Method for separating and recycling dichloropropanol hydrochloric acid solution

Abstract

The invention relates to a method for separating and recycling a dichloropropanol hydrochloric acid solution, which comprises the following steps: carrying out positive pressure desorption on the dichloropropanol hydrochloric acid solution to obtain recovered hydrogen chloride and a desorbed material; performing high-temperature layering on the analyzed material to obtain an oil layer and a water layer; mixing the oil layer with glycerol, and then separating to obtain a cyclization reaction raw material and a chlorination reaction raw material; carrying out negative pressure concentration on the water layer to obtain a cyclization reaction raw material and a concentrated material; and carrying out cyclization reaction on the cyclization reaction raw material to obtain the epoxy chloropropane. The method provided by the invention can effectively separate and recover all components of dichloropropanol, hydrogen chloride and water in the dichloropropanol hydrochloric acid solution, is low in treatment energy consumption, and meets the requirements of green and energy-saving production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical separation, and in particular to a method for separating and recycling a dichloropropane hydrochloride solution. Background Art

[0002] Epichlorohydrin (ECH) is an important organic chemical raw material used to synthesize epoxy resins, epichlorohydrin rubber, etc. It can also be used as a solvent, plasticizer, and surfactant. The production processes of epichlorohydrin mainly include propylene high-temperature chlorination method, propylene acetate method, glycerol method, and direct epoxidation of allyl chloride. Among them, the glycerol method is currently the mainstream production process of epichlorohydrin in industry. The glycerol method mainly generates water and dichloropropane (DCH) through chlorination reaction. Dichloropropane and hydrogen chloride form a pseudo-ternary azeotrope, namely dichloropropane hydrochloride solution. At present, traditional separation methods such as distillation, extraction, and common ion method are difficult to achieve efficient separation of dichloropropane hydrochloride solution.

[0003] For example, CN102471196A discloses a method for preparing a dichloropropane-rich product. This method uses a distillation process to separate a dichloropropane hydrochloride solution into a dichloropropane material with a lower hydrogen chloride content and a dichloropropane material with a higher hydrogen chloride content. However, this method requires the continuous addition of distilled water for dilution, producing a recyclable dichloropropane with a low hydrogen chloride content and an aqueous solution. This results in excessive water entering the system, leading to high energy consumption and increased wastewater production.

[0004] CN101481365A discloses a method for preparing epichlorohydrin from a hydrochloric acid solution of dichloropropane. This method uses an extraction process to extract and separate the hydrochloric acid solution of dichloropropane using an organic solvent such as an alcohol, aromatic hydrocarbon, or ether, thereby effectively purifying the dichloropropane. However, extraction and separation using an alkane organic solvent typically requires a multi-stage extraction process, which not only increases equipment investment and process complexity, but also leads to increased energy consumption, increased environmental risks, and significantly increased production costs.

[0005] CN112645798A discloses a method for separating a dichloropropane-hydrochloric acid azeotrope. This method involves adding calcium chloride to a pseudo-ternary copolymer of the dichloropropane-hydrochloric acid solution to destroy the ternary system. However, the introduction of calcium chloride not only increases production costs but also introduces other impurities, making subsequent processing more complicated.

[0006] Therefore, in the separation process of dichloropropane hydrochloride solution produced by glycerol chlorination, there are still problems such as low separation efficiency, high energy consumption, and large amount of three waste emissions. It is urgent to develop an efficient and environmentally friendly separation process to achieve green and energy-saving production of epichlorohydrin synthesized by glycerol method. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a method for separating and recycling a dichloropropane hydrochloride solution. Compared with the prior art, the method provided by the present invention can effectively separate and recover all components of dichloropropane, hydrogen chloride and water in the dichloropropane hydrochloride solution, and has low processing energy consumption, thus meeting the requirements of green and energy-saving production.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for separating and recycling a dichloropropane hydrochloride solution, the method comprising the following steps:

[0010] (1) subjecting a dichloropropane hydrochloride solution to positive pressure decomposition to obtain recovered hydrogen chloride and a decomposed material; subjecting the decomposed material to high-temperature decomposition to obtain an oil layer and a water layer;

[0011] (2) mixing the oil layer obtained in step (1) and glycerol, and then separating to obtain a cyclization reaction raw material and a chlorination reaction raw material;

[0012] (3) Concentrating the aqueous layer obtained in step (1) under negative pressure to obtain a cyclization reaction raw material and a concentrated material; the concentrated material is returned to the positive pressure analysis in step (1);

[0013] (4) mixing the cyclization reaction raw materials obtained in step (2) and step (3) and performing a cyclization reaction to obtain epichlorohydrin;

[0014] There is no order between steps (2) and (3).

[0015] In the method provided by the present invention, in step (1), a dichloropropane hydrochloride solution is subjected to positive pressure decomposition, and the temperature and pressure during the positive pressure decomposition are controlled so that hydrogen chloride is separated from the top of the tower in the form of a gas phase, and recovered hydrogen chloride is obtained by condensation. The recovered hydrogen chloride has high purity and can be directly reused in the process of producing dichloropropane by chlorination of glycerol. The material after decomposition mainly contains dichloropropane, water and residual hydrogen chloride, and is subjected to high-temperature stratification to obtain an oil layer and a water layer. The oil layer mainly contains dichloropropane, water and a small amount of hydrogen chloride, and the water layer mainly contains dichloropropane, water and residual hydrogen chloride; in step ( In step (2), glycerol is added to the oil layer to react with the residual hydrogen chloride to mainly generate monochloropropanediol and possibly a small amount of dichloropropane. The dichloropropanediol and water are separated and used as cyclization reaction materials for the subsequent preparation of epichlorohydrin. The remaining material containing monochloropropanediol and glycerol is used as a chlorination reaction raw material for the preparation of dichloropropane. In step (3), the water layer is concentrated under negative pressure to separate the dichloropropane and water, which are also used as cyclization reaction raw materials for the subsequent cyclization reaction to prepare epichlorohydrin. At the same time, a concentrated material with a high hydrogen chloride content is obtained and reused in the positive pressure analysis to improve the utilization rate of each component.

[0016] Preferably, the dichloropropane hydrochloride solution in step (1) is derived from a process for preparing dichloropropane by chlorination of glycerol.

[0017] Preferably, the dichloropropane hydrochloride solution is a homogeneous system.

[0018] Preferably, the dichloropropane hydrochloride solution comprises, by weight percentage, 25-35% of dichloropropane, 15-32% of hydrogen chloride, and 35-60% of water. Wherein, the content of dichloropropane is 25-35%, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, but is not limited to the enumerated values, and other values ​​not enumerated within the numerical range are equally applicable; the content of hydrogen chloride is 15-32%, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31% or 32%, but is not limited to the enumerated values, and other values ​​not enumerated within the numerical range are equally applicable; the content of water is 35-60%, for example, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58% or 60%, but is not limited to the enumerated values, and other values ​​not enumerated within the numerical range are equally applicable.

[0019] The positive pressure analysis in step (1) is carried out in an analysis tower.

[0020] Preferably, the hydrogen chloride in the dichloropropane hydrochloric acid solution is separated from the top of the desorption tower in the form of gas phase and then condensed to obtain recovered hydrogen chloride.

[0021] In the present invention, the top of the analytical tower condenses the extracted material, and the condensation temperature is -5 to 20°C.

[0022] Preferably, the bottom of the decomposition tower obtains the decomposed material.

[0023] Preferably, the absolute pressure of the positive pressure analysis is 200-800 kPa, for example, it can be 200 kPa, 250 kPa, 300 kPa, 350 kPa, 400 kPa, 450 kPa, 500 kPa, 550 kPa, 600 kPa, 650 kPa, 700 kPa, 750 kPa or 800 kPa, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 200-500 kPa.

[0024] Preferably, the temperature of the positive pressure analysis is 128-200°C, for example, it can be 128°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 128-155°C.

