A device and method for refining 1,2-dichloropropane, a by-product of a 3-chloropropene unit, by combining distillation, polymerization and adsorption

Abstract

A device and method for refining 1,2-dichloropropane, a by-product of a 3-chloropropene unit, by combining distillation, polymerization, and adsorption. The present invention discloses a device and method for refining 1,2-dichloropropane, a by-product of a 3-chloropropene unit. The device utilizes a combination of a light removal tower, a polymerization reactor, a heavy removal tower, and an adsorption tower to convert difficult-to-separate dichloropropene impurities into a polydichloropropene polymer through a polymerization reaction. Since the polymer has a large boiling point difference from dichloropropane, it is easy to separate and purify, thereby successfully achieving the refining and purification of 1,2-dichloropropane. The final 1,2-dichloropropane purity is ≥99.9%, and the residual dichloropropene content is <100 ppm. At the same time, the dichloropropene polymerization process conditions are mild, the equipment requirements are low, the process is simple, and it is conducive to expanding production.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical by-product purification, and specifically relates to a device and method for refining 1,2-dichloropropane, a by-product of a 3-chloropropene unit. In particular, the device utilizes a combination of distillation, polymerization and adsorption technology to achieve a purity of 1,2-dichloropropane, a by-product of the 3-chloropropene unit, of 99.9% or higher, with residual dichloropropene less than 100 ppm. Background Art

[0002] 1,2-Dichloropropane is an excellent organic solvent and chemical intermediate used in the formulation of paints, inks, thinners, and PVC adhesives. It can replace benzene compounds such as xylene in the production of benzene-free banana oil, thinner, and polyurethane thinners. It is also a key raw material for pesticide emulsifiers, lubricants, flame retardants, plasticizers, oilfield demulsifiers, detergents, and nonionic surfactants. Dichloropropane is also an important raw material for fine chemicals such as cosmetics and pharmaceuticals. Industrially, it is also used as a raw material for the production of tetrachloropropene. However, the use of 1,2-dichloropropane as a raw material for tetrachloropropene production requires that the dichloropropene content be below 100 ppm.

[0003] Industrial plants producing 3-chloropropene by high-temperature methods often produce a large amount of byproduct, DD mixture (a mixture of dichloropropane and dichloropropene), whose main components are 1,2-dichloropropane, cis-1,3-dichloropropene, trans-1,3-dichloropropene, 2,3-dichloropropene, and 3,3-dichloropropene. After 1,3-dichloropropene is separated from the DD mixture, crude 1,2-dichloropropane is produced, whose main components are 1,2-dichloropropane (75-85% by weight, the same below), 1-chloropropane (1-3%), 1-chloropropene (2-4%), 2-chloropropene (1-3%), 1,5-hexadiene (2-4%), cis-1,3-dichloropropene (4-6%), 2,3-dichloropropene (2-8%), and 3,3-dichloropropene (4-6%). Practice has shown that due to the small relative volatility of 3,3-dichloropropene, 2,3-dichloropropene and 1,2-dichloropropane, it is difficult to separate them by ordinary distillation and the energy consumption is high.

[0004] In summary, achieving high-precision purification of 1,2-dichloropropane, a byproduct of 3-chloropropene production, through a simple, low-cost process is a formidable challenge. This invention utilizes a combination of distillation, polymerization, and adsorption to produce a high-purity product with a 3-chloropropene content of less than 100 ppm and 1,2-dichloropropane content of ≥99.9%, saving energy and increasing the product's application value. Summary of the Invention

[0005] In view of this, the present invention proposes a new separation idea, which removes difficult-to-separate dichloropropene impurities through polymerization, and can effectively achieve high purity of 1,2-dichloropropane, a by-product of the 3-chloropropene unit. This method has good separation effect, and the final 1,2-dichloropropane purity is ≥99.9%, and the residual dichloropropene content is <100ppm.

[0006] One of the purposes of the present invention is to provide a purification device for 1,2-dichloropropane, a by-product of a 3-chloropropene unit.

[0007] The second object of the present invention is to provide a method for refining 1,2-dichloropropane which is a by-product of a 3-chloropropene unit.

