Clean production process and equipment for plasticizer

Abstract

The invention discloses a clean production process and equipment of a plasticizer. The invention provides a production method for a dealcoholization section in a non-acidic catalytic synthesis and refining process of a lipid plasticizer (such as phthalic acid, terephthalic acid, (iso) butyl ester of adipic acid and (iso) amyl ester of adipic acid). According to the present invention, the dealcoholization section of the synthesis process and the refining process is completed by using the novel under-pressure non-acidic catalysis (such as titanate, organic tin and the like) esterification process, and the heat of the material is adopted to perform rectification so as to effectively utilize the heat energy of the material, such that the moisture in the circulating alcohol does not cause the inactivation of the catalyst; the method has the following advantages: 1, the wastewater amount is small, the COD is low, no salt is contained, and the pollution is greatly reduced; 2, side reactions are few, and material consumption is reduced; 3, the catalyst does not corrode equipment, the material requirement of the equipment is low, and the construction investment is saved; and 4, the new process is energy-saving, and the energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to a preparation process and a device in the field of esters such as plasticizers, and in particular to a production process and equipment for butyl and amyl plasticizers. Background Art

[0002] The (iso)butyl and (iso)amyl esters of phthalic acid, terephthalic acid and adipic acid are commonly used plasticizers and can be used as plasticizers for polyvinyl chloride, polyvinyl acetate, alkyd resin, nitrocellulose, ethyl cellulose, chloroprene rubber and nitrile rubber. (Iso)butyl and (iso)amyl esters [hereinafter referred to as butyl (amyl) esters] are widely used plasticizers.

[0003] The current production method of butyl (pentyl) ester is sulfuric acid catalysis process. Sulfuric acid has the advantages of low reaction temperature and low price, but at the same time, sulfuric acid catalyst causes many side effects. (1) Sulfuric acid corrosion is serious, resulting in higher requirements for equipment materials. Some existing production enterprises use enamel equipment, but enamel cannot withstand sudden cooling and heating. Intermittent esterification is subject to repeated changes in temperature, which will cause the enamel to fall off over a long period of time, and corrosion and perforation often occur. Some enterprises use 316L, but the equipment is still severely corroded, resulting in a high failure rate and short equipment life. (2) The COD of the wastewater is too high and the salt content is too high to be directly treated biochemically. The wastewater must be concentrated first and the distilled wastewater can be treated biochemically, which results in high energy consumption for wastewater treatment. At the same time, the concentration produces waste residue and serious pollution. Sulfuric acid and (iso)butyl (amyl) alcohol react to produce mono (iso)butyl (amyl) sulfate, which is acidic and must be neutralized with an alkali solution of 15-20% of the output and washed with clean water of 15-20% of the output to partially remove it. Mono (iso)butyl (amyl) sulfate is neutralized to form sodium salt of mono (iso)butyl (amyl) sulfate, which is soluble in water. In addition, the dibasic acid mono (iso)butyl (amyl) ester generated by the unreacted raw acid is neutralized to form sodium salt, resulting in a high COD of the neutralization water washing wastewater, reaching 30000-50000 mg / L. Using alkali to neutralize the material results in the salinity in the wastewater reaching 40000-50000 mg / L. The amount of wastewater generated in the two steps of neutralization and washing is equivalent to 30-40% of the output. (3) Many side reactions, high consumption, and poor product quality Sulfuric acid, as a catalyst, promotes the esterification reaction while also causing the dehydration of (iso)butyl and (iso)amyl alcohol molecules to form (iso)butyl and (iso)amyl ethers; Sulfuric acid also causes the oxidation and dehydration of (iso)butyl and (iso)amyl alcohols to form (iso)butyl (pentyl)aldehyde, (iso)butyl (pentyl)ene, etc. All of these will lead to increased consumption. Sulfuric acid will react with alcohol in the esterification system to form sulfuric acid monoesters. The use of alkaline water (NaOH or NaCO in the refining process) of sulfuric acid monoesters is a process that uses alkali water (NaOH or NaCO 3) will generate sulfuric acid monoester sodium salt when neutralized. Sulfic acid monoester sodium salt has a certain solubility in ester and water, so it cannot be completely removed by neutralization and water washing process, resulting in the extremely difficult purity of dibutyl phthalate to reach the 99.5% required for superior products in GB / T 11405-2006. Existing large-scale butyl and amyl ester plasticizer manufacturers have built alcohol recovery, deetherification and distillation facilities. Although these measures cannot reduce side reactions, they can alleviate the impact of sulfuric acid-catalyzed side reaction products on production. (4) Unable to achieve continuous esterification production process The continuous esterification process has the advantages of low energy consumption, low equipment investment, high degree of automation and stable production. Therefore, large-scale production should adopt the continuous process as much as possible if the process allows. Due to the existence of back-mixing, the average residence time of materials in the continuous esterification process is about twice that of the intermittent process. Due to the strong oxidizing property of sulfuric acid, the reaction time needs to be shortened as much as possible. If the sulfuric acid catalysis method and continuous process are used, the residence time will be long due to the back-mixing phenomenon, and the side reactions will increase significantly, resulting in a darker product color and increased consumption, which will lose its industrial value. The sulfuric acid catalytic continuous esterification process has been tested on industrial equipment, and the product color is dark and there are too many side reactions, which has no industrial value. Therefore, the sulfuric acid process adopts an intermittent esterification process, which cannot meet the needs of large-scale industry.

