A method and apparatus for producing a methyl acrylate high carbon alcohol ester

Abstract

The application relates to a method and device for producing methyl high carbon alcohol methacrylate, which comprises an esterification reaction, a deacidification treatment, a hot extraction treatment, a decoloration treatment and an acid recovery treatment. The device and method can significantly simplify production operation procedures, reduce material consumption and energy consumption of the device, improve product yield, reduce wastewater discharge in the production process and be easy to be industrialized.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and device for producing methyl methacrylate high carbon alcohol ester. BACKGROUND

[0002] Methyl methacrylate high carbon alcohol ester is an important intermediate for synthesizing crude oil pour point depressant, which is usually generated by esterification reaction of methyl methacrylate and high carbon alcohol (carbon number 12 or more) under the action of a catalyst to form a monomer, and then polymerization reaction of the monomer to form pour point depressant, tackifier and other chemical products. The esterification reaction is a reversible reaction, and the equilibrium conversion rate is usually improved by timely removing the water generated in the reaction; since the high carbon alcohol has a high boiling point (> 250℃), in order to reduce the difficulty of subsequent separation, an excess amount of methyl methacrylate needs to be added in the esterification reaction; at the same time, methyl methacrylate is prone to self-polymerization at high temperature (greater than 80℃), and a certain concentration of polymerization inhibitor (hydroquinone, etc.) is usually added; liquid acid (methyl sulfonic acid, p-toluenesulfonic acid, etc.) is often used in the esterification reaction to accelerate the reaction. Therefore, after the esterification reaction is completed, a series of means (multiple alkali / water washing, extraction, etc.) are usually needed to remove the polymerization inhibitor, catalyst and excess methyl methacrylate in the product, and the process is complex, and the discharge amount of waste alkali, waste water, waste acid and waste solid is large, and the energy consumption is high; at the same time, due to the long time of the esterification reaction and the two-phase separation process of the alkali / water washing process, the operation is intermittent, which is not conducive to engineering scale-up.

[0003] TWI17280 discloses a method for manufacturing (meth) acrylate, which is realized by the steps of reaction, neutralization, water washing, passivation, etc. In the disclosed technology, the removal of water generated in the reaction process is realized by adding a solvent that is insoluble in water but azeotropic with water, a desolventizing step needs to be added in the subsequent process, and the alkali / water washing process is not completely eliminated.

[0004] Therefore, there is still a need for a method and device for producing methyl methacrylate high carbon alcohol ester that can be scaled up, stably and continuously operated, and implemented in industry. SUMMARY

[0005] The technical problem solved by the present application is to provide a device and method for preparing methyl methacrylate, which significantly simplifies the production operation process, reduces the material consumption and energy consumption of the device, improves the product yield, reduces the wastewater discharge in the production process, and is easy to scale up in industry.

[0006] The present application provides a method for producing methyl methacrylate high carbon alcohol ester, comprising:

[0007] The methyl methacrylate raw material and the high carbon alcohol raw material are subjected to esterification reaction in a reaction unit to obtain methyl methacrylate high carbon alcohol ester product;

[0008] subjecting the methyl acrylate high carbon alcohol ester product to a deacidification treatment to obtain a deacidified methyl acrylate high carbon alcohol ester material, and a methyl acrylate-water containing mixture material;

[0009] subjecting the deacidified methyl acrylate high carbon alcohol ester material to a hot extraction treatment with extraction water in a hot extraction unit to obtain a hot extraction treated methyl acrylate high carbon alcohol ester material;

[0010] subjecting the hot extraction treated methyl acrylate high carbon alcohol ester material to a decolorization treatment to obtain a product methyl acrylate high carbon alcohol ester;

[0011] subjecting the methyl acrylate-water containing mixture material to an acid recovery treatment to obtain a recovered material and an acid water containing material;

[0012] returning the recovered material to the reaction unit as part of the methyl acrylate raw material for the esterification reaction.

[0013] In one embodiment, the deacidification treatment comprises:

[0014] subjecting the methyl acrylate high carbon alcohol ester product to a steam treatment to obtain the deacidified methyl acrylate high carbon alcohol ester material.

[0015] In one embodiment, the deacidification treatment comprises:

[0016] subjecting the deacidified methyl acrylate high carbon alcohol ester material to a water treatment to obtain a water extracted methyl acrylate high carbon alcohol ester material, and

[0017] subjecting the water extracted methyl acrylate high carbon alcohol ester material to a steam treatment to obtain the deacidified methyl acrylate high carbon alcohol ester material.

[0018] In one embodiment, the steam treatment is at a temperature of 60-130°C, and the deacidified methyl acrylate high carbon alcohol ester material has a methyl acrylate content of 2-14% based on the total weight of the deacidified methyl acrylate high carbon alcohol ester material.

[0019] In one embodiment, the hot extraction unit has a hot extraction column operating temperature of 50-95°C, a column top pressure of 101-150 kPa, an extraction water temperature of 50-95°C, and a mass flow ratio of extraction water to the deacidified methyl acrylate high carbon alcohol ester material of 0.08-2:1.

[0020] In one embodiment, the mass fraction of methacrylic acid in the heat-extracted methacrylic acid higher alcohol ester material of the overhead of the heat-extraction column is 0.05-1.5%, the mass fraction of the polymerization inhibitor is 0.01-0.2%, and the mass fraction of the liquid acid catalyst is 0.03-1.5%, based on the total weight of the heat-extracted methacrylic acid higher alcohol ester material.

[0021] In one embodiment, the acid recovery process comprises:

[0022] extracting the methacrylic acid-water-containing mixture material with a higher alcohol material in an alcohol extraction column to obtain the recovered material and the acid-containing water material, wherein the feed mass ratio of the higher alcohol material to the methacrylic acid-water-containing mixture material is 0.1-5:1, and the operating pressure is 101-300 kPa; the mass fraction of methacrylic acid in the acid-containing water material is 0.01-0.5%, based on the acid-containing water material.

[0023] In one embodiment, the acid recovery process comprises:

[0024] rectifying the methacrylic acid-water-containing mixture material in an acid refining column, wherein the operating pressure of the acid refining column is 1-80 kPa, the overhead temperature is 25-65°C, the column bottom temperature is 80-130°C, and the overhead operating reflux ratio is 0.1-5; the mass fraction of methacrylic acid in the overhead material of the acid refining column is 0.5-15%, based on the total weight of the overhead material of the acid refining column; the mass fraction of the column bottom material of the acid refining column is 90-99.8%, based on the total weight of the column bottom material of the acid refining column;

[0025] extracting the column bottom material of the acid refining column with a higher alcohol material in an alcohol extraction column to obtain the recovered material and the acid-containing water material, wherein the feed mass ratio of the higher alcohol material to the recycled methacrylic acid of the column bottom material is 0.1-5:1, and the operating pressure is 101-300 kPa; the mass fraction of methacrylic acid in the acid-containing water material is 0.01-0.5%, based on the acid-containing water material.

[0026] In one embodiment, the acid-containing water material is fed into the heat-extraction unit as the extraction water of the heat-extraction unit.

[0027] In one embodiment, the method further comprises performing a washing process before performing the decolorization process, and the washing process comprises:

[0028] The water washing step is to wash the heat-extracted methyl acrylate product with desalted water, wherein the mass flow ratio of the desalted water to the heat-extracted methyl acrylate product is 0.1-1:1, the pH value of the neutral ester product after washing is 6.5-7.5, the operation temperature of the water washing process is 40-60°C, and the operation pressure is 101-300 kPa.

[0029] In an embodiment, the method further comprises a washing step before the decoloring step, wherein the washing step comprises:

[0030] The alkali washing step is to wash the heat-extracted methyl acrylate product with alkali solution, wherein the mass fraction of alkali in the alkali solution is 0.1-10%, the mass flow ratio of the alkali solution to the heat-extracted methyl acrylate product is 0.1-1:1, the pH value of the alkaline ester product is 7.5-11, the operation temperature of the alkali washing process is 40-60°C, and the operation pressure is 101-300 kPa.

[0031] The water washing step is to wash the heat-extracted methyl acrylate product with desalted water, wherein the mass flow ratio of the desalted water to the heat-extracted methyl acrylate product is 0.1-1:1, the pH value of the neutral ester product after washing is 6.5-7.5, the operation temperature of the water washing process is 40-60°C, and the operation pressure is 101-300 kPa.

[0032] The application further provides a device for producing methyl acrylate, comprising:

[0033] A reaction system is configured to perform esterification reaction of methyl acrylate raw material and high carbon alcohol raw material in an esterification reaction unit to obtain methyl acrylate product; the reaction system comprises the esterification reaction unit and a dehydration unit;

[0034] An acid removal unit is configured to perform acid removal treatment on the methyl acrylate product to obtain acid-removed methyl acrylate material and a mixture containing methyl acrylate and water;

[0035] An acid recovery unit is configured to process the mixture containing methyl acrylate and water to obtain a recovery material and an acid-containing water material; wherein the recovery material outlet of the acid recovery unit is connected to the reaction unit inlet of the reaction system, so that the recovery material returns to the reaction unit of the reaction system;

[0036] A heat extraction unit is configured to perform heat extraction on the acid-removed methyl acrylate material with extraction water in the heat extraction unit to obtain heat-extracted methyl acrylate material;

[0037] a decoloring unit for decoloring the hot-extracted high carbon alcohol methacrylate material to obtain a product of high carbon alcohol methacrylate.

[0038] In one embodiment, the deacidification unit comprises:

[0039] a water-stripping column, wherein the outlet of the reaction system is connected to the upper inlet of the water-stripping column so that the high carbon alcohol methacrylate product enters the water-stripping column; the outlet of the water-stripping column is connected to the outlet of the dehydration unit of the reaction system so that at least part of the acid water outlet from the reaction system enters the water-stripping column;

[0040] a steam-stripping column, wherein the upper liquid phase inlet of the steam-stripping column is connected to the outlet of the water-stripping column so that at least part of the water-stripping column outlet enters the steam-stripping column; the bottom of the steam-stripping column is provided with a steam inlet for introducing steam into the steam-stripping column.