[0008] According to one aspect of the present invention, the present invention provides a refining device for 1,2-dichloropropane produced as a by-product of a 3-chloropropene unit, comprising a light removal tower, a polymerization reactor, a heavy removal tower and an adsorption tower;

[0009] The light removal tower is provided with a gas outlet at the top for discharging gaseous substances, a feed inlet at the middle of the tower body for receiving raw materials, and a liquid outlet at the bottom of the tower for discharging liquid materials;

[0010] The polymerization reactor is located downstream of the light-removal tower, and is provided with a feed port, an initiator inlet, and a discharge port. The feed port is connected to the liquid outlet at the bottom of the light-removal tower through a pipeline for receiving the material from the light-removal tower, the initiator inlet is used for adding the initiator, and the discharge port is used for discharging the material after the polymerization reaction;

[0011] The deweighting tower is located downstream of the polymerization reactor. A feed port is provided in the middle of the deweighting tower, which is connected to the discharge port of the polymerization reactor through a pipeline for receiving materials from the polymerization reactor. A discharge port is provided at the top of the deweighting tower for discharging purified 1,2-dichloropropane. A polymer residue discharge port is provided at the bottom of the deweighting tower for discharging polymer residue after polymerization.

[0012] The adsorption tower is located downstream of the deweighting tower. The top of the adsorption tower is provided with a feed port, which is connected to the discharge port of the deweighting tower through a pipeline for receiving materials from the deweighting tower. The bottom of the adsorption tower is provided with a discharge port for discharging the purified 1,2-dichloropropane final product after adsorption treatment.

[0013] Preferably, the light-removal tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

[0014] Preferably, the polymerization reactor is a stirred tank reactor.

[0015] Preferably, the deweighting tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

[0016] Preferably, the adsorption tower is a molecular sieve packed tower, in which a packing support and a liquid distributor are provided.

[0017] Preferably, the gas outlet at the top of the light-removal tower is connected to a condenser for condensing the discharged gaseous substance into a liquid state. More preferably, the condenser is connected to a reflux tank for temporarily storing the condensed liquid substance and returning a portion of the condensed liquid substance to the light-removal tower to maintain the material balance in the tower, and the other portion passes through the discharge system.

[0018] Preferably, the liquid outlet at the bottom of the light-removal tower is connected to a reboiler for vaporizing the discharged liquid substance. The liquid substance discharged through the liquid outlet is partially vaporized by the reboiler and then partially refluxed to the light-removal tower to maintain the material balance in the tower, and the rest is transported to the polymerization reactor through a pipeline.

[0019] Preferably, the polymerization reactor is provided with a heat exchange jacket for introducing condensed water to control the temperature of the polymerization reactor.

[0020] Preferably, the polymerization reactor is provided with an agitator for maintaining the uniformity of dispersion of materials in the polymerization reactor.

[0021] Preferably, the discharge port at the top of the de-weighting tower is connected to a condenser for cooling and discharging the purified 1,2-dichloropropane. More preferably, the condenser is connected to a reflux tank for temporarily storing the condensed purified 1,2-dichloropropane, and refluxing a portion of it to the de-weighting tower to maintain the material balance in the tower, and the rest is transported to the adsorption tower through a pipeline.

[0022] Preferably, the polymer residue discharge port at the bottom of the de-weighting tower is connected to a reboiler for vaporizing the discharged liquid material. A portion of the material partially vaporized by the reboiler flows back to the de-weighting tower to maintain the material balance in the tower, and the rest is discharged from the system through a pipeline.

[0023] Preferably, a cooler is provided on the pipeline connected to the polymer residue discharge port at the bottom of the deweighting tower, for cooling the material containing the polymer residue.

[0024] Preferably, valves and pumps can be provided on each pipeline of the refining device for refining 1,2-dichloropropane, a by-product of the 3-chloropropene unit, to control the material flow rate and flow rate.

[0025] Preferably, there is at least one adsorption tower, more preferably at least two; when there are two or more adsorption towers, the adsorption towers are operated alternately to ensure continuous operation of the entire device.

