Method and device for preparing and separating tert-butyl acetate

Abstract

The invention relates to a method and a device for preparing and separating tert-butyl acetate, in particular to a method for separating tert-butyl acetate from a reaction product of preparing tert-butyl acetate by taking isobutene and acetic acid as raw materials, which comprises the following steps: (C) removing light components; (D) acetic acid removal: adopting reduced pressure rectification in an acetic acid removal tower, controlling the tower top temperature at 45-70 DEG C under the vacuum degree of 20-70 KPa according to an absolute pressure meter; (E) ester refining; (F) alcohol recovery. In the method, the deacidification tower adopts vacuum rectification, so that the adverse effect of tower pressure fluctuation caused by C4 content increase due to falling ester decomposition of the tower kettle of the deacidification tower in the actual production process is avoided, the loss of tert-butyl acetate is reduced, the separation effect of acetic acid and tert-butyl acetate is improved, and the purity and yield of crude ester are improved.

Description

Technical Field

[0001] The present invention relates to a method and a device for preparing and separating tert-butyl acetate, in particular to a method and a device for separating tert-butyl acetate from a reaction product of preparing tert-butyl acetate with isobutylene and acetic acid as raw materials. Background Art

[0002] Tert-butyl acetate, also known as tert-butyl acetate, has a molecular formula of CH3COOC(CH3)3 and a molecular weight of 116.16. It is one of the four isomers of butyl acetate. The chemical structure is as follows: .

[0003] It is a colorless, transparent liquid with a fruity aroma. It can be mixed with alcohol and ether, soluble in acetic acid, and almost insoluble in water (the solubility range in water at 23°C is 0.8%). Its physical and chemical properties are as follows: Relative density at 20°C 0.8665kg / m 3 , boiling point 97.8℃, melting point -62℃, flash point (closed loop) 40℃, saturated vapor pressure at 25℃ 6.3MPa, critical pressure 3.17MPa, autoignition temperature 518℃.

[0004] Tert-butyl acetate is a low-toxic, environmentally friendly solvent for polyurethane, which can significantly reduce the atmospheric photochemical reactivity and volatility of the target product at room temperature, thereby effectively preventing some harmful substances from entering the atmosphere and polluting the environment. Therefore, tert-butyl acetate solvent can become a substitute for a variety of volatile organic compounds and harmful air substances, such as toluene, xylene, esters, ketones and hydrocarbons. It can also be used in medicine, coatings, paints, industrial cleaners, etc.

[0005] The traditional method for producing tert-butyl acetate is to use acetic acid and tert-butyl alcohol as raw materials, widely use concentrated sulfuric acid as catalyst, the amount of acid is slightly higher than the stoichiometric ratio, in an intermittent or continuous reactor, maintain a specific reaction temperature, and the ratio of acid to alcohol is also determined. Under such conditions, a mixed system with relatively complex components can be obtained. Since this method not only seriously corrodes the equipment, the mixture after the reaction is difficult to separate, and the discarded concentrated sulfuric acid may even cause environmental pollution, it is not suitable for modern large-scale continuous production and does not meet environmental protection requirements.

[0006] In view of the shortcomings of traditional processes, catalytic continuous methods have been adopted in industrial production to replace traditional intermittent production processes to produce acetate products. The main equipment used is a fixed bed reactor. The tubular fixed bed reactor is filled with solid catalysts to provide a good reaction site for liquid-solid and gas-solid phase catalytic reactions. The present invention uses isobutylene produced by petrochemical enterprises as a raw material, adopts a tubular fixed bed filled with a strong acid ion exchange resin catalyst as a reactor, and synthesizes tert-butyl acetate by a method of direct esterification of acetic acid and isobutylene.

[0007] The earliest research on the synthesis of acetate from acetic acid and olefins was reported by Dorris TB et al. in 1934. They used BF3 as a catalyst to react acetic acid and propylene at 70°C and 0.03 MPa to obtain isopropyl acetate. In 1946, Altschul studied the acid-catalyzed process of acetic acid and isobutylene. Therefore, the acid / olefin method has become the main method for producing tert-butyl acetate.

[0008] There are relatively few research reports on the separation and purification of the tert-butyl acetate mixture after the reaction. Shi Huahui et al. from Nanjing University of Technology used Aspen Plus to study the distillation separation process in the document "Distillation Separation Process of Acid Esterification Synthesis of Tert-Butyl Acetate", and proposed a two-tower distillation separation process of deacidification followed by purification. According to the simulation results, the mass fraction of acetic acid at the bottom of the deacidification tower is 99.86%, and the top of the tower basically does not contain acetic acid. The mass fraction of tert-butyl acetate at the bottom of the purification tower is 99.53%, and the mass fraction of tert-butyl acetate at the top of the tower is 2.0%. The simulation data in this document is too idealized, and does not take into account the separation of unreacted isobutylene and the recovery of tert-butyl alcohol as an inhibitor. In addition, there are problems of decomposition of tert-butyl ester and azeotropic coexistence of ester, alcohol, and isobutylene dimer in the separation process, which increase the difficulty of separation and purification.

[0009] Hunan Changling Petrochemical Technology Development Co., Ltd. mentioned in patent CN1884248A a method for preparing and purifying tert-butyl acetate, which adopts a two-tower separation process, wherein the crude ester is deacidified at 85-100°C, dehydrocarbonized at 70-85°C, and dealcoholized at 78-90°C, and finally distilled at 90-100°C to obtain the tert-butyl acetate product. It is very difficult to complete the separation of deacidification, dehydrocarbonization, dealcoholization and other components in one distillation tower through continuous operation, which is not suitable for industrial operation.

[0010] The existing production process of tert-butyl acetate is as follows: isobutylene and acetic acid are used as raw materials, which are mixed with the polymerization inhibitor tert-butyl alcohol and then enter a fixed bed reactor to generate tert-butyl acetate, and the material at the outlet of the reactor enters a dehydrogenation component tower; the unreacted isobutylene at the top of the light component removal tower is recycled into the reactor, and the materials with higher boiling points in the bottom reaction materials (including acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol, water, etc.) enter the deacetylating tower; the material coming out of the top of the deacidification tower enters the tert-butyl acetate refining tower, and the circulating acetic acid in the side line below the tower is returned to the reaction part, and then used as a reaction raw material together with fresh acetic acid; tert-butyl acetate is produced from the side line of the refining tower, and the material at the top of the tower enters the alcohol recovery tower; tert-butyl alcohol is produced from the side line of the alcohol recovery tower, and mixed esters are discharged from the bottom of the tower.

