A method for preparing dichloropropane by low-temperature catalysis

Abstract

The present invention relates to a method for preparing dichloropropane by low-temperature catalysis. The method comprises the steps of preparing allyl alcohol by reacting allyl chloride, a polymerization inhibitor, and a catalyst. The method can achieve highly selective conversion of allyl chloride to dichloropropane, and the concentration of the dichloropropane produced by the photocatalytic reaction is as high as over 80% by weight. The method generates little wastewater when used to produce epichlorohydrin, thus being environmentally friendly.

Description

Technical field

[0001] The present invention belongs to the technical field of organic chemical raw material processing, and more specifically, relates to a method for preparing dichloropropanol by low-temperature catalysis. [Background Technology]

[0002] Dichloropropane is an important organic intermediate, and its main use is to produce epichlorohydrin. The traditional propylene high-temperature chlorination method, propylene acetate method and glycerol method epichlorohydrin process all require dichloropropane, which is then cyclized to produce epichlorohydrin.

[0003] The high-temperature chlorination method of propylene is tending to be eliminated due to the large amount of process wastewater it produces; the propylene acetate method is difficult to implement industrially due to the high price of the catalyst and the difficulty of regeneration; the glycerol method is restricted by the supply of crude glycerol from abroad, which is not conducive to the development of the industrial chain. Therefore, it is very necessary to explore new paths for the preparation of dichloropropane.

[0004] In order to solve some defects in the prior art, the inventor has finally completed the present invention after a lot of experiments and research. [Summary of the invention]

[0005] [Technical problems to be solved]

[0006] The object of the present invention is to provide a method for preparing dichloropropanol by low-temperature catalysis.

[0007] [Technical solution]

[0008] The present invention is achieved through the following technical solutions.

[0009] The invention relates to a method for preparing dichloropropanol by low-temperature catalysis.

[0010] The preparation steps of this preparation method are as follows:

[0011] Allyl chloride, inhibitor solution and catalyst solution are respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted for 1.0 to 3.0 hours under the conditions of reaction temperature of 30 to 60°C and pressure of 0.1 to 0.3 MPa to obtain an allyl alcohol solution; the allyl alcohol solution is transported from the bottom of the allyl alcohol reactor 1 to the middle of the distillation tower 3 through the first pump 2, and is separated in the distillation tower 3 under the conditions of normal pressure, tower top temperature of 78 to 80°C, tower bottom temperature of 100 to 102°C and reflux ratio of 0.25 to 1.50, and the high-concentration allyl alcohol solution is discharged from the top of the distillation tower 3, and the catalyst solution is discharged from the bottom of the distillation tower 3. The high-concentration allyl alcohol solution is recovered and reused through ion exchange; the high-concentration allyl alcohol solution is transported to the upper part of the absorption tower 4 through a pipeline, and at the same time, the hydrogen chloride gas is transported to the lower part of the absorption tower 4 through a pipeline. In the absorption tower 4, the high-concentration allyl alcohol absorbs the hydrogen chloride gas, and the high-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of the absorption tower 4. It is transported to the dichloropropanol reactor 6 by a second pump 5. At the same time, chlorine is also transported to the dichloropropanol reactor 6 through a pipeline. The reaction is carried out under photocatalytic conditions at a reaction temperature of -2 to 10° C. and a pressure of 0.1 to 0.3 MPa for 0.5 to 2.0 hours, thereby obtaining dichloropropanol with a concentration of more than 80% by weight.

[0012] According to a preferred embodiment of the present invention, the weight ratio of allyl chloride, inhibitor solution and catalyst solution is 1:2-4:6-10.

[0013] According to another preferred embodiment of the present invention, the polymerization inhibitor is hydroquinone, p-tert-butylcatechol, nitroxyl piperidinol or p-benzoquinone, and the concentration of the polymerization inhibitor solution is 0.05-0.2% by weight of the polymerization inhibitor.

[0014] According to another preferred embodiment of the present invention, the catalyst is cuprous chloride, ferrous chloride or stannous chloride, and the concentration of the catalyst solution is 0.1-1.0% by weight of the catalyst.