[0026] According to another aspect of the present invention, the present invention provides a method for refining 1,2-dichloropropane, a by-product of a 3-chloropropene unit, the method comprising:

[0027] 1) The crude 1,2-dichloropropane by-product of the 3-chloropropene unit is transported into the light components removal tower, and the light components in the crude product are removed by reflux treatment at a certain temperature, and the light components are discharged through the gas outlet at the top of the light components removal tower;

[0028] 2) the material after the lightness removal tower treatment enters the polymerization reactor, and an initiator is added thereto, and the dichloropropylene compound undergoes polymerization reaction at a certain temperature and pressure, thereby forming a polymer residue that is easily separated from 1,2-dichloropropane;

[0029] 3) the material containing the polymer residue after the reaction in the polymerization reactor enters the de-weighting tower, is refluxed at a certain temperature, and the polymer residue is discharged from the bottom outlet of the de-weighting tower, and the purified 1,2-dichloropropane is discharged from the top outlet of the de-weighting tower and enters the adsorption tower;

[0030] 4) In the adsorption tower, unreacted dichloropropylene compounds are further removed by adsorption by the adsorbent.

[0031] Preferably, the crude 1,2-dichloropropane contains, by weight percentage, 75-85% of 1,2-dichloropropane, 1-3% of 1-chloropropane, 2-4% of trans-1-chloropropene, 1-3% of 2-chloropropene, 2-4% of 1,5-hexadiene, 4-6% of cis-1,3-dichloropropene, 2-8% of 2,3-dichloropropene, 4-6% of 1,1-dichloropropene, 4-6% of 3,3-dichloropropene, etc.

[0032] Preferably, the light component includes one or more of 1-chloropropane, 1-chloropropene, 2-chloropropene, 1,5-hexadiene, and the like.

[0033] Preferably, the light removal tower in step 1) has 50 to 70 theoretical plates, the feed position is located at the 20th to 40th theoretical plates, the operating conditions are normal pressure, the operating reflux ratio is 1 to 3, and the tower top temperature is 30 to 37.4°C.

[0034] Preferably, the initiator used in step 2) is selected from one or more of ethylaluminum, butyl lithium, benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, and persulfate.

[0035] Preferably, the amount of the initiator in step 2) accounts for 0.1 to 5% of the total mass of the feed.

[0036] Preferably, in step 2), the polymerization reaction temperature is 45° C. to 55° C., and the reaction time is 3.5 h to 4.5 h.

[0037] Preferably, the number of theoretical plates of the deweighting tower in step 3) is 25-35, the feed position is the 18th to 23rd theoretical plates, the tower top temperature is 85-100° C., the pressure is 95-105 kPaA; and the operating reflux ratio is 1-6.

[0038] Preferably, both the light removal tower and the heavy removal tower are packed towers, and the packing is a small metal random packing, a metal corrugated packing, or a metal wire mesh corrugated packing, preferably a metal wire mesh corrugated packing.

[0039] Preferably, the temperature inside the adsorption tower is 40-50° C., the pressure inside the tower is 10-30 kPaG, and the adsorbent is filled therein, and the adsorbent is 3A, 4A, 5A or 13X molecular sieve.

[0040] Furthermore, the purity of the product 1,2-dichloropropane finally obtained after adsorption treatment in the adsorption tower is ≥99.9%, and the residual dichloropropylene is <100 ppm.

[0041] The beneficial effects of the present invention are:

[0042] (1) The initiators that can be used in the present invention are ethyl aluminum, butyl lithium, benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, and persulfate, which have excellent performance, controllable and sufficient polymerization reaction, and a conversion rate of up to 99.4%.

[0043] (2) The process conditions for the polymerization of dichloropropylene are mild, the equipment requirements are low, the process is simple, and it is conducive to expanding production;

[0044] (3) The boiling point difference between the generated polydichloropropylene and dichloropropane is large, making it easy to separate and purify, and the purified 1,2-dichloropropane has high purity.

