Preparation method of epoxy chloropropane

Abstract

The invention belongs to the technical field of preparation of epoxy compounds, and particularly discloses a preparation method of epoxy chloropropane. The method comprises the following steps: firstly, mixing a composite catalyst with glycerol, introducing the mixture into a four-stage tandem reaction kettle, introducing hydrogen chloride gas into the four-stage tandem reaction kettle, and carrying out chlorohydrination reaction to obtain dichloropropanol; the obtained dichloropropanol is rectified, the rectified dichloropropanol and lime milk are introduced into a cyclization reaction tower for cyclization reaction, and epoxy chloropropane and cyclization liquid are obtained; and carrying out post-treatment on the cyclized liquid to obtain calcium chloride. The invention discloses application of four stages of tandem reaction kettles, which improves the mass transfer effect among raw materials and is beneficial to sufficient reaction. The composite catalyst has excellent catalytic activity and dichloropropanol selectivity. For low-purity glycerol, the yield is relatively high; the invention also realizes the byproduct calcium chloride, and improves the economic benefit.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of epoxy compounds, and in particular to a method for preparing epichlorohydrin. Background Art

[0002] Biodiesel, i.e. fatty acid esters made from the alcoholysis of plant and animal fats, has been produced on a large scale in many countries as an alternative fuel to petroleum diesel. It is necessary to actively develop the industrialization of biodiesel. In the preparation of biodiesel, glycerol is a by-product, accounting for about 1 / 10 of the total amount of biodiesel. Therefore, a large amount of crude glycerol will be generated during the production of biodiesel. Purification of crude glycerol can reduce the cost of biodiesel development. Therefore, it is of great significance to utilize its high-value by-product, glycerol, while developing biodiesel.

[0003] At present, the main industrial production methods of epichlorohydrin in the world are propylene high temperature oxidation method, propylene acetate method and glycerol method. Among them, propylene high temperature chlorination method is the most important production method at home and abroad, and glycerol method will become the development direction of epichlorohydrin production in the future due to its economic and environmental protection.

[0004] At the same time, the glycerol method for preparing epichlorohydrin also uses hydrogen chloride as a reaction raw material. The sales pressure of hydrogen chloride (hydrochloric acid) is very high, and sometimes it has to be subsidized before it can be shipped out of the factory. Therefore, using hydrogen chloride as a raw material to produce high-value-added epichlorohydrin can improve economic benefits, save resources, protect the environment, promote development, and also solve the problem of the outlet of hydrochloric acid.

[0005] The existing glycerol method for preparing epichlorohydrin generally uses a carboxylic acid compound as a catalyst, which is introduced into a reactor together with glycerol and hydrogen chloride to react and prepare dichloropropanol; then dichloropropanol undergoes a cyclization reaction to obtain epichlorohydrin. This method has the following disadvantages: (1) The purity of glycerol as a raw material is relatively high, and the purity of glycerol will greatly affect the yield of dichloropropanol, and thus the yield of epichlorohydrin; (2) The catalyst has low catalytic efficiency, resulting in a low yield of dichloropropanol and a slow reaction time; the selectivity of 1,3-dichloropropanol is low, and the content of the isomer 2,3-dichloropropanol is large. Although the cyclization reaction of 2,3-dichloropropanol can also produce epichlorohydrin, the reaction of 2,3-dichloropropanol is more difficult and the reaction conditions are more complicated; (3) The reaction is not sufficient or the processing volume is too small; (4) The problem of by-products is not considered.

[0006] Therefore, how to provide a method for preparing epichlorohydrin, improve the selectivity of the intermediate product 1,3-dichloropropanol, improve the catalytic effect of the catalyst, reduce the requirement for glycerol purity, and at the same time make the reaction fully proceed to obtain high-value by-products is a difficult problem to be solved in the art. Summary of the invention

[0007] In view of this, the present invention provides a method for preparing epichlorohydrin, which solves the various drawbacks of the traditional method for preparing epichlorohydrin, improves the purity and yield of epichlorohydrin, and obtains high-value by-product calcium chloride.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing epichlorohydrin comprises the following steps:

[0010] 1) mixing the composite catalyst with glycerol, introducing the mixture into a four-stage series reactor, introducing hydrogen chloride gas into the four-stage series reactor, and performing a chlorohydrin reaction to obtain dichloropropanol;

[0011] 2) rectifying the obtained dichloropropane, and passing the dichloropropane and lime milk after rectification into a cyclization reaction tower for cyclization reaction to obtain epichlorohydrin and cyclization liquid;

[0012] 3) The cyclization liquid is post-treated to obtain calcium chloride.

