Benzyl alcohol rectification method and device capable of reducing generation of high-boiling-point substances

Abstract

The invention relates to the technical field of benzyl alcohol preparation, and provides a benzyl alcohol rectification method and device capable of reducing generation of high-boiling residues, the rectification method comprises the following steps: S1, benzyl chloride and an alkali solution are subjected to a hydrolysis reaction, and then reaction liquid is subjected to oil-water separation to obtain an oil-phase material and a water-phase material; s2, adding the oil-phase material obtained in the step S1 into a stirring kettle, adding recycled water generated after desalting the water-phase material, stirring, and adding alkali liquor into the stirring kettle at the same time; and S3, carrying out oil-water separation on the oil-water mixture in the step S2, and transferring an oil phase into a rectifying tower for rectification. After oil-water separation of the reaction liquid, stirring an oil phase with recycled water in a stirring kettle to elute brine water droplets entrained by the oil phase, and adding a trace amount of strong alkali into the stirring kettle at the same time, so that the rectified raw oil carries water and the trace amount of strong alkali to be alkaline; hCl generated by hydrolysis of benzyl chloride is prevented from forming an acidic environment in a gas phase and a liquid phase of the whole tower, so that benzaldehyde and benzyl alcohol are prevented from generating a condensation reaction under an acidic catalysis condition to generate a high-boiling residue.

Description

Technical Field

[0001] The invention relates to the technical field of benzyl alcohol preparation, and in particular to a benzyl alcohol distillation method and device for reducing the generation of high boiling points. Background Art

[0002] Benzyl alcohol, also known as benzyl alcohol, is a colorless, transparent, viscous liquid with a faint aromatic odor. It belongs to the group of phenyl-containing fatty alcohols. Due to its polarity, low toxicity and low vapor pressure, it is widely used in daily chemicals, coatings and polymer industries. It is environmentally friendly, non-toxic and has good solubility.

[0003] At present, the large-scale production of benzyl alcohol in China mainly adopts the benzyl chloride hydrolysis method. In this method, since the reaction raw material benzyl chloride contains trace amounts of benzyl dichloride, benzyl dichloride is hydrolyzed to produce benzaldehyde in the reaction process; the benzyl alcohol produced by the hydrolysis reaction is slowly oxidized to produce benzaldehyde; the benzyl chloride hydrolysis adopts continuous production, and the benzyl chloride in the reaction liquid after the reaction cannot be completely reacted, and contains trace amounts of benzyl chloride; in the reaction liquid after the reaction process, during the oil / water phase separation process, water is slightly soluble in the oil phase and cannot be completely separated. In summary, after the reaction liquid is separated by oil / water phase, the raw oil obtained in the distillation process contains trace amounts of water, benzaldehyde, and benzyl chloride. The subsequent oil phase distillation includes a multi-step process: the first step is to remove water, part of benzaldehyde and benzyl chloride; the second step is to purify benzyl alcohol; the third step is to purify dibenzyl ether. Each step of distillation will accumulate a large amount of high-boiling substances, which are usually treated as hazardous waste.

[0004] For example, in the first step of the distillation process, benzyl chloride is hydrolyzed to produce HCl, and the gas phase and liquid phase environment of the whole tower are under acidic conditions. Under acidic catalytic conditions, benzaldehyde and benzyl alcohol undergo condensation reaction to produce high-boiling substances. The boiling point of HCl is much lower than that of other components. The HCl produced by the hydrolysis of benzyl chloride in the tower is mass transferred to the gas phase and enriched in the gas phase. The boiling point of high-boiling substances is much higher than that of other components. During the gas-liquid exchange and mass transfer in the tower, the high-boiling substances produced by the gas phase reaction condense from the gas phase and are enriched in the liquid phase, which will greatly promote the progress of the gas phase reaction. The space velocity of the liquid phase in the tower is much lower than that of the gas phase, so that the residence time of the liquid phase in the tower is longer than that of the gas phase. The HCl in the liquid phase has catalyzed the reaction of the liquid phase before mass transfer. In the first step of the distillation process, both the gas phase and the liquid phase will react to produce high-boiling substances. The boiling point of high-boiling substances is higher than that of other components in the distillation process. In each step of the distillation process, high-boiling substances accumulate in the tower bottom and are finally enriched in the distillation residue.