[0045] The combination of distillation, polymerization and adsorption technology simplifies the separation process, reduces the difficulty of refining, saves energy, and increases the economic value of 1,2-dichloropropane, a by-product of the 3-chloropropene unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 Schematic diagram of the structure of the refining device according to the present invention.

[0048] Among them, T101 is a light removal tower, E101 is a top condenser of the light removal tower, E102 is a reboiler of the kettle of the light removal tower, R101 is a polymerization reactor, T102 is a heavy removal tower, E103 is a top condenser of the heavy removal tower, E104 is a reboiler of the kettle of the heavy removal tower, E105 is a cooler, T103 and T104 are adsorption towers, and S101 and S102 are reflux tanks. DETAILED DESCRIPTION

[0049] The present invention will be described in detail below. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that allows the inventor to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are merely preferred examples for illustrative purposes and are not intended to limit the scope of the present invention. It should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0050] As used herein, the terms "comprises," "includes," "has," "contains" or any other similar terms are open conjunctions that are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "comprises," "includes," "has," and "contains" should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of."

[0051] Throughout this document, all features or conditions defined as numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges, particularly integer values. For example, a description of a range "1 to 8" should be considered to specifically disclose all possible subranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, and so forth, particularly those defined by all integer values, and should be considered to specifically disclose individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, and 8. Unless otherwise indicated, the foregoing interpretation applies to all of the present disclosure, regardless of whether the ranges are comprehensive or not.

[0052] If a quantity or other value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and any lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0053] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0054] In order to clarify the present invention, parts that are not related to the description are omitted in the drawings, and the same or similar components are denoted by the same reference numerals throughout the specification.

[0055] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

[0056] Throughout the specification, when it is mentioned that a certain element is “connected” to another element, it includes not only “direct connection” but also “indirect connection” between other components. In addition, when it is mentioned that a certain element “includes” a certain component, it means that the element may further include other components rather than excluding other components, unless explicitly described otherwise.

[0057] The terms “first”, “second” and the like used herein are used to explain various constituent elements, and they are used merely for the purpose of distinguishing one constituent element from another constituent element.

[0058] Furthermore, the terms used herein are only used to explain exemplary embodiments and are not intended to limit the present invention. Singular expressions also include their plural expressions, unless otherwise clearly indicated in the context. Terms such as "comprising," "equipped with," or "having" used herein are used to specify the presence of practical characteristics, numbers, steps, constituent elements, or combinations thereof, and should be understood as not excluding the possibility of the addition or presence of one or more other characteristics, numbers, steps, constituent elements, or combinations thereof.

[0059] Also, if a layer or an element is referred to as being formed “on” or “over” a “layer” or “element,” this means that each layer or element is formed directly on the layer or element, or other layers or elements may be formed between layers, bodies, or substrates.

[0060] The following is combined with Figure 1 , a detailed description is given of the refining process of 1,2-dichloropropane, a by-product of the 3-chloropropene unit according to the present invention.

[0061] like Figure 1 As shown, the refining device for 1,2-dichloropropane produced as a by-product of a 3-chloropropene unit according to the present invention includes a light removal column T101, a polymerization reactor R101, a heavy removal column T102, and adsorption columns T103 and T104;

[0062] The de-lightening tower T101 is provided with a gas outlet at the top for discharging gaseous substances, a feed inlet at the middle of the tower body for receiving raw materials, and a liquid outlet at the bottom of the tower for discharging liquid materials;

[0063] The polymerization reactor R101 is located downstream of the lightness removal tower T101. The polymerization reactor R101 is provided with a feed port, an initiator inlet, and a discharge port. The feed port is connected to the liquid outlet at the bottom of the lightness removal tower T101 through a pipeline for receiving the material from the lightness removal tower T101. The initiator inlet is used to add the initiator, and the discharge port is used to discharge the material after the polymerization reaction.

[0064] The deweighting tower T102 is located downstream of the polymerization reactor R101. A feed port is provided in the middle of the deweighting tower T102, which is connected to the discharge port of the polymerization reactor R101 through a pipeline for receiving materials from the polymerization reactor R101. A discharge port is provided at the top of the deweighting tower T102 for discharging purified 1,2-dichloropropane. A polymer residue discharge port is provided at the bottom of the deweighting tower T102 for discharging polymer residue after polymerization.