[0041] In one embodiment, the acid recovery unit comprises

[0042] an acid refining column, wherein the inlet of the acid refining column is connected to the overhead outlet of the water-stripping column and the overhead outlet of the steam-stripping column so that the overhead materials from the water-stripping column and the steam-stripping column enter the acid refining column; the outlet of the acid refining column is connected to the inlet of the reaction unit of the reaction system so that the column bottom material of the acid refining column returns to the reaction unit of the reaction system;

[0043] an alcohol extraction column, wherein the upper inlet of the alcohol extraction column is connected to the overhead outlet of the acid refining column so that the overhead material of the acid refining column enters the alcohol extraction column; the alcohol extraction column is provided with a bottom high carbon alcohol material inlet for feeding high carbon alcohol material; the overhead outlet of the alcohol extraction column is connected to the inlet of the reaction unit of the reaction system so that the overhead material of the alcohol extraction column returns to the reaction unit of the reaction system.

[0044] In one embodiment, the overhead outlet of the acid refining column is also connected to the top inlet of the water-stripping column and / or the top inlet of the steam-stripping column so that the overhead material of the acid refining column enters the water-stripping column and / or the steam-stripping column.

[0045] In one embodiment, the operating pressure of the acid refining tower is 1-80 kPa, the overhead temperature is 25-65℃, the bottom temperature is 80-130℃, the operating reflux ratio of the overhead is 0.1-5, the mass fraction of methacrylic acid in the overhead material is 0.5-15%, and the mass fraction of methacrylic acid in the bottom material is 90-99.8%.

[0046] The operating pressure of the alcohol extraction tower is 101-300 kPa, the mass ratio of the high carbon alcohol material to the overhead material of the acid refining tower is 0.1-5:1, and the mass fraction of methacrylic acid in the bottom material is 0.01-0.5%.

[0047] In one embodiment, the hot extraction unit comprises a hot extraction tower, the lower inlet of the hot extraction tower is connected to the outlet of the bottom of the steam-stripping tower, so that the bottom material of the steam-stripping tower enters the hot extraction tower; the outlet of the bottom of the hot extraction tower is connected to the reaction unit of the reaction system, so that the bottom material of the hot extraction tower returns to the reaction unit.

[0048] In one embodiment, the upper inlet of the hot extraction tower is also connected to the outlet of the bottom of the alcohol extraction tower, so that the bottom material of the alcohol extraction tower enters the hot extraction tower as extraction water.

[0049] In one embodiment, a washing unit is further included for washing the high carbon alcohol ester of methacrylic acid material treated by hot extraction in the washing unit to obtain a washed ester material.

[0050] The washing unit comprises:

[0051] A water washing unit, the inlet of the water washing unit is connected to the overhead outlet of the hot extraction tower, so that the overhead material of the hot extraction tower enters the water washing unit for water washing.

[0052] In one embodiment, a washing unit is further included for washing the high carbon alcohol ester of methacrylic acid material treated by hot extraction in the washing unit to obtain a washed ester material.

[0053] The washing unit comprises:

[0054] An alkali washing unit, the inlet of the alkali washing unit is connected to the overhead outlet of the hot extraction tower, so that the overhead material of the hot extraction tower enters the alkali washing unit for alkali washing.

[0055] A water washing unit, the inlet of the water washing unit is connected to the outlet of the alkali washing unit, so that the material of the alkali washing unit enters the water washing unit for water washing.

[0056] In an embodiment, the device further comprises a vacuum system, the vacuum system comprising:

[0057] a vacuum pump for generating vacuum in the equipment requiring vacuum in the device;

[0058] a tail gas absorption tower, the vacuum pump being in communication with the tail gas absorption tower for absorbing tail gas from the vacuum pump.

[0059] In an embodiment, the reaction system comprises:

[0060] a dehydration unit for removing water produced in the esterification reaction of methacrylic acid and higher alcohol; the dehydration unit comprising one or more feed ports;

[0061] N-stage esterification reactors for continuously esterifying excess methacrylic acid and higher alcohol, wherein N is an integer and N≥2; the N-stage esterification reactors are connected in series one by one, so that the reaction material of the i-th stage esterification reactor can enter the (i+1)-th stage esterification reactor, i being an integer from 1 to N-1; the N-th stage esterification reactor is provided with a product discharge port for discharging higher alcohol methacrylic acid ester product;

[0062] wherein the top of each of the N-stage esterification reactors is in communication with one feed port of the dehydration unit, so that part of the material of the N-stage esterification reactors enters the dehydration unit for dehydration; one discharge port of the dehydration unit is in communication with one feed port of the first stage esterification reactor, so that the dehydrated material from the dehydration unit enters the first stage esterification reactor;

[0063] each of the M-th stage to N-th stage esterification reactors is provided with an external heater in communication with the respective esterification reactor, so that part of the reaction material in the M-th stage to N-th stage esterification reactor returns to the M-th stage to N-th stage esterification reactor after passing through the respective external heater, wherein M is an integer less than or equal to N.

[0064] In an embodiment, the first stage esterification reactor is not provided with an external heater in communication with the first stage esterification reactor.

[0065] In an embodiment, the top of at least one of the M-th stage to N-th stage esterification reactors is provided with a reinforced distribution element, so that the reaction material heated by the external heater circulates back to the esterification reactor provided with the reinforced distribution element after passing through the reinforced distribution element.

[0066] The device and method for preparing high-carbon alcohol methacrylate provided by the application remove the acidic catalyst and polymerization inhibitor in the product by means of hot extraction, thereby reducing the consumption of additives; the excess methacrylate in the reaction product can be removed by means of water stripping and steam stripping, thereby improving the utilization rate of methacrylate; the methacrylate in the acid water can be removed by means of rectification-alcohol extraction combination, thereby reducing the acid content of the waste water; the amount of lye and water used in the preparation process is reduced, the waste water discharge is reduced, and the environment is friendly; in particular, in the preferred device and method, the reaction system can remove the water generated in the reaction process in time by means of vacuum rectification and out-of-kettle circulation dehydration combination, thereby improving the conversion rate of high-carbon alcohol in the reaction equilibrium. The device and method provided by the application can significantly simplify the production operation process, reduce the material consumption and energy consumption of the device, improve the product yield, reduce the waste water discharge in the production process, and are easy to be scaled up in industry. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 A schematic diagram of a device and method for preparing high-carbon alcohol methacrylate provided by the application is shown;

[0068] Figures 2-4 A schematic diagram of the reaction system of the device of the application is shown;

[0069] Figure 5 A schematic diagram of a device for preparing high-carbon alcohol methacrylate provided by the application is shown;

[0070] Figure 6 A process flow diagram of a comparative example for preparing methacrylate is shown. DETAILED DESCRIPTION

[0071] The application will be further described in detail below with the aid of the accompanying drawings and examples. The features and advantages of the application will become more apparent through these descriptions.

[0072] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the drawings are not drawn to scale and are merely intended to conceptually illustrate aspects of the embodiments.

[0073] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as there is no conflict.

[0074] As defined in this application, higher alcohols refer to monohydric or polyhydric alcohols with 12 or more carbon atoms and a boiling point above 250°C at normal pressure. For example, they may include monohydric saturated alcohols with 12-22 carbon atoms, such as lauryl alcohol, tridecyl alcohol, tetradecyl alcohol, octadecyl alcohol, etc., and dihydric saturated alcohols with 12-22 carbon atoms, such as dodecanediol, tridecanediol, octadecanediol, etc.

[0075] This application provides a method for producing higher alcohol esters of methacrylate, comprising:

[0076] The esterification reaction of methacrylic acid and higher alcohol raw materials is carried out in the reaction unit to obtain higher alcohol methacrylic acid ester product;

[0077] The higher carbon alcohol ester of methacrylate is subjected to deacidification treatment to obtain a deacidified higher carbon alcohol ester of methacrylate material and a mixture containing methacrylate-water.

[0078] The deacidified higher carbon alcohol methacrylate material is thermally extracted with extraction water in a thermal extraction unit to obtain thermally extracted higher carbon alcohol methacrylate material.

[0079] The heat-extracted higher carbon alcohol methacrylate material is then washed and decolorized to obtain the product higher carbon alcohol methacrylate.

[0080] The mixture containing methacrylic acid and water is subjected to acid recovery treatment to obtain recovered material and acid-containing water material;

[0081] The recycled material is returned to the reaction unit and used as part of the methacrylic acid feedstock for esterification.

[0082] like Figure 1 As shown, this application also provides an apparatus for producing higher alcohol methacrylates, comprising:

[0083] The reaction system 100 is used to carry out an esterification reaction between methacrylic acid raw material and higher alcohol raw material in an esterification reaction unit to obtain a higher alcohol ester product of methacrylic acid; the reaction system includes a reaction unit and a dehydration unit.

[0084] The deacidification unit 200 is used to deacidify the higher carbon alcohol ester product of methacrylate to obtain deacidified higher carbon alcohol ester material of methacrylate and a mixture containing methacrylate-water.

[0085] The acid recovery unit 300 is used to process a mixture containing methacrylic acid and water to obtain recovered material and acid-containing water material; wherein, the recovered material outlet of the acid recovery unit is connected to the feed inlet of the reaction unit of the reaction system, so that the recovered material is returned to the reaction unit of the reaction system;

[0086] a thermal extraction unit 400 for subjecting the deacidification treated methyl acrylate high carbon alcohol ester material to thermal extraction with extraction water in the thermal extraction unit to obtain a thermal extraction treated methyl acrylate high carbon alcohol ester material;

[0087] a decolorization unit 600 for subjecting the thermal extraction treated methyl acrylate high carbon alcohol ester material to decolorization treatment in the decolorization unit to obtain a product methyl acrylate high carbon alcohol ester.

[0088] The method and device of the present application will be described below in conjunction with the accompanying drawings. It should be noted that the embodiments of the device and method can be combined with each other without conflict.

[0089] The method of the present application comprises subjecting a methyl acrylate raw material and a high carbon alcohol raw material to esterification reaction in a reaction unit to obtain a methyl acrylate high carbon alcohol ester product.

[0090] The raw materials, methyl acrylate, high carbon alcohol, and the circulating polymerization inhibitor (and catalyst) are subjected to esterification reaction in the reaction unit 1010, and the methyl acrylate high carbon alcohol ester product can be filtered through the filter device 30 to remove the catalyst before entering the deacidification unit 200. The water produced during the reaction is separated and removed in time by the dehydration unit 1020 to accelerate the reaction process. The esterification reaction unit can be either a batch reaction or a continuous reaction operation.