[0011] During the production process, the deacidification tower is operated at normal pressure to separate acetic acid and tert-butyl acetate, with a top temperature of 71-75°C, a bottom temperature of 120-125°C, and a lower side line temperature of 118-120°C. During operation, it was found that a small amount of tert-butyl acetate (1-5%) in the bottom of the tower was accelerated to decompose into isobutylene under acidic and high temperature conditions, and part of the isobutylene was further polymerized to form 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene. The accumulation of isobutylene gas phase production will cause the deacidification tower pressure to increase by 20-30Kpa and the bottom pressure to increase by 15-40Kpa. As the tower pressure increases, the bottom temperature further increases, and the increase in the bottom temperature leads to the intensified decomposition of tert-butyl acetate. As time goes by and esters accumulate in the bottom of the tower, the decomposition of tert-butyl acetate will intensify, the content of C4 and C8 will increase, making the operation of the deacidification tower unstable, and also consuming the generated tert-butyl acetate, reducing the separation yield of tert-butyl acetate. In addition, the increase in the content of C4 oligomers will have an adverse effect on the subsequent separation and recovery of tert-butyl acetate.

[0012] In order to control the decomposition and keep the tower pressure stable, the common operation is to increase the tower bottom temperature to prevent tert-butyl acetate from falling. However, increasing the tower bottom temperature increases energy consumption (steam consumption) on the one hand, and excessive temperature increase will cause the top material to carry acetic acid. Acetic acid entering the subsequent separation tower will aggravate the corrosion of the tower, thereby increasing the investment in anti-corrosion equipment. It can be seen that this operation adjustment does not solve the substantive problem of separating tert-butyl acetate and acetic acid, and brings new problems of high energy consumption and new equipment investment.

[0013] On the other hand, the top material of the deacidification tower is crude tert-butyl acetate containing tert-butyl acetate, tert-butyl alcohol, C8, and water. The tert-butyl acetate content in the top reflux tank is 50-60%, and the rest is tert-butyl alcohol and isobutylene dimer C8. The material enters the next ester refining tower for further purification. However, the top temperature range of the deacidification tower (top temperature 70-75°C, boiling point of tert-butyl acetate 98°C) is not the enrichment area of ​​tert-butyl acetate, and there are many other impurities and by-products mixed in. The purity of tert-butyl acetate in this stock is low, which increases the difficulty of separation entering the tert-butyl ester refining tower.

[0014] The process route of tert-butyl acetate is to use acetic acid and isobutylene as raw materials, strong acid ion exchange resin as catalyst, and adopt a tubular fixed bed reactor to directly synthesize tert-butyl acetate in one step by addition esterification. The main reaction of acetic acid and isobutylene is to produce tert-butyl acetate, and the reaction temperature is 15~30℃. The concentration of isobutylene in this system reaches 99.9%, which is very active and prone to self-polymerization. In order to minimize the formation of oligomers, a certain amount of inhibitor tert-butyl alcohol is added to acetic acid, and the alcohol content is controlled at 8-10%w / 乙酸w, and the molar acid-olefin ratio is not less than 4:1. The reaction pressure is controlled at 1.0MPa to ensure the isobutylene liquid phase state. The subsequent separation process is to first remove the unreacted isobutylene and other light components by flash evaporation, and then enter the deacetylating tower to extract the light components such as tert-butyl ester and tert-butyl alcohol from the top of the tower and enter the tert-butyl ester refining tower, and extract the circulating acetic acid from the side line under the tower kettle to return to the reactor to participate in the reaction, and extract high-purity tert-butyl acetate from the side line of the material entering the ester refining tower, and the top material enters the tert-butyl alcohol recovery tower to separate the by-products such as dimerized olefins, and then the tert-butyl alcohol is recycled as an inhibitor.

[0015] During the production process, it was found that a small amount of tert-butyl ester in the bottom of the deacidification tower was rapidly decomposed into isobutylene under acidic and high temperature conditions during the separation of acetic acid in the deacidification tower. Part of the isobutylene was further polymerized to form 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene. The accumulation of isobutylene gas phase production will cause the deacidification tower pressure to increase, and the tower pressure increase will further lead to the tower bottom temperature increase, which in turn leads to the intensified decomposition of tert-butyl ester. In order to avoid such a vicious circle and ensure the smooth operation of the deacidification tower, it is necessary to consider how to improve the separation effect of tert-butyl ester and acetic acid, slow down the decomposition of a small amount of tert-butyl acetate in the bottom of the tower, and reduce the generation of isobutylene and C8 by-products. Summary of the invention

[0016] The inventors of the present application have found through in-depth research that at a temperature of 120°C, acid-free tert-butyl acetate with a purity of more than 99% is stable and does not decompose. After heating a mixed solution containing tert-butyl acetate-tert-butyl alcohol-acetic acid for one hour, tert-butyl alcohol decomposes slightly and tert-butyl ester decomposes a small amount (decomposition rate 2-5%). As time goes by, the decomposition rate of tert-butyl alcohol slowly increases to 2%, and the decomposition rate of tert-butyl ester is 8%. At 100°C, tert-butyl alcohol and tert-butyl acetate basically do not decompose under acidic conditions.

[0017] The operation of the deacidification tower was investigated by vacuum distillation. The changes in the boiling point and azeotropic composition of the tower top material under different vacuum pressures are as follows: Table 1: Boiling points of various substances under different vacuum pressure conditions

[0018] Table 2: Main azeotropic compositions under different vacuum pressure conditions

[0019] Therefore, in order to avoid the decomposition of ester in the bottom of the deacidification tower, reduce the loss of tert-butyl acetate, improve the separation effect of acetic acid and tert-butyl acetate, and improve the purity and yield of crude ester, an optimized process of vacuum distillation and extraction of high-purity tert-butyl acetate in the tert-butyl acetate enrichment tray area on the upper side of the tower is adopted.

[0020] According to a first aspect of the present invention, there is provided a method for separating tert-butyl acetate from a reaction product of preparing tert-butyl acetate from isobutylene and acetic acid, the method comprising the following steps: (C) Removal of light components: The reaction product enters a light component removal tower, and light components including unreacted isobutylene with a relatively low boiling point (usually a boiling point below -5°C) are removed (at the top of the tower); (D) Deacetic acid removal: The mixture of acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol and water (i.e., materials with a higher boiling point) obtained at the bottom of the light component removal tower is sent to a deacetic acid removal tower for separation, and acetic acid is discharged from the bottom of the tower. The deacetic acid removal tower adopts vacuum distillation with a vacuum degree of 20-70 KPa. The tower top temperature is controlled at 45-70°C according to the absolute pressure gauge; (E) Ester refining: crude tert-butyl acetate containing a small amount of alcohol and a trace amount of C8 hydrocarbons is extracted from the upper side of the deacetylating tower and enters a tert-butyl acetate refining tower for refining. Preferably, the crude tert-butyl acetate is preheated (e.g., to 75-85° C., e.g., 80° C.) and then enters a tert-butyl acetate refining tower for refining. Tert-butyl acetate with a higher boiling point (generally with a purity of 99.5%-99.8%) is extracted from the side line of the tert-butyl acetate refining tower; (F) Alcohol recovery: The materials including tert-butyl alcohol, C8 olefins (mainly 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene), tert-butyl acetate and water from the top reflux tank of the deacidification tower and the ester refining tower enter the alcohol recovery tower to recover alcohol. The azeotrope formed by tert-butyl alcohol, C8 and water is extracted from the top of the tower, and tert-butyl alcohol is extracted from the side line.