[0065] Two adsorption towers, T103 and T104, are provided, which operate alternately and are located downstream of the deweighting tower T102. The tops of the adsorption towers T103 and T104 are provided with feed ports, which are connected to the discharge port of the deweighting tower T102 through a pipeline for receiving the material from the deweighting tower T102. The bottoms of the adsorption towers T103 and T104 are provided with discharge ports for discharging the purified 1,2-dichloropropane final product after adsorption treatment.

[0066] Preferably, the lightness removal tower T101 is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are provided.

[0067] Preferably, the polymerization reactor R101 is a stirred tank reactor.

[0068] Preferably, the deweighting tower T102 is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are provided.

[0069] Preferably, the adsorption towers T103 and T104 are molecular sieve packed towers, and packing supports and liquid distributors are provided inside the towers.

[0070] Preferably, the gas outlet at the top of the light-removal tower T101 is connected to a condenser E101 for condensing the discharged gaseous substance into a liquid state. More preferably, the condenser E101 is connected to a reflux tank S101 for temporarily storing the condensed liquid substance and refluxing a portion of it to the light-removal tower T101 to maintain the material balance in the tower, and the other portion passes through the discharge system.

[0071] Preferably, the liquid outlet at the bottom of the light-removal tower T101 is connected to a reboiler E102 for vaporizing the discharged liquid substance. The liquid substance discharged through the liquid outlet is partially vaporized by the reboiler E102 and partially refluxed to the light-removal tower to maintain the material balance in the tower, and the rest is transported to the polymerization reactor R101 through a pipeline.

[0072] Preferably, the polymerization reactor R101 is provided with a heat exchange jacket for introducing condensed water to control the temperature of the polymerization reactor R101.

[0073] Preferably, the polymerization reactor R101 is provided with an agitator for maintaining the uniformity of dispersion of materials in the polymerization reactor R101.

[0074] Preferably, the discharge port at the top of the de-weighting tower T102 is connected to a condenser E103 for condensing and discharging the purified 1,2-dichloropropane. More preferably, the condenser E103 is connected to a reflux tank S102, which is used to temporarily store the condensed purified 1,2-dichloropropane and return a portion of it to the de-weighting tower T102 to maintain the material balance in the tower, and the rest is transported to the adsorption towers T103 and T104 through pipelines.

[0075] Preferably, the polymer residue discharge port at the bottom of the deweighting tower T102 is connected to a reboiler E104 for vaporizing the discharged liquid material. A portion of the liquid material partially vaporized by the reboiler E104 flows back to the deweighting tower T102 to maintain the material balance in the tower, and the rest is discharged from the system through a pipeline.

[0076] Optionally, a cooler E105 is provided on the pipeline connected to the polymer residue discharge port at the bottom of the deweighting tower T102 for cooling the material containing the polymer residue.

[0077] Preferably, valves and pumps can be provided on each pipeline of the refining device for refining 1,2-dichloropropane, a by-product of the 3-chloropropene unit, to control the material flow rate and flow rate.

[0078] Preferably, there is at least one adsorption tower, more preferably at least two; when there are two or more adsorption towers, the adsorption towers are operated alternately to ensure the continuous operation of the entire device, for example Figure 1 As shown, it includes two adsorption towers T103 and T104.

[0079] The method for refining 1,2-dichloropropane as a by-product of a 3-chloropropene unit using the refining device according to the present invention comprises the following steps:

[0080] (1) The crude by-product 1,2-dichloropropane (DCP) produced by the 3-chloropropene unit is sent to the lightness removal tower T101. The number of theoretical plates of the lightness removal tower T101 is 50 to 70, and the feed position is the 20th to 40th theoretical plate. The operating conditions are normal pressure, the operating reflux ratio is 1 to 3, and the tower top temperature is 30 to 37.4°C. The light components of the tower top gas phase are condensed by the condenser E101 and enter the reflux tank S101. Then, part of it is refluxed and the rest is discharged from the system. The top discharge is the light components, water and azeotropic DCP. The tower bottom temperature is 96 to 105°C, the pressure is 110 to 120 kPaA, and the operating reflux ratio is 1 to 5. A part of the liquid phase at the bottom of the tower is reboiled and refluxed by the reboiler E102, and the rest is sent to the polymerization reactor R101.

