Method for treating and recycling epoxy chloropropane residues

Abstract

The invention relates to a method for treating epoxy chloropropane residues and recycling the epoxy chloropropane residues, which comprises the following steps: carrying out primary light component removal on the epoxy chloropropane rectification residues to obtain a first heavy component and a first light component containing an epoxy chloropropane crude product, and carrying out secondary light component removal on the first heavy component to obtain a second light component containing an epoxy chloropropane crude product; sequentially carrying out pressurized chlorination reaction and separation on the second heavy component to obtain a dichloropropanol crude product, carrying out liquid-liquid saponification reaction on the second light component, then carrying out oil-water separation to obtain an oil layer and a water layer, and respectively carrying out purification treatment on the oil layer and the water layer to obtain a dichloropropanol crude product. A crude epichlorohydrin product is obtained. According to the method, the epoxy chloropropane rectification residues can be subjected to resource recovery, the amount of the epoxy chloropropane residues is effectively reduced, and the yield of epoxy chloropropane is increased.

Description

Technical Field

[0001] The invention relates to the technical field of epichlorohydrin production, and in particular to a method for treating epichlorohydrin residue and recycling it. Background Art

[0002] Epichlorohydrin, referred to as ECH, is an important basic chemical raw material, mainly used in the production of epoxy resin, epichlorohydrin rubber, polyether polyols and rodenticides such as epichlorohydrin.

[0003] At present, the domestic production processes of epichlorohydrin are mainly propylene method, glycerol method and direct oxidation of allyl chloride. Among them, the propylene method is to use propylene to react with chlorine at high temperature to generate allyl chloride, and allyl chloride reacts with hypochlorous acid to generate dichloropropanol, and finally dichloropropanol is converted into epichlorohydrin through saponification reaction; the glycerol method is to use glycerol and hydrogen chloride to react under the action of a catalyst to generate dichloropropanol, and dichloropropanol is converted into epichlorohydrin through saponification reaction; and the direct oxidation of allyl chloride is to use peroxy acid and allyl chloride to directly synthesize epichlorohydrin by epoxidation reaction. At present, this method mainly uses hydrogen peroxide as the oxygen source. Among the above methods, the glycerol method has the advantages of less chlorinated by-products and low wastewater volume compared with other methods, and has good economic and environmental benefits. By the end of 2023, China's total epichlorohydrin production capacity has reached 2.1 million tons, of which the glycerol method accounts for more than 70%.

[0004] However, the chlorination process of the glycerol method uses industrial by-product hydrogen chloride as one of the raw materials. The chlorination product dichloropropanol and the by-product hydrogen chloride are carried into the saponification process together with impurities. Due to the incomplete saponification reaction, the unreacted dichloropropanol and some organic matter in the impurities cannot be effectively separated. In the saponification process, they are enriched in the epichlorohydrin distillation residue as heavy components. The above distillation residue contains 3-chloro-1,2-propanediol, 2-chloro-1,3-propanediol, glycerol, glycidol, dichloropropanol and other organic substances. Its composition is complex and difficult to recycle. However, if it cannot be effectively treated, it will not only cause waste of resources, but also cause pollution problems.

[0005] For example, CN111607067A discloses a method for synthesizing epoxy resin from epichlorohydrin distillation residue, wherein the epoxy resin is prepared by reacting the first oil phase obtained by mixing the epichlorohydrin distillation residue with a saponifier with bisphenol A. However, this method cannot further improve the yield of epichlorohydrin.

[0006] Therefore, for the glycerol process for producing epichlorohydrin, how to treat the epichlorohydrin distillation residue to achieve resource utilization of the residue and improve the yield of epichlorohydrin is a technical problem that needs to be solved at present. Summary of the invention

[0007] In view of the above problems, the object of the present invention is to provide a method for treating epichlorohydrin residue and recycling it. Compared with the prior art, the present invention can recycle epichlorohydrin distillation residue, effectively reduce the amount of epichlorohydrin residue, and improve the yield of epichlorohydrin.

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

[0009] In a first aspect, the present invention provides a method for treating epichlorohydrin residue and recycling it, the method comprising the following steps:

[0010] (1) performing primary light removal on the distillation residue of epichlorohydrin to obtain a first heavy component and a first light component containing a crude epichlorohydrin product;

[0011] (2) subjecting the first heavy component obtained in step (1) to secondary light removal to obtain a second heavy component and a second light component containing dichloropropane;

[0012] (3) subjecting the second heavy component obtained in step (2) to a pressure chlorination reaction and separation in sequence to obtain a crude product of dichloropropane;

[0013] (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction, and then subjecting the second light component to oil-water separation to obtain an oil layer and an aqueous layer; and subjecting the oil layer and the aqueous layer to purification treatments respectively to obtain a crude epichlorohydrin product;

[0014] There is no sequence relationship between step (3) and step (4).