[0004] The production of butyl and pentyl esters is huge, among which dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP) have the largest production. It is urgent to develop new processes to solve the wastewater pollution caused by sulfuric acid catalysis and related problems.

[0005] Some literature reports the use of solid superacids, powdered Al 2 O 3 The last one is because of the long reaction time (solid superacid, powdered Al 2 O 3 Butyl ester and pentyl ester plasticizer are incompatible and are heterogeneous catalysis, so the reaction speed is slow), the conversion rate is low (the industrial conversion rate cannot reach more than 99.5%), and the cost is high (the catalyst costs hundreds of thousands of yuan per ton, and the amount added is large). They have no industrial value and none of them can be industrialized. Therefore, the industrial production of butyl ester and pentyl ester plasticizers now uses sulfuric acid as a catalyst.

[0006] The process adopted by the present invention is a high-temperature non-acidic catalytic process with pressure. In a specially designed reaction system, the boiling point of (iso)butyl (pentanol) is increased by increasing the pressure of the reaction system, so that it reaches the initial activity temperature (160-165° C.) of a commonly used non-acidic catalyst (non-acidic catalysts such as titanate, organic tin, etc.), so that the non-acidic catalyst can be used, and the purpose of increasing the reaction speed (esterification reaction time is 4-5 hours, which is equivalent to the efficiency of sulfuric acid catalyst), increasing the product yield (phthalic anhydride conversion rate reaches more than 99.5%), reducing side reactions, and greatly reducing wastewater pollution (the refining process can adopt a process without neutralization and washing wastewater generation, which reduces wastewater by 75%, COD by 95%, and does not contain salt in the wastewater) is eradicated, and the shortcomings of large sewage volume, high COD, high salt content, many side reactions, and serious equipment corrosion caused by sulfuric acid catalyst are eliminated. This process can realize the full continuous production of esterification and refining, can realize highly automated control, reduce energy consumption and material consumption, improve product quality, and compared with the sulfuric acid method, the equipment material is lower (the material of the main equipment of the sulfuric acid method is at least 316L stainless steel, and the material of the main equipment of the non-acid method is 304 stainless steel), which can save 30% of the equipment investment and has significant industrial application value. The industrial device using the technology of the present invention has been built. Summary of the invention

[0007] The invention uses acid or anhydride (such as phthalic anhydride, terephthalic acid, adipic acid, hereinafter referred to as acids) and alcohol (such as butanol or amyl alcohol (including butanol or amyl alcohol isomers), butanol or amyl alcohol isomers and mixtures and mixtures with other alcohols, hereinafter referred to as alcohols) as raw materials, uses non-acidic catalysts (such as non-acidic catalysts such as titanates and organic tins), adopts a new pressure reaction process, completes the synthesis process, and then undergoes refining (the neutralization process in the refining can adopt a traditional neutralization and water washing refining process, and can also adopt a refining process without neutralization and water washing wastewater discharge) to obtain a finished product.

[0008] The present invention provides a synthesis process in a production method of the above-mentioned substance and a dealcoholization section in a refining process. The esterification process uses a non-acidic catalyst, and the acid and alcohol react under pressure to complete the synthesis of the substance. The esterification tower with an innovative structure can effectively separate the water dissolved in the circulating alcohol, ensuring that the circulating alcohol returned to the esterification kettle will not cause catalyst deactivation due to high water content; the dealcoholization section adopts a process of reflux of water-containing condensed alcohol and extraction after distillation, so that the water content of the extracted alcohol is less than 1%, and it can be directly returned to the esterification system for direct use without additional distillation and dehydration.

[0009] The esterification tower of the present invention adopts a structure in which the upper part is a packed tower and the lower part is a heat exchanger in the form of a falling film evaporator (see attached Figure 4), using the characteristic that the temperature of the vapor phase evaporated from the esterification kettle is 20-30°C higher than the boiling point of the alcohol under the same pressure (the ester in the esterification kettle accounts for 70-80%, and the alcohol accounts for 20-30%, which will cause the boiling temperature to be 20-30°C higher than the boiling point of the alcohol under the same pressure), the heat energy of the vapor phase material is used to heat the refluxed alcohol in the falling film evaporator to further remove the moisture in the refluxed alcohol. Only heat exchange is performed without material exchange, which can increase the temperature of the refluxed alcohol to reduce the moisture in the refluxed alcohol, ensure that the catalyst will not be deactivated due to the high moisture content in the refluxed alcohol, ensure the normal progress of the reaction, and at the same time increase the speed of discharging the reaction generated water from the esterification kettle, thereby increasing the reaction speed.