[0005] Therefore, reducing the number of distillation steps, reducing the generation and accumulation of high boiling points, and increasing the yield of benzyl alcohol are technical problems that need to be solved urgently. Summary of the invention

[0006] In view of this, the present invention proposes a benzyl alcohol distillation method and device for reducing the generation of high boiling points. Under the conditions of existing production equipment, by optimizing the current process conditions, the acidic conditions of the distillation process are destroyed, the distillation steps are reduced, and the amount of hazardous waste formed by the distillation residue is reduced, thereby achieving the technical effect of reducing the cost of industrial production of benzyl alcohol and increasing the benefits.

[0007] The technical solution of the present invention is achieved as follows: On the one hand, the present invention provides a benzyl alcohol distillation method, comprising the following steps:

[0008] S1, benzyl chloride and an alkali solution undergo a hydrolysis reaction, and then the reaction solution is separated into oil and water to obtain an oil phase material and a water phase material;

[0009] S2, adding the oil phase material obtained in step S1 into a stirring tank, adding the recycled water produced by evaporation and condensation of the water phase material, stirring, and adding alkali solution into the stirring tank at the same time;

[0010] S3, separating the oil-water mixture from step S2, and transferring the oil phase into a distillation tower for distillation.

[0011] On the basis of the above technical solution, preferably, the following steps are also included:

[0012] S4, separating the oil-water mixture from step S2 into oil-water and transferring it into a distillation raw material tank, and then transferring it into a distillation tower;

[0013] After the liquid ammonia is vaporized, it is divided into three paths, the first path is led to the bottom of the distillation raw material tank, the second path is led to the gas phase space at the top of the distillation tower, and the third path is led to below the liquid surface of the distillation tower;

[0014] When the content of benzyl chloride and high boiling point in the distillation tower is >300ppm, inject NH into the distillation raw material tank and the distillation tower in turn. 3 .

[0015] On the basis of the above technical solution, preferably, the ammonia pressure is 0.2-0.4MPa, and the amount of ammonia is:

[0016] Q NH3 =Q 油 ×C 氯化苄 ×M NH3 / M 氯化苄 ;

[0017] Among them, Q NH3 For single NH 3 Injection volume t / h, Q 油 is the oil phase material flow rate into the stirred tank t / h, M NH3 For NH 3 The molar mass, M 氯化苄 is the molar mass of benzyl chloride.

[0018] On the basis of the above technical solution, preferably, in step S2, the volume of the recovered water is equal to that of the oil phase, and the amount of the alkali solution is:

[0019] Q 氯化苄 =Q 油 ×C 氯化苄 ;

[0020] Q NaOH =Q 氯化苄 ×M NaOH / M 氯化苄 ;

[0021] C NaOH =Q NaOH / (Q NaOH +Q 油 ×C 水 );

[0022] Q 液碱 =Q 回收水 ×C NaOH / (C 液碱 -C NaOH );

[0023] Among them, Q 氯化苄 Q is the benzyl chloride flow rate t / h in the oil phase material entering the stirred tank, 油 is the oil phase material flow rate into the stirred tank t / h, C 氯化苄 Q is the average content of benzyl chloride in the oil phase material entering the stirred tank, NaOH is the NaOH demand for the benzyl chloride reaction in the oil phase material t / h, M NaOH is the molar mass of NaOH, M 氯化苄 is the molar mass of benzyl chloride, C NaOH is the concentration of NaOH in the recycled water of the stirred tank, C 水 is the average water carrying capacity of the oil phase, Q 液碱 is the amount of liquid caustic soda injected t / h, Q 回收水 is the demand for recycled water entering the stirred tank, same as Q 油 , C 液碱 It is the content of NaOH in the liquid alkali entering the stirring tank.

[0024] On the basis of the above technical scheme, preferably, the hydrolysis reaction of step S1 is as follows: benzyl chloride and alkaline solution are added to a hydrolysis reactor at a feed mass flow ratio of 1:(4-4.5), stirred at 80-150° C. and 0.1-0.6 MPa, and a hydrolysis reaction occurs, and the residence time of the hydrolysis reaction is 6-10 h;

[0025] The alkaline solution is 10%-15% Na 2 CO3 Aqueous solution.