[0021] The reaction product here is the reaction product of preparing tert-butyl acetate with isobutylene and acetic acid as raw materials, mainly comprising tert-butyl acetate, unreacted isobutylene, acetic acid, tert-butanol, C8 hydrocarbons and water, for example, tert-butyl acetate 33.0±5.0wt%, tert-butanol 7.5±2.0wt%, acetic acid 57.0±5.0wt%, C8 0.4±1.0wt%, isobutylene 0.8±1.0wt%, and water 0.2±0.5wt%.

[0022] Preferably, in step (C), the operating conditions of the light component removal tower are: atmospheric pressure operation, tower top temperature 0±6°C, preferably 0±4°C or 0±3°C, tower bottom temperature 105±5°C, preferably 105±3°C, and further preferably 105±1°C.

[0023] Preferably, in step (C), the unreacted isobutylene with a lower boiling point is vaporized by its own heat, rises to the top of the tower through step-by-step contact, condenses in the top condenser, enters the top reflux tank of the light component removal tower, separates C4 (isobutylene), and then returns to continue the cycle to participate in the reaction.

[0024] Preferably, the deacetylating tower in step (D) is a packed tower, the number of theoretical plates of the deacetylating tower is 20-30, the feed position is between the 10th and 17th plates, the reflux ratio is between 3-10, the upper side line crude ester extraction position is between the 3rd and 10th plates, the purity of tert-butyl acetate is 95%-98%, the yield can reach more than 96%, the acetic acid content in the bottom of the tower is 98-99.5%, and the yield can reach more than 97%. After the unreacted isobutylene C4 raw material is separated out by the light component removal tower, the materials with higher boiling points (including acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol, water, etc.) enter the deacetylating tower, and the materials after the reaction enter the deacetylating tower, and vacuum distillation is adopted, and the vacuum degree (absolute pressure) is 20-70KPa, preferably 25-65KPa or 30-60KPa, further 40-50KPa, for example 55KPa, the tower top temperature is controlled at 45-70°C, preferably 42-68°C, 50-65°C, 52-62°C, and the reflux ratio is 3-10:1, preferably 5-9:1 or further 6-8:1, and tert-butyl alcohol is used to azeotrope with C8 and water (the azeotropic point is lower than the boiling point of tert-butyl acetate under the corresponding negative pressure) to bring C8, water and other by-products to the top of the tower, and extract them from the top of the tower, After cooling, the material enters the reflux tank, part of the material is refluxed, and the other part enters the alcohol recovery tower; the temperature of the upper side is controlled at 60-85°C, preferably 65-80°C or further 70-75°C, which is the tert-butyl acetate content enrichment area. This stream of material mainly contains tert-butyl acetate (purity 95-98%), and only contains a small amount of tert-butyl alcohol and C8, which improves the separation efficiency of the subsequent ester refining tower; the temperature of the deacetylating tower bottom is controlled at 80-100°C, preferably 85-95°C, even if there is an adjustment fluctuation, a small amount of tert-butyl acetate falls into the bottom of the tower, the decomposition of tert-butyl acetate can be effectively avoided, and the ester decomposition and carbon four (such as isobutylene) accumulation will not cause the tower pressure to increase, giving the operator enough time to optimize and adjust to separate the tert-butyl acetate falling from the bottom of the tower. Acetic acid (purity 98.0-99.5%, called circulating acetic acid) is extracted from the lower side line, filtered through the circulating acetic acid filter and then enters the circulating acetic acid cooler, then returns to the acetic acid feed line after passing through the desalting tank, and then is used as a reaction raw material together with fresh acetic acid.

[0025] Preferably, in step (E), the tert-butyl acetate refining tower is operated at normal pressure, and the light components including tert-butyl alcohol are condensed in the top condenser of the tert-butyl acetate refining tower and then enter the reflux tank; a part of the material returns to the top of the tower for reflux, and the other part enters the alcohol recovery tower for alcohol recovery.

[0026] Preferably, in step (E), the top temperature of the tert-butyl acetate refining tower is 80±5°C, preferably 80±3°C or further 80±1°C, the bottom temperature is 97±5°C, preferably 97±3°C or further 97±2°C, the reflux ratio is 1:0.5-2, preferably 1:0.8-1.2, further about 1:1, the azeotropic mixture of tert-butyl alcohol, C8 hydrocarbons, tert-butyl acetate and the like enters the reflux tank after condensation in the top condenser, a part of the material returns to the top of the tower for reflux, and the other part enters the alcohol recovery tower, and tert-butyl acetate (purity 99.89%) with a higher boiling point is extracted from the side line below the refining tower, and after cooling, enters the finished product intermediate tank.

[0027] Preferably, in step (F), the alcohol recovery tower is operated at normal pressure, the tower top temperature is 75±5°C, preferably 75±2°C or further 75±1°C, the side extraction temperature is 85±5°C, preferably 85±2°C or further 85±1°C, the tower bottom temperature is 95±5°C, preferably 95±2°C or further 95±1°C, the reflux ratio is 2-6:1, preferably 3-5:1, further about 4:1, the azeotrope formed by tert-butyl alcohol, C8 hydrocarbons and water is extracted from the tower top, condensed by the tower top cooler and enters the alcohol recovery tower reflux tank, part of the material coming out of the reflux tank is refluxed to the tower top, and the other part is sent to the mixing tank as a mixed material.

[0028] Preferably, in step (F), the tert-butyl alcohol (with a purity of generally 98% or more, especially 99% or more) withdrawn from the side line is cooled in a cooler and then returned to the reactor for preparing tert-butyl acetate using isobutylene and acetic acid as raw materials and recycled for use as a polymerization inhibitor.