[0010] The heat exchanger in the form of a falling film evaporator at the bottom of the esterification tower can be heated by the alcohol vapor evaporated from the esterification kettle, or by another heat source. Preferably, the alcohol vapor evaporated from the esterification kettle is used for heating, which can fully utilize the thermal energy of the evaporated alcohol and is beneficial to energy saving. At the same time, because the amount of evaporated alcohol and the amount of refluxed alcohol increase and decrease at the same time, the amounts are basically equal, which is easy to control.

[0011] Preferably, the esterification process is carried out under a positive pressure of 0.2-0.5Mpa, and activated carbon may be added;

[0012] Preferably, the reaction is carried out at a temperature of 160-230°C;

[0013] The catalyst used in this reaction is a non-acidic catalyst (such as non-acidic catalysts such as titanates and organotin), preferably a titanate catalyst. Titanates have high catalytic efficiency (homogeneous reaction) and low price (10,000-40,000 yuan / ton), and have industrial application value;

[0014] The present invention adopts the method of controlling the cooling amount to adjust the relationship between the heating amount and the cooling amount so as to adjust the temperature and pressure in the kettle. If the temperature needs to be increased, the cooling amount can be reduced and the heating amount can be increased; during normal reaction, the heating amount is basically fixed, and the temperature and pressure in the kettle are controlled by controlling the cooling amount.

[0015] There are three ways to control the cooling amount in the present invention, one is to control the amount of gas from the top of the tower entering the condenser, one is to control the amount of alcohol in the alcohol-water separation tank that refluxes into the esterification tower, and one is to control the amount of cooling water in the condenser (control the outlet water temperature). In the pilot device of the present invention, the method of controlling the amount of cooling water inlet is adopted; the industrial device constructed by the present invention adopts the method of controlling the amount of refluxed alcohol. Controlling the amount of alcohol in the alcohol-water separation tank that refluxes into the esterification tower is actually to allow part of the volume of the condenser to hold liquid, and to adjust the area where the condenser actually works, thereby achieving the purpose of adjusting the condensation amount. This method requires a smaller regulating valve caliber, less equipment investment, and industrial production equipment proves that the control is convenient and efficient.

[0016] The dealcoholization tower (attached) used in the dealcoholization section of the refining process of the present invention Figure 7 ) is a new structure. The dealcoholization tower adopts a structure in which the upper part is a packed tower, the middle part is a falling film evaporator heat exchanger, and the bottom can be equipped with a heater. The dealcoholization section adopts a structure in which the water-containing condensed alcohol is fed back from the upper part of the tower and extracted after distillation by the falling film evaporator, so that the water content of the extracted alcohol is about 1%, and it can be directly returned to the esterification system for use without additional distillation and dehydration. The heater at the bottom is an ester phase heater, which can be selected according to the process.

[0017] The heat exchanger in the form of a falling film evaporator in the middle of the dealcoholization tower can be heated by the alcohol vapor evaporated from the dealcoholization material, or by another heat source. Preferably, it is heated by the alcohol vapor evaporated from the dealcoholization material. This can fully utilize the thermal energy of the evaporated alcohol and reduce the load of the top condenser, which is beneficial to energy saving. At the same time, because the amount of evaporated alcohol and the amount of refluxed alcohol increase and decrease at the same time, the amounts are basically equal, which is easy to control.

[0018] The production method can be carried out by batch process (see attached Figure 5 ), it is more suitable to be produced by continuous esterification process.

[0019] In the device where both esterification and refining are continuous processes (see Appendix Figure 6 ), an esterification decompression tank is added to the esterification system and the dealcoholization system. The pressure of the decompression tank is lower than that of the esterification system. In the decompression tank, when the pressure is reduced, part of the circulating alcohol and most of the water are removed, and at this time the system temperature is within the active temperature range of the catalyst, the esterification reaction can be carried out more thoroughly, and the acid value can be further reduced without increasing energy consumption.

[0020] The method and device of the present invention have the following advantages: less wastewater, low COD, no salt, and greatly reduced pollution; fewer side reactions and reduced material consumption; the catalyst does not corrode the equipment, the equipment material requirements are low, and construction investment is saved; the new process is energy-saving and energy consumption is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Attached Figure 1 : Vapor-liquid equilibrium diagram of n-butanol and water;

[0022] Attached Figure 2 : Titanate hydrolysis data provided by BASF;

[0023] Attached Figure 3 : Conventional esterification tower structure; In the figure: 3-1 is the inlet of the vapor phase evaporated from the esterification kettle into the esterification tower 3-2 is the inlet of reflux alcohol into the esterification tower 3-3 is the vapor phase outlet at the top of the tower 3-4 is the alcohol reflux into the esterification kettle outlet 3-5 is the distributor 3-6 is the packing layer