[0026] On the other hand, the present invention also provides a benzyl alcohol distillation device for reducing the generation of high boiling substances, comprising a liquid alkali tank, a stirring kettle, a No. 1 oil-water phase separator and a distillation tower;

[0027] The liquid alkali tank, the stirring kettle, the oil phase outlet of the 1# oil-water phase separator and the distillation tower are connected in sequence through pipelines;

[0028] The side of the stirring kettle is provided with an oil phase material feed port, a recycled water inlet and a pH meter, and the bottom of the distillation tower is provided with a discharge port;

[0029] A metering pump is arranged on the pipeline connecting the liquid alkali tank and the stirring kettle.

[0030] On the basis of the above technical solution, preferably, it further comprises a distillation raw material tank and a liquid ammonia tank, wherein the distillation raw material tank is arranged between the 1# oil-water phase separator and the distillation tower, and both are connected to the 1# oil-water phase separator and the distillation tower;

[0031] The liquid ammonia tank is connected to the distillation raw material tank through a first branch pipeline, the liquid ammonia tank is connected to the top of the distillation tower through a second branch pipeline, and the liquid ammonia tank is connected to the bottom of the distillation tower through a third branch pipeline.

[0032] On the basis of the above technical solution, preferably, a centrifugal pump is provided on the pipeline connecting the distillation raw material tank and the distillation tower.

[0033] On the basis of the above technical solution, preferably, the first branch pipeline, the second branch pipeline and the third branch pipeline are all provided with automatic regulating valves.

[0034] On the basis of the above technical scheme, preferably, it also includes a hydrolysis reactor, a 2# oil-water phase separator, an evaporator, and a condenser. The hydrolysis reactor, the liquid phase outlet of the 2# oil-water phase separator, the evaporator, and the condenser are connected in sequence through pipelines, the oil phase outlet of the 2# oil-water phase separator is connected to the oil phase material feed port, and the outlet of the condenser is connected to the recovered water liquid inlet.

[0035] The benzyl alcohol distillation method and device for reducing the generation of high boiling points of the present invention have the following beneficial effects compared with the prior art:

[0036] (1) After the oil and water in the reaction liquid are separated, the oil phase is stirred with recycled water in a stirring kettle to elute the brine droplets carried by the oil phase. At the same time, a trace amount of strong alkali is added to the stirring kettle, so that the distilled raw oil carries water and a trace amount of strong alkali and becomes alkaline; HCl produced by the hydrolysis of benzyl chloride is prevented from forming an acidic environment in the gas phase and liquid phase of the whole tower, thereby preventing benzaldehyde and benzyl alcohol from undergoing a condensation reaction under acidic catalytic conditions to produce high boiling products.

[0037] (2) When the benzyl chloride content in the distillation feed oil is high and the strong alkali is insufficient to inhibit the liquid phase reaction, ammonia is injected into the distillation feed tank, the gas phase area at the top of the distillation tower, and the liquid phase area at the bottom. Since the oil phase has to pass through the distillation feed tank from the stirred tank to the distillation tower, the oil phase stays for a long time. The strong alkali and ammonia carried in the distillation tower will promote the hydrolysis reaction of benzyl chloride and neutralize HCl, so that the benzyl chloride content in the feed oil entering the distillation tower is greatly reduced. The ammonia injected into the gas phase area of ​​the distillation tower reacts with the HCl produced by the hydrolysis of benzyl chloride, so that the gas phase in the tower maintains alkaline conditions and inhibits the reaction of the gas phase. The ammonia injected into the liquid phase of the distillation tower will maintain the alkaline conditions of the liquid phase and inhibit the production of high-boiling substances in the liquid phase.