[0015] According to another preferred embodiment of the present invention, the allyl alcohol reactor 1 is a glass-lined reactor with a stirrer.

[0016] According to another preferred embodiment of the present invention, the distillation tower 3 is a tower-type gas-liquid contact distillation device.

[0017] According to another preferred embodiment of the present invention, the absorption tower 4 is a packed tower consisting of a cylindrical tower body, an upper semicircular cover and a lower semicircular cover, and the ratio of the diameter to the height of the cylindrical tower body is 1:15-20.

[0018] According to another preferred embodiment of the present invention, a filler selected from Raschig rings, Pall rings, saddle rings or Taylor rosettes is packed in a cylindrical tower body in a random manner, and the ratio of the total volume of the filler to the volume of the cylindrical tower body is 1:1.1-2.0.

[0019] According to another preferred embodiment of the present invention, the dichloropropanol reactor 6 is a cylindrical photocatalytic reactor, a mechanical stirrer is vertically installed in the middle of its top, and the ratio of its blade diameter to the diameter of its cylindrical part is 1:2-3; a light source generator 7 is installed on its upper side wall.

[0020] According to another preferred embodiment of the present invention, the emission wavelength of the light source generator 7 is 190-315 nm, and its power is 10-80 W.

[0021] The present invention will be described in more detail below.

[0022] The invention relates to a method for preparing dichloropropanol by low-temperature catalysis.

[0023] The flow chart of the method for preparing dichloropropanol at low temperature catalysis according to the present invention is shown in the attached Figure 1 .

[0024] The preparation steps of this preparation method are as follows:

[0025] Allyl chloride, polymerization inhibitor solution and catalyst solution are respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted for 1.0 to 3.0 hours at a reaction temperature of 30 to 60° C. and a pressure of 0.1 to 0.3 MPa to obtain an allyl alcohol solution;

[0026] In the present invention, the role of the polymerization inhibitor is to inhibit the following reaction to increase the yield of allyl alcohol:

[0027] C=CC-OH+C=CC-OH→C=CCOCC=C+H2O

[0028] C=CC-OH+C=CC-Cl→C=CCOCC=C+HCl

[0029] The polymerization inhibitor used in the present invention is hydroquinone, p-tert-butylcatechol, nitroxide piperidinol or p-benzoquinone, which are all products currently sold on the market, such as products sold by Shandong Yingchuansheng Chemical Co., Ltd. under the trade names of hydroquinone and p-benzoquinone, products sold by Hubei Rishengchang New Materials Technology Co., Ltd. under the trade name of p-tert-butylcatechol, or products sold by Jiangsu Bisheng Chemical Co., Ltd. under the trade name of nitroxide piperidinol. The polymerization inhibitor solution used in the present invention is an aqueous solution with a concentration of 0.05 to 0.2% by weight of the polymerization inhibitor. In the present invention, if the concentration of the polymerization inhibitor solution is lower than 0.05%, the polymerization inhibition effect is poor; if the concentration of the polymerization inhibitor solution is higher than 0.2%, the polymerization inhibition effect is not greatly improved, but the cost is increased. Therefore, the concentration of the polymerization inhibitor solution is suitable to be 0.05 to 0.2%, preferably 0.10 to 0.15%.

[0030] The main role of the catalyst in this reaction is to catalyze the conversion of allyl chloride into allyl alcohol, thereby effectively lowering the reaction temperature, reducing the occurrence of side reactions, and shortening the reaction time.

[0031] The catalyst used in the present invention is cuprous chloride, ferrous chloride, or stannous chloride, all of which are currently available on the market, such as the product sold under the trade name cuprous chloride by Wujiang Tengxiang Chemical Co., Ltd., the product sold under the trade name ferrous chloride by Jiangsu Muhong Environmental Protection Technology Co., Ltd., and the product sold under the trade name stannous chloride by Nantong Runfeng Petrochemical Co., Ltd. The catalyst solution used in the present invention is an aqueous solution having a concentration of 0.1 to 1.0% by weight of the catalyst. In the present invention, if the catalyst solution concentration is less than 0.1%, the above-mentioned reaction effect is poor; if the catalyst solution concentration is greater than 1.0%, it will lead to an increase in side reactions. Therefore, a catalyst solution concentration of 0.1 to 1.0% is appropriate, preferably 0.2 to 0.8%.