[0091] The esterification reaction can be carried out in the reaction system 100. The reaction system 100 comprises a reaction unit 1010 and a dehydration unit 1020. The reaction unit 1010 can comprise a single-stage esterification reactor, which adopts a batch reaction scheme; or it can comprise a plurality of esterification reactors connected in series, which adopts a continuous multi-stage esterification reaction scheme.

[0092] In one embodiment, as shown in Figures 2-4 , the continuous multi-stage esterification reaction can be carried out in N-stage esterification reactors 01a, 01b, 01c, where N is an integer and N≥2. The N-stage esterification reactors are connected in series, so that the reaction material of the i-th stage esterification reactor can enter the (i+1)-th stage esterification reactor, where i is an integer from 1 to N-1; the N-th stage esterification reactor is provided with a product discharge port for discharging the methyl acrylate high carbon alcohol ester product. In one embodiment, N is 2-6, so that the esterification reaction process is carried out in 2-6 stage esterification reactors. For example, N can be 2, so that the esterification reaction process is carried out in 2-stage esterification reactors 01a, 01b (as shown in Figure 3 and Figure 4 ). For example, N can be 3, so that the esterification reaction process is carried out in 3-stage esterification reactors 01a, 01b, 01c (as shown in Figure 2 ). Generally, N can be 2-4, such as 2, 3, or 4.

[0093] During the reaction, the reactants, such as methacrylic acid 101, higher alcohols 102, and corresponding catalysts and polymerization inhibitors, are heated by heating equipment 06 and then fed into the first-stage esterification reactor 01a. The esterification reactors are connected in series. The reactant 110a discharged from the first-stage reactor enters the second-stage reactor, the reactant 110b discharged from the second-stage esterification reactor enters the third-stage reactor, and so on, until it enters the final first-stage reactor. The product 110 from the final first-stage reactor is then discharged from the reaction system.

[0094] In one embodiment, the catalyst can be a liquid organic acid, such as p-toluenesulfonic acid and / or other organic sulfonic acids, such as methanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, trifluoroacetic acid, etc., or an inorganic acid, such as one or more of sulfuric acid, phosphoric acid, and nitric acid; or a solid acidic substance, which can be selected from zeolite, polymer resin catalyst, porous molecular sieve, cation exchange resin, etc., wherein the content of the catalyst in the first-stage esterification reactor 01a is 0.1% to 35% by mass, based on the content of higher alcohols.

[0095] In one embodiment, the polymerization inhibitor can be an inorganic substance such as ferric chloride, cuprous chloride, active aluminum, or sodium thiocyanate, or an organic substance such as benzoquinone, 2-tert-butylhydroquinone, 1,4-naphthoquinone, 1,4-naphthoquinone-2-sulfonate, 4-tert-butylcatechol, bis(3,5-dimethyl-4-hydroxyphenyl) sulfone, phenol, hydroquinone, cresyl hydroquinone, hydroquinone monomethyl ether, bis-tert-butylhydroxytoluene, p-tert-butylphenol, p-nitrophenol, resorcinol, o-cresol, 1-heptene, or diphenylamine. These substances can be used alone or in combination. The amount of polymerization inhibitor added (based on the mass of methacrylic acid) is 0.005% to 10%.

[0096] like Figures 2-4 As shown, esterification reactors 01b and 01c can each be equipped with external heaters 05b and 05c connected to their respective esterification reactors. This allows a portion of the reactants from the Mth to Nth stage esterification reactors to be returned to their respective reactors 01b and 01c via these external heaters, where M is an integer less than or equal to N. By providing these external heaters 05b and 05c, the dehydration rate within each esterification reactor 01b and 01c can be increased, thereby improving the conversion rate of higher alcohols.

[0097] like Figures 2-4As shown, corresponding external circulation pumps 04b and 04c can also be provided. These external circulation pumps 04b and 04c are connected to external heaters 05b and 05c and the bottom discharge ports of esterification reactors 01b and 01c, respectively. This allows a portion of the bottom material from esterification reactors 01b and 01c to be circulated back to the tops 109b and 109c of esterification reactors 01b and 01c via the external circulation pumps 04b and 04c and the external heaters 05b and 05c, thereby increasing the dehydration rate within each esterification reactor 01b and 01c and improving the conversion rate of higher alcohols. In one embodiment, the operating conditions of the external heaters 05b and 05c for the Mth to Nth stage esterification reactors 01b and 01c are: a temperature of 80–130°C.

[0098] As will be described later, by setting these external heaters, the water content in the product, higher carbon alcohol methacrylate, can be reduced to a very low level, for example, below 0.5%, which can reduce subsequent processing costs and improve the conversion rate of higher carbon alcohols.

[0099] In one embodiment, for the j-th stage esterification reactor, the weight ratio of the reactant recycled back to the j-th stage esterification reactor to the reactant discharged from the j-th stage esterification reactor can be 1.2-20:1, where j is an integer from M to N. Further, this weight ratio can be 2-15:1, or 5-15:1.

[0100] For example, such as Figure 2 As shown, for esterification reactor 01b, a portion of the bottom material 109b is recycled back to the top of esterification reactor 01b via external circulation pump 04b and external heater 05b, and another portion of the bottom material 110b is transported to the next stage esterification reactor 01c via external circulation pump 04b. The ratio of the bottom material 109b recycled back to esterification reactor 01b (i.e., the reactant recycled back to esterification reactor 01b) to the bottom material 120b transported to esterification reactor 01c (i.e., the reactant discharged from esterification reactor 01b) can be 1.2-20:1 (2-15:1, or 5-15:1). For the final esterification reactor 01c, a portion of the bottom material is recycled back to the top of the esterification reactor 01c via the external circulation pump 04c and the external heater 05c, while another portion of the bottom material is transported to the subsequent processing equipment (i.e., discharged from the Nth stage esterification reactor 01c) via the external circulation pump 04c. The ratio of the bottom material 109c recycled back to the esterification reactor 01c (i.e., the reactant material recycled back to the esterification reactor 01c) to the bottom material 110 transported to the subsequent processing equipment (i.e., the reactant material discharged from the esterification reactor 01c) can also be 1.2-20:1 (2-15:1, or 5-15:1).

[0101] For example, such as Figure 3 and 4 As shown, for the final esterification reactor 01b, a portion of the bottom material is recycled back to the top of the esterification reactor 01b via the external circulation pump 04b and the external heater 05b, and another portion of the bottom material is transported to the subsequent processing equipment (i.e., discharged from the final esterification reactor 01b) via the external circulation pump 04b. The ratio of the bottom material 109b recycled back to the esterification reactor 01b (i.e., the reactant material recycled back to the esterification reactor 01b) to the bottom material 110 transported to the subsequent processing equipment (i.e., the reactant material discharged from the esterification reactor 01b) can also be 1.2-20:1 (2-15:1, or 5-15:1).

[0102] like Figure 3 As shown, the reactant 110 discharged from the final Nth stage esterification reactor 01b can first pass through the filtration device 30 to filter out the catalyst and other substances, and then enter the subsequent processing equipment.

[0103] In one embodiment, the esterification reactors 01a, 01b, and 01c can be either stirred tanks with stirring or horizontal reaction equipment with stirring and baffles. In one embodiment, the external heaters 05b / 05c can be one or a combination of two of the following: tube heaters, falling film evaporators, and rising film evaporators. These reactors and heaters can use various structures known in the art, which will not be described in detail here.

[0104] In one embodiment, at least one of the M- to N-stage esterification reactors 01b, 01c, externally equipped with external heaters 05b, 05c, is provided with enhanced distribution elements 25b, 25c at its top. This allows the reactants heated by the external heaters 05b, 05c to be recycled back to the esterification reactor 05b, 05c equipped with the enhanced distribution elements after passing through these elements. This enhances the distribution of reactants recycled back to each reactor, thereby increasing the dehydration rate within each esterification reactor and improving the conversion rate of higher alcohols.

[0105] In one implementation, M is an integer less than or equal to N. For example, M can be N, or an integer between 1 and N, or any integer between 2 and N.

[0106] In one embodiment, M can be N, i.e. the Nth esterification reactor is provided with an external heater in communication therewith, while the 1st to (N-1)th esterification reactors are not provided with respective external heaters, such that in the first N-1 esterification reactors, the reaction material of the kth esterification reactor is entirely transferred to the (k+1)th esterification reactor (k is an integer from 1 to N-1); and for the last Nth esterification reactor, a part of the reaction material is returned to the Nth esterification reactor after passing through the respective external heater, and another part of the reaction material is discharged from the reaction system. Such a mode is also covered by the protection scope of the present application.

[0107] In one embodiment, M is 2, i.e. the 1st esterification reactor is not provided with an external heater in communication therewith, such that the reaction material of the 1st esterification reactor is entirely transferred to the 2nd esterification reactor; and the other esterification reactors (2nd to Nth esterification reactors) are provided with respective external heaters, such that in the other esterification reactors except the 1st esterification reactor, a part of the reaction material is returned to the respective esterification reactor after passing through the respective external heater, and another part of the reaction material is transferred to the next esterification reactor, or discharged from the reaction system. Such a mode is also covered by the protection scope of the present application.

[0108] In one embodiment, M is any integer between 2 and N, i.e. from the Mth esterification reactor, the Mth to Nth esterification reactors are provided with respective external heaters in communication therewith, such that in the Mth to Nth esterification reactors, a part of the reaction material is returned to the respective esterification reactor after passing through the respective external heater, and another part of the reaction material is transferred to the next esterification reactor, or discharged from the reaction system; and the 1st to Mth esterification reactors are not provided with respective external heaters, such that the reaction material of these reactors is entirely transferred to the next esterification reactor.

[0109] In one embodiment, the temperature in the 1st to Nth esterification reactors is 60-150°C, the operating pressure is 5-150 kPa, and the residence time is 0.1-14 h. The reaction conditions in each esterification reactor, such as temperature, pressure, residence time, etc., can be set as required.

[0110] In one embodiment, the water content in the last Nth esterification reactor is 0-0.5 wt%, based on the total weight of the material in the Nth esterification reactor.