[0038] (3) The benzyl alcohol distillation method and device of the present patent, on the one hand, destroy the acidic conditions of the distillation process and inhibit the production reaction of high-boiling substances; on the other hand, it has the technical effect of reducing the production of high-boiling substances and the consumption of benzyl alcohol in the reaction, as well as reducing the amount of distillation residue treated as hazardous waste, thereby reducing the cost of industrial production of benzyl alcohol and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 The structure of benzyl alcohol distillation of the present invention is Figure I ;

[0041] Figure 2 The structure of benzyl alcohol distillation of the present invention is Figure II .

[0042] Among them, 1-liquid alkali tank, 2-stirring kettle, 3-1# oil-water phase separator, 4-distillation tower, 21-feed port, 22-recovery water inlet, 23-pH meter, 41-discharge port, 24-metering pump, 5-distillation raw material tank, 6-liquid ammonia tank, 7-centrifugal pump, 8-automatic regulating valve, 9-hydrolysis reactor, 10-2# oil-water phase separator, 11-evaporator, 12-condenser. DETAILED DESCRIPTION

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. Features defined by "1#", "2#", etc. may explicitly or implicitly include one or more of the features.

[0045] The benzyl alcohol distillation device used in the present invention comprises a hydrolysis device in which benzyl chloride and an alkaline solution are hydrolyzed (see Figure 2 ) and distillation units (see Figure 1 ) two parts, wherein the hydrolysis device also includes a hydrolysis reactor 9, a 2# oil-water phase separator 10, an evaporator 11, and a condenser 12. The hydrolysis reactor 9, the liquid phase outlet of the 2# oil-water phase separator 10, the evaporator 11, and the condenser 12 are connected in sequence through pipelines. The oil phase outlet of the 2# oil-water phase separator 10 is connected to the oil phase material feed port 21, and the outlet of the condenser 12 is connected to the recovered water liquid inlet 22.

[0046] Among them, the hydrolysis reactor 9 is a common atmospheric pressure reactor or pressure reactor, which is equipped with a heating element and a stirring element inside, and a pressure gauge and a liquid level gauge outside; the 2# oil-water phase separator 10 is used to separate the oil phase material and the water phase material; the evaporator 11 plays an evaporation role and is used to remove water; the condenser 12 is used to cool the steam and collect recycled water.

[0047] Benzyl chloride and the alkaline solution undergo a hydrolysis reaction in a hydrolysis reactor 9. After the reaction is completed, the reaction liquid enters the 2# oil-water phase separator 10 for oil-water separation. The separated oil phase enters the stirred tank 2 through the oil phase material feed port 21 to obtain the oil phase material required for the distillation of the present invention; the separated liquid phase enters the evaporator 11 and the condenser 12 in sequence, and after evaporation and condensation, recycled water is obtained, and finally enters the stirred tank 2 through the recycled water inlet 22 to obtain the recycled water required for the distillation of the present invention.

[0048] The devices required for distillation include a liquid alkali tank 1, a stirring kettle 2, a 1# oil-water phase separator 3 and a distillation tower 4; wherein the liquid alkali tank 1, the stirring kettle 2, the oil phase outlet of the 1# oil-water phase separator 3 and the distillation tower 4 are sequentially connected through pipelines; an oil phase material feed port 21, a recovered water inlet 22 and a pH meter 23 are arranged on the side of the stirring kettle 2, and a discharge port 41 is arranged at the bottom of the distillation tower 4; a metering pump 24 is arranged on the pipeline connecting the liquid alkali tank 1 and the stirring kettle 2, and a pH meter is arranged on the stirring kettle 2 for detecting the pH value of the material in the stirring kettle 2.

[0049] Among them, the liquid alkali tank 1 is used to store alkali solution and provide alkali solution for distillation; the stirring kettle 2 is provided with a stirring device for material mixing reaction; the 1# oil-water phase separator 3 has the same function as the 2# oil-water phase separator 10; the distillation tower 4 is used for distillation and purification of oil phase materials.

[0050] The oil phase material is added into the stirring tank 2, and the recycled water is added for stirring to elute the brine droplets entrained in the oil; at the same time, alkaline solution is injected into the stirring tank 2 to adjust the pH value of the recycled water in the stirring tank to make the recycled water alkaline to avoid the condensation reaction of benzaldehyde and benzyl alcohol in an acidic environment to produce high boiling products.