[0081] (2) The polymerization reactor R101 receives the material from the lightness removal tower T101 and adds an initiator at the same time. The initiator can be one or more selected from ethyl aluminum, butyl lithium, benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, and persulfate. The amount of initiator used accounts for 0.1-5% of the total mass of the feed. The reaction temperature is 45°C to 55°C, and the reaction time is 3.5h to 4.5h. After sufficient reaction, a DCP mixed liquid containing polydichloropropylene is obtained at the discharge port of the polymerization reactor R101. The product is analyzed by gas chromatography, and the conversion rate of dichloropropylene is 99.4%. The boiling point of the generated polydichloropropylene rises to above 200°C.

[0082] (3) The DCP mixed liquid containing polydichloropropylene is transported to the de-weighting tower T102, which has a theoretical plate number of 25 to 35 and a feed position of 18 to 23. The tower top temperature is 85 to 100°C and the pressure is 95 to 105 kPaA. The top gas phase is condensed by the condenser E103 to obtain a high-purity DCP material with a content of ≥99.5%, a part of which is refluxed and the rest is sent to the adsorption towers T103 and T104. The tower bottom temperature of the de-weighting tower T102 is 165 to 180°C and the pressure is 108 to 124 kPaA; the operating reflux ratio is 1 to 6. A part of the material containing polymer residue discharged through the polymer residue discharge port at the bottom of the tower is reboiled and refluxed by the reboiler E104, and the other part is cooled and discharged from the system by the cooler E105.

[0083] (4) Adsorption towers T103 and T104 are used for adsorption, while the other one is used for adsorbent regeneration. The two towers operate alternately. Adsorption towers T103 and T104 receive the top material of deweighting tower T102. After being fully adsorbed by adsorption towers T103 and T104, the purity of 1,2-dichloropropane in the outlet material reaches ≥99.9%, and dichloropropylene is <100ppm.

[0084] The following examples are merely examples of embodiments of the present invention and do not constitute any limitation thereto. Those skilled in the art will appreciate that modifications without departing from the spirit and scope of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0085] Example 1

[0086] The 3-chloropropene unit produces 1255 kg / h of crude 1,2-dichloropropane as a by-product, which is composed of 1,2-dichloropropane (80%, wt%, the same below), 1-chloropropane (1%), 1-chloropropene (2%), 2-chloropropene (1.5%), 1,5-hexadiene (2.1%), cis-1,3-dichloropropene (5%), 2,3-dichloropropene (3%), 3,3-dichloropropene (5%), and water (0.4%). The crude product is first fed into the lightness removal tower T101, which is filled with corrugated wire mesh packing with 60 theoretical plates. The feed position is the 30th theoretical plate. The operating conditions are normal pressure, the operating reflux ratio is 2, the tower top temperature is 36°C, and the tower bottom temperature is 104°C. The overhead vapor from the lightness removal tower T101 is condensed, with a portion refluxed and the remainder discharged from the system. Trace amounts of water, 1-chloropropane, 1-chloropropylene, 2-chloropropylene, and 1,5-hexadiene are removed overhead. The bottom discharge is 1,175 kg / h and enters polymerization reactor R101.

[0087] The initiator in the polymerization reactor R101 is azobisisobutyronitrile, the initiator feed rate is 2 kg / h, the reaction temperature is 49° C., and the reaction time is 4 hours.

[0088] The material from the outlet of polymerization reactor R101 enters de-weighting tower T102, which has 30 theoretical stages and is fed to the 20th stage. The tower top temperature is 94°C, and the pressure is atmospheric. The bottom temperature is 168.8°C, and the operating reflux ratio is 2. The overhead discharge is high-purity 1,2-dichloropropane with a purity of ≥99.5%, which is fed to adsorption towers T103 and T104. Polymer residue is discharged from the bottom of the tower.