[0015] The method provided by the present invention is aimed at the problem that the distillation residue obtained by the glycerol method for producing epichlorohydrin is complex in composition and difficult to separate and recycle. The crude epichlorohydrin is recovered in the form of light components by a first-level de-lightening, and then the heavy component is subjected to a second-level de-lightening. Dichloropropanol therein is separated as a light component (the second light component also contains entrained impurities), and the separated dichloropropanol is prepared and synthesized into epichlorohydrin by liquid-liquid saponification reaction, and the water layer and the oil layer are purified respectively after oil-water separation to obtain a crude epichlorohydrin; the heavy component obtained by the second-level de-lightening is converted into dichloropropanol by pressurized chlorination, and the substances such as glycerol, glycidol, and monochloropropanediol contained therein are obtained, and the crude dichloropropanol is obtained by separation and used for the preparation of epichlorohydrin. The method provided by the present invention can realize the resource utilization of epichlorohydrin distillation residues through the above-mentioned operation process, reduce the residue amount of epichlorohydrin, and improve the product quality and yield of epichlorohydrin.

[0016] Preferably, the distillation residue in step (1) contains, by mass percentage, 25-35% of epichlorohydrin, for example, 25%, 26%, 28%, 30%, 32%, 34% or 35%; 30-45% of dichloropropanol, for example, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44% or 45%; 1-3% of monochloropropanediol, for example, 1%, 2% or 3%; 0.5-5% of glycerol, for example, 0.5%, 1%, 2%, 3%, 4% or 5%; 1-3% of glycidol, for example, 1%, 2% or 3%; 1-3% of entrained impurities, for example, 1%, 2% or 3%; the rest are glycerol derivatives and tar produced by distillation, which are not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0017] Preferably, the entrained impurities include any one of o-dichlorobenzene, m-dichlorobenzene, isopropylbenzene, p-xylene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene or 2-ethyltoluene, or a combination of at least two thereof.

[0018] In the present invention, the entrained impurities refer to substances with a boiling point close to that of dichloropropanol (the boiling point is generally 170-190° C.) and cannot participate in the synthesis process of epichlorohydrin. Since the hydrogen chloride used in the chlorination section of the epichlorohydrin production process is usually industrial by-product hydrogen chloride, the entrained impurities in the residue mainly come from the impurities entrained in the chlorination product dichloropropanol and brought into the saponification section.

[0019] Preferably, the mass percentage of epichlorohydrin in the first light component is greater than 98%, for example, it can be 98.1%, 98.2% or 98.3%, and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the first light component is returned to the distillation and refining step to prepare the finished epichlorohydrin product.

[0021] Preferably, the absolute pressure of the first-stage light removal in step (1) is 5-20 kPa, for example, it can be 5 kPa, 8 kPa, 10 kPa, 12 kPa, 14 kPa, 16 kPa, 18 kPa or 20 kPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the absolute pressure of the secondary light removal in step (2) is ≥1 kPa and <5 kPa, for example, it can be 1 kPa, 2 kPa, 3 kPa or 4 kPa, and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the reflux ratios of the primary light removal and the secondary light removal are independently 0.5-2, for example, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 or 2, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the kettle temperatures of the primary delight removal and the secondary delight removal are independently ≤160°C, for example, they can be 160°C, 159°C, 158°C, 157°C, 156°C or 155°C, and are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, in the second heavy component of step (3), the content of epichlorohydrin is less than 1%, for example, 0.9%, 0.8%, 0.7%, 0.6% or 0.5%, the content of dichloropropanol is less than 3%, for example, 2.9%, 2.8%, 2.6%, 2.4%, 2.2% or 2%, the total content of glycidol, glycerol and monochloropropanediol is greater than 5%, for example, 6%, 6.5% or 7%, the water content is less than 0.2%, for example, 0.18%, 0.16%, 0.14%, 0.12% or 0.1%, and the rest is glycerol derivatives and tar produced by distillation.

[0026] In the present invention, the catalyst used in the pressurized chlorination reaction is a catalyst commonly used in the art for pressurized chlorination, for example, it can be any one of acetic acid, oxalic acid, adipic acid, succinic acid, sebacic acid, benzoic acid, terephthalic acid, isophthalic acid or citric acid, or a combination of at least two thereof.

[0027] Preferably, the amount of the catalyst used in the pressurized chlorination reaction accounts for 0.05-0.3% of the mass of the second heavy component, for example, it can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25% or 0.3%, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In the present invention, the pressure chlorination reaction is a conventional reaction in the art for preparing dichloropropane from glycerol and monochloropropanediol. Generally, the second heavy component is reacted with hydrogen chloride under the condition of the pressure chlorination reaction catalyst, and the molar ratio of hydrogen chloride to the glycerol derivative containing hydroxyl groups and ether bonds in the second heavy component is controlled to be 1:(0.95-0.98).

[0029] Preferably, the pressure of the hydrochlorination reaction is positive pressure in the range of 0.05-0.6 MPa, for example, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa or 0.6 MPa, not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0030] Preferably, the hydrochlorination reaction time is 0.5-4h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the temperature of the hydrochlorination reaction is 110-180°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, in the product of the hydrochlorination reaction, the content of dichloropropane is 30-50% by mass, for example, 30%, 35%, 40%, 45% or 50%, the total content of glycidol, glycerol and monochloropropanediol is less than 3%, for example, 2.8%, 2.6%, 2.4%, 2.2% or 2%, the water content is 0.5-3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5% or 3%, and the rest is glycerol derivatives and tar produced by distillation, which is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the separation method includes distillation.

[0034] Preferably, the crude dichloropropanol is used to prepare epichlorohydrin after purification.