[0032] In the allyl alcohol reactor 1, allyl chloride, inhibitor solution and catalyst solution are reacted in a weight ratio of 1:2-4:6-10 at a reaction temperature of 30-60° C. and a pressure of 0.1-0.3 MPa for 1.0-3.0 hours to obtain an allyl alcohol solution.

[0033] In this step, when the reaction temperature, reaction pressure and reaction time are within the described ranges, and the amounts of allyl chloride and catalyst solution are within the described ranges, if the amount of inhibitor solution is less than 2, the inhibition effect is poor and the above-mentioned side reactions will increase; if the amount of inhibitor solution is higher than 4, the above-mentioned catalytic reaction effect is not significantly improved, but the production cost is increased; therefore, it is reasonable to use an amount of inhibitor solution of 2 to 4, preferably 2.6 to 3.4; when the amounts of allyl chloride and inhibitor solution are within the described ranges, if the amount of catalyst solution is lower than 6, the above-mentioned catalytic reaction effect is poor and the reaction is not thorough; if the amount of catalyst solution is higher than 10, the increase in the amount of catalyst used does not significantly improve the above-mentioned catalytic reaction effect, but the production cost will increase; therefore, it is appropriate to use an amount of catalyst solution of 6 to 10, preferably 6.6 to 9.4.

[0034] When the amounts of allyl chloride, inhibitor solution, and catalyst solution are within the stated ranges, and the reaction pressure and reaction time are within the stated ranges, if the reaction temperature is below 30°C, the catalytic reaction will not proceed sufficiently. If the reaction temperature is above 60°C, numerous side reactions will occur, significantly affecting the yield of allyl alcohol. Therefore, a reaction temperature of 30-60°C is reasonable, preferably 35-55°C. When the reaction temperature and reaction time are within the stated ranges, if the reaction pressure is below 0.1 MPa, the catalytic reaction will not proceed sufficiently. If the reaction pressure is above 0.3 MPa, increasing the reaction pressure has little effect on the catalytic reaction results and instead increases equipment costs. Therefore, a reaction pressure of 0.1-0.3 MPa is appropriate, preferably 0.15-0.25 MPa. When the reaction temperature and reaction pressure are within the stated ranges, if the reaction time is less than 1.0 h, the catalytic reaction will not proceed sufficiently. If the reaction time is longer than 3.0 h, the reaction time is too long, increasing the number of side reactions and significantly affecting the yield of allyl alcohol. Therefore, the reaction time is preferably 1.0 to 3.0 h, preferably 1.2 to 2.6 h.

[0035] The allyl alcohol reactor 1 used in the present invention is a glass-lined reactor with a stirrer, which is a product currently sold on the market, for example, a glass-lined reactor sold by Zibo Taiji Industrial Enamel Co., Ltd. under the trade name Closed Glass-lined Reactor.

[0036] Adopt gas chromatographic analysis method to detect, the vinyl alcohol solution that the above-mentioned steps obtains usually contains multiple by-products such as 7.0~7.2% vinyl alcohol and 0.1~0.2% allyl ether by weight, therefore need to adopt rectification method to remove these by-products, reclaim employed catalyzer, so that reuse.Particularly, described vinyl alcohol solution is transported to the middle part of rectifying tower 3 through first pump 2 by the bottom of vinyl alcohol reactor 1, and is separated under the conditions of normal pressure, tower top temperature of 78~80 ℃, tower bottom temperature of 100~102 ℃ and reflux ratio of 0.25~1.50 in rectifying tower 3, high concentration vinyl alcohol solution is discharged by rectifying tower 3 tower tops, and catalyst solution is discharged by rectifying tower 3 tower bottoms, and it is recycled and reused by ion exchange.

