Preparation method of 2-chloroethanol and catalyst

Abstract

The invention relates to the technical field of fine chemical engineering, and particularly discloses a preparation method and a catalyst of 2-chloroethanol. Activated carbon provided by the invention has a high specific surface area and a porous structure, can be used as a mass transfer channel to promote diffusion of ethylene glycol and HCl to ZrO2 active sites, and can be used for preparing 2-chloroethanol through an addition reaction between double bonds. Maleic acid is grafted on the composite carrier, a carboxylic acid group passes through hydroxyl of protonated ethylene glycol to form a protonated intermediate, the nucleophilicity of the hydroxyl is reduced in the process, the electron deficiency of hydroxyl oxygen is enhanced, the hydroxyl oxygen is more easily substituted by Cl <->, and the catalytic effect of the catalyst is improved under the combined action of the carboxylic acid group and zirconium oxide; meanwhile, the activated carbon serves as a solid supporting body, so that the catalyst is easily recycled through filtration or centrifugation, the problem that a traditional homogeneous catalyst (such as adipic acid) is difficult to recycle is solved, and in addition, the catalyst provided by the invention still has a good catalytic effect after being recycled and reused.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemical engineering, and particularly relates to a preparation method of 2-chloroethanol and a catalyst therefor. Background Art

[0002] 2-Chloroethanol is an important organic solvent and organic synthesis raw material. It is not only an important raw material for synthesizing polythiirubber, but also widely used in the pharmaceutical, dye, and pesticide industries. Currently, the mainstream synthesis methods in industry include the addition method of ethylene oxide and hydrogen chloride, the hydrochlorination method of ethylene glycol, etc. Among them, the hydrochlorination method of ethylene glycol has gradually attracted attention due to the safety of raw materials and the controllability of the process. However, this process generally has the bottleneck problem of difficult catalyst recovery. For example, although traditional carboxylic acid catalysts (such as adipic acid) can improve the reaction rate, due to their homogeneous characteristics, they are miscible with the product system after the reaction and are difficult to recycle through simple separation, resulting in high catalyst consumption, increased production costs, and waste liquid pollution.

[0003] For example, Chinese patent document CN110922299A discloses a continuous preparation method of high-content 2-chloroethanol. The specific steps are as follows: quantitative ethylene glycol, 36% hydrochloric acid, water, and the catalyst adipic acid are used as the bottom material, and the reaction is carried out at 110-120 °C until reflux appears, and a mixed solution of ethylene glycol, 36% hydrochloric acid, and water is continuously dropped in; meanwhile, the generated 2-chloroethanol and water are distilled out as an azeotrope at this temperature. By controlling the reflux ratio of 2:3, a part of the condensate is refluxed to the packed tower, and the other part enters the receiving tank to obtain a crude product of about 42% 2-chloroethanol. Finally, the crude product is dehydrated with benzene, debenzene, and vacuum rectified to obtain 2-chloroethanol with a content of more than 99%. Although the yield of 2-chloroethanol in the above preparation method can reach more than 99%, the catalyst adipic acid in the above method is miscible with the product system after the reaction and is difficult to recycle through simple separation, resulting in high catalyst consumption and increased production costs.

[0004] In the existing process, the consumption of the catalyst accounts for 20%-30% of the total cost, and the treatment of waste catalysts increases the environmental burden. Therefore, developing a catalytic system with high activity, easy separation, and recyclability is of great significance for reducing production costs and promoting the development of green chemical engineering. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of 2-chloroethanol and a catalyst therefor.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A catalyst for preparing 2-chloroethanol, and the preparation method of the catalyst is as follows:

[0008] S1. Prepare a composite support

[0009] Disperse activated carbon in deionized water, then add zirconium oxychloride thereto, mix evenly, adjust the pH of the solution to 10 - 12, and then carry out a hydrothermal reaction. After the reaction is completed, wash and dry to obtain a composite support.

[0010] In this step, the mass ratio of the activated carbon to the zirconium oxychloride is 5 - 10:4 - 8. In some embodiments of the present invention, for example, 5:4, 5:6, 5:8, 8:4, 8:6, 8:8, 10:4, 10:5, 10:8 can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0011] In this step, the solution used to adjust the pH of the solution is NaOH solution.