[0024] Attached Figure 4 : Esterification tower structure of the present invention In the figure: 4-1 is the inlet of the vapor phase evaporated from the esterification kettle into the esterification tower 4-2 is the inlet of reflux alcohol into the esterification tower 4-3 is the vapor phase outlet at the top of the tower 4-4 is the alcohol reflux into the esterification kettle outlet 4-5 is the distributor 4-6 is the packing layer 4-7 is a falling film evaporator

[0025] Attached Figure 5 : Intermittent process of the present invention In the figure: 5-1 is the esterification kettle 5-11 is the esterification kettle feeding facility 5-2 is the esterification tower 5-21 Falling film evaporator for esterification tower 5-3 is the condenser 5-4 is the alcohol-water phase tank 5-5 is the circulating alcohol dripping tank 5-6 is the circulating alcohol receiving tank 5-7 is a safety valve

[0026] Attached Figure 6 : Continuous process of the present invention In the figure: R1-R8 are esterification kettles 6-1 is the esterification tower 6-2 is the esterification alcohol water phase tank 6-3 is the esterification buffer tank 6-4 is the esterification pressure reducing tank 6-5 is the dealcoholization tower 6-6 is the alcohol-water phase separation tank for dealcoholization 6-7 is the circulating alcohol buffer tank 6-8 is a safety valve

[0027] Attached Figure 7 :Dealcoholization tower structure of the present invention In the figure: 7-1 is the material inlet of the dealcoholization tower 7-2 is the inlet of reflux alcohol into the dealcoholization tower 7-3 is the vapor phase outlet of the dealcoholization tower 7-4 is the ester outlet 7-5 is the circulating alcohol outlet 7-6 is the distributor 7-7 is the packing layer 7-8 is a falling film evaporator 7-9 for ester heater

[0028] Attached Figure 5-7 Middle: TI is the temperature display PI is pressure display FI is flow rate display LI is the liquid level or interface display TV is a temperature regulating valve FV is the flow control valve PV is a pressure regulating valve LV is the interface control valve W is the heat exchanger PU is material pump PP is a vacuum unit HS for steam HC is steam condensate AL is fresh raw alcohol PA is phthalic anhydride CAT as a catalyst DETAILED DESCRIPTION

[0029] The process of the present invention is applicable to conventional esterification reactions, and is particularly applicable to the preparation of synthetic plasticizers such as dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate (DIPP), dibutyl terephthalate (DBTP), diisobutyl terephthalate (DIBTP), dipentyl terephthalate (DPTP), diisopentyl terephthalate (DIPTP), dibutyl adipate (DBA), diisobutyl adipate (DIBA), dipentyl adipate (DPA), diisopentyl adipate (DIPA) using butanol (including isomers) and amyl alcohol (including isomers) as raw materials.

[0030] It is particularly suitable for the preparation of esters having the following structure and their compositions: C 4 H 9 It is various isomers of butyl and their mixtures, C 5 H 11 Various isomers of pentyl and mixtures thereof, C 5 H 9 It is cyclopentyl.

[0031] The present invention provides a synthesis process in the production method of the above-mentioned substance and a dealcoholization section in the refining process. The esterification process uses a non-acidic catalyst, and the acid and alcohol react under pressure to complete the synthesis of the substance. The esterification tower with a new structure is used to fully separate the water dissolved in the circulating alcohol, ensuring that the circulating alcohol will not cause catalyst deactivation due to high water content; the dealcoholization section adopts a process of reflux of water-containing condensed alcohol and extraction after distillation, so that the water content of the extracted alcohol is less than 1%.

[0032] Preferably, the esterification process is carried out under a positive pressure of 0.2-0.5Mpa, and activated carbon may be added;

[0033] Preferably, the reaction is carried out at a temperature of 160-230°C;

[0034] The catalyst used in this reaction is a non-acidic catalyst (such as non-acidic catalysts such as titanates and organotin), preferably a titanate catalyst. Titanates have high catalytic efficiency (homogeneous reaction) and low price (10,000-40,000 yuan / ton), and have industrial application value;

[0035] The production method can adopt an intermittent process, and is more suitable for production using a continuous esterification process.

[0036] Both butanol and pentanol are substances that have a certain mutual solubility with water. Taking n-butanol as an example, when the temperature of the condensed material is 45°C in industrial production, the solubility of water in n-butanol is 22% (mass ratio), and the solubility of n-butanol in water is 8% (mass ratio).

[0037] In the production of di-n-butyl phthalate (DBP) using sulfuric acid as a catalyst, the water generated in the reaction system is taken out of the esterification reactor by circulating alcohol. The actual operating data in production shows that the amount of circulating alcohol is about 10 times the amount of water generated by the chemical reaction on average. In the middle of the reaction, when water is generated fastest, the water content in the circulating alcohol can reach about three times the average value, that is, the water content in the circulating alcohol reaches about 30%.