[0029] According to a second aspect of the present invention, there is provided a method for preparing tert-butyl acetate using isobutylene and acetic acid as raw materials, the method comprising the following steps: (A) Desalination: Fresh acetic acid feedstock and circulating acetic acid from the side line of the deacidification tower are fed into a desalination tank, and the metal ions carried by them are adsorbed by ion exchange resin (to reduce the metal ions in the acetic acid feedstock to less than 5 ppm, preferably less than 2 ppm, more preferably less than 1 ppm), thereby preventing them from entering the esterification reactor, thereby achieving the purpose of protecting the catalyst; (B) Reaction: the recovered tert-butyl alcohol from the alcohol recovery tower and the appropriately supplemented fresh tert-butyl alcohol are mixed with the acetic acid after metal ion removal in a certain proportion (the total amount of the polymerization inhibitor tert-butyl alcohol added is, for example, 10±2wt% of the amount of acetic acid added), the fresh raw material isobutylene and the isobutylene separated by light component removal are mixed with the acetic acid and tert-butyl alcohol in an esterification reactor for reaction, preferably precooled to 0-20° C., preferably 1-15° C., more preferably 5-10° C., and filtered (the filter mesh size may be 80-150 mesh, and the purpose of filtering is to remove solid particle impurities) before entering the esterification reactor for reaction; (C) Removal of light components: The reaction product enters a light component removal tower to remove light components with a lower boiling point (usually a boiling point below -5°C) including unreacted isobutylene; (D) Deacetylating: The mixture of acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol and water (i.e., materials with a higher boiling point) obtained at the bottom of the light component removal tower is sent to a deacetylating tower for separation. The deacetylating tower adopts vacuum distillation with a vacuum degree of 20-70 KPa. The tower top temperature is controlled at 45-70°C according to the absolute pressure gauge. (E) Ester refining: crude tert-butyl ester containing a small amount of alcohol and a trace amount of C8 hydrocarbons is extracted from the upper side of the deacidification tower and enters the tert-butyl acetate refining tower for refining. Preferably, the crude tert-butyl acetate is preheated (for example, to 75-85° C.) and then enters the tert-butyl acetate refining tower for refining. Tert-butyl acetate with a higher boiling point (generally with a purity of 99.5%-99.8%) is extracted from the side line of the tert-butyl acetate refining tower; (F) Alcohol recovery: The materials including tert-butyl alcohol, C8 olefins (mainly 2,4,4-trimethyl-1-pentene, 2,4,4-trimethyl-2-pentene), water and tert-butyl acetate from the top reflux tank of the deacidification tower and the ester refining tower enter the alcohol recovery tower to recover alcohol. The azeotrope formed by tert-butyl alcohol, C8 and water is extracted from the top of the tower, and tert-butyl alcohol is extracted from the side line. The bottom of the alcohol recovery tower discharges a small amount of tert-butyl alcohol and tert-butyl acetate mixture.

[0030] The reaction conditions of step (B) are known conditions, for example, the temperature of the reactor is controlled to be 15° C., the reaction pressure is 1.0 MPa, the acid-olefin ratio is 4:1, and the reaction residence time is 60 min.

[0031] In step (B), the purpose of precooling is to reduce the temperature of the reaction materials entering the reactor to control it at a low temperature. Because the reaction is an exothermic reaction, if the reaction feed is not controlled at a low temperature, the reactor jacket chilled water will not remove the heat in time after the reaction, which will cause local overheating and aggravate the polymerization. The feed precooler can be used to control the feed temperature, reduce the generation of side reactions, and increase the selectivity of tert-butyl acetate to more than 98%.

[0032] The reaction conditions of steps (C) to (F) are the same as those of the above method for separating tert-butyl acetate, including the preferred process parameters.

[0033] The present invention further provides a device for preparing tert-butyl acetate, which comprises an acetic acid desalting tank, a filter, a precooler, an esterification reactor, a light component removal tower, an acetic acid removal tower, a product refining tower, and an alcohol recovery tower connected in sequence. The light component removal tower, the acetic acid removal tower, the product refining tower and the alcohol recovery tower each comprise a tower top condenser, a reflux tank, a tower bottom reboiler, a feed inlet, a tower top reflux and a tower bottom discharge port, and the acetic acid removal tower, the product refining tower and the alcohol recovery tower each have a tower side line discharge port, The acetic acid feed pipeline is connected to the acetic acid desalting tank, the isobutylene feed pipeline is connected to the dehydrator, the outlets of the acetic acid desalting tank and the dehydrator are connected to the filter, the precooler and the esterification reactor in sequence, and the outlet of the esterification reactor is connected to the light component removal tower. The bottom discharge port of the light component removal tower is connected to the feed port of the deacetylating tower through a pipeline; the top discharge port of the deacetylating tower is connected to the top reflux tank of the deacetylating tower through a pipeline, the discharge port of the top reflux tank of the deacetylating tower is connected to the feed port of the alcohol recovery tower through a pipeline, the bottom discharge port of the deacetylating tower is connected to the feed port of the desalting tank through the bottom discharge pipeline of the deacetylating tower, and the upper discharge port (upper side line) of the deacetylating tower is connected to the product refining tower through a pipeline, and a preheater (preferably preheated to between 75-85°C) is preferably provided on the pipeline to facilitate the crude tert-butyl acetate to enter the refining tower. After the tower is made, the alcohol, C8 and water azeotropes can be quickly separated to the top of the tower, thereby improving the separation effect of the tower); the top discharge port of the product refining tower is connected to the top reflux tank through a pipeline, the discharge port of the top reflux tank is connected to the feed port of the alcohol recovery tower through the product refining tower reflux tank outlet pipeline, and the product refining tower side line is connected to the product intermediate tank; the top discharge port of the alcohol recovery tower is connected to the top reflux tank through a pipeline, the discharge port of the top reflux tank is connected to the mixed material tank through the alcohol recovery tower reflux tank outlet pipeline, and the alcohol recovery tower side line is connected to the filter through the filter feed pipeline. The discharge pipeline of the alcohol recovery tower kettle can be connected to the mixed material tank.

[0034] The best existing technology for tert-butyl acetate uses isobutylene and acetic acid as raw materials, and produces tert-butyl acetate through raw material pretreatment, esterification reaction, deacidification, dehydrocarbonization, dealcoholization, distillation and other processes. In the production process, the deacidification tower is operated at normal pressure to separate acetic acid and tert-butyl ester, wherein the tower top temperature is 71-75°C, the tower bottom temperature is 120-125°C, and the lower side line temperature is 118-120°C. During the operation process, it is found that a small amount of tert-butyl ester in the tower bottom is accelerated to decompose and generate isobutylene under acidic and high temperature conditions, and part of the isobutylene is further polymerized to generate C8, etc. The accumulation of isobutylene gas phase production will cause the deacidification tower pressure to increase by 20-30Kpa, and the tower bottom pressure to increase by 15-40Kpa. As the tower pressure increases, the tower bottom temperature further increases, and the tower bottom temperature increases, which in turn leads to the intensified decomposition of tert-butyl acetate. As time goes by and esters accumulate in the bottom of the tower, the decomposition of tert-butyl ester will intensify, the content of C4 and C8 will increase, making the operation of the deacidification tower unstable, and also consuming the generated tert-butyl acetate, reducing the separation yield of tert-butyl acetate. In addition, the increase in the content of C4 oligomers will have an adverse effect on the subsequent separation and recovery of tert-butanol.