[0012] In this step, the temperature of the hydrothermal reaction is 190 - 210 °C, for example, 190 °C, 195 °C, 200 °C, 205 °C, 210 °C can be selected; the time of the hydrothermal reaction is 1 - 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0013] Activated carbon has an extremely high specific surface area (usually reaching 500 - 2000 m 2 / g) and a porous structure. Zirconia has excellent acid resistance and thermal stability. In the present invention, through the hydrothermal reaction, the ZrO2 nanoparticles generated by the hydrolysis of zirconium oxychloride can be embedded in the pores of the activated carbon to form highly dispersed active sites. This structure not only increases the active surface area of the catalyst, but also inhibits the aggregation of ZrO2 particles through the pore confinement effect of the activated carbon. Zirconia has both Lewis acid (Zr 4+ ) and basic (surface hydroxyl) sites. Loading it on the activated carbon improves the catalytic performance of the activated carbon.

[0014] S2. Preparation of a double - bond - modified composite support

[0015] Disperse the composite support in an ethanol - aqueous solution, then add a vinylsilane coupling agent thereto, stir, wash and dry to obtain a double - bond - modified composite support.

[0016] In this step, the mass ratio of the composite support to the vinylsilane coupling agent is 10 - 15:1 - 3. For example, 10:1, 10:2, 10:3, 12:1, 12:2, 12:3, 15:1, 15:2, 15:3 can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] In this step, the vinyl silane coupling agent is selected from vinyltrimethoxysilane or vinyltriethoxysilane.

[0018] In this step, by using the vinyl silane coupling agent to perform surface treatment on the composite support, double bonds are introduced onto the surface of the composite support, which is beneficial to the subsequent reaction.

[0019] S3. Preparation of the catalyst

[0020] Disperse the double-bond modified composite support in deionized water, then add maleic anhydride thereto, mix evenly, and then add an initiator, and carry out the reaction in a nitrogen atmosphere. After the reaction is completed, wash and dry to obtain the catalyst.

[0021] In this step, the mass ratio of the double-bond modified composite support, maleic anhydride and the initiator is 5 - 10:4 - 8:1 - 2.

[0022] Specifically, the initiator is selected from persulfates, for example, potassium persulfate, sodium persulfate or ammonium persulfate can be selected.

[0023] In this step, the reaction temperature is 50 - 80 °C, for example, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C can be selected; the reaction time is 2 - 5 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h can be selected, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] In this step, maleic anhydride is first hydrolyzed to form maleic acid, and then through the addition reaction between double bonds, carboxylic acid groups are grafted onto the composite support. The carboxylic acid groups protonate the hydroxyl groups of ethylene glycol to form a protonated intermediate. This process reduces the nucleophilicity of the hydroxyl groups and at the same time enhances the electron-deficiency of the hydroxyl oxygen, making it more easily substituted by Cl-. The combined action of the carboxylic acid groups and zirconia improves the catalytic effect of the catalyst.

[0025] The present invention provides a method for preparing 2-chloroethanol, comprising the following steps:

[0026] Put ethylene glycol, hydrochloric acid, water and the above catalyst as the bottom material into the reaction kettle, stir and heat up. When the temperature in the kettle reaches 110 - 120 °C and reflux appears, continuously drop a mixed solution of ethylene glycol, hydrochloric acid and water into the bottom material at a dropping rate of 150 - 200 g / h. The 2-chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises through the packing tower to the top condenser. The condenser condenses the rising steam, adjusts the reflux ratio, enables a part of the condensed liquid to reflux and fully contact with the continuously rising steam in the packing tower, and the other part enters the receiving tank to obtain the crude 2-chloroethanol.

[0027] Specifically, the mass ratio of ethylene glycol, hydrochloric acid, water and catalyst in the base material is 8.45 - 8.50:5.10 - 5.15:1.30 - 1.31:1.2 - 1.5.

[0028] Specifically, the mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.1 - 2.4:3.5 - 3.8:1.

[0029] The present invention also provides a purification method for the above-mentioned crude 2-chloroethanol, comprising the following steps:

[0030] (1) Put the crude 2-chloroethanol into a distillation kettle, add benzene as a water-carrying agent, and keep the top temperature at 67 - 72 °C to remove sufficient water;

[0031] (2) Heat and keep the kettle temperature at 110 - 130 °C to remove sufficient benzene as the water-carrying agent;

[0032] (3) Cool the distillation kettle to 60 ± 5 °C, start and maintain the vacuum degree at -0.095 Mpa to -0.1 Mpa, and distill out high-content 2-chloroethanol at a kettle temperature between 65 - 130 °C.