[0089] The adsorbent in adsorption towers T103 and T104 is 5A molecular sieve, the temperature in the tower is 42.5°C, the pressure in the tower is 21 kPaG, the residual dichloropropylene content after adsorption is <100 ppm, and a dichloropropylene product with a purity of ≥99.9% is obtained.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A refining device for 1,2-dichloropropane, a by-product of a 3-chloropropylene unit, comprising a light removal tower, a polymerization reactor, a heavy removal tower, and an adsorption tower; The light removal tower is provided with a gas outlet at the top for discharging gaseous substances, a feed inlet at the middle of the tower body for receiving raw materials, and a liquid outlet at the bottom of the tower for discharging liquid materials; The polymerization reactor is located downstream of the light-removal tower, and is provided with a feed port, an initiator inlet, and a discharge port. The feed port is connected to the liquid outlet at the bottom of the light-removal tower through a pipeline for receiving the material from the light-removal tower, the initiator inlet is used for adding the initiator, and the discharge port is used for discharging the material after the polymerization reaction; The deweighting tower is located downstream of the polymerization reactor. A feed port is provided in the middle of the deweighting tower, which is connected to the discharge port of the polymerization reactor through a pipeline for receiving materials from the polymerization reactor. A discharge port is provided at the top of the deweighting tower for discharging purified 1,2-dichloropropane. A polymer residue discharge port is provided at the bottom of the deweighting tower for discharging polymer residue after polymerization. The adsorption tower is located downstream of the deweighting tower. The top of the adsorption tower is provided with a feed port, which is connected to the discharge port of the deweighting tower through a pipeline for receiving materials from the deweighting tower. The bottom of the adsorption tower is provided with a discharge port for discharging the purified 1,2-dichloropropane final product after adsorption treatment.

2. The refining device according to claim 1, characterized in that The light removal tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

3. The refining device according to claim 1, characterized in that The polymerization reactor is a stirred tank reactor.

4. The refining device according to claim 1, characterized in that The deweighting tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

5. The refining device according to claim 1, characterized in that The adsorption tower is a molecular sieve packed tower, in which a packing support and a liquid distributor are arranged.

6. The refining device according to claim 1, characterized in that The gas outlet at the top of the light-removal tower is connected to a condenser for condensing the discharged gaseous substance into liquid. The condenser is connected to a reflux tank for temporarily storing the condensed liquid substance and returning part of it to the light-removal tower to maintain the material balance in the tower, and the other part passes through the discharge system.

7. The refining device according to claim 1, characterized in that The liquid outlet at the bottom of the light-removal tower is connected to a reboiler for vaporizing the discharged liquid substance. The liquid substance discharged through the liquid outlet is partially vaporized by the reboiler and then partially refluxed to the light-removal tower to maintain the material balance in the tower, and the rest is transported to the polymerization reactor through a pipeline.

8. The refining device according to claim 1, characterized in that The polymerization reactor is provided with a heat exchange jacket for introducing condensed water to control the temperature of the polymerization reactor.

9. The refining device according to claim 1, characterized in that The polymerization reactor is provided with an agitator for maintaining the uniformity of dispersion of materials in the polymerization reactor.

10. The refining device according to claim 1, characterized in that The discharge port at the top of the de-weighting tower is connected to a condenser for cooling and discharging the purified 1,2-dichloropropane. The condenser is connected to a reflux tank for temporarily storing the condensed purified 1,2-dichloropropane and refluxing a portion of it to the de-weighting tower to maintain the material balance in the tower, and the rest is transported to the adsorption tower through a pipeline.

11. The refining device according to claim 1, characterized in that The polymer residue discharge port at the bottom of the de-weighting tower is connected to a reboiler for vaporizing the discharged liquid material. Part of the material partially vaporized by the reboiler flows back to the de-weighting tower to maintain the reaction balance of the material in the tower, and the rest is discharged from the system through a pipeline.

12. The refining device according to claim 1, characterized in that A cooler is provided on the pipeline connected to the polymer residue discharge port at the bottom of the deweighting tower, for cooling the material containing the polymer residue.