[0035] On the other hand, the top material of the deacidification tower is crude tert-butyl acetate containing tert-butyl acetate, tert-butyl alcohol, C8, and water. The tert-butyl acetate content in the top reflux tank is 50-60wt%, and the rest is tert-butyl alcohol (30-40wt%) and isobutylene dimer (8-15wt%). The material enters the next ester refining tower for further purification. However, the top temperature range of the deacidification tower (top temperature 70-75°C, boiling point of tert-butyl acetate 98°C) is not the enrichment area of ​​tert-butyl acetate, and there are many other impurities and by-products mixed in. The purity of tert-butyl ester in this stock is low, which increases the difficulty of separation into the tert-butyl ester refining tower.

[0036] In the present invention, the deacidification tower adopts vacuum distillation operation and adjusts the extraction position of tert-butyl acetate. By controlling the tower pressure and temperature, the decomposition of a small amount of tert-butyl acetate in the tower bottom and the polymerization of isobutylene are avoided. Tert-butyl acetate is extracted at the tert-butyl ester enrichment tray, so that the purity of tert-butyl acetate entering the refining tower is increased from 50.52wt% before the adjustment to 97.81wt%, and the carbon eight impurity content in the refining tower feed is reduced from 8.49wt% to 0.39wt%. On the one hand, it is avoided that more carbon eight and tert-butyl acetate co-azeotropy to the top of the distillation tower affects the separation effect, on the one hand, the C8 content in the side line extraction is reduced, and the product purity is improved. The purity of the side line product tert-butyl acetate under the product refining tower reaches 99.89%, and after calculation, the yield of tert-butyl acetate reaches 96.58%. The optimization adjustment of the deacetylating tower not only improves the purity of tert-butyl acetate collected from the upper side, but also improves the purity of acetic acid circulating in the bottom of the tower, from 97.04% before the adjustment to 99.66%, thus avoiding the mixing of tert-butyl ester, C8, etc. into the raw materials and affecting the reaction conversion rate.

[0037] On the other hand, due to the process adjustment and optimization of the deacidification tower, the side reaction of tert-butyl acetate caused by the separation process was avoided, and the selectivity of tert-butyl acetate reached 99.58%. The content of heavy substances such as C8 in the whole separation system was significantly reduced, and the C8 content in the tert-butyl alcohol and C8 mixture at the top of the deacidification tower and the refining tower was reduced from 15% before the transformation to 1.5%. When the material is recycled for tert-butyl alcohol, its separation purity and yield can be improved. The purity of tert-butyl alcohol can reach more than 99%, and the separation recovery rate can be calculated to be more than 98%.

[0038] Advantages of the present invention: 1. The deacidification tower adopts vacuum distillation to avoid the adverse effects of tower pressure fluctuation caused by the decomposition of ester in the deacidification tower bottom during actual production, which leads to an increase in carbon four content and reduces the loss of tert-butyl acetate, improves the separation effect of acetic acid and tert-butyl acetate, and improves the purity and yield of crude ester; 2. Change the process of extracting the ester-containing mixture from the top of the conventional tower and entering the refining tower to separate tert-butyl acetate. According to the azeotropic point and azeotropic composition under negative pressure operation conditions, high-purity tert-butyl acetate is extracted from the tert-butyl acetate enrichment tray area on the upper side of the tower, thereby improving the separation effect of tert-butyl acetate from acetic acid, C8, tert-butyl alcohol, etc. in the deacidification tower; 3. The deacidification tower described in this process is preferably a packed tower, the theoretical number of plates of the deacidification tower is 20-30, the feed position is between the 10th and 17th plates, the reflux ratio is between 3-10, and the upper side line crude ester extraction position is between the 3rd and 10th plates. The material enters the deacetic acid tower and adopts vacuum distillation, the vacuum degree (absolute pressure) is 20-70KPa, the tower top temperature is controlled at 45-70℃, the reflux ratio is 5-10:1, the upper side extraction temperature is controlled at 60-85℃, and the deacidification tower kettle temperature is 80-100℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the device for preparing tert-butyl acetate of the present invention.

[0040] Description of reference numerals: 1-fresh acetic acid feed; 2-acetic acid desalting tank; 3-raw material isobutylene; 4-dehydrator; 5-acetic acid after metal ion removal; 6-filter; 7-precooler; 8-esterification reactor; 9-light component removal tower feed pipeline; 10-reaction pressure control valve; 11-light component removal tower; 12-light component removal tower top outlet pipeline; 13-light component removal tower top condenser; 14-light component removal tower reflux tank; 15-light component removal tower top reflux; 16-isobutylene separated from light component removal; 17-reboiler at the bottom of the light component removal tower; 18-reflux pipeline at the bottom of the light component removal tower; 19-export pipeline at the bottom of the light component removal tower; 20-deacetic acid tower; 21-deacetic acid tower top outlet pipeline; 22-deacetic acid tower top condenser; 23-deacetic acid tower reflux tank; 24-deacetic acid tower top reflux; 25-deacetic acid tower reflux tank outlet pipeline; 26-deacetic acid tower upper side production pipeline; 27-deacetic acid tower bottom reboiler; 28-deacetic acid tower bottom reflux pipeline; 29-deacetic acid tower bottom discharge pipeline; 30-product refining tower; 31-product refining tower top outlet pipeline; 32-product refining tower top condenser; 33- Reflux tank of product refining tower; 34- product refining tower top reflux; 35- product refining tower reflux tank outlet pipeline; 36-alcohol recovery tower feed port; 37- product refining tower side line; 38- product refining tower bottom reboiler; 39- product refining tower bottom reflux pipeline; 40-alcohol recovery tower; 41-alcohol recovery tower kettle outlet pipeline; 42-alcohol recovery tower top outlet pipeline; 43-alcohol recovery tower top condenser; 44-alcohol recovery tower reflux tank; 45-alcohol recovery tower top reflux; 46-alcohol recovery tower reflux tank outlet pipeline; 47-alcohol recovery tower bottom reboiler; 48-alcohol recovery tower bottom reflux pipeline; 49-alcohol recovery tower side line; 50-supplemented fresh tert-butyl alcohol; 51-filter feed pipeline; 52-preheater. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to the accompanying drawings.