[0111] The esterification process of this application further includes a dehydration treatment, which includes feeding the methacrylic acid-water mixture 105 from the first to Nth stage esterification reactors into a dehydration unit 1020 for dehydration, and feeding the dehydrated material from the dehydration unit into the first stage esterification reactor. For example... Figures 2-4 As shown, in one embodiment, the dehydration process is carried out in dehydration tower 02. The top spaces of all esterification reactors 01a, 01b, and 01c are connected to the bottom feed inlet of dehydration tower 02, so that the methacrylic acid-water mixture 105 (gas phase material) distilled from the top of esterification reactors 01a, 01b, and 01c enters dehydration tower 02 for rectification, separating the water. The liquid phase 106 at the bottom of dehydration tower 02 contains a large amount of methacrylic acid and can be returned to the first-stage esterification reactor 01a for further reaction. The methacrylic acid-water azeotrope 142 at the top of the tower is condensed by condenser 03, with a portion flowing back to dehydration tower 02 and the remaining material 108 discharged from dehydration tower 02. The top of the dehydration tower is controlled by a vacuum system 31 to maintain negative pressure operation and collect tail gas 143. In one embodiment, the dehydration process is carried out in a distillation column, wherein the operating pressure at the top of the column is 5–150 kPa, the temperature is 30–150 °C, and the reflux ratio is 0.1–5.

[0112] Therefore, in one embodiment, the reaction system 100 used in this application includes:

[0113] The dehydration unit 1020 is used to remove water produced by the esterification reaction of methacrylic acid and higher alcohols; the dehydration unit includes one or more feed inlets;

[0114] The reaction unit 1010 includes an N-stage esterification reactor for continuously esterifying excess methacrylic acid and higher alcohols, where N is an integer and N≥2; the N-stage esterification reactors are connected in series so that the reactants from the i-th stage esterification reactor can enter the (i+1)-th stage esterification reactor, where i is an integer from 1 to N-1; the N-th stage esterification reactor is provided with a product discharge port for discharging the higher alcohol methacrylic acid ester product;

[0115] The top of each of the N-stage esterification reactors is connected to an inlet of the dehydration unit, allowing a portion of the material from the N-stage esterification reactor to enter the dehydration unit for dehydration. An outlet of the dehydration unit is connected to an inlet of the first-stage esterification reactor, allowing the dehydrated material from the dehydration unit to enter the first-stage esterification reactor.

[0116] The Mth to Nth esterification reactors are each provided with an external heater in communication with the respective esterification reactor, such that a portion of the reaction material in the Mth to Nth esterification reactors is returned to the Mth to Nth esterification reactors via the respective external heater, wherein M is an integer less than or equal to N.

[0117] As shown in Figure 2 and 5 In one embodiment, the reaction unit 1010 includes three esterification reactors 01a / b / c connected in series, wherein the 2nd and 3rd esterification reactors are each provided with an external circulation fixed tube-plate heater 05b / c and a top enhanced distribution element 25b / c. The liquid phase 110a from the outlet of the 1st esterification reactor 01a overflows into the 2nd esterification reactor 01b. Most of the material from the outlet of the 2nd esterification reactor 01b is heated by the external circulation heater 05b and returned to the 2nd esterification reactor 01b through the enhanced distribution element 25b for further reaction, and a small portion 110b enters the 3rd esterification reactor 01c for further reaction until the reaction endpoint (wherein the weight ratio of the circulating material to the material entering the 3rd esterification reactor 01c is 1.2-20:1). Most of the material from the outlet of the 3rd esterification reactor 01c is heated by the external circulation heater 05c and returned to the 3rd esterification reactor 01c through the enhanced distribution element 25c for further reaction, and a small portion 110 is pumped out of the reaction system (wherein the weight ratio of the circulating material to the material discharged from the reaction system is 1.2-20:1).

[0118] The dehydration treatment is carried out in a dehydration column 02. The headspace of all the esterification reactors 01a, 01b, 01c is in communication with the bottom inlet of the dehydration column 02, such that the methyl methacrylate-water mixture 105 (gaseous material) vaporized from the top of the esterification reactors 01a, 01b, 01c all enters the dehydration column 02 for rectification and separation of water, and the liquid phase 106 from the bottom of the dehydration column 02 contains a large amount of methyl methacrylate, which can be returned to the 1st esterification reactor 01a for further reaction. The methyl methacrylate-water azeotrope 142 from the top of the dehydration column is condensed by a condenser 03, and a portion of the condensed material is returned to the dehydration column 02, and another portion of the material 108, 129 is discharged from the dehydration column 02 into subsequent equipment. The top of the dehydration column is controlled by a vacuum system (vacuum pump) 31 to operate under negative pressure, and tail gas 143 is collected. As described later, the tail gas 143 can be further absorbed and treated in a tail gas absorption column 26. In one embodiment, the dehydration column 02 is a distillation column, and the dehydration treatment is carried out in the distillation column, wherein the operating pressure at the top of the column is 5-150 kPa, the temperature is 30-150°C, and the reflux ratio is 0.1-5.

[0119] As shown in Figure 2 and 5As shown, the first-stage esterification reactor is not equipped with an external heater connected to it.

[0120] This reaction system 100 can promptly remove the water generated during the reaction, which is beneficial for improving the equilibrium conversion rate. Simultaneously, by using an external heater to enhance dehydration within the reactor, the reaction temperature can be controlled, reducing the self-polymerization of methacrylic acid. The method and reaction system provided in this application can effectively improve the conversion rate of higher alcohols and the yield of higher carbon methacrylic acid esters. The process is simple to operate, environmentally friendly, and simultaneously addresses both timely dehydration and temperature control, facilitating engineering scale-up, stable continuous operation, and simple industrial implementation.

[0121] The reaction system 100 increases the dehydration rate in the reactor and improves the conversion rate of higher alcohols by providing an external circulating heating device; it is also equipped with a dehydration distillation unit 1020 connected to the reaction unit 1010 to continuously remove water generated by the esterification reaction, thereby realizing the continuous preparation of higher alcohol methacrylates.

[0122] After the esterification reaction, the higher alcohol methacrylate product 110 is fed into the deacidification unit 200 for deacidification treatment. This deacidification treatment can be carried out by removing methacrylic acid by steam stripping alone, or by first using water distillation followed by steam stripping.

[0123] In one embodiment, the deacidification treatment includes: treating the higher carbon alcohol methacrylate product with steam to obtain the deacidified higher carbon alcohol methacrylate material.

[0124] In one embodiment, the deacidification treatment includes: treating the deacidified higher alcohol methacrylate material with water to obtain a water-extracted higher alcohol methacrylate material, and

[0125] The water-extracted higher carbon alcohol methacrylate material is treated with steam to obtain the deacidified higher carbon alcohol methacrylate material.

[0126] In one embodiment, the steam treatment temperature is 60-130°C, and the methacrylic acid content in the deacidified higher carbon alcohol methacrylate material is 2-14%, based on the total weight of the deacidified higher carbon alcohol methacrylate material.

[0127] like Figure 5 As shown, in one embodiment, the deacidification unit 200 includes:

[0128] a water-stripping column 07, wherein the outlet of the reaction system is connected to the upper inlet of the water-stripping column 07, so that the methyl acrylate high carbon alcohol ester product 110 enters the water-stripping column 07; the outlet of the dehydration unit 02 of the reaction system is connected to the reboiler E1 inlet of the water-stripping column 07, so that at least part of the acid water from the reaction system 108 enters the water-stripping column 07;

[0129] a steam-stripping column 10, wherein the upper liquid phase inlet of the steam-stripping column 10 is connected to the outlet of the water-stripping column 07, so that at least part of the water-stripping column bottom material 115 enters the steam-stripping column 10; the bottom of the steam-stripping column is provided with a steam inlet for introducing steam 116 into the steam-stripping column.

[0130] Through the deacidification unit 200, the methyl acrylate-methyl acrylate high carbon alcohol ester mixture (acid ester containing, methyl acrylate high carbon alcohol ester product) 110 of the esterification reaction is removed from the excess methyl acrylate under the action of water (or) and steam, and the specific process is as follows: the acid ester containing 110 enters the water-stripping column 07, the acid water (or desalted water) 108 enters the reboiler E1 of the water-stripping column 07, the acid ester containing 115 enters from the top of the steam-stripping column 10, and the methyl acrylate in the acid ester is removed by the action of the steam 116 in the column; part of the acid water from the top of the acid recovery column 14 123, 124 enters the top of the water-stripping column 07 and the steam-stripping column 10, and the acid water mixture gas 113 from the top of the water-stripping column 07 and the acid water mixture gas 117 from the top of the steam-stripping column 10 are mixed (marked as 118) and cooled (marked as 119) by the condenser 11, and then enter the acid recovery unit 300 after the pump 12; the methyl acrylate monomer ester 111 at the bottom of the steam-stripping column 10 enters the hot extraction unit 400 through the pump 13.

[0131] As Figure 5As shown, the deacidification unit 200 is used to separate the excess methacrylic acid in the esterification reaction product, and the main process is described below by taking the combination of the water-stripping column 07 and the steam-stripping column 10 as an example. The deacidification unit 200 mainly includes the water-stripping column 07, the water-stripping column bottom pump 08, the water-stripping column bottom reboiler E1, the steam-stripping column 10, and the steam-stripping column bottom pump 13. The esterification reaction unit discharge 110 is connected to the upper feeding port of the water-stripping column 07, the acid water discharge 108 of the dehydration unit is connected to the water-stripping column bottom reboiler E1, the water-stripping column bottom liquid phase discharge 09 is connected to the water-stripping column bottom pump 08, a part of which is heated by the water-stripping column bottom reboiler E1 to be partially gasified and returned to the water-stripping column 07 (indicated by reference numeral 114), and the other part (indicated by reference numeral 115) is connected to the upper liquid phase feeding port of the steam-stripping column 10 and enters the steam-stripping column; the steam-stripping column bottom liquid phase discharge is connected to the steam-stripping column bottom pump 13, and the steam-stripping column bottom pump 13 outlet material (low acid ester) 111 is connected to the top liquid phase feeding port of the hot extraction column 06 to enter the hot extraction column 06 for hot extraction; the water-stripping column 07 and the steam-stripping column 10 are both provided with a liquid phase feeding port connected to the acid refining column 14 top discharge 122. The acid-containing water 108 from the dehydration column 02 enters the water-stripping column 07 after entering the water-stripping column bottom reboiler E1 as a deacidification agent, and the water vapor 116 enters the steam-stripping column 10 as a deacidification gas.