[0033] Specifically, the addition amount of the water-carrying agent benzene is 30% of the weight of the crude 2-chloroethanol put in. After the dehydration stage is completed, continue to heat to remove sufficient benzene, and the removed benzene can be recycled and used as the water-carrying agent for the next dehydration stage.

[0034] Specifically, during the vacuum distillation process, the fraction distilled out at a kettle temperature between 65 - 80 °C is the fore fraction, which can be separately collected and put into the distillation kettle for use in the next distillation stage; the fraction distilled out at a kettle temperature between 80 - 130 °C is 2-chloroethanol with a content of more than 99%.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Through the hydrothermal reaction of the present invention, the ZrO2 nanoparticles generated by the hydrolysis of zirconium oxychloride can be embedded in the pores of activated carbon to form highly dispersed active sites. This structure not only increases the active surface area of the catalyst, but also inhibits the agglomeration of ZrO2 particles through the pore confinement effect of activated carbon. Zirconium oxide has both Lewis acid (Zr 4+ ) and basic (surface hydroxyl) sites. Loading it on activated carbon improves the catalytic performance of activated carbon.

[0037] (2) Through the addition reaction between double bonds of the present invention, maleic acid is grafted onto the composite support. The carboxylic acid group protonates the hydroxyl group of ethylene glycol to form a protonated intermediate. This process reduces the nucleophilicity of the hydroxyl group and at the same time enhances the electron-deficient property of the hydroxyl oxygen, making it more easily substituted by Cl-. The combined action of the carboxylic acid group and zirconium oxide improves the catalytic effect of the catalyst.

[0038] (3) The activated carbon provided by the present invention has a high specific surface area and a porous structure, which can serve as a mass transfer channel to promote the diffusion of ethylene glycol and HCl to the active sites of ZrO2. At the same time, as a solid support, the activated carbon makes the catalyst easy to be recovered by filtration or centrifugation, solving the problem that traditional homogeneous catalysts (such as adipic acid) are difficult to recover. In addition, the catalyst provided by the present invention still has good catalytic effect after being recycled. Description of the Drawings

[0039] Figure 1 It is a graph of the reuse results of the catalyst prepared in Example 1 of the present invention. Detailed Embodiments

[0040] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0041] It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are all purchased through commercial channels.

[0042] The activated carbon used in the embodiments of the present invention is coconut shell activated carbon with a mesh number of 200; the mass fraction of hydrochloric acid is 36%.

[0043] Example 1

[0044] A method for preparing 2-chloroethanol includes the following steps:

[0045] Put 425 g of ethylene glycol, 257.5 g of hydrochloric acid, 65 g of water and 60 g of catalyst as the bottom material into the reaction kettle, stir and heat up. When the temperature in the kettle reaches 110 °C, reflux appears. At a dropping rate of 150 g / h, continuously drop the mixed solution into the bottom material. The mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.2:3.6:1. The 2-chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises to the top condenser through the packed tower. The condenser condenses the rising steam, adjusts the reflux ratio to 2:3, so that a part of the condensate realizes reflux and fully contacts with the continuously rising steam in the packed tower, and the other part enters the receiving tank, thus obtaining the crude product of 2-chloroethanol.

[0046] Among them, the preparation method of the catalyst is as follows:

[0047] S1. Disperse 5 g of activated carbon in 100 mL of deionized water, then add 4 g of zirconium oxychloride thereto, mix evenly, adjust the pH of the solution to 10, and then carry out a hydrothermal reaction. The temperature of the hydrothermal reaction is 190 °C and the time of the hydrothermal reaction is 3 h. After the reaction is completed, wash and dry to obtain a composite support;

[0048] S2. Disperse 10 g of the composite support in 100 mL of an 80 wt% ethanol aqueous solution, then add 1 g of vinyltriethoxysilane thereto, stir for 2 h, wash and dry to obtain a double-bond modified composite support;

[0049] S3. Disperse 5 g of the double-bond modified composite support in 100 mL of deionized water, then add 4 g of maleic anhydride thereto, mix evenly, and then add 1 g of initiator ammonium persulfate, and carry out the reaction in a nitrogen atmosphere. The reaction temperature is 50 °C and the reaction time is 5 h. After the reaction is completed, wash and dry to obtain the catalyst.