[0042] like Figure 1As shown, a device for preparing tert-butyl acetate comprises an acetic acid desalting tank 2, an esterification reactor 8, a light component removal tower 11, a deacetic acid removal tower 20, a product refining tower 30, and an alcohol recovery tower 40 which are connected in sequence. The light component removal tower 11, the deacetic acid removal tower 20, the product refining tower 30, and the alcohol recovery tower 40 each comprise a tower top condenser (13, 22, 32, 43), a reflux tank (14, 23, 33, 44), a tower bottom reboiler (17, 27, 38, 47), a feed port of each tower, a tower top reflux and a discharge port. The deacetic acid removal tower 20, the product refining tower 30, and the alcohol recovery tower 40 each have a tower side line discharge port. The esterification reactor 8 is provided with a feed port, a precooler 7, and a discharge port. After the raw materials are mixed, they are connected to the bottom of the esterification reactor through a precooler 7 and a filter 6. The discharge port of the esterification reactor 8 is connected to the feed port of the light component removal tower 11 through a light component removal tower feed pipeline 9 and a reaction pressure control valve 10; the bottom discharge port of the light component removal tower 11 is connected to the feed port of the deacetation tower 20 through a light component removal tower bottom outlet pipeline 19; the top discharge port of the deacetation tower 20 is connected to the top reflux tank 23 through a light component removal tower bottom outlet pipeline 21, the discharge port of the top reflux tank is connected to the feed port of the alcohol recovery tower through a deacetation tower reflux tank outlet pipeline 25, the bottom discharge port of the deacetation tower 20 is connected to the feed port of the desalting tank 2 through a deacetation tower bottom discharge pipeline 29, and the upper side discharge port of the deacetation tower 20 is connected to the product refined product through a deacetation tower upper side production pipeline 26. The top discharge port of the product refining tower 30 is connected to the top reflux tank 33 through the top outlet pipeline 31 of the product refining tower, the discharge port of the top reflux tank is connected to the feed port 36 of the alcohol recovery tower through the outlet pipeline 35 of the product refining tower reflux tank, and the side line 37 of the product refining tower is connected to the product intermediate tank; the top discharge port of the alcohol recovery tower 40 is connected to the top reflux tank 44 through the top outlet pipeline 42 of the alcohol recovery tower, the discharge port of the top reflux tank is connected to the mixed material tank through the outlet pipeline 46 of the alcohol recovery tower reflux tank, the side line 49 is connected to the reaction feed precooler through the filter feed pipeline 51, and the bottom discharge port is connected to the mixed material tank through the bottom outlet pipeline 41 of the alcohol recovery tower.

[0043] The process adopted by the invention is mainly divided into desalting, reaction, light component removal, acetic acid removal, ester refining and tert-butyl alcohol recovery parts.

[0044] (1) Desalination: Fresh acetic acid feed 1 and circulating acetic acid 29 from the side line of the deacidification tower 20 enter the desalination tank 2. The metal ions carried by them can be adsorbed by ion exchange resin to prevent them from entering the esterification reactor 8, thereby achieving the purpose of protecting the catalyst.

[0045] (2) Reaction: The tert-butyl alcohol 49 from the alcohol recovery tower 40 and the appropriately supplemented fresh tert-butyl alcohol 50 are mixed with the acetic acid 5 after metal ion removal in a certain proportion under pressure. The purchased raw material isobutylene 3 and the isobutylene 16 separated from the light component are dehydrated and mixed with acetic acid and tert-butyl alcohol, and then enter the esterification reactor 8 through the precooler 7 and the filter 6 for reaction.

[0046] (3) Removal of light components: The reaction material 9 enters the light component removal tower 11 from the esterification reactor 8 through the reaction pressure control valve 10 (pressure controlled to 101kPa~125kPa). Since there is a pressure difference between the reactor 10 and the light component removal tower 11, it is equivalent to undergoing a flash evaporation process when entering the light component removal tower 11, in which the unreacted isobutylene with a lower boiling point is vaporized by its own heat, and rises to the top of the tower step by step. After condensation in the tower top condenser 13, it enters the light component removal tower top reflux tank 14, separates the carbon four 16, and then returns to continue the cycle to participate in the reaction. The materials with higher boiling points in the bottom reaction materials of the tower, the light component removal tower bottom materials 19 (including acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol, water, etc.) enter the deacetylating tower 20.

[0047] (4) Deacetic acid removal: Material 19 enters the deacetic acid removal tower 20, and is subjected to vacuum distillation with a vacuum degree (absolute pressure) of 20-70 KPa. The tower top temperature is controlled at 45-70°C, and the reflux ratio is 3-10:1. Tertiary butyl alcohol is used to azeotropize carbon eight and water (the azeotropic point is lower than the boiling point of tertiary butyl acetate under negative pressure) to bring carbon eight, water and other by-products to the tower top. 21 is extracted from the tower top, condensed in a condenser 22, and then enters a reflux tank 23. A portion of the reflux is used as the deacetic acid removal tower top reflux 24, and the other portion enters the alcohol recovery tower 40 through the deacetic acid removal tower reflux tank outlet pipeline 25; the upper side is taken out The temperature is controlled at 60-85℃, which is the area where tert-butyl acetate is enriched. The material 26 mainly contains tert-butyl acetate (purity 95-98%), and only contains a small amount of tert-butyl alcohol and C8, which improves the separation efficiency of the subsequent ester refining tower 30; the temperature of the deacidification tower 20 kettle is controlled at 80-100℃. Even if there is an adjustment fluctuation, a small amount of tert-butyl acetate falls into the kettle, which can effectively avoid the decomposition of tert-butyl acetate, and there will be no ester decomposition, carbon four aggregation leading to increased tower pressure, etc., giving the operator enough time to optimize and adjust, and separate the tert-butyl ester in the kettle. Acetic acid (purity 98.0-99.5%, called circulating acetic acid) is extracted from the lower part 29, returned to the acetic acid feed line 5 after passing through the desalting tank, and then used as a reaction raw material together with fresh acetic acid.

[0048] (5) Ester refining: The crude tert-butyl ester 26 containing a small amount of alcohol and a trace amount of C8 is extracted from the upper side of the deacidification tower 20, preheated to 75-85°C and then enters the tert-butyl ester refining tower 30. The tower is operated at normal pressure. The light components such as tert-butyl alcohol are condensed in the tower top condenser 32 and enter the reflux tank 33. A part of the material 34 returns to the top of the tower for reflux, and the other part 35 enters the alcohol recovery tower 40. Tert-butyl acetate 37 (purity 99.5%-99.8%) with a higher boiling point is extracted from the side line of the refining tower, cooled, and enters the finished product intermediate tank.

[0049] (6) Alcohol recovery: After the tert-butyl alcohol, C8, water, tert-butyl acetate, etc. from the reflux tank at the top of the deacidification tower 20 and the ester refining tower 30 enter the alcohol recovery tower 40 through the alcohol recovery tower feed port 36, the azeotrope formed by tert-butyl alcohol, C8 and water is extracted from the top of the tower, condensed by the top cooler 43, and enters the reflux tank 44 of the alcohol recovery tower. A part of the material coming out of the reflux tank 45 is refluxed to the top of the tower, and the other part 46 is sent to the mixing tank as a mixed material for subsequent separation and treatment according to demand. The tert-butyl alcohol extracted from the side line 49 (middle side line) of the alcohol recovery tower and the supplementary fresh tert-butyl alcohol 50 are cooled by the cooler and returned to the reactor 8 for recycling as an inhibitor. A small amount of tert-butyl alcohol and tert-butyl acetate mixture is discharged from the bottom of the tower, and is sent to the mixing tank together with the top discharge material for subsequent separation and treatment according to demand. Example