[0051] When the benzyl chloride content in the distillation raw oil is high, the strong alkali is not enough to inhibit the alcohol-aldehyde condensation reaction. At this time, alkali needs to be added to avoid the generation of high-boiling products. Therefore, the distillation raw material tank 5 and the liquid ammonia tank 6 are set.

[0052] Specifically, the distillation raw material tank 5 is arranged between the 1# oil-water phase separator 3 and the distillation tower 4, and is connected to the 1# oil-water phase separator 3 and the distillation tower 4; the liquid ammonia tank 6 is connected to the distillation raw material tank 5 through a first branch pipeline, the liquid ammonia tank 6 is connected to the top of the distillation tower 4 through a second branch pipeline, and the liquid ammonia tank 6 is connected to the bottom of the distillation tower 4 through a third branch pipeline. A centrifugal pump 7 is provided on the pipeline connecting the distillation raw material tank 5 and the distillation tower 4, and automatic regulating valves 8 are provided on the first branch pipeline, the second branch pipeline, and the third branch pipeline, and the liquid ammonia tank 6 is provided with a vaporizer-automatic pressure reducing valve.

[0053] The liquid ammonia tank 6 is discharged through the vaporizer-automatic pressure reducing valve and forms a constant pressure and constant flow NH 3 . Part of NH 3 In the form of bubbling, quantitative injection is made from the bottom of the distillation raw material tank 5 to make NH 3 Soluble in distillation feed oil. Part of NH 3 A portion of NH 3 Inject NH4 into the bottom liquid of the distillation tower quantitatively below the liquid level in the distillation tower. 3 Dissolve in the kettle liquid and maintain the alkaline condition of the kettle liquid. Make the liquid phase and gas phase in an alkaline environment to avoid the generation of high boiling products.

[0054] According to the benzyl chloride content of the reaction liquid oil phase and the benzyl chloride and acetal content of the distillation tower bottom liquid, on the one hand, the liquid caustic soda and NH 3 On the one hand, different injection methods can be selected according to the injection amount.

[0055] The preferred method of adding alkali solution is to inject NH 3 According to the changes in the content of benzyl chloride and acetal, the gas phase space and liquid phase space of the distillation tower are injected with NH 3 way.

[0056] Example

[0057] The benzyl alcohol rectification method of the present embodiment comprises the following steps:

[0058] S1, benzyl chloride and alkaline solution are fed at a feed mass flow ratio of 1:4.2 (the feed flow rate of benzyl chloride is 10 t / h, the feed flow rate of alkaline solution is 42 t / h, and the concentration of alkaline solution is 11% Na 2 CO 3 After being evenly mixed with water and the mixture is put into a hydrolysis reactor 9, and stirred continuously at 130°C and 0.4MPa pressure to cause a hydrolysis reaction, and the residence time of the hydrolysis reaction liquid is 6h. After the reaction is completed, the reaction liquid after the hydrolysis reaction is transferred to a 2# oil-water separation tank 10, and after oil-water separation at 55°C, an oil phase material and an aqueous phase material are obtained.

[0059] The aqueous phase material enters the evaporator 11 in turn, evaporates at 80° C. and vacuum 60 KPa, and then enters the condenser 12 for condensation to obtain recycled water.

[0060] S2, adding the oil phase material obtained in step S1 into a stirring tank, adding recycled water in an equal proportion to the oil phase, and stirring the brine droplets entrained in the oil phase.

[0061] S3, the metering pump 24 injects liquid caustic soda from the liquid caustic soda tank 1 into the stirring tank 2, and the pH value after the recovered water and the liquid caustic soda are fully mixed is 11.58. An online pH meter 23 is set to monitor the mixing effect.

[0062] S4, the oil-water mixture of step S3 is separated into oil and water by a 1# oil-water separator 3, and the oil phase is transferred to a distillation raw material tank 5;

[0063] S5, the oil phase is further transported to the distillation tower 4 by the centrifugal pump 7 and enters the distillation process.

[0064] S6, the liquid ammonia in the liquid ammonia tank 6 is vaporized by the vaporizer-pressure reducing valve and then divided into three paths, and the pipeline flow of each path is controlled by the automatic regulating valve 8.