[0025] In the present invention, the absolute pressure and temperature of the positive pressure analysis refer to the pressure and temperature of the bottom of the tower.

[0026] Preferably, the high-temperature stratification in step (1) includes utilizing the residual heat of the material after analysis to perform stratification.

[0027] Preferably, the temperature of the material after analysis is 128-200°C, for example, it can be 128°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 128-155°C.

[0028] Preferably, the glycerol in step (2) reacts with residual hydrogen chloride in the oil layer.

[0029] Preferably, the reaction temperature is 60-200°C, for example, it can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 100-140°C.

[0030] Preferably, the molar ratio of glycerol to hydrogen chloride in the oil layer is (0.5-4.0):1, for example, it can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4.0:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably (1.5-2.0):1.

[0031] Preferably, the separation method in step (2) includes fractional distillation.

[0032] Preferably, the fractionation is performed in a fractionation column.

[0033] Preferably, the cyclization reaction raw material is obtained at the top of the fractionation tower.

[0034] Preferably, the cyclization reaction raw materials include dichloropropanol and water.

[0035] Preferably, the chlorination reaction raw material is obtained in the bottom of the fractionation tower.

[0036] Preferably, the chlorination reaction raw materials include monochloropropylene glycol and glycerol.

[0037] Preferably, the chlorination reaction raw materials are used for chlorination reaction to synthesize dichloropropanol.

[0038] Preferably, the water layer is subjected to heat exchange before the negative pressure concentration in step (3) to cool the water layer.

[0039] Preferably, the cold source used for the heat exchange comprises a dichloropropane hydrochloric acid solution and / or the concentrated material obtained from the bottom of the concentration tower.

[0040] Preferably, the absolute pressure of the negative pressure concentration in step (3) is 1-50 kPa, for example, it can be 1 kPa, 2 kPa, 5 kPa, 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa or 50 kPa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 5-15 kPa.

[0041] Preferably, the temperature of the negative pressure concentration is 52-70°C, for example, it can be 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 56-62°C.

[0042] Preferably, the negative pressure concentration is carried out in a concentration tower.

[0043] Preferably, the cyclization reaction raw material is obtained at the top of the concentration tower.

[0044] Preferably, the cyclization reaction raw materials include dichloropropanol and water.

[0045] Preferably, the bottom of the concentration tower obtains concentrated material.

[0046] Preferably, the reflux ratio of the concentration tower is 0.25-4, for example, it can be 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 1-2.

[0047] In the present invention, the reflux ratio of the concentration tower refers to the ratio of the flow rate of the material refluxed from the top of the concentration tower to the flow rate of the material withdrawn from the top of the tower.

[0048] Preferably, the cyclization reaction in step (4) comprises: mixing cyclization reaction raw materials and a solid base to cause dichloropropanol to undergo cyclization reaction to generate epichlorohydrin.

[0049] In the present invention, the solid base can be any solid base commonly used in the art, for example, NaOH.

[0050] Preferably, the temperature of the cyclization reaction is 30-60°C, for example, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C or 60°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 40-50°C.

[0051] Preferably, the cyclization reaction time is 10-15 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] As a preferred technical solution of the present invention, the method comprises the following steps:

[0053] (1) performing positive pressure desorption of a dichloropropane hydrochloride solution in a desorption tower under conditions of an absolute pressure of 200-800 kPa and a temperature of 128-200° C., separating hydrogen chloride in the dichloropropane hydrochloride solution from the top of the desorption tower in the form of a gas phase, and then condensing to obtain recovered hydrogen chloride, and obtaining a desorbed material in the tower bottom; and subjecting the desorbed material to high-temperature separation to obtain an oil layer and a water layer;

[0054] (2) mixing the oil layer obtained in step (1) with glycerol to react at a reaction temperature of 60-200° C., with a molar ratio of glycerol to hydrogen chloride in the oil layer of (0.5-4.0):1, and then fractionating in a fractionating tower to obtain a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and a chlorination reaction raw material containing monochloropropanediol and glycerol at the bottom of the tower, wherein the chlorination reaction raw material is used for a chlorination reaction to synthesize dichloropropane;