[0050] Fresh acetic acid and circulating acetic acid taken from the bottom of the deacidification tower enter the desalting tank to exchange the metal ions they carry, tert-butyl alcohol and acetic acid after metal ion removal are mixed at the feed inlet, and the purchased raw material isobutylene is mixed with acetic acid and tert-butyl alcohol after dehydration, and enters the esterification reactor for reaction through a precooler (precooled to about 8°C) and a filter (filter screen size 120 mesh). The temperature of the reactor is controlled to be 15°C, the reaction pressure is 1.0MPa, the acid-olefin ratio is 4:1, the reaction residence time is 60min, and the amount of polymerization inhibitor tert-butyl alcohol added is 10wt% of the amount of acetic acid added. The content of the mixture obtained after the reaction is 33.26wt% of tert-butyl acetate, 7.67wt% of tert-butyl alcohol, 57.59wt% of acetic acid, 0.88wt% of isobutylene, 0.41wt% of carbon eight, and 0.19wt% of water. The reaction materials enter the light component removal tower from the reactor through the reaction pressure control valve (pressure controlled to 101kPa), and are operated at normal pressure. The tower top temperature is 5°C, and the tower bottom temperature is 105°C. The unreacted isobutylene with a lower boiling point is condensed in the tower top condenser and enters the reflux tank of the light component removal tower. The reflux ratio is 2:1. The separated isobutylene continues to circulate and participate in the reaction. The mixture of acetic acid, tert-butyl acetate, C8 and tert-butanol obtained at the bottom of the light component removal tower is sent to the deacetylating tower for separation. The deacetylating tower is a packed tower with 25 theoretical plates. The material enters the deacetylating tower at the 11th plate. Vacuum distillation is adopted with a vacuum degree (absolute pressure) of 50 KPa. The top temperature is controlled at 63°C and the reflux ratio is 6:1. Tert-butyl alcohol, C8 and water are azeotropically brought to the top of the tower to bring C8, water and other by-products. The by-products are extracted from the top of the tower and cooled before entering the reflux tank. The material content of the reflux tank is 93.86wt% of tert-butyl alcohol, 4.98wt% of C8, 0.62wt% of water and 0.54wt% of tert-butyl acetate. Part of the material is refluxed and the other part enters the alcohol recovery tower. The upper side sampling temperature is controlled at 75°C and the sampling position is at the 4th plate, which is the tert-butyl acetate content enrichment area. The material mainly contains 97.81wt% tert-butyl acetate, 1.80wt% tert-butyl alcohol and 0.39wt% tert-butyl acetate. C8; the temperature of the deacidification tower kettle is controlled at 95°C, and acetic acid with a purity of 99.66wt% is extracted from the lower side line, enters the circulating acetic acid cooler, returns to the acetic acid feed line after passing through the desalting tank, and then is used as a reaction raw material together with fresh acetic acid. The 97.81wt% crude tert-butyl ester extracted from the upper side of the deacetation tower is preheated (to about 83°C) and enters the tert-butyl acetate refining tower. It is operated at normal pressure, with a top temperature of 80°C, a bottom temperature of 99°C, and a reflux ratio of 1:1. The azeotropic mixture of tert-butyl alcohol, C8, tert-butyl acetate, etc. enters the reflux tank after condensation in the top condenser. Part of the material returns to the top of the tower for reflux, and the other part enters the alcohol recovery tower. Tert-butyl acetate (purity 99.89wt%) with a higher boiling point is extracted from the lower side line of the refining tower, and after cooling, enters the finished product intermediate tank.The tert-butyl alcohol, C8, tert-butyl acetate and other materials from the top of the deacidification tower and the reflux tank at the top of the ester refining tower are mixed and then enter the alcohol recovery tower. The feed composition of the alcohol recovery tower is 94.06wt%, C8 5.05wt%, tert-butyl acetate 0.59wt%, and water 0.30wt%. The operation is at normal pressure, the top temperature is 75°C, the side sampling temperature is 85°C, the bottom temperature is 95°C, and the reflux ratio is 4:1. The azeotrope formed by tert-butyl alcohol, C8 and water is extracted from the top of the tower, and enters the reflux tank of the alcohol recovery tower after condensation in the top cooler. Part of the material coming out of the reflux tank is refluxed to the top of the tower, and the other part is sent to the mixing tank as a mixed material. The tert-butyl alcohol with a purity of 99.36wt% extracted from the side line (the side line is in the middle of the tower) is cooled by the cooler and returned to the tert-butyl alcohol intermediate tank, and then returned to the reactor for recycling as an inhibitor. A small amount of tert-butyl alcohol and tert-butyl acetate mixture is discharged from the bottom of the tower and sent to the mixing tank for subsequent separation and treatment according to demand.

[0051] Since the decomposition of tert-butyl acetate and the polymerization of isobutylene are avoided in the deacetation tower, the purity of tert-butyl acetate entering the refining tower is increased from the previous 50.52wt% to 97.81wt%, and the carbon eight impurity content in the refining tower feed is reduced from the previous 8.49wt% to 0.39wt%. On the one hand, it avoids the azeotropic effect of more carbon eight and tert-butyl acetate to the top of the tower, and on the other hand, it reduces the C8 content in the side line production, improves the product purity, and the production of heavy components such as C8 in the tower bottom with a boiling point higher than tert-butyl acetate is greatly reduced, which slows down the emission of heavy components at the bottom of the tower. The purity of tert-butyl acetate, the side line product under the product refining tower, reaches 99.89wt%. After calculation, the yield of tert-butyl acetate reaches 96.58%. In addition to improving the purity of tert-butyl acetate extracted from the upper side, the optimization adjustment of the deacetylating tower also increased the purity of the acetic acid circulating in the bottom of the tower from 97.04wt% before the adjustment to 99.66wt%, avoiding the mixing of tert-butyl acetate, C8, etc. into the raw materials and affecting the reaction conversion rate. After calculation, the separation recovery rate of acetic acid reached 97.83%.

[0052] On the other hand, due to the process adjustment and optimization of the deacidification tower, the occurrence of tert-butyl acetate side reactions caused by the separation process was avoided, and the selectivity of tert-butyl acetate reached 99.58%. The content of heavy substances such as C8 in the entire separation system was significantly reduced, and the C8 content in the tert-butyl alcohol and C8 mixture at the top of the deacidification tower and the refining tower was reduced from 15wt% before the transformation to 5.05wt%. When the material is recycled for tert-butyl alcohol, its separation purity and yield can be improved, and the purity reaches 99.36wt%, and the separation recovery rate is calculated to reach 98.17%.

[0053] Finally, it should be noted that the above content is only for illustrative purposes and not for limiting the scope of protection of the present invention. A person skilled in the art may modify or substitute equivalents for the technical solution of the present invention without departing from the essence of the present invention, and the modifications or equivalent substitutions shall be included in the scope of protection of the claims of the present invention.