[0132] Thus, the methacrylic acid in the mixture is removed by first using water injection stripping and then using steam stripping.

[0133] In one embodiment, the acid recovery process comprises:

[0134] extracting the methacrylic acid-containing water mixture in an alcohol extraction column by using a high-carbon alcohol material to obtain the recovered material and the acid-containing water material, wherein the feeding mass ratio of the high-carbon alcohol material to the methacrylic acid-containing water mixture is 0.1-5:1, and the operating pressure is 101-300 kPa; the mass fraction of methacrylic acid in the acid-containing water material is 0.01-0.5%, based on the acid-containing water material.

[0135] In one embodiment, the acid recovery process comprises:

[0136] The mixture containing methacrylic acid and water is rectified in an acid refining tower, wherein the operating pressure of the acid refining tower is 1-80 kPa, the overhead temperature is 25-65°C, the bottom temperature is 80-130°C, and the operating reflux ratio of the overhead is 0.1-5; the mass fraction of methacrylic acid in the overhead material of the acid refining tower is 0.5-15% based on the total weight of the overhead material of the acid refining tower; the mass fraction of the bottom material of the acid refining tower is 90-99.8% based on the total weight of the bottom material of the acid refining tower.

[0137] The bottom material of the acid refining tower is extracted in an alcohol extraction tower with a high carbon alcohol material to obtain the recovered material and the acid-containing water material, wherein the feed mass ratio of the high carbon alcohol material to the circulating methacrylic acid in the bottom material is 0.1-5:1, and the operating pressure is 101-300 kPa; the mass fraction of methacrylic acid in the acid-containing water material is 0.01-0.5%.

[0138] As shown in Figure 5 In an embodiment, the acid recovery process is carried out in an acid recovery unit 300, which comprises:

[0139] an acid refining tower 14, the feed inlet of which is connected to the overhead outlet of the water-stripping tower 07 and the overhead outlet of the steam-stripping tower 10, so that the overhead material 113 from the water-stripping tower and the overhead material 117 from the steam-stripping tower (mixed together and marked as 118) enter the acid refining tower 14 after being cooled by the condenser 11 and pumped by the pump 12 as the feed 121 of the acid refining tower 14; the bottom outlet of the acid refining tower 14 is connected to the reaction unit feed inlet of the reaction system, so that the bottom material 125 of the acid refining tower returns to the reaction unit of the reaction system 100;

[0140] an alcohol extraction tower 19, the upper feed inlet of which is connected to the overhead outlet of the acid refining tower 14, so that the overhead material 145 of the acid refining tower 14 is pumped by the pump 16 and enters the alcohol extraction tower 19; the alcohol extraction tower 19 is provided with a bottom high carbon alcohol material feed inlet for feeding the high carbon alcohol material 103; the overhead outlet of the alcohol extraction tower 19 is connected to the reaction unit feed inlet of the reaction system, so that the overhead material 104 of the alcohol extraction tower returns to the reaction unit of the reaction system.

[0141] In the acid recovery unit 300, the mixed acid water 121 from the deacidification unit 200 enters the acid refining column 14, and high-purity methacrylic acid 125 is discharged from the column bottom to be recycled back to the reaction unit for further reaction. The acid water mixture in the column top cannot be directly discharged from the equipment. The column top material 146 of the acid refining column 14 is cooled by the condenser 15, and part of it is refluxed back to the acid refining column 14; the other part is discharged from the acid refining column 14, which can be divided into two streams 145 and 122. The stream 145 enters the alcohol extraction column 19, and the stream 122 enters the water-stripping column 07 and the steam-stripping column 10 as the column top feed 123 and 124, respectively.

[0142] In an embodiment, the operating pressure of the acid refining column 14 is 1-80 kPa, the column top temperature is 25-65°C, the column bottom temperature is controlled at 80-130°C, the column top operating reflux ratio is 0.1-5, the acid water in the column top material contains 0.5-15% of methacrylic acid by mass, and the methacrylic acid in the column bottom material circulating acid is 90-99.8% by mass.

[0143] The stream 145 from the acid refining column 14 and the stream 129 from the dehydration column 02 enter the alcohol extraction column 19 to be countercurrently contacted with the high-carbon alcohol material 103, so as to remove the methacrylic acid therefrom by using the high-carbon alcohol 103, and return to the reaction unit for further reaction (as indicated by the reference numeral 104). The column bottom discharges wastewater containing trace acid, part of which (indicated by the reference numeral 107) is heated by the heater 20 and then enters the hot extraction column 06, and the other part is discharged from the equipment (indicated by the reference numeral 126).

[0144] In an embodiment, the extractant in the alcohol extraction column is the high-carbon alcohol used in the reaction, the mass ratio of the extractant to the acid water feed (the sum of the materials of the reference numerals 145 and 129) is 0.1-5:1, the raffinate 104 can be directly returned to the reaction system for further use, the operating pressure is 101-300 kPa, and the methacrylic acid in the trace acid water at the column bottom is 0.01-0.5% by mass. Part of the trace acid water material 107 enters the hot extraction column 06, and the other part is discharged as waste acid water 126.

[0145] In an embodiment, as Figure 5As shown, in the thermal extraction unit 400, high-temperature water extraction is used to remove the polymerization inhibitor and any catalyst that may be present in the low-acid ester 111 from the deacidification unit 200, yielding a trace amount of high-carbon alcohol methacrylate (micro-ester) 120 and raffinate 112 containing the polymerization inhibitor and liquid acid catalyst. The liquid-phase micro-ester outlet is simultaneously connected to the washing unit, decolorization unit, and device outlet, while the raffinate outlet is connected to the esterification reaction unit for further reaction. The extractant used in the thermal extraction unit can be either demineralized water or slightly acidic water discharged from the alcohol extraction tower (bottom material 107 of the alcohol extraction tower 19), with an acid content of 0.001–0.5%.

[0146] like Figure 5 As shown, the thermal extraction unit 400 includes a thermal extraction tower 06 and a heater 20, etc. The top of the thermal extraction tower 06 is equipped with an ester outlet connected to the bottom inlet of the alkali tower 21. The bottom discharge of the thermal extraction tower 06 contains a polymerization inhibitor or catalyst and can be connected to the primary esterification reactor 01a. The heater 20 is used to heat the extractant, and its outlet is connected to the top inlet of the thermal extraction tower, allowing the thermal extractant to enter the thermal extraction tower. The outlet material (low acid ester) 111 of the steam-stripping tower bottom pump 13 is connected to the thermal extraction tower 06, allowing it to enter the bottom of the thermal extraction tower 06. A portion 107 of the slightly acidic water from the bottom of the alcohol extraction tower 19 is heated by the heater 20 and then enters the top of the thermal extraction tower 06. This allows the wastewater from the alcohol extraction tower 14 (a portion of the slightly acidic water 107 from the bottom of the alcohol extraction tower 14) to be used as an extractant for heating before entering the thermal extraction tower 06, thus reducing the water consumption of the unit. The bottom material 112 of the thermal extraction tower 06 is returned to the reaction unit to continue the reaction.

[0147] In one embodiment, the thermal extraction unit operates at a thermal extraction tower temperature of 50–95°C, a tower top pressure of 101–150 kPa, an extraction water temperature of 50–95°C, and a mass flow ratio of extraction water to the deacidified methacrylate high carbon alcohol ester material of 0.08–2:1.

[0148] In one embodiment, the thermally extracted higher carbon alcohol methacrylate material discharged from the top of the thermal extraction tower contains 0.05-1.5% methacrylic acid by mass, 0.01-0.2% polymerization inhibitor by mass, and 0.03-1.5% liquid acid catalyst by mass, based on the total weight of the thermally extracted higher carbon alcohol methacrylate material.

[0149] In one embodiment, the acidic aqueous material is introduced into the thermal extraction unit as the extraction water of the thermal extraction unit.

[0150] In one embodiment, the method further comprises a washing treatment before the decoloring treatment. Thus, the device of the present application further comprises a washing unit 500 for washing the hot-extracted high carbon alcohol methacrylate ester material in the washing unit to obtain a washed ester material. The washed ester material is then delivered to the subsequent decoloring unit 600 for subsequent decoloring treatment.

[0151] In one embodiment, the washing treatment comprises:

[0152] water washing step: washing the hot-extracted high carbon alcohol methacrylate ester material with desalted water, wherein the mass flow ratio of the desalted water to the hot-extracted high carbon alcohol methacrylate ester material is 0.1-1:1, the pH value of the neutral ester material after washing is 6.5-7.5, the water washing process is operated at a temperature of 40-60°C and a pressure of 101-300 kPa.

[0153] In one embodiment, the washing treatment comprises:

[0154] alkali washing step: washing the hot-extracted high carbon alcohol methacrylate ester material with alkali solution, wherein the mass fraction of alkali in the alkali solution is 0.1-10%, the mass flow ratio of the alkali solution to the hot-extracted high carbon alcohol methacrylate ester material is 0.1-1:1, the pH value of the basic ester is 7.5-11, the alkali washing process is operated at a temperature of 40-60°C and a pressure of 101-300 kPa.

[0155] water washing step: washing the basic ester with desalted water, wherein the mass flow ratio of the desalted water to the basic ester is 0.1-1:1, the pH value of the neutral ester material after washing is 6.5-7.5, the water washing process is operated at a temperature of 40-60°C and a pressure of 101-300 kPa.

[0156] The washing treatment can be performed in the washing unit 500 to remove the residual catalyst, polymerization inhibitor and other residual substances in the ester product after hot extraction. The continuous washing of alkali solution / desalted water can be used, or the intermittent alkali / water washing process can be used.