[0035] In the present invention, the mass percentage of dichloropropanol in the dichloropropanol crude product obtained by separation is generally 90-97%. The separation in the present invention mainly separates dichloropropanol from glycidol, glycerol, monochloropropanediol and the like. The crude dichloropropanol is purified and used in the front-end epichlorohydrin production process for saponification to prepare epichlorohydrin, thereby further improving the yield of epichlorohydrin, while glycidol, glycerol, monochloropropanediol and the like are subsequently used as raw materials in the glycerol chlorination process.

[0036] Preferably, the liquid-liquid saponification reaction in step (4) is carried out in a microchannel reactor.

[0037] In the present invention, the liquid-liquid saponification reaction is controlled to be carried out in a microchannel reactor, and the excellent heat transfer effect of the microchannel reactor can be utilized to effectively increase the reaction temperature, accelerate the speed of the saponification reaction, and shorten the residence time of the reaction, so that the saponification reaction of dichloropropanol is more complete and the yield of epichlorohydrin is improved.

[0038] Preferably, the total residence time of the feed liquid in the microchannel reactor is 0.2-5s, for example, it can be 0.2s, 0.4s, 0.6s, 0.8s, 1s, 2s, 3s, 4s or 5s, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the liquid-liquid saponification reaction comprises a preheating stage, a reaction stage and a cooling stage which are sequentially performed in a microchannel reactor.

[0040] In the present invention, the liquid-liquid saponification reaction is a conventional reaction for preparing epichlorohydrin from dichloropropanol in the art. Generally, the alkali is a sodium hydroxide aqueous solution, and the theoretical molar ratio of the reaction is 1:1. However, in order to control the complete saponification reaction, the molar ratio of dichloropropanol to sodium hydroxide in the second light component is controlled to be 1:(1.01-1.03).

[0041] Preferably, the temperature in the preheating stage is 60-100°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In the present invention, the preheating stage is carried out in a microchannel reactor, and generally the liquid alkali and the second light component are controlled to be preheated through different preheating tubes.

[0043] Preferably, the temperature in the reaction stage is 80-120°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the pH value of the material controlled in the reaction stage is 10-12, for example, it can be 10, 10.2, 10.4, 10.6, 10.8, 11, 11.2, 11.4, 11.6, 11.8 or 12, and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the cooling stage cools the material to an end temperature of 5-25°C, for example, 5°C, 6°C, 8°C, 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C or 25°C, not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, pH value adjustment is also performed during the cooling stage.

[0047] Preferably, during the cooling stage, the pH value of the material is adjusted to an end point pH value of 6.5-8.5, for example, 6.5, 6.8, 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4 or 8.5, not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the purification treatment of the oil layer in step (4) includes subjecting the oil layer to distillation separation.

[0049] Preferably, the bottom temperature of the distillation separation tower is ≤140°C, for example, it can be 140°C, 130°C, 120°C, 118°C, 116°C, 114°C, 112°C or 110°C, and is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, the mass percentage of epichlorohydrin in the bottom product of the distillation separation is less than 1%, for example, it can be 0.9%, 0.8%, 0.7%, 0.6% or 0.5%, and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the distillation separation is a negative pressure operation.

[0052] Preferably, the distillation separation pressure is -65 to -85 kPa, for example, it can be -65 kPa, -68 kPa, -70 kPa, -72 kPa, -74 kPa, -76 kPa, -78 kPa, -80 kPa, -82 kPa, -84 kPa or -85 kPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the crude epichlorohydrin is taken out from the top of the distillation separation tower, and the obtained crude epichlorohydrin is returned to the distillation and refining step to prepare the finished epichlorohydrin.

[0054] In the present invention, the organic by-products are extracted from the bottom of the distillation separation tower, and the organic by-products are entrained impurities, including any one of o-dichlorobenzene, m-dichlorobenzene, isopropylbenzene, p-xylene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene or 2-ethyltoluene, or a combination of at least two thereof.

[0055] Preferably, the purification treatment of the water layer in step (4) comprises steam stripping the water layer.

[0056] Preferably, the stripping produced material is a gas phase containing crude epichlorohydrin, and the gas phase containing crude epichlorohydrin is returned to the distillation and refining step to prepare finished epichlorohydrin.

[0057] Preferably, the mass percentage of epichlorohydrin in the crude epichlorohydrin produced by stripping is 80-90%, for example, it can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89% or 90%, not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] Preferably, the stripping tower bottom obtains brine, and the brine is sent to a brine treatment system.