[0065] S7, the first route injects NH into the bottom of the distillation raw material tank 5 3 , NH 3 It is introduced in the form of bubbles and dissolved in the distillation feed oil.

[0066] S8, the second route injects NH into the top of the distillation tower 10 kettle 3 , NH 3 Distributed in the gas phase space inside the tower.

[0067] S9, the third route injects NH into the lower part of the reactor of the distillation tower 4 3 , NH 3 Dissolved in the bottom liquid.

[0068] Based on the embodiments of the present invention, liquid caustic soda and NH 3 The injection volume is calculated as follows:

[0069] Assume that the benzyl chloride content of the oil phase of the reaction liquid fluctuates between 100 and 500 ppm, the liquid alkali injected into the stirring tank is completely mixed in the recycled water, and after the oil / water phase is separated, the average water carrying capacity of the oil phase is 8%. After the oil phase and the water phase are fully mixed in the stirring tank, the oil phase removes the salt water droplets carried, and the water carried again is slightly alkaline water with the same concentration of NaOH as the recycled water in the stirring tank. The amount of NaOH carried by the oil phase is calculated according to the reaction demand with an average benzyl chloride content of 300 ppm; a single branch pipeline NH 3 The injection amount is calculated based on the reaction requirement of 100ppm benzyl chloride content.

[0070] The amount of lye used is:

[0071] Q 氯化苄 =Q 油 ×C 氯化苄 ;

[0072] Q NaOH =Q 氯化苄 ×M NaOH / M 氯化苄 ;

[0073] C NaOH =Q NaOH / (Q NaOH +Q 油 ×C 水 );

[0074] Q 液碱 =Q 回收水 ×C NaOH / (C 液碱 -C NaOH );

[0075] Among them, Q 氯化苄Q is the benzyl chloride flow rate t / h in the oil phase material entering the stirred tank, 油 is the oil phase material flow rate into the stirred tank t / h, C 氯化苄 Q is the average content of benzyl chloride in the oil phase material entering the stirred tank, NaOH is the NaOH demand for the benzyl chloride reaction in the oil phase material t / h, M NaOH is the molar mass of NaOH, M 氯化苄 is the molar mass of benzyl chloride, C NaOH is the concentration of NaOH in the recycled water of the stirred tank, C 水 is the average water carrying capacity of the oil phase, Q 液碱 is the injection volume of liquid caustic soda t / h, Q 回收水 is the demand for recycled water entering the stirred tank, same as Q 油 , C 液碱 It is the content of NaOH in the liquid alkali entering the stirring tank.

[0076] The ammonia pressure is 0.2-0.4MPa, and the amount of ammonia is:

[0077] Q NH3 =Q 油 ×C 氯化苄 ×M NH3 / M 氯化苄 ;

[0078] Among them, Q NH3 For single NH 3 Injection volume t / h, Q 油 is the oil phase material flow rate into the stirred tank t / h, M NH3 For NH 3 The molar mass, M 氯化苄 is the molar mass of benzyl chloride.

[0079] The calculation can be obtained:

[0080] Benzyl chloride feed flow rate: 10t / h;

[0081] Oil phase flow into the stirred tank: 8.476t / h;

[0082] Recycled water flow into the stirred tank: 8.476t / h;

[0083] Benzyl chloride content of the oil phase entering the stirred tank: 8.476*0.0300%=0.002543t / h;

[0084] NaOH requirement for benzyl chloride reaction: 0.002543 / 126*40=0.000807t / h;

[0085] The amount of water carried by the oil phase: 8.476*8%=0.678080t / h;

[0086] The concentration of NaOH in the recycled water of the stirring tank: 0.000807 / (0.000807+0.678080)=0.1189%;

[0087] Liquid alkali concentration: 32%;

[0088] Liquid caustic soda injection amount: 8.476*0.1189% / (32%-0.1189%)=0.032t / h=32kg / h;

[0089] Single branch line NH 3 Injection amount: 8.476*0.0100% / 126*17=1.14*10-4t / h=0.114kg / h.