[0157] The washing process is described below by way of example of continuous washing. As shown in FIG. 5, the washing unit 500 comprises a washing tank 501, a pump 502, a pH value detector 503, a temperature detector 504, a pressure detector 505, a control unit 506, and a washing liquid tank 507. Figure 5As shown, the washing unit 500 mainly comprises: an alkali tower 21 and a water tower 22, wherein the alkali liquor 140 enters the alkali tower 21 through the top alkali liquor inlet, and the ester product 120 (from the top of the hot extraction tower 06) enters the bottom of the alkali tower 21 through the lower liquid phase inlet; the top liquid phase outlet of the alkali tower 21 is connected to the bottom liquid phase inlet of the water tower 22, so that the alkali tower top material 127 enters the water tower 22, and the desalted water 130 enters the water tower 22 through the top inlet; the top outlet of the water tower 22 is connected to the subsequent decolorization unit 600, so that the water tower top material (neutral ester) 131 enters the decolorization unit 600 for decolorization treatment. The bottom liquid phase outlets of the alkali tower 21 and the water tower 22 are connected to the top of the tail gas absorption tower 26 of the vacuum system 700 for tail gas absorption. Through the two-stage continuous alkali tower 21 and the water tower 22, the residual acidic substances such as polymerization inhibitors and catalysts in the ester product can be further removed. Of course, when the acidic substance content in the slightly acidic ester discharged by the hot extraction unit is low, the washing unit 500 can be omitted.

[0158] The top material (monomer ester) from the hot extraction tower can first enter the alkali washing unit, and the trace amount of acidic substances therein is first removed to weak alkaline by the neutralization of alkali; then it enters the water washing unit, and is washed to neutral monomer ester by water and sent to the decolorization unit. The waste alkali liquor can be reused as an absorbent of the vacuum system.

[0159] In an embodiment, the alkali liquor can be an aqueous solution of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, or a combination of two or more thereof. In an embodiment, the mass fraction of alkali in the alkali liquor is 0.1-10%, the mass flow ratio of the alkali liquor to the top material (monomer ester) from the hot extraction tower is 0.1-1:1, the pH value of the alkali ester of the outlet is controlled to be 7.5-11, the alkali washing operation temperature is 40-60°C, and the operation pressure is 101-300 kPa.

[0160] In an embodiment, the mass flow ratio of the desalted water used for water washing to the alkali ester (the outlet of the alkali tower) is 0.1-1:1, the pH value of the neutral ester of the outlet is controlled to be 6.5-7.5, the water washing process operation temperature is 40-60°C, and the operation pressure is 101-300 kPa.

[0161] Subsequently, decolorization treatment is performed. As described above, the hot extraction treated methyl high carbon alcohol methacrylate material can be directly subjected to decolorization treatment without the above washing treatment; of course, the hot extraction treated methyl high carbon alcohol methacrylate material can also be subjected to decolorization treatment after the above washing treatment. Both technical solutions belong to the protection scope of the present application.

[0162] Decolorization can be carried out in decolorization unit 600. In decolorization unit 600, adsorbents such as clay can be used to treat the qualified acid value micro ester 120 from the autothermal extraction unit or the neutral ester 131 from the washing unit to remove trace by-products and a small amount of free water from the ester product. The resulting solid waste is connected to the unit outlet, and the obtained qualified higher alcohol methacrylate 134 is connected to the unit outlet.

[0163] The decolorization unit 600 can operate intermittently with in-vessel stirring, or it can operate continuously with a fixed bed. In one embodiment, such as... Figure 5 As shown, the decolorization unit 600 may include multiple decolorization kettles 28a / b connected in parallel, a filtration device 29, etc. The ester products 120 and 131 from the previous unit (thermal extraction unit or washing unit) are connected to the inlet of the decolorization kettle 28a / b, allowing them to enter the decolorization kettle 28a / b. The outlet of the decolorization kettle is connected to the filtration device 29, so that the decolorized material 133 is filtered through the filtration device 29 to obtain qualified higher alcohol methacrylate 134. The top gas phase space of the decolorization kettle 28a / b is connected to a vacuum pump 31 to generate a vacuum in the decolorization kettle (28a / b), and the vacuum pump 31 is used to absorb the exhaust gas. The adsorbent used for decolorization can be an adsorbent such as kaolin.

[0164] In one embodiment, the apparatus further includes a vacuum system 700, which provides a negative pressure system for each vacuum operation unit in the apparatus and simultaneously handles acidic substances that may be carried in the vacuum exhaust gas.

[0165] In one embodiment, the vacuum system 700 includes:

[0166] Vacuum pump 31 is used to generate a vacuum in equipment that requires a vacuum in the device.

[0167] The exhaust port of the vacuum pump 31 is connected to the tail gas absorption tower 26 to absorb the tail gas 143 from the vacuum pump 31. The waste alkaline solution 135 from the washing unit 500 (including the bottom material 128 of the alkaline tower 21 and the bottom discharge 132 of the water tower 22) can be connected to the top of the tail gas absorption tower as an absorbent to absorb and remove acidic substances and small molecule organic substances from the tail gas 143 from the vacuum pump 31. The waste gas 137 is discharged from the top of the tower.

[0168] The outlet of the alkaline solution circulation pump 27 is connected to the top of the tail gas absorption tower 26, so that the alkaline solution in the tail gas absorption tower 26 can be recycled. The recycled alkaline wastewater 136 is connected to the discharge equipment and discharged from the device of the present invention.

[0169] The device and method for preparing high carbon alcohol methacrylate provided by the present application will be described below with reference to the accompanying drawings, and the present application will be further illustrated by the following examples, but the present application is not limited in any way by the following examples.

[0170] Example 1

[0171] Esterification reaction unit: lauryl methacrylate is generated by reacting methacrylic acid and lauryl alcohol, and the catalyst is methanesulfonic acid. The specific process is as follows: Figure 2 and 5 ): The three esterification reactors (01a / b / c) are in the form of kettle stirrers, and the second and third esterification reactors are both provided with an external circulation fixed tube plate heater (05b / c), and a reinforced distribution element (25b / c) is arranged at the top, respectively. The liquid phase overflowed from the outlet of the first esterification reactor (01a) flows into the second esterification reactor, most of the outlet material of the second esterification reactor (01b) is heated by the external circulation heater (05b) (heated to 110°C) and then returned to the second esterification reactor (01b) through the reinforced distribution element (25b) for continuous reaction, a small part enters the third esterification reactor (01c) for continuous reaction to the reaction endpoint (wherein the weight ratio of the circulating material to the material entering the third esterification reactor (01c) is 8.5:1), most of the outlet material of the third esterification reactor (01c) is heated by the external circulation heater (05c) (heated to 105°C) and then returned to the third esterification reactor (01c) through the reinforced distribution element (25c) for continuous reaction, and a small part is pumped out of the reaction system (wherein the weight ratio of the circulating material to the material discharged from the reaction system is 13:1). The material balance of the reaction system is shown in Table 1, and the structural parameters of the esterification reaction equipment are shown in Table 2. The reaction temperature of the first esterification reactor (01a) is 95°C, the reaction temperature of the second esterification reactor (01b) is 102°C, and the reaction temperature of the third esterification reactor (01c) is 110°C. The outlet material of the third esterification reactor (01c) is filtered through the filter (30) to remove the solid catalyst, and then enters the deacidification unit;

[0172] Dehydration unit: The acid-containing gas phase (105) at the top of the third esterification reactor enters the dehydration unit dehydration tower (02) for vacuum distillation to remove the water generated in the esterification reaction, and the liquid phase (106) at the bottom of the dehydration tower returns to the first esterification reactor (01a) for continuous reaction. The acid-containing water (108, 129) collected at the top of the dehydration tower enters the water-stripping column (07) and the alcohol extraction column (19), respectively;

[0173] Deacidification unit: the acid-containing ester (110) from the esterification reaction unit enters the upper layer of the water-stripping column (07), the acid-containing water (108) enters the kettle bottom of the water-stripping column (07) through the kettle reboiler (E1) of the water-stripping column (07), the low-acid water (123) from the overhead of the acid recovery unit's acid distillation column (14) enters from the top of the water-stripping column (07), the water-stripping column (07) kettle outflow enters the upper layer of the steam-stripping column (10), 0.4 MPa water vapor (116) enters the kettle of the steam-stripping column (10), the low-acid water (124) from the overhead of the acid recovery unit's acid distillation column (14) enters from the top of the steam-stripping column (10), the kettle obtains the high-carbon alcohol methacrylate ester containing a small amount of acid (low-acid ester) (111) which enters the hot extraction unit, the acid-containing gas (113) from the overhead of the water-stripping column (07) and the acid-containing gas (117) from the overhead of the steam-stripping column (10) are mixed (mixed acid-containing gas 118) and then enter the acid recovery unit after being partially cooled (high-acid water (119)) by the condenser (11);

[0174] Hot extraction unit: the low-acid ester (111) from the deacidification unit enters the bottom of the hot extraction column (06), the slightly-acidic water (107) from the bottom of the alcohol extraction column (19) is heated to 75°C by the heater (20) and then enters the top of the hot extraction column (06), the polymerization inhibitor and catalyst methanesulfonic acid in the low-acid ester (111) are extracted, the hot extraction column's kettle bottom material (112) returns to the esterification reaction kettle (01a), and the ester product (120) at the top of the hot extraction column (06) enters the washing unit;

[0175] Acid recovery unit: the high-acid water (119) from the deacidification unit is pumped (stream (121)) by the pump (12) to the acid refining column (14) of the acid recovery unit, high-purity methacrylic acid (125) is obtained at the bottom to return to the reaction kettle (01a) for continuous reaction, and the azeotrope (146) of methacrylic acid-water (with a mass content of 15% of methacrylic acid) is obtained at the top, which is cooled by the condenser (15), part of which is refluxed to the acid refining column (14), and the other part (145) enters the top of the alcohol extraction column (19) together with the stream (129) from the dehydration column (02); the lauryl alcohol (103) used in the reaction enters the bottom of the alcohol extraction column (19), absorbs the methacrylic acid therein, and returns to the esterification reaction kettle (01a) for continuous reaction (indicated by stream (104)), and the slightly-acidic water at the bottom is partially (107) introduced into the hot extraction column (06) for extracting the polymerization inhibitor and catalyst in the low-acid ester, and part of the slightly-acidic water (126) is discharged as waste acid water;

[0176] Washing unit: the slightly-acidic ester product (120) from the hot extraction unit successively enters the alkali column (21) and the water column (22), and the neutral ester product (131) is obtained by using the neutralization of alkali to remove the methacrylic acid in the product and using water washing;

[0177] Decolorization unit: neutral ester product (131) from the washing unit enters the decolorization kettle (28a / b) to remove esterification by-products, and after filtration by the filter (29), the qualified high-carbon methacrylate product (134) is discharged.