[0055] (3) exchanging heat between the water layer obtained in step (1) and the dichloropropane hydrochloride solution and / or the concentrated material obtained in the bottom of the concentration tower to cool the water layer, and then performing negative pressure concentration in a concentration tower under the conditions of a temperature of 52-70° C., an absolute pressure of 1-50 kPa, and a reflux ratio of 0.25-4, obtaining a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and obtaining a concentrated material in the bottom of the tower, and returning the concentrated material to the positive pressure analysis in step (1);

[0056] (4) mixing the cyclization reaction raw materials obtained in step (2) and step (3), adding a solid base, and carrying out a cyclization reaction at a temperature of 30-60° C. for 10-15 minutes to obtain epichlorohydrin.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] In the present invention, the hydrogen chloride in the dichloropropane hydrochloride solution is separated and recovered by positive pressure analysis, it is possible to obtain hydrogen chloride with higher purity, by high temperature stratification and respectively carrying out glycerol removal hydrogen chloride and negative pressure concentration to oil layer and water layer, it is possible to fully recycle the dichloropropane and water contained therein as cyclization reaction raw materials for the preparation of epichlorohydrin, improve the yield of epichlorohydrin, the monochloropropylene glycol produced by the additional glycerol reaction and the remaining glycerol can be used as the raw material for preparing dichloropropane in chlorination reaction, without introducing other impurities, and negative pressure concentration obtains the higher concentrated rear material of hydrogen chloride concentration and can also be recycled. Therefore, the method provided by the present invention can realize the full recycling of components such as dichloropropane, hydrogen chloride, water and glycerol, and energy utilization rate is higher, processing energy consumption is lower, will not cause separation difficulty to increase due to the introduction of other impurity additives, meets the requirement of green energy-saving production. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 1 is a process flow chart of the method described in Example 1 of the present invention. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] Example 1

[0062] This embodiment provides a method for separating and recycling dichloropropane hydrochloride solution, such as Figure 1 As shown, the method includes the following steps:

[0063] (1) a dichloropropane hydrochloride solution is subjected to positive pressure desorption in a desorption tower under conditions of an absolute pressure of 400 kPa and a temperature of 149.7° C., with a feed rate of 100 kg / h; hydrogen chloride in the dichloropropane hydrochloride solution is separated from the top of the desorption tower in the form of a gas phase and then condensed at a temperature of 20° C. to obtain recovered hydrogen chloride, and a desorbed material is obtained in the bottom of the tower; waste heat of the desorbed material is used for high-temperature stratification to obtain an oil layer and a water layer, wherein the oil layer comprises, by weight percentage, 82.75% of dichloropropane, 2.64% of hydrogen chloride, and 14.61% of water; and the water layer comprises, by weight percentage, 23.26% of dichloropropane, 13.54% of hydrogen chloride, and 63.20% of water;

[0064] The dichloropropane hydrochloride solution is derived from a process for preparing dichloropropane by chlorination of glycerol and is a homogeneous system comprising 34.82% dichloropropane, 21.70% hydrogen chloride, and 43.48% water by weight.

[0065] (2) mixing the oil layer obtained in step (1) with glycerol to react at a temperature of 120° C. for 1 hour, with a molar ratio of glycerol to hydrogen chloride in the oil layer of 1.5:1, and then fractionating in a fractionating tower to obtain a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and a chlorination reaction raw material containing monochloropropanediol and glycerol at the bottom of the tower, wherein the chlorination reaction raw material is used for a chlorination reaction to synthesize dichloropropane;

[0066] (3) exchanging heat between the water layer obtained in step (1) and a dichloropropane hydrochloride solution to cool the water layer, and then performing negative pressure concentration in a concentration tower under the conditions of a temperature of 59° C., an absolute pressure of 10 kPa, and a reflux ratio of 1, obtaining a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and obtaining a concentrated material in the bottom of the tower, and returning the concentrated material to the positive pressure analysis in step (1);

