C.) to obtain a mixed solution; Step 2) crude hydrogen chloride gas is introduced into the mixed solution to obtain dichloropropanol after reaction.

[0030] Comparative Example 2 Comparative Example 2 is based on the preparation method of Example 1, except that in step 2), no catalyst is added and other conditions remain unchanged.

[0031] Performance testing The products of Example 1-2 and Comparative Example 1-2 were subjected to the following performance tests, and the test results are shown in Table 1: The yield of dichloropropanol was analyzed by gas chromatography. The chromatographic column was a weak polar capillary column SE-54. The operating conditions were nitrogen 0.04 MPa and hydrogen 0.02 MPa for chromatographic analysis. The injector was 250°C, the detector was 260°C, and the column temperature was 150°C. n-Butanol was selected as the internal standard to prepare standard solutions of different concentrations of dichloropropanol (the mass ratios of dichloropropanol and n-butanol were 0.25:1, 0.50:1, 0.75:1, 1.00:1, and 1.25:1, respectively). The standard solution was subjected to the above chromatographic analysis, and the standard curve formula was obtained by fitting. The product samples after the reaction of Examples 1-2 and Comparative Example 1-2 of the present application were respectively weighed, and a test solution was prepared, wherein the mass ratio of the sample to n-butanol was 0.75:1. The above chromatographic analysis was performed on the test solution, and the mass concentration of dichloropropanol was calculated by substituting the above standard curve formula, thereby calculating the actual mass of dichloropropanol, and then calculating the yield of dichloropropanol: Yield of dichloropropane = (actual mass of dichloropropane obtained / theoretical mass of glycerol converted into dichloropropane) × 100%.

[0032] Table 1 Product performance test table of preparing dichloropropanol by chlorination of glycerol in Example 1-2 and Comparative Example 1-2 Referring to Table 1, by comparing Examples 1-2 and Comparative Examples 1-2, it can be seen that the yield of dichloropropane in Comparative Example 1 is much lower than that in Example 1-2, indicating that the yield of dichloropropane can be effectively improved by adding adipaldehyde and a catalyst, which may be due to the oxidation-reduction reaction between adipaldehyde and chlorine in the crude hydrogen chloride gas to generate adipic acid and hydrochloric acid, which consumes the content of chlorine impurities in the crude hydrogen chloride gas, reduces the consumption of glycerol by the side reaction between chlorine and glycerol, and thus significantly improves the yield of dichloropropane; the yield of dichloropropane in Comparative Example 2 is also much lower than that in Example 1-2, which may be due to the fact that tungsten oxide and molybdenum oxide in Example 1-2 participate in the oxidation-reduction reaction as electron donors or acceptors, promote electron transfer between reactants, and effectively consume chlorine in the crude hydrogen chloride gas.

[0033] In comparison, the yield of dichloropropane obtained by the preparation method of Example 1 is higher, and the catalytic effect of tungsten oxide on the reaction of adipaldehyde and chlorine is better than that of molybdenum oxide, which is preferred in Examples 1-2.

[0034] Embodiment 3-6 In Example 3-6, based on the preparation method of Example 1, the amount of tungsten oxide added was adjusted, and the specific adjustment is shown in Table 2.

[0035] The products of Examples 3-6 were subjected to the above performance tests, and the test results are shown in Table 2.

[0036] Table 2 Addition amount and performance test table of tungsten oxide in Example 1, Examples 3-6 Referring to Table 2, it can be seen from the comparison between Example 1 and Examples 3-6 that, as the amount of tungsten oxide added increases, the yield of dichloropropane shows a trend of increasing and then leveling off. This may be because as the amount of tungsten oxide added increases, tungsten oxide continuously promotes the electron transfer between adipaldehyde molecules and chlorine molecules, thereby promoting adipaldehyde to continuously absorb chlorine in the crude hydrogen chloride gas, reducing the additional consumption of glycerol by chlorine impurities, thereby increasing the yield of dichloropropane; When the amount of tungsten oxide added exceeds a certain range, the purity of hydrogen chloride and the yield of dichloropropanol are difficult to continue to increase, probably because the content of the added tungsten oxide is sufficient to fully react adipaldehyde and chlorine.

[0037] Example 7 Example 7 Based on the preparation method of Example 1, in step 2), the catalyst is replaced with a mixture of tungsten oxide and molybdenum oxide, wherein the mass ratio of tungsten oxide to molybdenum oxide is 10:1.5, and the other conditions remain unchanged.