[0178] Table 1 Material balance of the reaction system of Example 1

[0179]

[0180] Table 2 Structural parameters of the reactor

[0181] Primary esterification reactor Secondary esterification reactor Tertiary esterification reactor Diameter, mm 180 180 180 Tangent height, mm 320 320 320 Volume, L 8 8 8 Calculated residence time, h 7.5 7.5 7.5 External loop ratio —— 8.5 13

[0182] Example 2

[0183] Esterification reaction unit: excess methacrylic acid (101) and lauryl alcohol (102) are fed into the batch kettle-type stirred esterification reactor (01), and after the reaction is completed, the product material (110) is transported to the outside via the pump (04); the top of the batch kettle-type stirred esterification reactor (01) is provided with a dehydration tower (02) for removing the material (105) distilled from the top of the esterification reactor (01), and recycling the recovered material (106) back to the esterification reactor (01) for further reaction. Similarly, the overhead material of the dehydration tower (02) is condensed by the condenser (03), and part of the overhead material is recycled back to the dehydration tower (02), and part of the material (108) is discharged from the dehydration tower (02); the dehydration tower (02) is also connected with a vacuum pump (31), and the overhead of the dehydration tower (02) is controlled by the vacuum system (31) to operate under negative pressure conditions, and tail gas (143) is collected. The temperature of the esterification reaction kettle (01) is controlled at 110°C, and continuous stirring is carried out for 12h. The material balance of the reaction system is shown in Table 3, and the structural parameters of the equipment of the batch esterification reaction are shown in Table 4.

[0184] Dehydration unit: the overhead acid-containing gas phase (105) of the esterification reaction enters the dehydration unit dehydration tower (02) for vacuum distillation to remove the water generated in the esterification reaction, and the liquid phase (106) at the bottom of the dehydration tower is returned to the first esterification reaction kettle (01a) for continuous reaction; after the reaction is completed, the acid-containing water (108, 129) collected at the top of the dehydration tower (02) is respectively fed into the water-stripping tower (07) and the alcohol extraction tower (19); the structure and operating parameters of the dehydration tower are the same as those of Example 1;

[0185] Deacidification unit: the acid-containing ester (110) from the esterification reaction unit enters the upper layer of the water-stripping column (07), the acid-containing water (108) enters the kettle bottom of the water-stripping column (07) through the kettle reboiler (E1) of the water-stripping column (07), the low-acid water (123) from the overhead of the acid recovery unit's acid distillation column (14) enters from the top of the water-stripping column (07), the water-stripping column (07) kettle outflow enters the upper layer of the steam-stripping column (10), 0.4 MPa water vapor (116) enters the kettle of the steam-stripping column (10), the low-acid water (124) from the overhead of the acid recovery unit's acid distillation column (14) enters from the top of the steam-stripping column (10), the kettle obtains the high-carbon alcohol methacrylate ester containing a small amount of acid (low-acid ester) (111) which enters the hot extraction unit, the acid-containing gas (113) from the overhead of the water-stripping column (07) and the acid-containing gas (117) from the overhead of the steam-stripping column (10) are mixed (mixed acid-containing gas 118) and then enter the acid recovery unit after being partially cooled (high-acid water (119)) by the condenser (11);

[0186] Hot extraction unit: the low-acid ester (111) from the deacidification unit enters the bottom of the hot extraction column (06), the slightly-acidic water (107) from the bottom of the alcohol extraction column (19) is heated to 75°C by the heater (20) and then enters the top of the hot extraction column (06), the polymerization inhibitor and catalyst methanesulfonic acid in the low-acid ester (111) are extracted, the hot extraction column's kettle bottom material (112) returns to the esterification reaction kettle (01a), and the ester product (120) at the top of the hot extraction column (06) enters the washing unit;

[0187] Acid recovery unit: the high-acid water (119) from the deacidification unit is pumped (stream (121)) by the pump (12) to the acid refining column (14) of the acid recovery unit, high-purity methacrylic acid (125) is obtained at the bottom to return to the reaction kettle (01a) for continuous reaction, and the azeotrope (146) of methacrylic acid-water (with a mass content of 15% of methacrylic acid) is obtained at the top, which is cooled by the condenser (15), part of which is refluxed to the acid refining column (14), and the other part (145) enters the top of the alcohol extraction column (19) together with the stream (129) from the dehydration column (02); the lauryl alcohol (103) used in the reaction enters the bottom of the alcohol extraction column (19), absorbs the methacrylic acid therein, and returns to the esterification reaction kettle (01a) for continuous reaction (indicated by stream (104)), and the slightly-acidic water at the bottom is partially (107) introduced into the hot extraction column (06) for extracting the polymerization inhibitor and catalyst in the low-acid ester, and part of the slightly-acidic water (126) is discharged as waste acid water;

[0188] Washing unit: the slightly-acidic ester product (120) from the hot extraction unit successively enters the alkali column (21) and the water column (22), and the neutral ester product (131) is obtained by using the neutralization of alkali to remove the methacrylic acid in the product and using water washing;

[0189] The neutral ester product (131) from the washing unit enters the decolorization kettle (28a / b) to remove the esterification by-products, and the qualified high carbon methacrylate ester product (134) is discharged after filtration by the filter (29).

[0190] Table 3 Material balance of the reaction system of Example 2

[0191]

[0192] Table 4 Structural parameters of the reactor

[0193]

[0194] Comparative Example 1

[0195] The process of the comparative example is as shown in Figure 6 wherein the esterification reaction of methacrylic acid and high carbon alcohol is completed in a batch operation mode, and the esterification reaction process and the dehydration process are the same as the esterification reaction unit and the dehydration unit of Example 2.

[0196] After the reaction is completed, the reaction product (110) (containing excess unreacted methacrylic acid) in the esterification kettle (01) is discharged by pump (04) to the neutralization kettle (32), and under the action of excess lye (140), it is stirred for 1-2 h, and after standing for 1 h, it is separated into layers, and the lower layer of waste lye is discharged. Continue to add water (130) to the neutralization kettle (32), stir for 1-2 h, and after standing for 1 h, separate into layers, and the lower layer of waste water is discharged; repeat this water washing step 3 times until the oil phase ester pH is about 7. The neutral ester (320) in the neutralization kettle (32) is introduced into the decolorization kettle (28) by pump (04), powdered alumina clay is added, and after stirring for 1-2 h, continuous stirring is continued, and the solid-liquid mixture is continuously pumped to the filter (29) for filtration to obtain the qualified ester product (134).

[0197] The comparison of raw materials, products, etc. of Example 1, Example 2 and Comparative Example 1 is summarized in Tables 5-6.

[0198] Table 5 Comparison of raw materials and products used in Example 1, Example 2 and Comparative Example 1

[0199] Example 1 Example 2 Comparative Example 1 Feed acid: alcohol molar ratio 1.05 1.5 1.5 High carbon alcohol conversion, % 99.5 92.1 92.1 High carbon methacrylate ester yield, % 98.9 96 96

[0200] Table 6 Comparison of consumption amounts of Example 1, Example 2 and Comparative Example 1

[0201] Comparison to ester product Example 1 Example 2 Comparative Example 1 Caustic (vol) 0.1 0.15 0.9 Desalting water (vol) 0.3 0.33 0.9 Waste water discharge (vol) 0.45 0.53 2.1 Polymerization inhibitor (mass) 0.012 0.018 0.017 Catalyst consumption (mass) 0.05 0.08 0.17

[0202] It can be seen from the results that compared with Comparative Example 1, although the number of equipment is increased in Examples 1 and 2, there are the following advantages:

[0203] 1) The conversion rate of esterification reaction is improved: the conversion rate of high carbon alcohol in Comparative Example 1 is 92.1%, and the conversion rate of high carbon alcohol in Example 1 is 99.5%;

[0204] 2) The emission of three wastes is significantly reduced: compared with Comparative Example 1, the total wastewater emission of Example 1 is reduced by 79%, which is only about 21%; the total wastewater emission of Example 2, which is also a batch reaction, is reduced by 75%, which is only about 25%;

[0205] 3) The consumption of chemicals is reduced: compared with Comparative Example 1, the consumption of catalyst in Example 1 is saved by 70%, and the consumption of polymerization inhibitor is saved by 29%;

[0206] 4) The loss of raw materials is reduced: compared with Comparative Example 1, the loss of methacrylic acid in Example 1 is saved by 30%;

[0207] 5) The yield of product is improved: the yield of product in Comparative Example 1 is 96%, and the yield of product in Example 1 is 98.9% respectively;

[0208] 6) The continuous production of high carbon ester of methacrylic acid is realized in Example 1.

[0209] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting" and "connecting" should be interpreted broadly. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0210] The above describes the present application in combination with the preferred embodiments, but these embodiments are only exemplary and serve only to illustrate. On this basis, various substitutions and improvements can be made to the present application, which all fall within the scope of protection of the present application.