[0067] (4) A total of 9.82 kg of the cyclization reaction raw materials obtained by mixing steps (2) and (3) were added to a cyclization reaction kettle, wherein the mass percentage of dichlorohydrin in the cyclization reaction raw materials was 29.79%, the mass percentage of water was 70.204%, and the mass percentage of hydrogen chloride was 0.006%. 1.25 kg of solid base NaOH was added, and a cyclization reaction was carried out at a temperature of 45° C. for 12 minutes. After the cyclization reaction, the feed liquid was separated into a 2.03 kg cyclization oil layer and a 9.04 kg cyclization water layer, and the cyclization oil layer obtained epichlorohydrin.

[0068] Examples 2-6

[0069] Examples 2-6 provide a method for separating and recycling a dichloropropane hydrochloride solution, respectively. The difference from Example 1 is only that the bottom pressure and bottom temperature of the decomposition tower in step (1) are changed, as shown in Table 1.

[0070] In the desorption tower, the mass percentage of HCl in the top gas phase, the mass percentage of HCl in the desorbed material obtained in the tower bottom, the desorption efficiency of HCl, and the recovery rate of dichloropropanol in the oil layer were measured and calculated. The results of Examples 1-6 are shown in Table 1. The calculation method of the desorption efficiency of HCl is Where m(hydrogen chloride in the gas phase at the top of the tower) represents the mass of hydrogen chloride in the gas phase at the top of the tower, and m(hydrogen chloride in the raw material) represents the mass of hydrogen chloride in the dichloropropane hydrochloride solution; the recovery rate of dichloropropane (DCH) in the oil layer is calculated as follows: Wherein m(DCH in the oil layer of the decomposition tower bottom) represents the mass of DCH in the oil layer of the decomposition tower bottom, and m(DCH in the raw material) represents the mass of DCH in the dichloropropane hydrochloric acid solution.

[0071] Table 1

[0072]

[0073] From the data of Examples 1-6, it can be seen that, by preferably controlling the bottom pressure and bottom temperature of the desorption tower in step (1), Examples 1 and Examples 3-6 can improve the purity of hydrogen chloride in the top gas phase, reduce the content of hydrogen chloride in the bottom, improve the desorption efficiency of hydrogen chloride, and improve the recovery rate of dichloropropane in the oil layer, compared with Example 2 in which the bottom pressure and bottom temperature of the desorption tower are not within the preferred range of the present invention.

[0074] Examples 7-8

[0075] Examples 7-8 provide a method for separating and recycling a dichloropropane hydrochloride solution. The difference from Example 1 is only that the composition of the dichloropropane hydrochloride solution in step (1) is changed, as shown in Table 2.

[0076] The mass percentage of HCl in the top gas phase of the desorption tower, the mass percentage of HCl in the desorbed material obtained in the bottom of the tower, the desorption efficiency of HCl, and the recovery rate of dichloropropanol in the oil layer were measured and calculated. The results are shown in Table 2.

[0077] Table 2

[0078]

[0079]

[0080] As can be seen from Table 2, the mass percentage of HCl in the dichloropropane hydrochloric acid solution increased from 21.7% to 30.12%, and the HCl desorption efficiency increased from 64.96% to 74.75%. The mass percentage of HCl in the overhead gas phase and the desorbed material in the bottom of the tower, as well as the DCH recovery rate in the oil layer, did not change much.

[0081] Examples 9-13

[0082] Examples 9-13 provide a method for separating and recycling a dichloropropane hydrochloride solution. The only difference from Example 1 is the change in the reflux ratio of the negative pressure concentration in step (3), as shown in Table 3. The top discharge temperature is 42-43°C, the bottom discharge temperature is 58-60°C, and the aqueous layer comprises, by weight percentage, 23.26% dichloropropane, 13.54% hydrogen chloride, and 63.20% water.