[0059] As a preferred technical solution of the present invention, the method comprises the following steps:

[0060] (1) performing primary light removal on the epichlorohydrin distillation residue under the conditions of an absolute pressure of 5-20 kPa, a reflux ratio of 0.5-2, and a kettle temperature of ≤160° C. to obtain a first heavy component and a first light component containing a crude epichlorohydrin product, wherein the first light component is returned to a distillation and refining step to prepare a finished epichlorohydrin product;

[0061] (2) subjecting the first heavy component obtained in step (1) to secondary light removal under the conditions of an absolute pressure of ≥1 kPa and <5 kPa, a reflux ratio of 0.5-2, and a kettle temperature of ≤160° C. to obtain a second heavy component and a second light component containing dichloropropanol;

[0062] (3) subjecting the second heavy component obtained in step (2) to a pressure chlorination reaction under the conditions of controlling the catalyst dosage to 0.05-0.3% of the mass of the second heavy component, a pressure of 0.05-0.6 MPa, a time of 0.5-4 h, and a temperature of 110-180° C., and then separating to obtain a crude dichloropropane product, which is purified and used to prepare epichlorohydrin;

[0063] (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction in a microchannel reactor, controlling the total residence time of the liquid in the microchannel reactor to be 0.2-5 s, wherein the liquid-liquid saponification reaction comprises first a preheating stage and controlling the temperature to be 60-100° C., then a reaction stage and controlling the temperature to be 80-120° C. and the pH value of the material to be 10-12, then a cooling stage and controlling the terminal temperature to be 5-25° C. and adjusting the pH value to be 6.5-8.5, and then performing oil-water separation to obtain an oil layer and a water layer;

[0064] The oil layer is subjected to distillation separation under the condition that the bottom temperature is less than 120° C. and the pressure is -65 to -85 kPa, and the crude epichlorohydrin is obtained at the top of the tower and returned to the distillation and refining step to prepare the finished epichlorohydrin, and the organic by-product is obtained in the bottom of the tower;

[0065] The water layer is stripped to obtain a gas phase containing crude epichlorohydrin and returned to the distillation and refining process to prepare finished epichlorohydrin. Brine is also obtained and sent to a brine treatment system.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) The present invention can realize resource recovery and utilization of epichlorohydrin distillation residue through processes such as primary light removal, secondary light removal, liquid-liquid saponification and hydrochlorination, effectively reduce the amount of epichlorohydrin residue, and improve the yield of epichlorohydrin.

[0068] (2) The epichlorohydrin generated by the liquid-liquid saponification reaction of the present invention has the effect of dissolving and extracting the entrained impurities, and can make most of the organic impurities enter the oil layer. Then, by utilizing the large difference in boiling points between epichlorohydrin and organic impurities, a crude epichlorohydrin product is obtained by distillation separation, thereby further improving the total yield of epichlorohydrin.

[0069] (3) The present invention adopts a pressurized chlorination process, which can effectively break the chain of long-chain glycerol derivatives that are difficult to break by controlling the reaction temperature and increasing the solubility of hydrogen chloride by controlling the pressure, thereby generating a dichloropropanol intermediate, and further synthesizing dichloropropanol, thereby further improving the total yield of epichlorohydrin, achieving full resource utilization of the effective components in the residue, and significantly improving the resource utilization rate.

[0070] (4) The method provided by the present invention can make the one-way yield of epichlorohydrin reach more than 93.17%, the total yield of epichlorohydrin reach more than 95.46%, and the recovery rate of organic by-products reach more than 86.28%. Under optimal conditions, the one-way yield of epichlorohydrin reaches more than 94.17%, the total yield of epichlorohydrin reaches more than 96.49%, and the recovery rate of organic by-products reaches more than 92.22%. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a schematic diagram of the process of the method described in Example 1 of the present invention;

[0072] Figure 2 This is a schematic flow chart of the liquid-liquid saponification reaction in the microchannel reactor described in Example 1 of the present invention. DETAILED DESCRIPTION

[0073] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0074] In the following examples and comparative examples, the molar ratio of hydrogen chloride to the glycerol derivative containing hydroxyl groups and ether bonds in the second heavy component in the pressurized chlorination reaction is controlled to be 1:0.98; and the molar ratio of dichloropropanol to sodium hydroxide in the second light component in the liquid-liquid saponification reaction is controlled to be 1:1.02.

[0075] Example 1

[0076] The present embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The epichlorohydrin residue is: a distillation residue (mass: 300 kg) produced by distilling and refining 10 t of epichlorohydrin crude product, and 9700 kg of ECH finished product is also produced. The distillation residue contains 32.52% of ECH, 32.04% of dichloropropanol, 1.51% of monochloropropanediol, 1.38% of glycerol, 3.37% of glycidol and 2.11% of entrained impurities in terms of mass percentage, wherein the entrained impurities are o-dichlorobenzene, such as Figure 1 As shown, the method comprises the following steps:

[0077] (1) The distillation residue of ECH is subjected to primary light removal under the conditions of an absolute pressure of 10 kPa, a reflux ratio of 1, and a kettle temperature of 150° C. to obtain a first heavy component and 99.46 kg of a first light component containing crude ECH (mass percentage content>98%), and the first light component is returned to the distillation and refining process to prepare a finished ECH product;

[0078] (2) subjecting the first heavy component obtained in step (1) to secondary light removal under the conditions of an absolute pressure of 1 kPa, a reflux ratio of 1, and a kettle temperature of 150° C. to obtain 55.63 kg of a second heavy component (including 0.01% ECH, 1.07% dichloropropane, 8.15% monochloropropylene glycol, 7.44% glycidol, and 18.18% glycerol) and 140.29 kg of a second light component containing dichloropropane (including 94.32% dichloropropane, 4.51% o-dichlorobenzene, and 0.92% glycidol);