[0037] When the allyl alcohol solution obtained in the above step is separated in the distillation tower 3 under normal pressure, if the tower bottom temperature and the reflux ratio are within the range, if the tower top temperature is lower than 78°C, the allyl alcohol content of the tower bottom discharge will be too high, increasing the raw material consumption per unit product; if the tower top temperature is higher than 80°C, the allyl alcohol concentration of the tower top discharge will be reduced, thereby increasing the amount of wastewater generated in the subsequent reaction step; therefore, a tower top temperature of 78 to 80°C is appropriate; when the tower top temperature and the reflux ratio are within the range, if the tower bottom temperature is lower than 100°C, the reaction material will be No vaporization; If the tower top temperature is higher than 102°C, the amount of steam in the tower will be too large, which will cause the heat transfer rate to increase, the temperature to rise sharply, and the temperature inside the distillation tower to be too high, thereby damaging the tower plates; Therefore, a tower top temperature of 100-102°C is appropriate; When the tower top temperature and the tower bottom temperature are within the range, if the reflux ratio is lower than 0.25, the distillation effect will be poor and the concentration of the tower top product will not meet the separation requirements; If the reflux ratio is greater than 1.5, it will increase unnecessary energy consumption and condensation load; Therefore, a reflux ratio of 0.25-1.5 is appropriate;

[0038] The distillation tower 3, which primarily functions in the preparation method of the present invention to separate and concentrate allyl alcohol from the reaction solution, is a tower-type gas-liquid contact distillation device having a tray structure therein. The tray structure may be, for example, a bubble cap, float valve, or sieve structure. The distillation tower 3 used in the present invention is a commercially available product, such as one sold under the trade name "Distillation Tower" by Shandong Zhengtai Haikun Distillation Technology Co., Ltd. The first pump 2 and the second pump 5 used in the present invention are both commonly used infusion pumps in the art.

[0039] Next, the high-concentration allyl alcohol solution is piped to the upper portion of absorption tower 4 at a flow rate of 10 to 20 ml / min. Simultaneously, hydrogen chloride gas is piped to the lower portion of absorption tower 4 at a flow rate of 1,000 to 3,000 ml / min. The gas remains in absorption tower 4 for 20 to 60 minutes to allow the high-concentration allyl alcohol solution to fully absorb the hydrogen chloride gas, achieving a concentration of at least 0.9 ml of hydrogen chloride gas per milliliter of the high-concentration allyl alcohol solution.

[0040] The absorption tower 4 used in the present invention is a packed tower consisting of a cylindrical tower body, an upper semicircular cover, and a lower semicircular cover. The ratio of the diameter to the height of the cylindrical tower body is 1:15 to 20. The cylindrical tower body is packed in a random pile with a filler selected from Raschig rings, Pall rings, saddle rings, or Taylor rosettes. These fillers are commonly used in the art and widely available on the market, for example, Raschig rings sold under the trade name Raschig Ring Filler by Pingxiang Keyuan Environmental Protection Equipment Filler Co., Ltd. and saddle rings sold under the trade name Saddle Ring Filler by Jiangxi Aite Mass Transfer Technology Co., Ltd.

[0041] In the preparation method of the present invention, the ratio of the total volume of the packing to the volume of the cylindrical tower body is 1:1.1 to 2.0. If this volume ratio is greater than 1:1.1, the resistance between the packing layers will increase, affecting the gas-liquid distribution and mass transfer efficiency; if this volume ratio is less than 1:2.0, the processing capacity of the tower will be reduced; therefore, this volume ratio of 1:1.1 to 2.0 is appropriate;

[0042] Then, the highly concentrated allyl alcohol containing hydrogen chloride is discharged from the bottom of the absorption tower 4 and transported to the dichloropropanol reactor 6 by a second pump 5 at a flow rate of 10 to 20 ml / min. Simultaneously, chlorine is also transported to the dichloropropanol reactor 6 via a pipeline at a flow rate of 2500 to 5500 ml / min. The allyl alcohol reacts under photocatalytic conditions at a reaction temperature of -2 to 10° C. and a pressure of 0.1 to 0.3 MPa for 0.5 to 2.0 hours, thereby producing dichloropropanol with a concentration of more than 80% by weight.