[0013] Preferably, the preparation method of the composite catalyst is to disperse adipic acid, ferric oxide and zinc oxide in water for reaction to obtain an intermediate product, and then disperse the intermediate product in acetic anhydride to obtain the composite catalyst.

[0014] Preferably, the molar ratio of adipic acid, ferric oxide and zinc oxide is 5:2-3:2-3; the reaction in the process of preparing the intermediate product is a reflux reaction, and the reaction time is 2-3 hours.

[0015] Preferably, the mass volume ratio of the intermediate product to acetic anhydride is 10 g:8-20 mL.

[0016] Preferably, in step 1), the volume ratio of the composite catalyst to glycerol is 1-3:100; the molar ratio of glycerol to hydrogen chloride gas is 1:2.4-2.8; and the mass purity of the glycerol is ≥80%.

[0017] Preferably, the temperature of the chlorohydrinization reaction is 100-120° C., the reaction time is 5-6 hours, and the reaction pressure is 0.07-0.1 MPa.

[0018] Preferably, in step 2), the molar ratio of dichloropropanol to calcium hydroxide in lime milk is 2:1.5-2.5.

[0019] Preferably, the post-processing step in step 3) includes sequentially performing stepwise temperature concentration under reduced pressure, evaporation concentration, and slice drying.

[0020] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention discloses the application of a four-stage series reactor. Glycerol with a catalyst added is first introduced into the first-stage reactor. As the amount of glycerol added increases, it will gradually overflow to the next-stage reactor until the four-stage series reactor is full. Hydrogen chloride gas is introduced into each stage of the reactor. The present invention distributes the chlorohydrin reaction to the four-stage series reactor, improves the contact between glycerol and hydrogen chloride gas, enhances the mass transfer effect, is conducive to promoting the full progress of the reaction, and avoids the waste of raw materials; the four-stage series reactor also increases the generation rate of dichloropropanol, providing sufficient raw materials for the subsequent cyclization reaction.

[0022] 2. The present invention discloses the addition of a composite catalyst. The catalyst disclosed in the present invention has excellent catalytic activity, showing an extremely high dichloropropanol yield, thereby also improving the yield of epichlorohydrin; at the same time, the catalyst of the present invention also has high selectivity for dichloropropanol and 1,3-dichloropropanol. When low-purity glycerol is used as a raw material, a yield close to the theoretical yield can also be obtained, and the yield is relatively high; and the catalyst of the present invention can also improve the selectivity of 1,3-dichloropropanol to more than 90%, which is beneficial to the subsequent cyclization reaction.

[0023] 3. The present invention also achieves by-product calcium chloride, thereby improving economic benefits; the preparation method disclosed in the present invention is simple and efficient, has low requirements for raw materials and operation, is highly efficient, and is suitable for large-scale promotion and application. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing epichlorohydrin, comprising the following steps:

[0025] 1) mixing the composite catalyst with glycerol, introducing the mixture into a four-stage series reactor, introducing hydrogen chloride gas into the four-stage series reactor, and performing a chlorohydrin reaction to obtain dichloropropanol;

[0026] 2) rectifying the obtained dichloropropane, and passing the dichloropropane and lime milk after rectification into a cyclization reaction tower for cyclization reaction to obtain epichlorohydrin and cyclization liquid;

[0027] 3) The cyclization liquid is post-treated to obtain calcium chloride.

[0028] In the present invention, the preparation method of the composite catalyst is to disperse adipic acid, ferric oxide and zinc oxide in water for reaction to obtain an intermediate product, and then disperse the intermediate product in acetic anhydride to obtain the composite catalyst.

[0029] In the present invention, the molar ratio of adipic acid, ferric oxide and zinc oxide is 5:2-3:2-3, preferably 5:2.2-2.8:2.2-2.8, more preferably 5:2.4-2.6:2.4-2.6, and most preferably 5:2.5:2.5.

[0030] In the present invention, the ferric oxide and zinc oxide are preferably added in equimolar amounts. When the two are added in equimolar amounts, the catalytic activity and selectivity of the catalyst both reach optimal values.

[0031] In the present invention, the reaction in the process of preparing the intermediate product is a reflux reaction, and the reaction time is 2 to 3 hours, specifically 2.2 hours, 2.4 hours, 2.5 hours, 2.6 hours, and 2.8 hours.