[0038] Embodiment 8-11 Examples 8-11 are based on the preparation method of Example 7, and the mass ratio of tungsten oxide to molybdenum oxide in the mixture is adjusted. The specific adjustment is shown in Table 3.

[0039] The products of Examples 7-11 were subjected to the above performance tests, and the test results are shown in Table 3.

[0040] Table 3 Mixture ratio and performance test table of Example 1 and Examples 7-11 Referring to Table 3, by comparing Example 1 with Examples 7-11, it can be seen that using the mixture of tungsten oxide and molybdenum oxide as a catalyst for the reaction of adipaldehyde and chlorine can effectively improve the yield of dichloropropanol, which may be due to the formation of an electron transfer channel when tungsten oxide and molybdenum oxide are mixed, which promotes the flow of electrons on the catalyst surface, thereby accelerating the redox reaction; As the ratio of tungsten oxide: molybdenum oxide decreases, the yield of dichloropropanol shows a trend of increasing and then decreasing. This may be because as the content of molybdenum oxide in the mixture continues to increase, molybdenum oxide continuously forms electron transfer channels with tungsten oxide, promoting the flow of electrons on the catalyst surface. When the content of molybdenum oxide exceeds a certain range, the content of molybdenum oxide in the mixture is relatively low, resulting in a decrease in the catalytic performance of the mixture.

[0041] Examples 12-15 In Examples 12-15, based on the preparation method of Example 1, in step 4), the cooling temperature of the feed liquid is adjusted, and the specific adjustments are shown in Table 4.

[0042] Performance testing The performance of Example 1 and Examples 12-15 was tested, and the test results are shown in Table 4.

[0043] Adipic acid crystals yield In the preparation methods of Example 1 and Examples 12-15, weigh the mass of the adipic acid crystals obtained in step 4).

[0044] Table 4 Cooling temperature and performance test table of Example 1, Example 12-15 Referring to Table 4, it can be seen from the comparison of Example 1 and Examples 12-15 that, as the cooling temperature continues to decrease, the mass of the adipic acid crystals precipitated in the slurry increases and then gradually tends to be stable. This may be because as the cooling temperature continues to decrease, the solubility of adipic acid in water continues to decrease, resulting in an increasing number of precipitated adipic acid crystals; when the cooling temperature is reduced to a certain level, the mass of the adipic acid crystals precipitated in the slurry is difficult to continue to increase. This is because the solubility of adipic acid in water changes at a relatively small rate as the temperature decreases within this temperature range.

[0045] Examples 16-19 In Examples 16-19, based on the preparation method of Example 1, in step 5), the amount of adipic acid crystals added was adjusted, and the specific adjustments are shown in Table 5.

[0046] The products of Examples 16-19 were subjected to the above performance tests, and the test results are shown in Table 5.

[0047] Table 5 Addition amount and performance test table of adipic acid crystals of Example 1 and Examples 16-19 Referring to Table 5, it can be seen from the comparison of Example 1 and Examples 16-19 that with the increase of the content of adipic acid crystals, the yield of dichloropropanol continues to increase. This may be because with the increase of the content of adipic acid crystals, adipic acid continuously provides active sites to catalyze the reaction of glycerol and hydrogen chloride, thereby promoting the formation of dichloropropanol. When the content of adipic acid crystals exceeds a certain range, the yield of dichloropropanol is difficult to continue to increase, which may be because adipic acid has provided enough active sites to catalyze the reaction between glycerol and hydrogen chloride.

[0048] Examples 20-23 In Examples 20-23, based on the preparation method of Example 1, in step 5), the preheating temperature of glycerol is adjusted, and the specific adjustments are shown in Table 6.

[0049] The products of Examples 20-23 were subjected to the above performance tests, and the test results are shown in Table 6.

[0050] Table 6 Preheating temperature and performance test data of Example 1, Examples 20-23 Referring to Table 6, it can be seen from the comparison of Example 1 and Examples 20-23 that, as the preheating temperature of glycerol increases, the yield of dichloropropanol shows a trend of continuously increasing and then tending to be flat. This may be because as the preheating temperature of glycerol continues to increase, the solubility of adipic acid in glycerol continues to increase, thereby continuously promoting the reaction of glycerol and hydrogen chloride gas; when the preheating temperature of glycerol exceeds a certain range, the added adipic acid has been fully dissolved in glycerol, and at this time, the effect of increasing the preheating temperature on the improvement of the yield of dichloropropanol is no longer significant, so the yield of dichloropropanol shows a trend of tending to be flat.