[0079] (3) using oxalic acid as a catalyst, the second heavy component obtained in step (2) is subjected to a pressure chlorination reaction at a pressure of 0.2 MPa, a time of 2 h, and a temperature of 150° C., wherein the weight of the material increases to 81.53 kg, and the content of dichloropropane increases to 47.20%, and then the material is separated to obtain a crude dichloropropane product, and the crude dichloropropane product is purified and used to prepare ECH;

[0080] (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction in a microchannel reactor, and controlling the total residence time of the feed liquid in the microchannel reactor to be 2 s. Figure 2 As shown, the liquid-liquid saponification reaction includes a preheating stage and controlling the temperature to 80°C, then a reaction stage controlling the temperature to 100°C and the pH value of the material to 11, then a cooling stage controlling the terminal temperature to 10°C and adjusting the pH value to 7, and then oil-water separation to obtain an oil layer and a water layer; the oil layer is distilled and separated under the conditions of a bottom temperature of 140°C and a pressure of -80kPa to obtain 98.21kg of ECH crude product (mass percentage 98.72%) at the top of the tower, the obtained ECH crude product is returned to the distillation and refining process to prepare the ECH finished product, the bottom of the tower obtains 6.03kg of organic by-product o-dichlorobenzene, the water layer is stripped to obtain a gas phase containing the ECH crude product and returned to the distillation and refining process to prepare the ECH finished product, the stripping kettle obtains brine and sends it to the brine treatment system.

[0081] Example 2

[0082] The present embodiment provides a method for treating epichlorohydrin residue and recycling it. The epichlorohydrin residue is: distillation residue (mass: 303 kg) produced by distillation and refining of 10 t of epichlorohydrin crude product, wherein the distillation residue contains 34.26% of ECH, 31.89% of dichloropropane, 1.84% of monochloropropanediol, 1.41% of glycerol, 3.34% of glycidol and 2.08% of entrained impurities in terms of mass percentage, wherein the entrained impurity is m-dichlorobenzene. The method comprises the following steps:

[0083] (1) performing primary light removal on the distillation residue of ECH under the conditions of an absolute pressure of 5 kPa, a reflux ratio of 2, and a kettle temperature of 150° C. to obtain a first heavy component and a first light component containing crude ECH (mass percentage content>98%), and the first light component is returned to the distillation and refining step to prepare a finished ECH product;

[0084] (2) subjecting the first heavy component obtained in step (1) to secondary light removal under the conditions of an absolute pressure of 2 kPa, a reflux ratio of 0.5, and a kettle temperature of 150° C. to obtain a second heavy component (including 0.02% ECH, 1.14% dichloropropane, 8.23% monochloropropylene glycol, 7.49% glycidol, and 18.22% glycerol) and a second light component containing dichloropropane (including 94.36% dichloropropane, 4.43% o-dichlorobenzene, and 1.19% glycidol);

[0085] (3) using acetic acid as a catalyst, controlling the amount of the catalyst to be 0.05% of the mass of the second heavy component, and subjecting the second heavy component to a pressurized chlorination reaction at a pressure of 0.6 MPa, a time of 0.8 h, and a temperature of 180° C., wherein the content of dichloropropane increases to 39.46%, and then separating to obtain a crude dichloropropane product, wherein the crude dichloropropane product is purified and used to prepare ECH;

[0086] (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction in a microchannel reactor, controlling the total residence time of the feed liquid in the microchannel reactor to 0.5 s, wherein the liquid-liquid saponification reaction comprises first a preheating stage and controlling the temperature to 100° C., then a reaction stage and controlling the temperature to 80° C. and the pH value of the material to 12, then a cooling stage and controlling the terminal temperature to 5° C. and adjusting the pH value to 8.5, and then performing oil-water separation to obtain an oil layer and a water layer; the oil layer is subjected to rectification and separation under the conditions of a bottom temperature of 140° C. and a pressure of -85 kPa to obtain a crude ECH product at the top of the tower, the crude ECH product is returned to the rectification and refining step to prepare an ECH finished product, the bottom of the tower obtains an organic by-product, meta-dichlorobenzene, the water layer is stripped to obtain a gas phase containing the crude ECH product and returned to the rectification and refining step to prepare an ECH finished product, and the stripping kettle obtains brine and sends it to a brine treatment system.

[0087] Example 3

[0088] The present embodiment provides a method for treating epichlorohydrin residue and recycling it. The epichlorohydrin residue is: distillation residue (mass is 298 kg) produced by distillation and refining 10 tons of epichlorohydrin crude product, and the distillation residue contains 33.88% ECH, 32.09% dichloropropanol, 1.90% monochloropropanediol, 1.39% glycerol, 3.31% glycidol and 1.93% entrained impurities in terms of mass percentage, wherein the entrained impurity is cumene. The method comprises the following steps:

[0089] (1) performing primary light removal on the ECH distillation residue under the conditions of an absolute pressure of 20 kPa, a reflux ratio of 0.5, and a kettle temperature of 150° C. to obtain a first heavy component and a first light component containing crude ECH (mass percentage content>98%), and the first light component is returned to the distillation and refining step to prepare a finished ECH product;

[0090] (2) subjecting the first heavy component obtained in step (1) to secondary light removal under the conditions of an absolute pressure of 4 kPa, a reflux ratio of 2, and a kettle temperature of 140° C. to obtain a second heavy component;