[0038] Take the vapor-liquid equilibrium diagram of n-butanol and water at normal pressure (see attached Figure 1) is used as a basis to obtain the composition data of the material. When the water content of n-butanol in the vapor phase is 20% by weight, the molar ratio of water in the vapor phase is 0.5, the efficiency of the esterification tower is optimal, and the complete phase equilibrium of the vapor and liquid phase can be achieved (if the tower efficiency decreases, the water content in the liquid phase alcohol will be higher). At this time, the corresponding n-butanol water content in the liquid phase is 17% (molar ratio), and the converted weight ratio is 4.7%, that is, the weight of water in the reflux alcohol refluxed back to the esterification kettle will reach 4.7%; when the water content of n-butanol in the vapor phase is 25% by weight, the molar ratio of water in the vapor phase is 0.58, the efficiency of the esterification tower is optimal, and the complete phase equilibrium of the vapor and liquid phase can be achieved. Complete phase equilibrium of the vapor-liquid phase is reached. At this time, the corresponding water content of n-butanol in the liquid phase is 21% (molar ratio), which is converted to 6.0% by weight, that is, the weight of water in the reflux alcohol flowing back to the esterification kettle will reach 6%; when the water content of butanol in the vapor phase is 30% by weight, the molar ratio of water in the vapor phase is 0.64, and the efficiency of the esterification tower is optimal, and complete phase equilibrium of the vapor-liquid phase can be achieved. At this time, the corresponding water content of n-butanol in the liquid phase is 27% (molar ratio), which is converted to 8.3% by weight, that is, the weight of water in the reflux alcohol flowing back to the esterification kettle will reach 8%.

[0039] Titanate has a certain tolerance to water. If the tolerance exceeds this limit, the titanate will hydrolyze. See attached Figure 2 : Titanate data provided by BASF.

[0040] Using a conventional esterification tower (see attached Figure 3 ), taking the production of dibutyl phthalate (DBP) as an example, the evaporated n-butanol contains up to 20-30% water by weight, the refluxed liquid n-butanol contains about 20% water by weight, the liquid phase and the vapor phase exchange energy and matter, the water therein roughly reaches phase equilibrium, and the water weight ratio of the discharged liquid n-butanol is between 4.7% and 8%.

[0041] Without considering the catalyst activity temperature, at normal pressure, conventional towers have poor separation capabilities for water in liquid n-butanol, resulting in a reflux alcohol water content between 4.7% and 8%, which can lead to hydrolysis and deactivation of the titanate catalyst.

[0042] In a conventional pressurized system, the solubility of water in alcohol increases with increasing pressure. Therefore, previous experiments using conventional esterification towers, pressurizing to increase the temperature of the reaction system, and using non-acidic catalysts all failed due to catalyst deactivation.

[0043] For example, in the patent publication number: CN100999590 B, the invention name is: Dialkyl terephthalate and its use, item

[0085] , it is indicated that the amount of liquid removed is partially or completely supplemented by fresh alcohol. For the water-containing alcohol evaporated from the esterification system, the amount of liquid refluxed to the reaction system can be partially or completely composed of alcohol obtained by post-treatment of azeotropic distillation. It is also possible to carry out post-treatment at a later time.

[0044] This invention cannot solve the problem of catalyst deactivation caused by water in the refluxed alcohol. Instead, the alcohol in the alcohol-water separation tank is partially refluxed or completely extracted, and the evaporated alcohol causes the alcohol amount in the reactor to decrease, which is supplemented by another dehydrated alcohol or fresh alcohol. This leads to three problems: 1. The esterification system is difficult to control. The amount of water generated during the reaction varies greatly, and the amount of alcohol removed from the system varies greatly. The corresponding amount of alcohol to be supplemented varies greatly, and this is to remove and supplement alcohol when the pressure and temperature in the kettle are changing. The amount of removed and supplemented alcohol has a significant impact on the temperature and pressure of the reaction, resulting in extremely complex industrial production control, difficult to control, and production cannot be kept stable, which is difficult to achieve in industrial equipment; 2. A refining system for removing the water-containing alcohol in the esterification system must be equipped, and the investment is greatly increased; 3. The heat of the evaporated alcohol in the esterification system cannot be used, and the cooling capacity must be increased; in addition, the removed alcohol must be distilled separately, and the energy consumption increases significantly. The above three factors have caused this method to lose its industrial significance.

[0045] These patents all rely on common sense to increase the boiling temperature of the material by pressurizing it to reach the active temperature of the titanate catalyst, but they cannot solve the problem of catalyst deactivation caused by water in the reflux alcohol and have no theoretical or application value. None of them has been industrialized.

[0046] The esterification tower of the present invention adopts a structure with a falling film evaporator heat exchanger at the bottom (see attached Figure 4 ), using the characteristic that the vapor phase temperature is 20-30°C higher than the boiling point of alcohol (ester accounts for 70-80% and alcohol accounts for 20-30% in the esterification kettle, which will cause the boiling temperature to be 20-30°C higher than the boiling point of alcohol under the same pressure), the heat energy of the vapor phase material is used to heat the refluxed alcohol, only heat exchange is carried out, and no material exchange is carried out (the higher water content in the vapor phase does not affect the water content in the liquid phase), and the water in the refluxed alcohol is further removed, which can increase the temperature of the refluxed alcohol to reduce the water content in the refluxed alcohol, ensure that the catalyst will not be deactivated due to the high water content in the refluxed alcohol, ensure the normal progress of the reaction, and at the same time increase the speed of discharging the reaction generated water out of the esterification kettle, thereby increasing the reaction speed.