[0032] In the present invention, the mass volume ratio of the intermediate product to acetic anhydride is 10g:8-20mL, preferably 10g:10-18mL, further preferably 10g:12-16mL, and further preferably 10g:15mL.

[0033] In the present invention, the intermediate product mixed with acetic anhydride has the best glycerol conversion rate and dichloropropanol yield; in the present invention, acetic anhydride has a co-catalytic effect and also has a certain water absorption.

[0034] In the present invention, the volume ratio of the composite catalyst to glycerol in step 1) is 1-3:100, specifically 1.2:100, 1.5:100, 1.8:100, 2:100, 2.2:100, 2.5:100, 2.8:100; the molar ratio of glycerol to hydrogen chloride gas is 1:2.4-2.8, preferably 1:2.5-2.7, and more preferably 1:2.6.

[0035] In the present invention, the purity of glycerol is preferably ≥ 80%, specifically 82%, 84%, 85%, 90%, 95%, or 99.5%.

[0036] In the present invention, the composite catalyst and glycerol are preferably fully mixed before being introduced into the four-stage series reactor.

[0037] In the present invention, the temperature of the chlorohydrin reaction is 100-120°C, specifically 102°C, 105°C, 108°C, 110°C, 112°C, 115°C, 118°C; the reaction time is 10-14h, specifically 11h, 12h, 13h; the reaction pressure is 0.07-0.1MPa, specifically 0.075MPa, 0.08MPa, 0.085MPa, 0.09MPa, 0.095MPa.

[0038] In the present invention, the molar ratio of the dichloropropanol to the calcium hydroxide in the lime milk in step 2) is 2:1.5-2.5, preferably 2:1.8-2.2, and more preferably 2:2.

[0039] In the present invention, the post-processing step described in step 3) includes stepwise temperature concentration, evaporation concentration, and slice drying under reduced pressure conditions.

[0040] In the present invention, the post-treatment step is specifically as follows: the cyclized liquid from the bottom of the cyclization tower is filtered through a filter press to obtain a 15% calcium liquid, the 15% calcium liquid is sequentially pumped into a second-effect preheater, a second-effect evaporator, and a first-effect evaporator, and is gradually heated and concentrated to a 40% calcium liquid under reduced pressure conditions, the 40% calcium liquid is sent to a rising film evaporator for further evaporation and concentration, and is concentrated again to 70%, and enters a slice drying and packaging unit to produce solid calcium chloride.

[0041] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] Adipic acid, ferric oxide and zinc oxide were dispersed in water at a molar ratio of 5:2.5:2.5 for reflux reaction. The intermediate product was obtained after being reacted for 2.5 hours. The intermediate product was dried and fully ground, and dispersed in acetic anhydride (the ratio of the intermediate product to acetic anhydride was 10 g: 10 mL) to obtain a composite catalyst.

[0044] The composite catalyst is fully mixed with glycerol with a purity of 80%, and added to the four-stage series reactor of chlorohydrinization (the volume ratio of the composite catalyst to glycerol is 2.5:100). With the addition of raw materials, it overflows from the previous stage to the next stage until the four-stage series reactor is filled, and slowly heated to 60°C through a heat exchanger. At the same time, HCl gas is introduced into the bottom of each reactor (the molar ratio of glycerol to the introduced HCl gas is 1:2.5), the reaction temperature is maintained at 120°C, the pressure is 0.09MPa, the reaction residence time is 12 hours, and the reaction continues to generate dichloropropanol (dichloropropanol has two isomers, namely 2,3-dichloropropanol and 1,3-dichloropropanol, of which 1,3-dichloropropanol accounts for more than 90% of the total mass of dichloropropanol). The materials in the reactor are sent to the chlorohydrinization distillation process through a liquid pump. The tail gas of the reactor passes through the tail gas absorption tower, and the excess HCl is absorbed by glycerol. The absorption temperature is controlled below 50°C, and the absorbed glycerol is continuously extracted to the reactor. The total yield of the chlorohydrinization reaction was 93.6% (compared with the theoretical yield, the same below).