[0050] Based on HCl, the yield of 2-chloroethanol in the reaction stage of this example is 99.6%.

[0051] Example 2

[0052] A method for preparing 2-chloroethanol, comprising the following steps:

[0053] Put 282 g of ethylene glycol, 171 g of hydrochloric acid, 43.5 g of water and 40 g of catalyst as the bottom material into the reaction kettle, stir and heat up. When the temperature in the kettle reaches 110 °C, reflux appears. Add the mixed solution continuously to the bottom material at a dropping rate of 150 g / h. The mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.2:3.6:1. The 2-chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises to the top condenser through the packed tower. The condenser condenses the rising steam, adjusts the reflux ratio to 2:3, so that a part of the condensate realizes reflux and fully contacts with the continuously rising steam in the packed tower, and the other part enters the receiving tank to obtain the crude product of 2-chloroethanol.

[0054] Among them, the preparation method of the catalyst is as follows:

[0055] S1. Disperse 10 g of activated carbon in 100 mL of deionized water, then add 8 g of zirconium oxychloride thereto, mix evenly, adjust the pH of the solution to 10, and then carry out hydrothermal reaction. The temperature of the hydrothermal reaction is 210 °C and the time of the hydrothermal reaction is 1 h. After the reaction is completed, wash and dry to obtain the composite support;

[0056] S2. Disperse 15 g of the composite support in 100 mL of an 80 wt% ethanol aqueous solution, then add 3 g of vinyltriethoxysilane thereto, stir for 2 h, wash and dry to obtain a double-bond modified composite support;

[0057] S3. Disperse 10 g of the double-bond modified composite support in 100 mL of deionized water, then add 8 g of maleic anhydride thereto, mix evenly, and then add 2 g of the initiator ammonium persulfate. React in a nitrogen atmosphere at a reaction temperature of 80 °C for 2 h. After the reaction is completed, wash and dry to obtain the catalyst.

[0058] Based on HCl, the yield of 2-chloroethanol in the reaction stage of this example is 99.4%.

[0059] Comparative Example 1

[0060] A method for preparing 2-chloroethanol includes the following steps:

[0061] Put 425 g of ethylene glycol, 257.5 g of hydrochloric acid, 65 g of water and 60 g of catalyst as the bottom material into the reaction kettle, stir and heat up. When the temperature in the kettle reaches 110 °C, reflux appears. At a dropping rate of 150 g / h, continuously drop the mixed solution into the bottom material. The mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.2:3.6:1. The 2-chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises through the packing tower to the top condenser. The condenser condenses the rising steam, adjusts the reflux ratio to 2:3, makes a part of the condensate return, fully contacts with the continuously rising steam in the packing tower, and the other part enters the receiving tank to obtain the crude 2-chloroethanol.

[0062] Among them, the preparation method of the catalyst is as follows:

[0063] S1. Disperse 10 g of activated carbon in 100 mL of 80 wt% ethanol aqueous solution, then add 1 g of vinyltriethoxysilane thereto, stir for 2 h, wash and dry to obtain the double-bond modified activated carbon.

[0064] S2. Disperse 5 g of the double-bond modified activated carbon in 100 mL of deionized water, then add 4 g of maleic anhydride thereto, mix evenly, and then add 1 g of the initiator ammonium persulfate. React in a nitrogen atmosphere at a reaction temperature of 50 °C for 5 h. After the reaction is completed, wash and dry to obtain the catalyst.

[0065] Compared with Example 1, there is no zirconia loaded on the activated carbon in Comparative Example 1. Based on HCl, the yield of 2-chloroethanol in the reaction stage of Comparative Example 1 is 93.7%.

[0066] Comparative Example 2

[0067] A method for preparing 2-chloroethanol includes the following steps:

[0068] Put 425 g of ethylene glycol, 257.5 g of hydrochloric acid, 65 g of water and 60 g of catalyst as the bottom material into the reaction kettle, stir and heat up. When the temperature in the kettle reaches 110 °C, reflux appears. At a dropping rate of 150 g / h, continuously drop the mixed solution into the bottom material. The mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.2:3.6:1. The 2-chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises to the top condenser through the packed column. The condenser condenses the rising steam, adjusts the reflux ratio to 2:3, makes a part of the condensate return, fully contacts with the continuously rising steam in the packed column, and the other part enters the receiving tank, thus obtaining the crude product of 2-chloroethanol.