[0043] In the dichloropropane reactor 6, high concentration allyl alcohol containing hydrogen chloride reacts with chlorine as follows:

[0044] C=CC-OH+Cl2→CCl-CCl-C-OH

[0045] In this step, when the reaction pressure and reaction time are within the range, if the reaction temperature is lower than -2°C, the chlorination reaction is not easy to proceed; if the reaction temperature is higher than 10°C, dichloropropane hydrolysis will occur; therefore, a reaction temperature of -2 to 10°C is reasonable; when the reaction temperature and reaction time are within the range, if the reaction pressure is lower than 0.1 MPa, the chlorination reaction is not easy to proceed completely; if the chlorination reaction pressure is higher than 0.3 MPa, increasing the pressure has little effect on the reaction results, but increases the equipment investment; therefore, a reaction pressure of 0.1 to 0.3 MPa is appropriate; when the reaction temperature and reaction pressure are within the range, if the reaction time is shorter than 0.5h, the chlorination reaction is not complete; if the reaction time is longer than 2.0h, the reaction time is too long and the product will be hydrolyzed; therefore, a reaction time of 0.5 to 2.0h is appropriate;

[0046] The dichloropropane reactor 6 used in the present invention is a cylindrical photocatalytic reactor, with a mechanical stirrer mounted vertically in the middle of its top, the ratio of its blade diameter to the diameter of the cylindrical portion of the reactor being 1:2 to 3; a light source generator 7 is mounted on its upper sidewall, the emission wavelength of the light source generator 7 being 190 to 315 nm and the power being 10 to 80 W. The light source generator used in the present invention is a product commonly used in the art and currently sold on the market, such as the product sold by Ningbo Youwei Optoelectronics Co., Ltd. under the trade name Ultraviolet Lamp.

[0047] The dichloropropanol reactor 6 used in the present invention is a device currently sold on the market, for example, a device sold by Zibo Taiji Industrial Enamel Co., Ltd. under the trade name of Closed Glass-lined Reactor.

[0048] According to gas chromatography analysis, the concentration of dichloropropanol, a product of the photocatalytic reaction of high-concentration allyl alcohol containing hydrogen chloride with chlorine, is greater than 80% by weight.

[0049] [Beneficial Effects]

[0050] The beneficial effects of the present invention are: the preparation method of the present invention can achieve highly selective conversion of allyl chloride to dichloropropanol, and the concentration of dichloropropanol, a photocatalytic reaction product, is as high as more than 80% by weight. When the method is used to produce epichlorohydrin, the amount of wastewater generated is small, and the method is green and environmentally friendly.

Brief Description of the Drawings

[0051] Attachment Figure 1 This is a process flow chart of the low-temperature catalytic preparation of dichloropropanol according to the present invention;

[0052] In the picture:

[0053] 1-allyl alcohol reactor; 2-first pump; 3-distillation column; 4-absorption column; 5-second pump; 6-dichloropropanol reactor; 7-light source generator; [Specific implementation method]

[0054] The present invention will be better understood through the following examples.

[0055] Example 1: Preparation of dichloropropanol by low-temperature catalysis of the present invention

[0056] The implementation steps of this embodiment are as follows:

[0057] According to the weight ratio of allyl chloride, polymerization inhibitor solution and catalyst solution of 1:3:8, allyl chloride, hydroquinone polymerization inhibitor solution with a concentration of 0.10% based on the weight of polymerization inhibitor, and cuprous chloride catalyst solution with a concentration of 0.7% based on the weight of catalyst were respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted at a reaction temperature of 30° C. and a pressure of 0.2 MPa for 3.0 hours to obtain an allyl alcohol solution;

[0058] The allyl alcohol solution is transported from the bottom of the allyl alcohol reactor 1 to the middle of the distillation tower 3 via the first pump 2, and is separated in the distillation tower 3 under the conditions of atmospheric pressure, a tower top temperature of 80°C, a tower bottom temperature of 102°C, and a reflux ratio of 1.50. The high-concentration allyl alcohol solution is discharged from the top of the distillation tower 3, and the catalyst solution is discharged from the bottom of the distillation tower 3 and is recovered and reused through ion exchange.