[0091] (3) using oxalic acid as a catalyst, the second heavy component obtained in step (2) is subjected to a pressure chlorination reaction at a pressure of 0.05 MPa, a time of 4 hours, and a temperature of 110° C., with the catalyst amount being controlled to be 0.3% of the mass of the second heavy component, and the dichloropropane content is increased to 36.41%, followed by separation to obtain a crude dichloropropane product, which is purified and used to prepare ECH;

[0092] (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction in a microchannel reactor, controlling the total residence time of the feed liquid in the microchannel reactor to 5 s, wherein the liquid-liquid saponification reaction comprises first a preheating stage and controlling the temperature to 60° C., then a reaction stage and controlling the temperature to 120° C. and the pH value of the material to 10, then a cooling stage and controlling the terminal temperature to 25° C. and adjusting the pH value to 6.5, and then performing oil-water separation to obtain an oil layer and a water layer; the oil layer is subjected to rectification and separation under the conditions of a bottom temperature of 140° C. and a pressure of -85 kPa to obtain a crude ECH product at the top of the tower, the crude ECH product is returned to the rectification and refining step to prepare a finished ECH product, the bottom of the tower obtains an organic by-product, isopropylbenzene, the water layer is stripped to obtain a gas phase containing the crude ECH product and returned to the rectification and refining step to prepare a finished ECH product, the stripping kettle obtains brine and sends it to a brine treatment system.

[0093] Example 4

[0094] This embodiment provides a method for treating epichlorohydrin residue and recycling it. The only difference from Example 1 is that the epichlorohydrin residue has a different composition from that of Example 1 due to the difference in by-product hydrogen chloride used in the production. The epichlorohydrin residue (i.e., the distillation residue) contains, by weight percentage, 33.26% of epichlorohydrin, 31.09% of dichloropropanol, 1.92% of monochloropropylene glycol, 1.41% of glycerol, 3.45% of glycidol and 1.98% of entrained impurities, wherein the entrained impurities are p-xylene.

[0095] Example 5

[0096] This embodiment provides a method for treating epichlorohydrin residue and recycling it. The only difference from Example 1 is that the epichlorohydrin residue has a different composition from that of Example 1 due to the difference in by-product hydrogen chloride used in the production. The epichlorohydrin residue (i.e., the distillation residue) contains, by weight percentage, 34.02% epichlorohydrin, 32.64% dichloropropanol, 2.05% monochloropropylene glycol, 1.44% glycerol, 3.41% glycidol and 1.93% entrained impurities, wherein the entrained impurities are 1,2,4-trimethylbenzene.

[0097] Example 6

[0098] This embodiment provides a method for treating epichlorohydrin residue and recycling it. The only difference from Embodiment 1 is that the epichlorohydrin residue has a different composition from that of Embodiment 1 due to the difference in by-product hydrogen chloride used in the production. The epichlorohydrin residue (i.e., the distillation residue) contains, by weight percentage, 33.56% of epichlorohydrin, 32.67% of dichloropropanol, 1.96% of monochloropropylene glycol, 1.39% of glycerol, 3.27% of glycidol and 1.86% of entrained impurities, wherein the entrained impurity is 2-ethyltoluene.

[0099] Example 7

[0100] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the absolute pressure of the first-stage light removal is 4 kPa.

[0101] Example 8

[0102] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the absolute pressure of the first-stage light removal is 25 kPa.

[0103] Example 9

[0104] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the absolute pressure of the secondary light removal is 0.5 kPa.

[0105] Example 10

[0106] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the absolute pressure of the secondary light removal is 6 kPa.

[0107] Embodiment 11

[0108] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the amount of catalyst used in the pressurized chlorination reaction accounts for 0.02% of the mass of the second heavy component.

[0109] Example 12

[0110] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the amount of catalyst used in the pressurized chlorination reaction accounts for 0.4% of the mass of the second heavy component.

[0111] Example 13

[0112] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the hydrochlorination reaction time is 0.2 h.

[0113] Embodiment 14

[0114] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the hydrochlorination reaction time is 6 hours.

[0115] Embodiment 15

[0116] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the pressure of the hydrochlorination reaction is 0.02 MPa.

[0117] Example 16

[0118] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the pressure of the hydrochlorination reaction is 0.9 MPa.

[0119] Embodiment 17

[0120] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the total residence time of the feed liquid in the microchannel reactor in the liquid-liquid saponification reaction is 0.1 s.

[0121] Embodiment 18

[0122] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the total residence time of the feed liquid in the microchannel reactor in the liquid-liquid saponification reaction is 8 s.

[0123] Embodiment 19

[0124] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the temperature of the reaction stage in the liquid-liquid saponification reaction is 75°C.

[0125] Embodiment 20

[0126] This embodiment provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the temperature of the reaction stage in the liquid-liquid saponification reaction is 130°C.

[0127] Comparative Example 1

[0128] This comparative example provides a method for treating epichlorohydrin residue and recycling it as a resource. The only difference compared with Example 1 is that the first light component containing the crude epichlorohydrin is not used for refining and preparing the finished epichlorohydrin product.

[0129] Comparative Example 2

[0130] This comparative example provides a method for treating epichlorohydrin residue and recycling it as a resource, and the only difference compared with Example 1 is that step (3) is not performed.