[0090] Based on the embodiments of the present invention, the contents of the bottoms of the distillation towers in each step are shown in the table below:

[0091]

[0092]

[0093] Based on the embodiments of the present invention, the contents of the bottoms of the distillation towers in each step are shown in the table below:

[0094]

[0095] Based on the embodiments of the present invention, the economic benefits are calculated as follows:

[0096] The amount of high boiling substances produced by the original process t / y 872 The amount of high boiling substances produced in the embodiment t / y 24 Benzyl alcohol consumed in the original process t / y 620 Benzyl alcohol consumed in the embodiment t / y 17 Benzyl alcohol price￥ / t 15000 Cost savings￥ / y 9037895 Hazardous waste from the original process t / y 1336 Hazardous waste t / y of the embodiment 271 Hazardous waste treatment cost ￥ / t 1800 Savings in processing costs￥ / y 1917000 Liquid caustic soda input t / y 250 Liquid caustic soda price ￥ / t 784 Liquid caustic soda cost ￥ / y 196292 Liquid ammonia input t / y 2.72 Liquid ammonia price￥ / t 3343 Liquid ammonia cost ￥ / y 9083 Example Annual benefit ￥ / y 10749519

[0097] Comparative Example

[0098] Comparative Example Compared with the embodiment, the oil phase is directly distilled without adding liquid caustic soda and ammonia. The contents of the bottom of each distillation step are as follows:

[0099] ％ Toluene Benzaldehyde Benzyl chloride Benzyl alcohol Dibenzyl ether Acetal other Step 1: Distillation tower 0.009 0.698 0.017 88.141 9.924 0.771 0.441 Step 2: Distillation tower 0 0.009 0 38.354 52.766 7.079 1.792 Step 3: Distillation residue 0 0 0 0 20.543 65.248 14.210

[0100] Assuming the benzyl chloride feed rate is 10t / h, calculate:

[0101]

[0102] Benzyl alcohol consumed to produce high boiling products: 872 / 304*108*2=620t / y;

[0103] The cost of treating distillation residue as hazardous waste: 1336*1800=2404800￥ / y.

[0104] By comparison, it can be seen that the distillation method of the present invention has the technical effect of reducing the content of high-boiling substances and distillation residues, and also reduces the consumption of benzyl alcohol, thereby reducing the cost of hazardous waste treatment.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A benzyl alcohol distillation method for reducing the generation of high boiling substances, characterized in that: The following steps are involved: S1, benzyl chloride and an alkali solution undergo a hydrolysis reaction, and then the reaction solution is separated into oil and water to obtain an oil phase material and a water phase material; S2, adding the oil phase material obtained in step S1 into a stirring tank, adding the recycled water produced by evaporation and condensation of the water phase material, stirring, and adding alkali solution into the stirring tank at the same time; S3, separating the oil-water mixture from step S2, and transferring the oil phase into a distillation tower for distillation.

2. A benzyl alcohol distillation method for reducing the generation of high boiling substances as claimed in claim 1, characterized in that: The following steps are also included: S4, separating the oil-water mixture from step S2 into oil-water and transferring it into a distillation raw material tank, and then transferring it into a distillation tower; After the liquid ammonia is vaporized, it is divided into three paths, the first path is led to the bottom of the distillation raw material tank, the second path is led to the gas phase space at the top of the distillation tower, and the third path is led to below the liquid surface of the distillation tower; When the content of benzyl chloride and high boiling point substances in the distillation tower is >100ppm, NH3 is injected into the distillation raw material tank and the distillation tower in sequence.

3. A benzyl alcohol distillation method for reducing the generation of high boiling substances as claimed in claim 2, characterized in that: The ammonia pressure is 0.2-0.4MPa, and the amount of ammonia is: Q NH3 =Q 油 ×C 氯化苄 ×M NH3 / M 氯化苄 ; Among them, Q NH3 is the injection volume of single-channel NH3 t / h, Q 油 is the oil phase material flow rate into the stirred tank t / h, M NH3 is the molar mass of NH3, M 氯化苄 is the molar mass of benzyl chloride.