[0047] Taking the vapor-liquid equilibrium data of n-butanol and water at normal pressure (see the table below) as an example, when the azeotropic temperature increases by 10°C from 101°C to 111°C, the water content in the liquid alcohol decreases from 4.8% to 1.2%. n-Butanol-Water Vapor-Liquid Equilibrium Data temperature Liquid alcohol mol composition Liquid alcohol weight composition Vapor phase alcohol mol composition Vapor phase alcohol weight composition 117.6 1 100 1 100 111.4 0.951 98.8 0.755 92.7 106.7 0.9 97.4 0.603 86.2 102 0.839 95.5 0.48 79.1 101 0.827 95.2 0.466 78.2 98.5 0.768 93.2 0.395 72.9 96.7 0.712 91.0 0.346 68.5 95.2 0.642 88.1 0.307 64.6 93.6 0.513 81.2 0.261 59.2 93.1 0.449 77 0.249 57.7 93 0.42 74.9 0.248 57.6 92.9 0.372 70.1 0.242 56.8 92.9 0.073 24.5 0.242 56.8 93.2 0.014 5.5 0.24 56.5 95.2 0.007 2.8 0.168 45.4 96.8 0.004 1.6 0.117 35.3 100 0 0 0 0

[0048] It is measured that when the esterification tower of the present invention is used to produce dibutyl phthalate (DBP), during the reaction process, at a pressure of 0.4 MPa, the water content of n-butanol at the bottom of the tower is about 1%. This data is within the water content range allowed by titanate, does not cause deactivation of titanate, and the reaction can proceed normally.

[0049] The bottom of the esterification tower of the present invention is provided with a heat exchanger in the form of a falling film evaporator structure. The falling film evaporator can have a higher heat transfer efficiency under the condition of a lower temperature difference, can fully utilize the heat under the condition of a lower temperature difference, and at the same time, it is not affected by the static pressure of the liquid, will not cause the boiling point of the substance to increase, and is conducive to the evaporation of volatile substances, that is, it is conducive to the removal of water in this process.

[0050] The heat exchanger at the bottom of the esterification tower can be heated by the heat of the vapor phase material itself, because the amount of evaporated alcohol vapor and the weight of refluxed alcohol are basically the same and change in the same trend, which makes it easy to control and saves heat energy at the same time; the heat exchanger can also be heated by other heat sources such as steam or heat transfer oil.

[0051] The present invention adopts the method of controlling the cooling amount to adjust the relationship between the heating amount and the cooling amount so as to adjust the temperature and pressure in the kettle. If the temperature needs to be increased, the cooling amount can be reduced and the heating amount can be increased; during normal reaction, the heating amount is basically fixed, and the temperature and pressure in the kettle are controlled by controlling the cooling amount.

[0052] There are three ways to control the cooling amount in the present invention, one is to control the amount of gas from the top of the tower entering the condenser, one is to control the amount of alcohol in the alcohol-water separation tank that refluxes into the esterification tower, and one is to control the amount of cooling water in the condenser (control the outlet water temperature). In the pilot device of the present invention, the method of controlling the amount of cooling water inlet is adopted; the industrial device constructed by the present invention adopts the method of controlling the amount of alcohol in the alcohol-water separation tank that refluxes into the esterification tower. Controlling the amount of alcohol in the alcohol-water separation tank that refluxes into the esterification tower is actually to allow part of the volume of the condenser to hold liquid, and to adjust the area where the condenser actually works, thereby achieving the purpose of adjusting the condensation amount. This method requires a smaller regulating valve caliber, less equipment investment, and production practice proves that it is easy to control.

[0053] The esterification system of the present invention is pressurized in an intermittent device (see attached process flow sheet for intermittent process flow sheet). Figure 5), at the end of esterification, there is a process of reducing the system pressure to normal pressure. During this process, most of the alcohol in the material will evaporate, and the water will evaporate more thoroughly, so the acid value of the material will be further reduced.

[0054] In the intermittent device, the system pressure is reduced by extracting the circulating alcohol from the bottom of the esterification tower and then gradually opening the vent control valve to reduce the pressure to normal pressure. The water content of the circulating alcohol extracted from the bottom of the esterification tower during the decompression process is about 1%, while the water content of the circulating alcohol directly extracted from the condenser is about 5%.

[0055] In a continuous device (see the attached continuous process flow sheet) Figure 6 ), add an esterification decompression tank in the esterification system and the dealcoholization system. The pressure of the decompression tank is lower than that of the esterification system. In the decompression tank, when the pressure is reduced, part of the circulating alcohol and most of the water in the material are removed, and the temperature of the liquid material is reduced by 10-30°C. At this time, the system temperature is within the active temperature range of the catalyst, and the esterification reaction can be carried out more thoroughly, and the acid value can be further reduced without increasing energy consumption.