[0131] Comparative Example 3

[0132] This comparative example provides a method for treating epichlorohydrin residue and recycling it as a resource, and the only difference compared with Example 1 is that step (4) is not performed.

[0133] In Examples 1-20 and Comparative Examples 1-3, the distillation residue of epichlorohydrin is recycled and utilized, which can further improve the single-pass yield and total yield of epichlorohydrin compared with the epichlorohydrin production process before treatment in the present invention. The material content is detected by a chromatographic quantitative method and the improvement effect is calculated as shown in Table 1.

[0134] In addition, step (4) of the present invention can also obtain impurities entrained in the distillation residue of the organic by-product epichlorohydrin, and the material content is detected by a chromatographic quantitative method and its recovery rate is calculated. The results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138]

[0139] From the data in Table 1, we can see the following points:

[0140] (1) It can be seen from the data of Examples 1-20 that the method provided by the present invention can achieve a one-way yield of epichlorohydrin of more than 93.17%, a total yield of epichlorohydrin of more than 95.46%, and a recovery rate of organic by-products of more than 86.28%. Under optimal conditions, the one-way yield of epichlorohydrin can reach more than 94.17%, the total yield of epichlorohydrin can reach more than 96.49%, and the recovery rate of organic by-products can reach more than 92.22%.

[0141] (2) Comprehensive comparison of the data of Example 1 and Examples 7-10 shows that the single-pass yield, total yield and organic by-product recovery rate in Example 1 are significantly better than those in Examples 7-10. It can be seen that the present invention can further improve the single-pass yield and total yield of epichlorohydrin by preferably controlling the absolute pressure of the primary light removal and the secondary light removal, which is beneficial to improving the recovery of organic by-products.

[0142] (3) Comprehensive comparison of the data of Example 1 and Examples 11-16 shows that the single-pass yield, total yield and organic by-product recovery rate in Example 1 are significantly better than those in Examples 11-16. It can be seen that the present invention can further improve the single-pass yield and total yield of epichlorohydrin by optimally controlling the amount of catalyst used in the pressurized chlorination reaction, the time of the hydrochlorination reaction and the pressure of the hydrochlorination reaction.

[0143] (4) A comprehensive comparison of the data of Example 1 and Examples 17-20 shows that the single-pass yield, total yield and organic by-product recovery rate in Example 1 are significantly better than those in Examples 17-20. It can be seen that the present invention can further improve the single-pass yield and total yield of epichlorohydrin by preferably controlling the total residence time of the feed liquid in the microchannel reactor and the temperature of the reaction stage in the liquid-liquid saponification reaction, which is beneficial to improving the recovery of organic by-products.

[0144] (5) Comprehensive comparison of the data of Example 1 and Comparative Examples 1-3 shows that the single-pass yield, total yield and organic by-product recovery rate of Example 1 are significantly better than those of Comparative Examples 1-3. It can be seen that the present invention can recover ECH from the products of the three steps of primary light removal, distillation separation and stripping, and can also recover organic by-products, effectively reducing the amount of epichlorohydrin residue and improving the yield of epichlorohydrin.

[0145] In summary, the present invention can recycle epichlorohydrin distillation residue, achieve full resource utilization of effective components in the residue, and significantly improve product yield.

[0146] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope 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 shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for treating epichlorohydrin residue and recycling it, characterized in that: The method comprises the following steps: (1) performing primary light removal on the distillation residue of epichlorohydrin to obtain a first heavy component and a first light component containing a crude epichlorohydrin product; (2) subjecting the first heavy component obtained in step (1) to secondary light removal to obtain a second heavy component and a second light component containing dichloropropane; (3) subjecting the second heavy component obtained in step (2) to a pressure chlorination reaction and separation in sequence to obtain a crude product of dichloropropane; (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction, and then subjecting the second light component to oil-water separation to obtain an oil layer and an aqueous layer; and subjecting the oil layer and the aqueous layer to purification treatments respectively to obtain a crude epichlorohydrin product; There is no sequence relationship between step (3) and step (4).

2. The method according to claim 1, characterized in that The distillation residue in step (1) contains, by mass percentage, 25-35% of epichlorohydrin, 30-45% of dichloropropanol, 1-3% of monochloropropylene glycol, 0.5-5% of glycerol, 1-3% of glycidol and 1-3% of entrained impurities, and the rest is glycerol derivatives and tar produced by distillation; Preferably, the entrained impurities include any one or a combination of at least two of o-dichlorobenzene, m-dichlorobenzene, isopropylbenzene, p-xylene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene or 2-ethyltoluene; Preferably, the mass percentage of epichlorohydrin in the first light component is greater than 98%; Preferably, the first light component is returned to the distillation and refining step to prepare the finished epichlorohydrin product.

3. The method according to claim 1 or 2, characterized in that: The absolute pressure of the first-stage light removal in step (1) is 5-20 kPa; Preferably, the absolute pressure of the secondary light removal in step (2) is ≥1 kPa and <5 kPa; Preferably, the reflux ratios of the primary light removal and the secondary light removal are independently 0.5-2; Preferably, the kettle temperatures of the primary light removal and the secondary light removal are independently ≤160°C.