[0059] A high-concentration allyl alcohol solution was piped to the upper portion of absorption tower 4 at a flow rate of 10 ml / min. Simultaneously, hydrogen chloride gas was piped to the lower portion of absorption tower 4 at a flow rate of 1000 ml / min. The solution remained in absorption tower 4 for 20 minutes to allow the high-concentration allyl alcohol to absorb the hydrogen chloride gas, yielding a high-concentration allyl alcohol solution containing hydrogen chloride. Potentiometric titration revealed that the solution contained 0.91 ml of hydrogen chloride gas per ml. Absorption tower 4 was a cylindrical tower having a diameter-to-height ratio of 1:18. Raschig rings were randomly packed in the cylindrical tower.

[0060] High-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of absorption tower 4 and delivered to dichloropropanol reactor 6 by second pump 5 at a flow rate of 10 ml / min. Simultaneously, chlorine gas is delivered to dichloropropanol reactor 6 via a pipeline at a flow rate of 2500 ml / min. The reaction is carried out at a reaction temperature of -2°C and a pressure of 0.1 MPa under the catalytic action of light from light source generator 7 with a power of 60 W and an emission wavelength of 270 nm for 1.5 hours. A dichloropropanol solution having a dichloropropanol concentration of 82.1% by weight is obtained, as determined by analysis according to the standard analytical method described in the specification of this application.

[0061] Example 2: Preparation of dichloropropanol by low-temperature catalysis of the present invention

[0062] The implementation steps of this embodiment are as follows:

[0063] According to the weight ratio of allyl chloride, polymerization inhibitor solution and catalyst solution of 1:2:6, allyl chloride, a polymerization inhibitor solution of 0.05% by weight of the polymerization inhibitor and a ferrous chloride catalyst solution of 0.1% by weight of the catalyst were respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted at a reaction temperature of 60° C. and a pressure of 0.1 MPa for 1.0 h to obtain an allyl alcohol solution;

[0064] The allyl alcohol solution is transported from the bottom of the allyl alcohol reactor 1 to the middle of the distillation tower 3 via the first pump 2, and is separated in the distillation tower 3 under the conditions of atmospheric pressure, a tower top temperature of 78°C, a tower bottom temperature of 100°C, and a reflux ratio of 0.25. The high-concentration allyl alcohol solution is discharged from the top of the distillation tower 3, and the catalyst solution is discharged from the bottom of the distillation tower 3 and is recovered and reused through ion exchange.

[0065] A high-concentration allyl alcohol solution was piped to the upper portion of absorption tower 4 at a flow rate of 20 ml / min. Simultaneously, hydrogen chloride gas was piped to the lower portion of absorption tower 4 at a flow rate of 3000 ml / min. The solution remained in absorption tower 4 for 60 minutes, allowing the high-concentration allyl alcohol to absorb the hydrogen chloride gas. This yielded a high-concentration allyl alcohol solution containing hydrogen chloride, which, when measured by potentiometric titration, contained 0.92 ml of hydrogen chloride gas per ml. Absorption tower 4 was a cylindrical tower with a diameter-to-height ratio of 1:15. Ball ring packing was randomly packed within the cylindrical tower.

[0066] High-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of absorption tower 4 and delivered to dichloropropanol reactor 6 by second pump 5 at a flow rate of 20 ml / min. Simultaneously, chlorine gas is delivered to dichloropropanol reactor 6 via a pipeline at a flow rate of 5500 ml / min. The reaction is carried out at a reaction temperature of 2°C and a pressure of 0.3 MPa under the catalytic action of light emitting from light source generator 7 with a power of 10 W and an emission wavelength of 190 nm for 0.5 h. A dichloropropanol solution having a dichloropropanol concentration of 85.2% by weight is obtained, as determined by analysis according to the standard analytical method described in the specification of this application.