[0056] In the dealcoholization section of the continuous refining process, if the alcohol is directly extracted from the condenser, the alcohol will contain about 5% of water, and directly entering the esterification system will deactivate the catalyst. The present invention adopts a dealcoholization tower with an innovative structure. The dealcoholization tower is an alcohol phase heater in the form of a falling film evaporator structure with a packing layer at the top and an ester phase heater at the bottom. The process adopts the method of condensing alcohol water vapor at the top of the tower, stratifying in the phase separation tank, refluxing the alcohol phase into the tower, distilling the circulating alcohol in the falling film evaporator by relying on the heat of alcohol removal, and then extracting the circulating alcohol from the bottom of the falling film evaporator (the structure of the dealcoholization tower of the present invention is shown in the attached figure). Figure 7 ), which can ensure that the water content in the circulating alcohol is about 1%, and can directly enter the esterification system to achieve the purpose of energy saving. At the same time, the ester content in the alcohol removed by using this structure tower is significantly lower than that of the traditional dealcoholization tower without reflux, which can improve the production efficiency of the device.

[0057] The heat exchanger in the form of a falling film evaporator in the middle of the dealcoholization tower can be heated by the alcohol vapor evaporated from the dealcoholization material, or by another heat source. Preferably, it is heated by the alcohol vapor evaporated from the dealcoholization material. This can fully utilize the thermal energy of the evaporated alcohol and reduce the load of the top condenser, which is beneficial to energy saving. At the same time, because the amount of evaporated alcohol and the amount of refluxed alcohol change in the same direction, the amount is basically equal, which is easy to control.

[0058] The principle of the present invention is also applicable to tower reactors. Example

[0059] The esterification reaction system includes esterification kettle, esterification tower, condenser, alcohol-water separation tank and other equipment, and contains esterification heating, reflux alcohol quantity control, venting control and other adjustment facilities. The process and main equipment are attached. Figure 5 .

[0060] The esterification kettle can bear a pressure of 0.5-1.0Mpa.

[0061] The structure of the esterification tower is a heat exchanger with a falling film evaporator (see attached Figure 4 ). In the falling film evaporator, the alcohol vapor only heats the reflux alcohol, and the high water content in the alcohol vapor will not cause the high water content in the reflux alcohol.

[0062] The pressure of the esterification kettle is adjusted by controlling the amount of reflux alcohol (or the amount of alcohol vapor entering the condenser).

[0063] Nitrogen is introduced into the reactor to replace the air therein and reduce the effect of oxygen on the reaction; (iso)butyl (pentanol) is added in an amount of about 3 times the molar amount of the corresponding phthalic anhydride, stirring is started, and then phthalic anhydride is added. Activated carbon can be added to improve the product color number, and the temperature begins to rise;

[0064] When the temperature reaches 120-145℃, the material begins to boil, and alcohol refluxes in the alcohol-water separator. Reflux for about 10 minutes (recycled alcohol is used in the production process, and the recycled alcohol contains water, and the water is removed by reflux). Then add a catalyst (such as non-acidic catalysts such as titanates and organic tin). This device uses n-butyl titanate. The amount of catalyst added is 0.3-1.0‰ of the material amount, then close the vent regulating valve of the esterification system, turn off the nitrogen, close the valve for the reflux alcohol to enter the esterification tower (or the regulating valve for the alcohol vapor to enter the condenser), and continue to heat up. At this time, as the temperature rises, the pressure also begins to rise.

[0065] When the temperature reaches 160-165°C, the active temperature of the catalyst, the reaction begins, and the pressure at this time reaches 0.3-0.5MPa. Slightly open the regulating valve for the reflux alcohol into the esterification tower (or slightly open the regulating valve for the alcohol vapor to enter the condenser) to ensure that the temperature continues to rise with a small reflux. As the temperature rises and the reaction proceeds, the alcohol content in the material system gradually decreases. As the system pressure gradually decreases, gradually open the regulating valve for the reflux alcohol into the esterification tower (or open the regulating valve for the alcohol vapor to enter the condenser) to increase the amount of reflux alcohol and speed up the reaction. (If there is a circulating alcohol dropping tank, such as the attached Figure 4 In the circulating alcohol dropping tank, the regulating valve can be opened to slowly add the circulating alcohol into the esterification kettle. In the continuous device, each esterification kettle is supplemented with alcohol to achieve the final reaction temperature of 180-230℃ and the pressure of 0.10-0.50MPa. When the acid value of the sample is lower than 0.8mgKOH / g material, the esterification is completed.

[0066] Open the valve for the reflux alcohol at the bottom of the esterification tower to enter the circulating alcohol buffer tank, so that the reflux alcohol enters the circulating alcohol buffer tank. When the reflux alcohol flow rate is small, open the vent control valve to slowly reduce the pressure in the kettle. At this time, the alcohol continues to evaporate, then condenses and refluxes into the circulating alcohol buffer tank. Until the pressure of the esterification kettle is normal pressure. At this time, along with the evaporation of n-butanol and water, the acid value of the material can reach ≤0.5mgKOH / g material. This process is achieved in the continuous device by relying on the esterification pressure reducing tank.