4. A benzyl alcohol distillation method for reducing the generation of high boiling substances as claimed in claim 1, characterized in that: In step S2, the volume of the recovered water is equal to that of the oil, and the amount of the alkali solution is: Q 氯化苄 =Q 油 ×C 氯化苄 ; Q NaOH =Q 氯化苄 ×M NaOH / M 氯化苄 ; C NaOH =Q NaOH / (Q NaOH +Q 油 ×C 水 ); Q 液碱 =Q 回收水 ×C NaOH / (C 液碱 -C NaOH ); Among them, Q 氯化苄 Q is the benzyl chloride flow rate t / h in the oil phase material entering the stirred tank, 油 is the oil phase material flow rate into the stirred tank t / h, C 氯化苄 Q is the average content of benzyl chloride in the oil phase material entering the stirred tank, NaOH is the NaOH demand for the benzyl chloride reaction in the oil phase material t / h, M NaOH is the molar mass of NaOH, M 氯化苄 is the molar mass of benzyl chloride, C NaOH is the concentration of NaOH in the recycled water of the stirred tank, C 水 is the average water carrying capacity of the oil phase, Q 液碱 is the injection volume of liquid caustic soda t / h, Q 回收水 is the demand for recycled water entering the stirred tank, same as Q 油 , C 液碱 It is the content of NaOH in the liquid alkali entering the stirring tank.

5. A benzyl alcohol distillation method for reducing the generation of high boiling substances as claimed in claim 1, characterized in that: The hydrolysis reaction of step S1 is as follows: benzyl chloride and alkaline solution are added into a hydrolysis reactor at a feed mass flow ratio of 1:(4-4.5), stirred at 80-150° C. and 0.1-0.6 MPa, and a hydrolysis reaction occurs, and the residence time of the hydrolysis reaction is 6-10 hours; The alkaline solution is a Na2CO3 aqueous solution with a mass fraction of 10%-15%.

6. A benzyl alcohol distillation device for reducing the generation of high boiling substances, characterized in that: It comprises a liquid alkali tank (1), a stirring kettle (2), a No. 1 oil-water phase separator (3) and a distillation tower (4); The liquid alkali tank (1), the stirring kettle (2), the oil phase outlet of the 1# oil-water phase separator (3) and the distillation tower (4) are connected in sequence through pipelines; The side of the stirring tank (2) is provided with an oil phase material feed port (21), a recovered water inlet (22) and a pH meter (23), and the bottom of the distillation tower (4) is provided with a discharge port (41); A metering pump (24) is provided on the pipeline connecting the liquid alkali tank (1) and the stirring kettle (2).

7. A benzyl alcohol distillation device for reducing the generation of high boiling substances as claimed in claim 6, characterized in that: It also includes a distillation raw material tank (5) and a liquid ammonia tank (6), wherein the distillation raw material tank (5) is arranged between the first oil-water phase separator (3) and the distillation tower (4), and is connected to the first oil-water phase separator (3) and the distillation tower (4); The liquid ammonia tank (6) is connected to the distillation raw material tank (5) through a first branch pipeline, the liquid ammonia tank (6) is connected to the top of the distillation tower (4) through a second branch pipeline, and the liquid ammonia tank (6) is connected to the bottom of the distillation tower (4) through a third branch pipeline.

8. A benzyl alcohol distillation device for reducing the generation of high boiling substances as claimed in claim 7, characterized in that: A centrifugal pump (7) is provided on the pipeline connecting the distillation raw material tank (5) and the distillation tower (4).

9. A benzyl alcohol distillation device for reducing the generation of high boiling substances as claimed in claim 7, characterized in that: The first branch pipeline, the second branch pipeline and the third branch pipeline are all provided with automatic regulating valves (8).

10. A benzyl alcohol distillation device for reducing the generation of high boiling substances as claimed in claim 7, characterized in that: The invention also comprises a hydrolysis reactor (9), a second oil-water phase separator (10), an evaporator (11), and a condenser (12); the hydrolysis reactor (9), the liquid phase outlet of the second oil-water phase separator (10), the evaporator (11), and the condenser (12) are connected in sequence through pipelines; the oil phase outlet of the second oil-water phase separator (10) is connected to the oil phase material feed port (21); and the outlet of the condenser (12) is connected to the recovered water liquid inlet (22).

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