[0051] Examples 24-28 Example 24 Based on the preparation method of Example 1, in step 6), before the introduction of hydrogen chloride gas, 0.5 kg of carboxyferrocene is added to the second mixed solution, and the other conditions remain unchanged.

[0052] Examples 25-28 are based on the preparation method of Example 24. In step 6), the amount of carboxyferrocene added is adjusted. The specific adjustments are shown in Table 7.

[0053] The products of Examples 24-28 were subjected to the above performance tests, and the test results are shown in Table 7.

[0054] Table 7: Addition amount and performance test data of carboxyferrocene of Example 1 and Examples 24-28 Referring to Table 7, by comparing Example 1 with Examples 24-28, it can be seen that the addition of carboxyferrocene can further catalyze the reaction between glycerol and hydrogen chloride gas, thereby further improving the yield of dichloropropanol. This may be due to the interaction between the carboxyl group in carboxyferrocene and the hydroxyl group in the glycerol molecule and the hydrogen ion in the hydrogen chloride molecule. At the same time, the iron ion, as an electron donor, participates in the electron transfer process and promotes the breaking of the carbon-hydrogen bond in the glycerol molecule.

[0055] As the content of carboxyferrocene continues to increase, the yield of dichloropropanol increases and then tends to be flat. This may be because as the dry food of carboxyferrocene continues to increase, carboxyl groups and iron ions are continuously introduced into the reaction system, thereby continuously promoting the occurrence of the reaction; when the content of carboxyferrocene exceeds a certain range, the number of carboxyl groups and iron ions introduced into the reaction system has reached saturation. At this time, even if the content of carboxyferrocene is increased, it is difficult to further significantly promote the reaction, so the yield of dichloropropanol tends to be flat.

[0056] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing dichloropropane by chlorination of glycerol, characterized in that: The following steps are involved: Step 1) dissolving adipaldehyde to obtain an adipaldehyde solution, wherein the solvent is water or a hydrochloric acid solution; Step 2) adding a catalyst to the adipaldehyde solution to obtain a first mixed solution; Step 3) introducing crude hydrogen chloride gas into the first mixed liquid, filtering after the reaction, and obtaining a feed liquid and hydrogen chloride gas; Step 4) cooling the feed liquid, filtering and drying to obtain adipic acid crystals and hydrochloric acid solution; Step 5) dissolving the adipic acid crystals in the preheated glycerol to obtain a second mixed solution; Step 6) introducing hydrogen chloride gas into the second mixed liquid to obtain dichloropropanol after reaction.

2. The method for preparing dichloropropane by chlorination of glycerol according to claim 1, characterized in that: In the step 2), the catalyst includes at least one of tungsten oxide and molybdenum oxide.

3. The method for preparing dichloropropane by chlorination of glycerol according to claim 2, characterized in that: The catalyst is tungsten oxide.

4. The method for preparing dichloropropane by chlorination of glycerol according to claim 3, characterized in that: The mass ratio of the adipaldehyde solution to tungsten oxide is 100:3-6.

5. The method for preparing dichloropropane by chlorination of glycerol according to claim 2, characterized in that: The catalyst is a mixture of tungsten oxide and molybdenum oxide.

6. The method for preparing dichloropropane by chlorination of glycerol according to claim 5, characterized in that: The weight ratio of the tungsten oxide to the molybdenum oxide is 10:2-3.

7. The method for preparing dichloropropane by chlorination of glycerol according to claim 1, characterized in that: In the step 5), in the second mixed liquid, the mass ratio of the preheated glycerol to the adipic acid crystals is 100:4-5.

8. The method for preparing dichloropropane by chlorination of glycerol according to claim 1, characterized in that: In the step 6), carboxyferrocene is further added to the second mixed solution, and the weight ratio of the preheated glycerol to carboxyferrocene is 100:0.3-0.

5.

9. The method for preparing dichloropropane by chlorination of glycerol according to claim 1, characterized in that: In the step 4), the cooling temperature of the feed liquid is 25-30°C.

10. The method for preparing dichloropropane by chlorination of glycerol according to claim 1, characterized in that: In the step 5), the preheating temperature of the preheated glycerol is 55-65°C.

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