[0067] Example 3: Preparation of dichloropropanol by low-temperature catalysis of the present invention

[0068] The implementation steps of this embodiment are as follows:

[0069] According to the weight ratio of allyl chloride, polymerization inhibitor solution and catalyst solution of 1:3:10, allyl chloride, a 0.2% by weight of the polymerization inhibitor p-nitroxylpiperidinol polymerization inhibitor solution and a 1.0% by weight of the catalyst stannous chloride catalyst solution were respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted at a reaction temperature of 40° C. and a pressure of 0.3 MPa for 2.4 hours to obtain an allyl alcohol solution;

[0070] The allyl alcohol solution is transported from the bottom of the allyl alcohol reactor 1 to the middle of the distillation tower 3 via the first pump 2, and is separated in the distillation tower 3 under the conditions of atmospheric pressure, a tower top temperature of 80°C, a tower bottom temperature of 102°C, and a reflux ratio of 0.65. The high-concentration allyl alcohol solution is discharged from the top of the distillation tower 3, and the catalyst solution is discharged from the bottom of the distillation tower 3 and is recovered and reused through ion exchange.

[0071] A high-concentration allyl alcohol solution was piped to the upper portion of absorption tower 4 at a flow rate of 15 ml / min. Hydrogen chloride gas was simultaneously piped to the lower portion of absorption tower 4 at a flow rate of 2000 ml / min. The solution remained in absorption tower 4 for 40 minutes, allowing the high-concentration allyl alcohol to absorb the hydrogen chloride gas. This yielded a high-concentration allyl alcohol solution containing hydrogen chloride, which, as determined by potentiometric titration, contained 0.92 ml of hydrogen chloride gas per ml. Absorption tower 4 was a cylindrical tower with a diameter-to-height ratio of 1:20. It was packed with random packing of rectangular saddle rings.

[0072] High-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of absorption tower 4 and delivered to dichloropropanol reactor 6 by second pump 5 at a flow rate of 15 ml / min. Simultaneously, chlorine gas is delivered to dichloropropanol reactor 6 via a pipeline at a flow rate of 4500 ml / min. The reaction is carried out at a reaction temperature of 10° C. and a pressure of 0.2 MPa under the catalytic action of light having a power of 80 W and an emission wavelength of 230 nm from light source generator 7 for 1.0 hour. Analysis according to the standard analytical method described in the specification of this application yields a dichloropropanol solution having a dichloropropanol concentration of 81.6% by weight.

[0073] Example 4: Preparation of dichloropropanol by low-temperature catalysis of the present invention

[0074] The implementation steps of this embodiment are as follows:

[0075] According to the weight ratio of allyl chloride, polymerization inhibitor solution and catalyst solution of 1:4:7, allyl chloride, p-benzoquinone polymerization inhibitor solution with a concentration of 0.15% based on the weight of polymerization inhibitor, and ferrous chloride catalyst solution with a concentration of 0.4% based on the weight of catalyst were respectively transported to the allyl alcohol reactor 1 through pipelines, and reacted at a reaction temperature of 50° C. and a pressure of 0.2 MPa for 1.8 hours to obtain an allyl alcohol solution;

[0076] The allyl alcohol solution is transported from the bottom of the allyl alcohol reactor 1 to the middle of the distillation tower 3 via the first pump 2, and is separated in the distillation tower 3 under the conditions of atmospheric pressure, a tower top temperature of 78°C, a tower bottom temperature of 100°C, and a reflux ratio of 1.05. The high-concentration allyl alcohol solution is discharged from the top of the distillation tower 3, and the catalyst solution is discharged from the bottom of the distillation tower 3 and is recovered and reused through ion exchange.

[0077] A high-concentration allyl alcohol solution was piped to the upper portion of absorption tower 4 at a flow rate of 12 ml / min. Simultaneously, hydrogen chloride gas was piped to the lower portion of absorption tower 4 at a flow rate of 1500 ml / min. The solution remained in absorption tower 4 for 30 minutes to allow the high-concentration allyl alcohol to absorb the hydrogen chloride gas, thereby obtaining a high-concentration allyl alcohol solution containing hydrogen chloride. Potentiometric titration revealed that the solution contained 0.91 ml of hydrogen chloride gas per ml. Absorption tower 4 was a cylindrical tower having a diameter-to-height ratio of 1:18. Taylor rosette packing was packed in a loose pile.