[0083] The mass percentage of HCl in the top material and the mass percentage of HCl in the bottom material of the concentration tower were measured. The results are shown in Table 3.

[0084] Table 3

[0085]

[0086] As can be seen from Table 3, as the reflux ratio increases, under the condition that the same mass of material is produced from the top of the tower, the content of hydrogen chloride in the top material decreases. In Examples 1 and 10-13, the reflux ratio is preferably controlled within the range of 0.25-4. Compared with the reflux ratio of 0.1 in Example 9, the content of hydrogen chloride in the top of the tower can be reduced to below 0.12%. Furthermore, a larger reflux ratio will result in a longer concentration process. Therefore, the present invention further preferably controls the reflux ratio to 1-2, which can save process time while ensuring an extremely low content of hydrogen chloride in the top material.

[0087] Examples 14-17

[0088] Examples 14-17 provide methods for separating and recycling dichloropropane hydrochloride solutions, respectively. The only difference from Example 1 is the change in the pressure for negative pressure concentration in step (3), as shown in Table 4. The top discharge temperature is 40-45°C, the bottom discharge temperature is 56-62°C, and the aqueous layer comprises, by weight percentage, 23.26% dichloropropane, 13.54% hydrogen chloride, and 63.20% water.

[0089] The mass percentage of HCl in the top material and the mass percentage of HCl in the bottom material of the concentration tower were measured. The results are shown in Table 4.

[0090] Table 4

[0091]

[0092] As can be seen from Table 4, in Example 1 and Examples 14-16, the pressure of the negative pressure concentration is controlled in the range of 5-50 kPa. Compared with Example 17 in which the pressure of the negative pressure concentration is not within the preferred range of the present invention, the content of hydrogen chloride in the overhead material in Example 17 is significantly higher than that in Example 1 and Examples 14-16. It can be seen that the present invention can further improve the separation effect of negative pressure concentration by preferably controlling the pressure of the negative pressure concentration.

[0093] Examples 18-21

[0094] Examples 18-21 provide a method for separating and recycling a dichloropropane hydrochloride solution. The only difference from Example 1 is that the molar ratio of glycerol to hydrogen chloride in the oil reservoir in step (2) is varied, as shown in Table 5. The oil reservoir comprises, by mass percentage, 82.75% dichloropropane, 2.64% hydrogen chloride, and 14.61% water. In the above examples, the glycerol used has a purity of 98.29%, with the remainder being 1.71% water.

[0095] The mass percentages of glycerol, dichloropropane (DCH), monochloropropylene glycol (MCH), hydrogen chloride and water in the reaction liquid after the reaction in step (2) were measured, and the results are shown in Table 5.

[0096] Table 5

[0097]

[0098] As can be seen from Table 5 and the data from Examples 1 and 18-21, as the molar ratio of glycerol to hydrogen chloride in the oil reservoir increases, the hydrogen chloride content in the reaction liquid decreases. In Examples 1 and 20, controlling the molar ratio within the range of (1.5-2.0):1 allows, compared to Examples 18-19 and 21, for substantially complete reaction of the hydrogen chloride while reducing the amount of glycerol used, thus preventing excessive glycerol from increasing the load on subsequent steps.

[0099] Examples 22-27

[0100] Examples 22-27 provide methods for separating and recycling a dichloropropane hydrochloride solution. The only difference from Example 1 is the change in the reaction temperature in step (2), as shown in Table 6. The oil layer comprises, by mass percentage, 82.75% dichloropropane, 2.64% hydrogen chloride, and 14.61% water. In the above examples, the glycerol used was 98.29% pure, with the remainder being 1.71% water.

[0101] The mass percentages of glycerol, dichloropropane (DCH), monochloropropylene glycol (MCH), hydrogen chloride and water in the reaction liquid after the reaction in step (2) were measured, and the results are shown in Table 6.