[0045] The materials in the four-stage series reactor of chlorohydrinization are pumped to the chlorohydrinization dehydration tower (packed tower) through a liquid pump, and the temperature of the dehydration tower is controlled at 100°C, and the vacuum of the dehydration tower is controlled at -95KPa. A small amount of dichloropropanol azeotropic liquid distilled from the top of the tower is condensed in a condenser and passed into an azeotropic liquid tank to enter the cyclization process; then the materials in the tower bottom are taken into the distillation tower, and the temperature of the distillation tower is controlled at 130°C, and the vacuum of the distillation tower is controlled at -98KPa. The dichloropropanol with a positive boiling point is taken from the top of the tower, condensed in a condenser, and collected in a positive boiling point receiving tank to enter the cyclization reaction process.

[0046] Add dichloropropanol in the positive boiling point and azeotropic liquid receiving tank to the cyclization reaction tower for reaction, control the vacuum of the cyclization tower at -55KPa, control the temperature of the tower bottom at 90℃, and pump the lime milk to the pipeline mixer, fully mix with dichloropropanol and add it to the cyclization reaction tower for reaction (the molar ratio of dichloropropanol to calcium hydroxide in lime milk is 2:2). The crude epichlorohydrin stripped by steam is condensed into the oil-water separator, and the liquid is separated after standing. The upper layer is the stripping water returned to the reaction tower, and the lower layer is the crude epichlorohydrin, which is sent to the cyclization distillation process; the bottom of the tower is the cyclization liquid sent to the filter press for disposal.

[0047] The crude epichlorohydrin obtained by the cyclization reaction adopts a vacuum distillation process, and the temperature of the tower kettle is first controlled in the dehydration tower to distill out low-boiling water and trace epichlorohydrin, which are condensed in the condenser and collected in a low-boiling point receiving tank. The mixed liquid is sent to the cyclization oil-water separator for stratification and then re-enters the dehydration tower; the tower kettle enters the distillation tower, controls the tower kettle temperature, distills out the product epichlorohydrin, and is condensed in the condenser and collected. The yield of epichlorohydrin in the cyclization reaction stage is 98.5%, and the purity is greater than 99%.

[0048] The cyclized liquid from the bottom of the cyclization tower is filtered through a filter press to obtain a 15% calcium liquid. The 15% calcium liquid is pumped into a second-effect preheater, a second-effect evaporator, and a first-effect evaporator in sequence. The temperature is gradually increased under reduced pressure and concentrated to a 40% calcium liquid. The 40% calcium liquid is sent to a rising film evaporator for further evaporation and concentration. After being concentrated again to 70%, it enters a slice drying and packaging unit to produce solid calcium chloride.

[0049] Example 2

[0050] Adipic acid, ferric oxide and zinc oxide are dispersed in water at a molar ratio of 5:3:3 for reflux reaction. The reaction is carried out for 3 hours to obtain an intermediate product. The intermediate product is dried and fully ground, and then dispersed in acetic anhydride (the ratio of the intermediate product to acetic anhydride is 10 g: 10 mL) to obtain a composite catalyst.

[0051] The composite catalyst is fully mixed with 90% glycerol, and added to the chlorohydrin four-stage series reactor (the volume ratio of the composite catalyst to glycerol is 1.5:100). With the addition of raw materials, it overflows from the previous stage to the next stage until the four-stage series reactor is filled, and slowly heated to 60°C through a heat exchanger. At the same time, HCl gas is introduced into the bottom of each reactor (the molar ratio of glycerol to the introduced HCl gas is 1:2.8), and the reaction temperature is maintained at 110°C, the pressure is 0.08MPa, and the reaction time is 5h. The reaction continues to generate dichloropropanol (dichloropropanol has two isomers, namely 2,3-dichloropropanol and 1,3-dichloropropanol, of which 1,3-dichloropropanol accounts for more than 90% of the total mass of dichloropropanol). The materials in the reactor are sent to the chlorohydrin distillation process through a liquid pump. The tail gas of the reactor passes through the tail gas absorption tower, and the excess HCl is absorbed by glycerol. The absorption temperature is controlled below 50°C, and the absorbed glycerol is continuously extracted to the reactor. The total yield of the chlorohydrinization reaction was 92.1%.

[0052] The materials in the four-stage series reactor of chlorohydrinization are pumped to the chlorohydrinization dehydration tower (same as above) through a liquid pump, and the temperature of the dehydration tower is controlled at 100°C, and the vacuum of the dehydration tower is controlled at -95KPa. A small amount of dichloropropanol azeotropic liquid distilled from the top of the tower is condensed by a condenser, and then passed into the azeotropic liquid tank to enter the cyclization process; then the materials in the tower bottom are taken into the distillation tower, and the temperature of the distillation tower is controlled at 130°C, and the vacuum of the distillation tower is controlled at -98KPa. The dichloropropanol with a positive boiling point is taken from the top of the tower, condensed by a condenser, and collected in a positive boiling point receiving tank to enter the cyclization reaction process.