[0069] Among them, the preparation method of the catalyst is as follows:

[0070] Disperse 5 g of activated carbon in 100 mL of deionized water, then add 4 g of zirconium oxychloride to it, mix evenly, adjust the pH of the solution to 10, and then carry out a hydrothermal reaction. The temperature of the hydrothermal reaction is 190 °C, and the time of the hydrothermal reaction is 3 h. After the reaction is completed, wash and dry to obtain the catalyst.

[0071] Compared with Example 1, maleic acid was not grafted on the composite support in Comparative Example 2. Calculated by HCl, the yield of 2-chloroethanol in the reaction stage in Comparative Example 2 was 87.2%.

[0072] Recover the catalyst in Example 1, then immerse it in a 36 wt% hydrochloric acid solution for 2 h for activation, then wash and dry, and carry out a reuse test according to the steps in Example 1. Denote the catalyst used for the first time as the 1st time, and reuse it 5 times. The results are as Figure 1 shown. It can be seen from Figure 1 that the catalyst prepared by the present invention still has good catalytic effect after being recovered and reused. After being reused 5 times, the yield of 2-chloroethanol in the reaction stage can still reach more than 95%.

[0073] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, based on the present invention, some modifications and improvements can be made to it. Therefore, any modification or improvement made without departing from the spirit of the present invention falls within the scope of protection required by the present invention.

Claims

1. A catalyst for preparing 2-chloroethanol, characterized in that, The preparation method of the catalyst is as follows: S1. Disperse activated carbon in deionized water, then add zirconium oxychloride thereto, mix evenly, adjust the pH of the solution to 10 - 12, then carry out a hydrothermal reaction. After the reaction ends, wash and dry to obtain a composite support; S2. Disperse the composite support in an ethanol - aqueous solution, then add a vinylsilane coupling agent thereto, stir, wash and dry to obtain a double - bond - modified composite support; S3. Disperse the double - bond - modified composite support in deionized water, then add maleic anhydride thereto, mix evenly, then add an initiator, and carry out a reaction in a nitrogen atmosphere. After the reaction is completed, wash and dry to obtain the catalyst.

2. The catalyst according to claim 1, wherein In step S1, the mass ratio of the activated carbon to zirconium oxychloride is 5 - 10:4 - 8.

3. The catalyst according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 190 - 210 °C, and the time of the hydrothermal reaction is 1 - 3 h.

4. The catalyst according to claim 1, wherein In step S2, the mass ratio of the composite support to the vinylsilane coupling agent is 10 - 15:1 - 3.

5. The catalyst according to claim 1, characterized in that, In step S3, the mass ratio of the double - bond - modified composite support, maleic anhydride and the initiator is 5 - 10:4 - 8:1 - 2.

6. The catalyst according to claim 1, characterized in that, In step S3, the initiator is selected from persulfates.

7. The catalyst according to claim 1, characterized in that, In step S3, the reaction temperature is 50 - 80 °C, and the reaction time is 2 - 5 h.

8. A method for preparing 2-chloroethanol, characterized in that, It includes the following steps: Put ethylene glycol, hydrochloric acid, water and the catalyst according to any one of claims 1 - 7 into a reaction kettle as the bottom material, stir and heat up. When the temperature in the kettle reaches 110 - 120 °C and reflux appears, continuously drip a mixed solution of ethylene glycol, hydrochloric acid and water into the bottom material at a dropping rate of 150 - 200 g / h. The 2 - chloroethanol generated in the system gradually increases and continuously azeotropes with sufficient water in the system. The steam rises through a packed tower to the top condenser. The condenser condenses the rising steam, adjusts the reflux ratio, so that a part of the condensed liquid is refluxed to fully contact with the continuously rising steam in the packed tower, and the other part enters the receiving tank to obtain the crude 2 - chloroethanol.

9. The preparation method according to claim 8, characterized in that, The mass ratio of ethylene glycol, hydrochloric acid, water and the catalyst in the bottom material is 8.45 - 8.50:5.10 - 5.15:1.30 - 1.31:1.2 - 1.

5.

10. The preparation method according to claim 8, wherein The mass ratio of ethylene glycol, hydrochloric acid and water in the mixed solution is 2.1 - 2.4:3.5 - 3.8:1.

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