13. The refining device according to claim 1, characterized in that Valves and pumps are provided on each pipeline of the refining device for refining 1,2-dichloropropane, a by-product of the 3-chloropropene device, to control the material flow rate and flow rate.

14. The refining device according to claim 1, characterized in that There is at least one adsorption tower. When two or more adsorption towers are provided, the adsorption towers are operated alternately to ensure the continuous operation of the entire device.

15. The refining device according to claim 14, characterized in that There are at least two adsorption towers; when there are two or more adsorption towers, the adsorption towers are operated alternately to ensure the continuous operation of the entire device.

16. A method for refining 1,2-dichloropropane as a by-product of a 3-chloropropene unit, the method comprising: 1) The crude 1,2-dichloropropane by-product of the 3-chloropropene unit is transported to a light components removal tower, where it is refluxed at a certain temperature to remove light components from the crude product. The light components are then discharged through a gas outlet at the top of the light components removal tower; 2) the material after the lightness removal tower treatment enters a polymerization reactor, and an initiator is added thereto, and the dichloropropylene compound undergoes polymerization reaction at a certain temperature and pressure, thereby forming a polymer residue that is easily separated from 1,2-dichloropropane; 3) After the reaction in the polymerization reactor, the material containing the polymer residue enters the de-weighting tower, is refluxed at a certain temperature, and the polymer residue is discharged from the bottom outlet of the de-weighting tower. The purified 1,2-dichloropropane is discharged from the top outlet of the de-weighting tower and enters the adsorption tower; 4) In the adsorption tower, unreacted dichloropropylene compounds are further removed by adsorption by the adsorbent.

17. The purification method according to claim 16, characterized in that Calculated by weight, the crude 1,2-dichloropropane contains 75-85% of 1,2-dichloropropane, 1-3% of 1-chloropropane, 2-4% of trans-1-chloropropene, 1-3% of 2-chloropropene, 2-4% of 1,5-hexadiene, 4-6% of cis-1,3-dichloropropene, 2-8% of 2,3-dichloropropene, 4-6% of 1,1-dichloropropene, and 4-6% of 3,3-dichloropropene.

18. The purification method according to claim 16, characterized in that The light components include one or more of 1-chloropropane, 1-chloropropylene, 2-chloropropylene, and 1,5-hexadiene.

19. The purification method according to claim 16, wherein The lightness removal tower in step 1) has 50 to 70 theoretical plates, the feed position is located at the 20th to 40th theoretical plates, the operating conditions are normal pressure, the operating reflux ratio is 1 to 3, and the tower top temperature is 30 to 37.4°C.

20. The purification method according to claim 16, characterized in that The initiator used in step 2) is selected from one or more of ethylaluminum, butyl lithium, benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, and persulfate.

21. The purification method according to claim 16, characterized in that The amount of the initiator in step 2) is 0.1-5% of the total mass of the feed.

22. The purification method according to claim 16, wherein In step 2), the polymerization temperature is 45 o C~55 o C, the reaction time is 3.5 h~4.5 h.

23. The purification method according to claim 16, wherein The theoretical plate number of the deweighting tower in step 3) is 25-35, the feed position is the 18th to 23rd theoretical plate, and the tower top temperature is 85-100 o C, pressure is 95~105 kPaA; operating reflux ratio is 1~6.

24. The purification method according to claim 16, characterized in that The light removal tower and heavy removal tower are both packed towers, and the packings are small metal random packings and metal corrugated packings.

25. The purification method according to claim 24, characterized in that The filler is a metal wire mesh corrugated filler.

26. The purification method according to claim 16, wherein The temperature in the adsorption tower is 40-50 o C, the pressure inside the tower is 10~30 kPaG, and the adsorbent is filled therein, and the adsorbent is 3A, 4A, 5A or 13X molecular sieve.

27. The purification method according to claim 16, characterized in that The final product 1,2-dichloropropane after adsorption treatment in the adsorption tower has a purity of ≥99.9% and residual dichloropropylene <100ppm.

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