[0102] Table 6

[0103]

[0104] As can be seen from Table 6, in Example 1 and Examples 23-27, the reaction temperature is controlled within the range of 60-200° C., which can reduce the content of hydrogen chloride in the reaction liquid and promote the completion of the reaction, compared with the reaction temperature in Example 22 being not within the preferred range of the present invention. Furthermore, in Example 1 and Examples 25-26, it is further preferred to control the reaction temperature to 100-140° C., which can significantly reduce the content of hydrogen chloride in the reaction liquid while reducing the reaction energy consumption.

[0105] Examples 28-29

[0106] Examples 28 and 29 provide a method for separating and recycling a dichloropropane hydrochloride solution. The only difference from Example 1 is that the reaction temperature and time in step (4) are changed, as shown in Table 7. The mass percentage of dichloropropane in the cyclization reaction raw material is 29.79%, the mass percentage of water is 70.204%, and the mass percentage of hydrogen chloride is 0.006%. The purity of the solid base used in the above examples is 99.00%.

[0107] The mass percentages of epichlorohydrin (ECH), dichloropropanol (DCH), glycidol (abbreviated as glycidol), and water in the cyclized oil layer and the cyclized water layer obtained by the cyclization reaction, as well as the yield of ECH, were measured. The results are shown in Table 7. The calculation method of the yield of ECH is Wherein m(actually generated ECH) represents the mass of epichlorohydrin actually generated by the cyclization reaction, and m(theoretically generated ECH) represents the mass of epichlorohydrin theoretically generated by the cyclization reaction.

[0108] Table 7

[0109]

[0110] As can be seen from Table 7 and the data of Examples 1 and 28-29, in the cyclization reaction, when the reaction temperature is preferably controlled within the range of 30-60° C. and the reaction time is within the range of 10-15 min, the yield of epichlorohydrin can reach above 98.34%, and can further reach 99.10%.

[0111] In summary, the method provided by the present invention can effectively separate and recover all components of dichloropropane, hydrogen chloride and water in a dichloropropane hydrochloric acid solution, and has low processing energy consumption, which meets the requirements of green and energy-saving production.

[0112] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for separating and recycling dichloropropane hydrochloride solution, characterized in that: The method comprises the following steps: (1) subjecting a dichloropropane hydrochloride solution to positive pressure decomposition to obtain recovered hydrogen chloride and a decomposed material; subjecting the decomposed material to high-temperature decomposition to obtain an oil layer and a water layer; (2) mixing the oil layer obtained in step (1) and glycerol, and then separating to obtain a cyclization reaction raw material and a chlorination reaction raw material; (3) Concentrating the aqueous layer obtained in step (1) under negative pressure to obtain a cyclization reaction raw material and a concentrated material; the concentrated material is returned to the positive pressure analysis in step (1); (4) mixing the cyclization reaction raw materials obtained in step (2) and step (3) and performing a cyclization reaction to obtain epichlorohydrin; There is no order between steps (2) and (3).

2. The method according to claim 1, characterized in that The dichloropropane hydrochloride solution in step (1) is derived from a process for preparing dichloropropane by chlorination of glycerol; Preferably, the dichloropropane hydrochloride solution is a homogeneous system; Preferably, the dichloropropane hydrochloride solution comprises, by weight percentage, 25-35% of dichloropropane, 15-32% of hydrogen chloride, and 35-60% of water.

3. The method according to claim 1 or 2, characterized in that The positive pressure analysis in step (1) is carried out in an analysis tower; Preferably, the hydrogen chloride in the dichloropropane hydrochloride solution is separated from the top of the desorption tower in the form of gas phase and then condensed to obtain recovered hydrogen chloride; Preferably, the bottom of the decomposition tower obtains the decomposed material; Preferably, the absolute pressure of the positive pressure analysis is 200-800 kPa, preferably 200-500 kPa; Preferably, the temperature of the positive pressure desorption is 128-200°C, preferably 128-155°C.

4. The method according to any one of claims 1 to 3, characterized in that The high-temperature stratification in step (1) includes utilizing the residual heat of the material after decomposition to perform stratification; Preferably, the temperature of the material after desorption is 128-200°C.