4. The method according to any one of claims 1 to 3, characterized in that: In step (2), the second heavy component has, by weight percentage, an epichlorohydrin content of less than 1%, a dichloropropane content of less than 3%, a total content of glycidol, glycerol and monochloropropanediol of greater than 5%, a water content of less than 0.2%, and the remainder being glycerol derivatives and tar produced by distillation.

5. The method according to any one of claims 1 to 4, characterized in that: The amount of catalyst used in the pressurized chlorination reaction in step (3) is 0.05-0.3% of the mass of the second heavy component; Preferably, the pressure of the hydrochlorination reaction is 0.05-0.6MPa; Preferably, the hydrochlorination reaction time is 0.5-4h; Preferably, the temperature of the hydrochlorination reaction is 110-180°C; Preferably, the product of the hydrochlorination reaction contains 30-50% dichloropropanol, less than 3% glycidol, glycerol and monochloropropanediol in total, 0.5-3% water, and the rest is glycerol derivatives and tar produced by distillation.

6. The method according to any one of claims 1 to 5, characterized in that: The separation method in step (3) includes distillation; Preferably, the crude dichloropropanol is used to prepare epichlorohydrin after purification.

7. The method according to any one of claims 1 to 6, characterized in that: The liquid-liquid saponification reaction in step (4) is carried out in a microchannel reactor; Preferably, the total residence time of the feed liquid in the microchannel reactor is 0.2-5s; Preferably, the liquid-liquid saponification reaction comprises a preheating stage, a reaction stage and a cooling stage sequentially performed in a microchannel reactor; Preferably, the temperature in the preheating stage is 60-100°C; Preferably, the temperature of the reaction stage is 80-120°C; Preferably, the pH value of the material is controlled to be 10-12 during the reaction stage; Preferably, the temperature reduction stage reduces the temperature of the material to a terminal temperature of 5-25°C; Preferably, the pH value is also adjusted during the cooling stage; Preferably, during the cooling stage, the pH value of the material is adjusted to an end point pH value of 6.5-8.

5.

8. The method according to any one of claims 1 to 7, characterized in that: The purification treatment of the oil layer in step (4) includes distilling and separating the oil layer; Preferably, the bottom temperature of the distillation separation tower is ≤140°C; Preferably, the mass percentage of epichlorohydrin in the bottom product of the distillation separation is less than 1%; Preferably, the distillation separation is a negative pressure operation; Preferably, the pressure of the distillation separation is -65 to -85 kPa; Preferably, the crude epichlorohydrin is taken out from the top of the distillation separation tower, and the obtained crude epichlorohydrin is returned to the distillation and refining step to prepare the finished epichlorohydrin.

9. The method according to any one of claims 1 to 8, characterized in that: The purification treatment of the water layer in step (4) comprises steam stripping the water layer; Preferably, the stripping produced material is a gas phase containing a crude epichlorohydrin product, and the gas phase containing the crude epichlorohydrin product is returned to the distillation and refining step to prepare a finished epichlorohydrin product; Preferably, the mass percentage of epichlorohydrin in the crude epichlorohydrin produced by stripping is 80-90%; Preferably, the stripping tower bottom obtains brine, and the brine is sent to a brine treatment system.

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) performing primary light removal on the epichlorohydrin distillation residue under the conditions of an absolute pressure of 5-20 kPa, a reflux ratio of 0.5-2, and a kettle temperature of ≤160° C. to obtain a first heavy component and a first light component containing a crude epichlorohydrin product, wherein the first light component is returned to a distillation and refining step to prepare a finished epichlorohydrin product; (2) subjecting the first heavy component obtained in step (1) to secondary light removal under the conditions of an absolute pressure of ≥1 kPa and <5 kPa, a reflux ratio of 0.5-2, and a kettle temperature of ≤160° C. to obtain a second heavy component and a second light component containing dichloropropanol; (3) subjecting the second heavy component obtained in step (2) to a pressure chlorination reaction under the conditions of controlling the catalyst dosage to 0.05-0.3% of the mass of the second heavy component, a pressure of 0.05-0.6 MPa, a time of 0.5-4 h, and a temperature of 110-180° C., and then separating to obtain a crude dichloropropane product, which is purified and used to prepare epichlorohydrin; (4) subjecting the second light component obtained in step (2) to a liquid-liquid saponification reaction in a microchannel reactor, controlling the total residence time of the liquid in the microchannel reactor to be 0.2-5 s, wherein the liquid-liquid saponification reaction comprises first a preheating stage and controlling the temperature to be 60-100° C., then a reaction stage and controlling the temperature to be 80-120° C. and the pH value of the material to be 10-12, then a cooling stage and controlling the terminal temperature to be 5-25° C. and adjusting the pH value to be 6.5-8.5, and then performing oil-water separation to obtain an oil layer and a water layer; The oil layer is subjected to distillation separation under the condition that the bottom temperature is less than 120° C. and the pressure is -65 to -85 kPa, and the crude epichlorohydrin is obtained at the top of the tower and returned to the distillation and refining step to prepare the finished epichlorohydrin, and the organic by-product is obtained in the bottom of the tower; The water layer is stripped to obtain a gas phase containing crude epichlorohydrin and returned to the distillation and refining process to prepare finished epichlorohydrin. Brine is also obtained and sent to a brine treatment system.

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