[0053] Add dichloropropanol in the positive boiling point and azeotropic liquid receiving tank to the cyclization reaction tower for reaction, control the vacuum of the cyclization tower at -55KPa, control the temperature of the tower bottom at 90℃, and pump the lime milk to the pipeline mixer, fully mix with dichloropropanol and add it to the cyclization reaction tower for reaction (the molar ratio of dichloropropanol to calcium hydroxide in lime milk is 2:2). The crude epichlorohydrin stripped by steam is condensed into the oil-water separator, and the liquid is separated after standing. The upper layer is the stripping water returned to the reaction tower, and the lower layer is the crude epichlorohydrin, which is sent to the cyclization distillation process; the bottom of the tower is the cyclization liquid sent to the filter press for disposal.

[0054] The crude epichlorohydrin obtained by the cyclization reaction adopts a vacuum distillation process, and the temperature of the tower kettle is first controlled in the dehydration tower to distill out low-boiling water and trace epichlorohydrin, which are condensed in the condenser and collected in a low-boiling point receiving tank. The mixed liquid is sent to the cyclization oil-water separator for stratification and then re-enters the dehydration tower; the tower kettle enters the distillation tower, controls the tower kettle temperature, distills out the product epichlorohydrin, and is condensed in the condenser and collected. The yield of epichlorohydrin in the cyclization reaction stage is 98.3%, and the purity is greater than 99%.

[0055] The cyclized liquid from the bottom of the cyclization tower is filtered through a filter press to obtain a 15% calcium liquid. The 15% calcium liquid is pumped into a second-effect preheater, a second-effect evaporator, and a first-effect evaporator in sequence. The temperature is gradually increased under reduced pressure and concentrated to a 40% calcium liquid. The 40% calcium liquid is sent to a rising film evaporator for further evaporation and concentration. After being concentrated again to 70%, it enters a slice drying and packaging unit to produce solid calcium chloride.

[0056] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0057] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing epichlorohydrin, characterized in that: The steps include: 1) mixing the composite catalyst with glycerol, introducing the mixture into a four-stage series reactor, introducing hydrogen chloride gas into the four-stage series reactor, and performing a chlorohydrin reaction to obtain dichloropropanol; 2) rectifying the obtained dichloropropane, and passing the dichloropropane and lime milk after rectification into a cyclization reaction tower for cyclization reaction to obtain epichlorohydrin and cyclization liquid; 3) The cyclization liquid is post-treated to obtain calcium chloride.

2. The method for preparing epichlorohydrin according to claim 1, characterized in that: The preparation method of the composite catalyst comprises the following steps: dispersing adipic acid, ferric oxide and zinc oxide in water for reaction to obtain an intermediate product, and then dispersing the intermediate product in acetic anhydride to obtain the composite catalyst.

3. The method for preparing epichlorohydrin according to claim 2, characterized in that: The molar ratio of adipic acid, ferric oxide and zinc oxide is 5:2-3:2-3; the reaction in the process of preparing the intermediate product is a reflux reaction, and the reaction time is 2-3 hours.

4. The method for preparing epichlorohydrin according to claim 2 or 3, characterized in that: The mass volume ratio of the intermediate product to acetic anhydride is 10 g:8-20 mL.

5. The method for preparing epichlorohydrin according to any one of claims 1 to 3, characterized in that: Step 1) The volume ratio of the composite catalyst to glycerol is 1-3:100; the molar ratio of glycerol to hydrogen chloride gas is 1:2.4-2.8; and the mass purity of the glycerol is ≥80%.

6. The method for preparing epichlorohydrin according to claim 5, characterized in that: The temperature of the chlorohydrinization reaction is 100-120° C., the reaction time is 5-6 hours, and the reaction pressure is 0.07-0.1 MPa.

7. The method for preparing epichlorohydrin according to claim 6, characterized in that: The molar ratio of the dichloropropanol to the calcium hydroxide in the lime milk in step 2) is 2:1.5-2.

5.

8. The method for preparing epichlorohydrin according to claim 6 or 7, characterized in that: The post-processing step described in step 3) includes stepwise temperature concentration, evaporation concentration, and slice drying under reduced pressure.