5. The method according to any one of claims 1 to 4, characterized in that The glycerol in step (2) reacts with the residual hydrogen chloride in the oil layer; Preferably, the reaction temperature is 60-200°C, preferably 100-140°C; Preferably, the molar ratio of the glycerol to the hydrogen chloride in the oil layer is (0.5-4.0):1, preferably (1.5-2.0):

1.

6. The method according to any one of claims 1 to 5, characterized in that The separation method in step (2) includes fractional distillation; Preferably, the fractionation is carried out in a fractionation tower; Preferably, the cyclization reaction raw material is obtained at the top of the fractionation tower; Preferably, the cyclization reaction raw materials include dichloropropanol and water; Preferably, the chlorination reaction raw material is obtained in the bottom of the fractionation tower; Preferably, the chlorination reaction raw materials include monochloropropylene glycol and glycerol; Preferably, the chlorination reaction raw materials are used for chlorination reaction to synthesize dichloropropanol.

7. The method according to any one of claims 1 to 6, characterized in that Before the negative pressure concentration in step (3), the water layer is subjected to heat exchange to cool the water layer; Preferably, the cold source used for the heat exchange comprises a dichloropropane hydrochloric acid solution and / or the concentrated material obtained from the bottom of the concentration tower.

8. The method according to any one of claims 1 to 7, characterized in that The absolute pressure of the negative pressure concentration in step (3) is 1-50 kPa, preferably 5-15 kPa; Preferably, the temperature of the negative pressure concentration is 52-70°C, preferably 56-62°C; Preferably, the negative pressure concentration is carried out in a concentration tower; Preferably, the cyclization reaction raw material is obtained at the top of the concentration tower; Preferably, the bottom of the concentration tower obtains concentrated material; Preferably, the reflux ratio of the concentration tower is 0.25-4, preferably 1-2.

9. The method according to any one of claims 1 to 8, characterized in that The cyclization reaction in step (4) comprises: mixing cyclization reaction raw materials and solid base to cause dichloropropanol to undergo cyclization reaction to generate epichlorohydrin; Preferably, the temperature of the cyclization reaction is 30-60°C, preferably 40-50°C; Preferably, the cyclization reaction time is 10-15 min.

10. The method according to any one of claims 1 to 9, characterized in that The method comprises the following steps: (1) performing positive pressure desorption of a dichloropropane hydrochloride solution in a desorption tower under conditions of an absolute pressure of 200-800 kPa and a temperature of 128-200° C., separating hydrogen chloride in the dichloropropane hydrochloride solution from the top of the desorption tower in the form of a gas phase, and then condensing to obtain recovered hydrogen chloride, and obtaining a desorbed material in the tower bottom; and subjecting the desorbed material to high-temperature separation to obtain an oil layer and a water layer; (2) mixing the oil layer obtained in step (1) with glycerol to react at a reaction temperature of 60-200° C., with a molar ratio of glycerol to hydrogen chloride in the oil layer of (0.5-4.0):1, and then fractionating in a fractionating tower to obtain a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and a chlorination reaction raw material containing monochloropropanediol and glycerol at the bottom of the tower, wherein the chlorination reaction raw material is used for a chlorination reaction to synthesize dichloropropane; (3) exchanging heat between the water layer obtained in step (1) and the dichloropropane hydrochloride solution and / or the concentrated material obtained in the bottom of the concentration tower to cool the water layer, and then performing negative pressure concentration in a concentration tower under the conditions of a temperature of 52-70° C., an absolute pressure of 1-50 kPa, and a reflux ratio of 0.25-4, obtaining a cyclization reaction raw material containing dichloropropane and water at the top of the tower, and obtaining a concentrated material in the bottom of the tower, and returning the concentrated material to the positive pressure analysis in step (1); (4) mixing the cyclization reaction raw materials obtained in step (2) and step (3), adding a solid base, and carrying out a cyclization reaction at a temperature of 30-60° C. for 10-15 minutes to obtain epichlorohydrin.

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