[0067] The material in the esterification kettle is transferred to the refining kettle to start the refining process. The refining process can adopt the traditional neutralization and water washing process, or the refining process without neutralization and water washing wastewater discharge. Then, the product is obtained by steam stripping and filtering according to the conventional process.

[0068] Drain the water in the alcohol-water separation tank of the esterification system, pump the alcohol in the alcohol-water separation tank of the refining system into the alcohol-water separation tank of the esterification system; pump the alcohol in the circulating alcohol buffer tank into the circulating alcohol dripping tank (or into the esterification kettle). Start the production preparation for the next kettle.

[0069] The products produced by non-acidic catalysis and water-free washing process have higher quality than those produced by existing water-washing process under the condition of the same raw material quality. When using high-quality raw materials, the product quality can reach high-quality.

[0070] The product testing index (GB / T11405-2006) of the device constructed by the process of the present invention when producing dibutyl phthalate (DBP) is: Serial number Test index name Superior products Measured value 1 Chroma (platinum-cobalt) No. ≤ 20 15 2 Purity / % ≥ 99.5 99.7 3 <![CDATA[Density (20 °C) / (g / cm 3 )]]> 1.044-1.048 1.046 4 Acid value (in KOH) mgKOH / g ≤ 0.07 0.04 5 Flash point / ℃ ≥ 160 163 6 Moisture / % ≤ 0.10 0.05

[0071] When the device constructed by the process of the present invention is used to produce dipentyl phthalate (DPP), the product inspection indicators are as follows: Serial number Test index name Measured value 1 Chroma(Platinum-Cobalt) No. 20 2 purity / % 99.6 3 <![CDATA[Density (20 °C) / (g / cm 3 )]]> 1.023 4 Acid value (in KOH) mgKOH / g 0.03 5 Flash point / ℃ 175 6 Moisture / % 0.05

[0072] The present invention has achieved industrial production. When producing DBP, actual operation data proves that the material consumption per ton of product can be reduced by 8 kg (phthalic anhydride and n-butanol) compared with the sulfuric acid method, the energy consumption can be reduced by 0.2 tons of steam, the wastewater discharge can be reduced by 75%, the salt content can be reduced by 99%, and the COD discharge can be reduced by 95%. The main equipment adopts 304 material. Compared with the existing sulfuric acid process using 316L material, the equipment investment is reduced by 30%, the comprehensive processing cost is reduced by 30%, and the economic benefit is remarkable.

[0073] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing an ester plasticizer. The preparation process includes an esterification step of esterifying an acid or anhydride with an alcohol and a dealcoholization step of a refining process. The feature is that the esterification step uses a non-acidic catalyst. The acid or anhydride is any one of phthalic anhydride, terephthalic acid, adipic acid and a combination thereof, and the alcohol is selected from butyl alcohol, amyl alcohol and its isomers or mixtures; the dealcoholization process can achieve a water content of less than 1% in the removed alcohol.

2. The method for producing the substance according to claim 1, wherein the esterification step uses a non-acidic catalyst, which is a titanate or an organotin catalyst.

3. The production method according to claim 1, characterized in that The esterification process is carried out under positive pressure to ensure that the esterification temperature is above the active temperature of the non-acidic catalyst.

4. The production method according to claim 3, characterized in that The pressure and temperature of the esterification system are regulated by adjusting the heating and cooling capacity. There are three ways to adjust the cooling capacity: one is to control the amount of gas from the top of the tower entering the condenser, one is to control the amount of alcohol refluxed from the alcohol-water separation tank into the esterification tower, and one is to control the amount of cooling water entering the condenser.

5. The method for producing a substance according to claim 1, wherein the esterification tower adopts a heater of a packed tower plus a falling film evaporator structure. The heater of the falling film evaporator structure can be heated by the steam of the evaporated material of the esterification, or by an external heat source.

6. The production method according to any one of claims 3 to 5, wherein: The water content of the alcohol refluxed from the bottom of the esterification tower to the esterification kettle is lower than the amount causing the deactivation of the non-acidic catalyst.

7. The method for producing the substance according to claim 1, wherein an esterification decompression tank is provided between the esterification step and the refining dealcoholization step in the continuous process.

8. The method for producing the substance of claim 1, wherein in the dealcoholization section of the refining process, the dealcoholization tower used is a packed tower with a heater of a falling film evaporator structure. The evaporated alcohol and water enter the condenser from the top of the tower for condensation, and after alcohol-water separation, the alcohol phase flows back into the dealcoholization tower, first passes through the packed layer, and then passes through the falling film evaporator before being discharged. The heater of the falling film evaporator structure in the dealcoholization tower can be heated by the steam of the evaporated material of the dealcoholization, or can be heated by an external heat source.

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