[0078] High-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of absorption tower 4 and delivered to dichloropropanol reactor 6 by second pump 5 at a flow rate of 12 ml / min. Simultaneously, chlorine gas is delivered to dichloropropanol reactor 6 via a pipeline at a flow rate of 3500 ml / min. The reaction is carried out for 2.0 hours at a reaction temperature of 6°C and a pressure of 0.2 MPa under the catalytic action of light from light source generator 7 with a power of 35 W and an emission wavelength of 315 nm. Analysis according to the standard analytical method described in the specification of this application yields a dichloropropanol solution having a dichloropropanol concentration of 86.2% by weight.

Claims

1. A method for preparing dichloropropane by low temperature catalysis, characterized in that The preparation steps of this preparation method are as follows: Allyl chloride, an inhibitor solution and a catalyst solution are respectively transported to an allyl alcohol reactor (1) through pipelines, and reacted for 1.0 to 3.0 hours under the conditions of a reaction temperature of 30 to 60° C. and a pressure of 0.1 to 0.3 MPa to obtain an allyl alcohol solution; the allyl alcohol solution is transported from the bottom of the allyl alcohol reactor (1) to the middle of a distillation tower (3) via a first pump (2), and is separated in the distillation tower (3) under the conditions of normal pressure, a tower top temperature of 78 to 80° C., a tower bottom temperature of 100 to 102° C. and a reflux ratio of 0.25 to 1.50; a high-concentration allyl alcohol solution is discharged from the top of the distillation tower (3), and a catalyst solution is discharged from the bottom of the distillation tower (3) and is recovered and reused through ion exchange; the high-concentration allyl alcohol solution is transported to the upper part of an absorption tower (4) through a pipeline, and at the same time, hydrogen chloride gas is transported to the absorption tower through a pipeline. (4) In the lower part, high-concentration allyl alcohol absorbs hydrogen chloride gas in the absorption tower (4), and the high-concentration allyl alcohol containing hydrogen chloride is discharged from the bottom of the absorption tower (4) and transported to the dichloropropanol reactor (6) by the second pump (5). At the same time, chlorine is also transported to the dichloropropanol reactor (6) through a pipeline, and reacts under the conditions of a reaction temperature of -2 to 10°C and a pressure of 0.1 to 0.3 MPa for 0.5 to 2.0 hours under the action of photocatalysis, thereby obtaining dichloropropanol with a concentration of more than 80% by weight; the said polymerization inhibitor is hydroquinone, p-tert-butylcatechol, nitroxyl piperidinol or p-benzoquinone, and the concentration of the said polymerization inhibitor solution is 0.05 to 0.2% by weight of the polymerization inhibitor; the said catalyst is cuprous chloride, ferrous chloride or stannous chloride, and the concentration of the said catalyst solution is 0.1 to 1.0% by weight of the catalyst.

2. The preparation method according to claim 1, wherein The weight ratio of allyl chloride, inhibitor solution and catalyst solution is 1:2-4:6-10.

3. The preparation method according to claim 1, wherein The allyl alcohol reactor (1) is a glass-lined reactor with a stirrer.

4. The preparation method according to claim 1, characterized in that The distillation tower (3) is a tower-type gas-liquid contact distillation device.

5. The preparation method according to claim 1, characterized in that The absorption tower (4) is a packed tower consisting of a cylindrical tower body, a semicircular cover at the upper end and a semicircular cover at the lower end. The ratio of the diameter to the height of the cylindrical tower body is 1:15-20.

6. The preparation method according to claim 5, characterized in that A filler selected from Raschig rings, Pall rings, saddle rings or Taylor rosettes is packed in a cylindrical tower body in a random manner, and the ratio of the total volume of the filler to the volume of the cylindrical tower body is 1:1.1-2.

0.

7. The preparation method according to claim 1, characterized in that The dichloropropane reactor (6) is a cylindrical photocatalytic reactor, wherein a mechanical stirrer is vertically installed in the middle of its top, and the ratio of the diameter of its blade to the diameter of its cylindrical part is 1:2-3; and a light source generator (7) is installed on its upper side wall.

8. The preparation method according to claim 7, characterized in that The emission wavelength of the light source generator (7) is 190-315 nm, and its power is 10-80 W.

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