Claims

1. A method for producing a methyl acrylate high carbon alcohol ester, comprising: carrying out an esterification reaction of a methyl acrylate raw material and a high carbon alcohol raw material in a reaction unit to obtain a methyl acrylate high carbon alcohol ester product, the esterification reaction being achieved by continuous reaction operation using a continuous multi-stage esterification reaction scheme; carrying out a deacidification treatment of the methyl acrylate high carbon alcohol ester product to obtain a deacidification treated methyl acrylate high carbon alcohol ester material and a methyl acrylate-water containing mixture material, the deacidification treatment comprising: treating the deacidification treated methyl acrylate high carbon alcohol ester material with water to obtain a water extracted methyl acrylate high carbon alcohol ester material and treating the water extracted methyl acrylate high carbon alcohol ester material with steam to obtain the deacidification treated methyl acrylate high carbon alcohol ester material, wherein the temperature of the steam treatment is 60-130℃, the content of methyl acrylate in the deacidification treated methyl acrylate high carbon alcohol ester material is 2-14%, based on the total weight of the deacidification treated methyl acrylate high carbon alcohol ester material; carrying out a hot extraction of the deacidification treated methyl acrylate high carbon alcohol ester material with extraction water in a hot extraction unit to obtain a hot extraction treated methyl acrylate high carbon alcohol ester material, the hot extraction unit having a hot extraction column operating temperature of 50-95℃, a column top pressure of 101-150 kPa, an extraction water temperature of 50-95℃, a mass flow ratio of extraction water to the deacidification treated methyl acrylate high carbon alcohol ester material of 0.08-2:1, and a mass fraction of methyl acrylate in the hot extraction column top discharge of the hot extraction treated methyl acrylate high carbon alcohol ester material of 0.05-1.5%, based on the total weight of the hot extraction treated methyl acrylate high carbon alcohol ester material; carrying out a decolorization treatment of the hot extraction treated methyl acrylate high carbon alcohol ester material to obtain a product methyl acrylate high carbon alcohol ester; carrying out an acid recovery treatment of the methyl acrylate-water containing mixture material to obtain a recovered material and an acid water containing material, the acid recovery treatment comprising: rectifying the methyl acrylate-water containing mixture material in an acid refining column, wherein the acid refining column has an operating pressure of 1-80 kPa, a column top temperature of 25-65℃, a column bottom temperature of 80-130℃, and a column top operating reflux ratio of 0.1-5; the mass fraction of methyl acrylate in the acid refining column top material is 0.5-15%, based on the total weight of the acid refining column top material; and the mass fraction of the acid refining column bottom material is 90-99.8%, based on the total weight of the acid refining column bottom material; extracting the acid refining column top material with a high carbon alcohol material in an alcohol extraction column to obtain the recovered material and the acid water containing material, wherein the feed mass ratio of the high carbon alcohol material to the column top material circulating methyl acrylate is 0.1-5:1, and the operating pressure is 101-300 kPa; the mass fraction of methyl acrylate in the acid water containing material is 0.01-0.5%, based on the acid water containing material; returning the recovered material to the reaction unit to be used as part of the methyl acrylate raw material for the esterification reaction.

2. The method of claim 1, wherein, The inhibitor mass fraction in the heat-extracted methyl acrylate material discharged from the top of the heat-extraction column is 0.01-0.2%, and the liquid acid catalyst mass fraction is 0.03-1.5%, based on the total weight of the heat-extracted methyl acrylate material.

3. The method of claim 1, wherein, The acid-containing water material is fed into the heat-extraction unit as extraction water of the heat-extraction unit.

4. The method of claim 1, wherein, The method further comprises a washing treatment before the decoloring treatment, and the washing treatment comprises: a water washing step of washing the heat-extracted methyl acrylate material with desalted water, wherein the mass flow ratio of the desalted water to the heat-extracted methyl acrylate material is 0.1-1:1, the pH value of the neutral ester material after washing is 6.5-7.5, the water washing process is operated at a temperature of 40-60°C and a pressure of 101-300 kPa.

5. The method of claim 1, wherein, The method further comprises a washing treatment before the decoloring treatment, and the washing treatment comprises: an alkali washing step of washing the heat-extracted methyl acrylate material with alkali liquor, wherein the alkali mass fraction in the alkali liquor is 0.1-10%, the mass flow ratio of the alkali liquor to the heat-extracted methyl acrylate material is 0.1-1:1, the pH value of the basic ester discharged is 7.5-11, the alkali washing is operated at a temperature of 40-60°C and a pressure of 101-300 kPa; a water washing step of washing the basic ester discharged with desalted water, wherein the mass flow ratio of the desalted water to the basic ester is 0.1-1:1, the pH value of the neutral ester material after washing is 6.5-7.5, the water washing process is operated at a temperature of 40-60°C and a pressure of 101-300 kPa.

6. An apparatus for producing methyl acrylate, comprising: a reaction system for performing esterification reaction of methyl acrylate raw material and high carbon alcohol raw material in an esterification reaction unit to obtain methyl acrylate product; the reaction system comprises a reaction unit and a dehydration unit, and the reaction unit comprises multiple esterification reactors connected in series; an acid removal unit for performing acid removal treatment on the methyl acrylate product to obtain acid-removed methyl acrylate material and a mixture containing methyl acrylate and water; the acid removal unit comprises a water-stripping column, wherein the discharge port of the reaction system is connected to the upper feed port of the water-stripping column, so that the methyl acrylate product enters the water-stripping column; the column still of the water-stripping column is connected to the discharge port of the dehydration unit of the reaction system, so that at least part of the acid water discharged from the reaction system enters the water-stripping column; a steam-stripping column, wherein the upper liquid phase feed port of the steam-stripping column is connected to the column still discharge port of the water-stripping column, so that at least part of the water-stripping column still material enters the steam-stripping column; and a steam inlet is arranged at the bottom of the steam-stripping column for introducing steam into the steam-stripping column; An acid recovery unit for processing a mixture containing methacrylic acid and water to obtain a recovered material and an acid-containing water material; wherein the recovered material outlet of the acid recovery unit is connected to the reaction unit feed inlet of the reaction system, so that the recovered material returns to the reaction unit of the reaction system; The acid recovery unit comprises an acid refining column, the feed inlet of the acid refining column is connected to the overhead outlet of the water-stripping column and the overhead outlet of the steam-stripping column, so that the overhead material from the water-stripping column and the overhead material from the steam-stripping column enter the acid refining column; the column bottom outlet of the acid refining column is connected to the reaction unit feed inlet of the reaction system, so that the column bottom material of the acid refining column returns to the reaction unit of the reaction system; an alcohol extraction column, the upper feed inlet of the alcohol extraction column is connected to the overhead outlet of the acid refining column, so that the overhead material of the acid refining column enters the alcohol extraction column; the alcohol extraction column is provided with a bottom high carbon alcohol material feed inlet for feeding high carbon alcohol material; the overhead outlet of the alcohol extraction column is connected to the reaction unit feed inlet of the reaction system, so that the overhead material of the alcohol extraction column returns to the reaction unit of the reaction system; wherein the operating pressure of the acid refining column is 1-80 kPa, the overhead temperature is 25-65℃, the column bottom temperature is 80-130℃, the overhead operating reflux ratio is 0.1-5, the mass fraction of methacrylic acid in the overhead material is 0.5-15%, and the mass fraction of methacrylic acid in the column bottom material is 90-99.8%; the operating pressure of the alcohol extraction column is 101-300 kPa, the mass ratio of the high carbon alcohol material to the overhead material of the acid refining column is 0.1-5:1, and the mass fraction of methacrylic acid in the bottom material is 0.01-0.5%; A hot extraction unit for hot extraction of the deacidified methacrylic acid high carbon alcohol ester material with extraction water in the hot extraction unit to obtain a hot extraction treated methacrylic acid high carbon alcohol ester material, wherein the operating temperature of the hot extraction column in the hot extraction unit is 50-95℃, the overhead pressure is 101-150 kPa, the extraction water temperature is 50-95℃, and the mass flow ratio of the extraction water to the deacidified methacrylic acid high carbon alcohol ester material is 0.08-2:1; the hot extraction unit comprises a hot extraction column, the lower feed inlet of the hot extraction column is connected to the column bottom outlet of the steam-stripping column, so that the column bottom material of the steam-stripping column enters the hot extraction column; the column bottom outlet of the hot extraction column is connected to the reaction unit of the reaction system, so that the column bottom material of the hot extraction column returns to the reaction unit; A decolorization unit for decolorization treatment of the hot extraction treated methacrylic acid high carbon alcohol ester material in the decolorization unit to obtain a product methacrylic acid high carbon alcohol ester.

7. The apparatus of claim 6, wherein, The overhead outlet of the acid refining column is also connected to the top feed inlet of the water-stripping column and / or the top feed inlet of the steam-stripping column, so that the overhead material of the acid refining column enters the water-stripping column and / or the steam-stripping column.

8. The apparatus of claim 6, wherein, The upper inlet of the hot extraction column is also connected with the outlet of the alcohol extraction column, so that the column material of the alcohol extraction column enters the hot extraction column as extraction water.

9. The apparatus of claim 6, wherein, A washing unit is further included for washing the hot-extracted high-carbon alcohol methacrylate material in the washing unit to obtain a washed ester material. The washing unit includes: A water washing unit, the inlet of which is connected with the overhead outlet of the hot extraction column, so that the overhead material of the hot extraction column enters the water washing unit for water washing.

10. The apparatus of claim 6, wherein, A washing unit is further included for washing the hot-extracted high-carbon alcohol methacrylate material in the washing unit to obtain a washed ester material. The washing unit includes: An alkali washing unit, the inlet of which is connected with the overhead outlet of the hot extraction column, so that the overhead material of the hot extraction column enters the alkali washing unit for alkali washing; A water washing unit, the inlet of which is connected with the outlet of the alkali washing unit, so that the material of the alkali washing unit enters the water washing unit for water washing.

11. The apparatus of claim 6, wherein, The device further includes a vacuum system, which includes: A vacuum pump for generating vacuum in the equipment requiring vacuum in the device; A tail gas absorption tower, the vacuum pump being connected with the tail gas absorption tower for absorbing the tail gas from the vacuum pump.

12. The apparatus of claim 6, wherein, The reaction system includes: A dehydration unit for removing water generated in the esterification reaction of methacrylic acid and high-carbon alcohol; the dehydration unit includes one or more inlets; N-stage esterification reactors for continuously esterifying excess methacrylic acid and high-carbon alcohol, wherein N is an integer and N≥2; the N-stage esterification reactors are connected in series, so that the reaction material of the i-th stage esterification reactor can enter the i+1-th stage esterification reactor, i being an integer from 1 to N-1; the N-th stage esterification reactor is provided with a product discharge outlet for discharging high-carbon alcohol methacrylate product; The top of each of the N-stage esterification reactors is connected with an inlet of the dehydration unit, so that part of the material of the N-stage esterification reactors enters the dehydration unit for dehydration; one outlet of the dehydration unit is connected with one inlet of the first stage esterification reactor, so that the dehydrated material from the dehydration unit enters the first stage esterification reactor; The M-th to N-th stage esterification reactors are each provided with an external heater connected with the respective esterification reactor, so that part of the reaction material in the M-th to N-th stage esterification reactors returns to the M-th to N-th stage esterification reactors after being heated by the respective external heater, wherein M is an integer less than or equal to N.

13. The apparatus of claim 12, wherein, The first stage esterification reactor is not provided with an external heater connected with the first stage esterification reactor.

14. The apparatus of claim 12, wherein, The top of at least one of the M-th to N-th stage esterification reactors is provided with a reinforced distribution element, so that the reaction material heated by the external heater circulates back to the esterification reactor provided with the reinforced distribution element after passing through the reinforced distribution element.

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