Claims

1. A method for separating tert-butyl acetate from a reaction product of preparing tert-butyl acetate using isobutylene and acetic acid as raw materials, characterized in that: The method comprises the following steps: (C) Removal of light components: The reaction product enters a light component removal tower to remove light components with lower boiling points including unreacted isobutylene; (D) Deacetic acid removal: A mixture of acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol and water obtained at the bottom of the light component removal tower is sent to a deacetic acid removal tower for separation, and acetic acid is discharged from the bottom of the tower. The deacetic acid removal tower adopts vacuum distillation with a vacuum degree of 20-70 KPa. The tower top temperature is controlled at 45-70° C. according to the absolute pressure gauge; (E) Ester refining: crude tert-butyl acetate containing a small amount of alcohol and a trace amount of C8 hydrocarbons is extracted from the upper side of the deacetylating tower and enters the tert-butyl acetate refining tower for refining, preferably after being preheated (for example, to 75-85° C.) and then enters the tert-butyl acetate refining tower for refining, and tert-butyl acetate with a higher boiling point is extracted from the side line of the tert-butyl acetate refining tower; (F) Alcohol recovery: The materials including tert-butyl alcohol, C8 hydrocarbons, water and tert-butyl acetate from the top reflux tank of the deacidification tower and the ester refining tower enter the alcohol recovery tower to recover alcohol. The azeotrope formed by tert-butyl alcohol, C8 hydrocarbons and water is extracted from the top of the tower, and tert-butyl alcohol is extracted from the side line. Wherein, the reaction product is the reaction product of preparing tert-butyl acetate using isobutylene and acetic acid as raw materials.

2. The method according to claim 1, characterized in that: In step (C), the operating conditions of the light component removal tower are: normal pressure operation, tower top temperature 0±6°C, preferably 0±4°C or 0±3°C, tower bottom temperature 105±5°C, preferably 105±3°C, and also preferably 105±1°C; and / or In step (C), the unreacted isobutylene with a lower boiling point is vaporized by its own heat, rises to the top of the tower step by step, and after condensing in the top condenser, enters the top reflux tank of the light component removal tower, and after isobutylene is separated, it returns to continue the cycle and participate in the reaction.

3. The method according to claim 1 or 2, characterized in that: The deacetylating tower in step (D) is a packed tower, the number of theoretical plates of the deacetylating tower is 20-30, the feed position is between the 10th and 17th plates, the reflux ratio is between 3-10, the upper side line crude ester extraction position is between the 3rd and 10th plates, the purity of tert-butyl acetate is 95%-98%, and the acetic acid content in the bottom of the tower is 98-99.5%; and / or The deacetylating tower uses tert-butyl alcohol, carbon eight and water to azeotrope the by-products including carbon eight and water to the top of the tower, and then extracts them from the top of the tower, cools them, and then enters a reflux tank, where part of the material is refluxed and the other part enters an alcohol recovery tower; the upper side temperature is controlled at 60-85°C, preferably 65-80°C or further 70-75°C; and / or The temperature of the deacetylating tower bottom is controlled at 80-100°C, preferably 85-95°C.

4. The method according to any one of claims 1 to 3, characterized in that In step (E), the tert-butyl acetate refining tower is operated at normal pressure, and the light components including tert-butyl alcohol are condensed in the top condenser of the tert-butyl acetate refining tower and then enter the reflux tank; a part of the material returns to the top of the tower for reflux, and the other part enters the alcohol recovery tower for alcohol recovery; and / or In step (E), the top temperature of the tert-butyl acetate refining tower is 80±5°C, preferably 80±3°C or further 80±1°C, the bottom temperature is 97±5°C, preferably 97±3°C or further 97±2°C, the reflux ratio is 1:0.5-2, preferably 1:0.8-1.2, further about 1:1, the azeotropic mixture including tert-butyl alcohol, C8 hydrocarbons and tert-butyl acetate enters the top condenser for condensation and then enters the reflux tank, a part of the material returns to the top of the tower for reflux, and the other part enters the alcohol recovery tower, and the tert-butyl acetate with a higher boiling point is extracted from the side line below the refining tower, and after cooling, enters the finished product intermediate tank.

5. The method according to any one of claims 1 to 4, characterized in that In step (F), the alcohol recovery tower is operated at normal pressure, the tower top temperature is 75±5°C, preferably 75±2°C or further 75±1°C, the side extraction temperature is 85±5°C, preferably 85±2°C or further 85±1°C, the tower bottom temperature is 95±5°C, preferably 95±2°C or further 95±1°C, the reflux ratio is 2-6:1, preferably 3-5:1, further about 4:1, the azeotrope formed by tert-butyl alcohol, C8 hydrocarbons and water is extracted from the tower top, condensed by the tower top cooler and enters the alcohol recovery tower reflux tank, part of the material coming out of the reflux tank is refluxed to the tower top, and the other part is sent to the mixing tank as a mixed material; and / or In step (F), the tert-butyl alcohol withdrawn from the side line is cooled in a cooler and then returned to the reactor for preparing tert-butyl acetate using isobutylene and acetic acid as raw materials and recycled as a polymerization inhibitor.

6. A method for preparing tert-butyl acetate using isobutylene and acetic acid as raw materials, the method comprising the following steps: (A) Desalination: Fresh acetic acid feed and circulating acetic acid from the side line of the deacidification tower are fed into a desalination tank, and the metal ions carried by them are adsorbed by ion exchange resin (preferably to reduce the metal ions in the acetic acid feed to below 5 ppm, preferably below 2 ppm, and more preferably below 1 ppm), thereby preventing them from entering the esterification reactor, thereby achieving the purpose of protecting the catalyst; (B) Reaction: the recovered tert-butyl alcohol from the alcohol recovery tower and the appropriately supplemented fresh tert-butyl alcohol are mixed with the acetic acid after metal ion removal in a certain proportion, and the fresh raw material isobutylene and the isobutylene separated by light component removal are dehydrated and mixed with acetic acid and tert-butyl alcohol in an esterification reactor for reaction, preferably precooled to 0-20° C., preferably 1-15° C., more preferably 5-10° C. in a precooler and filtered through a filter before entering the esterification reactor for reaction; (C) Removal of light components: The reaction product enters a light component removal tower to remove light components with a lower boiling point (usually a boiling point below -5°C) including unreacted isobutylene; (D) Deacetylating: The mixture including acetic acid, tert-butyl acetate, C8 hydrocarbons, tert-butyl alcohol and water obtained at the bottom of the light component removal tower is sent to the deacetylating tower for separation, wherein: The deacetic acid tower adopts vacuum distillation with a vacuum degree of 20-70KPa. According to the absolute pressure gauge, the tower top temperature is controlled at 45-70℃; (E) Ester refining: crude tert-butyl acetate containing a small amount of alcohol and a trace amount of C8 hydrocarbons is extracted from the upper side of the deacidification tower and enters the tert-butyl acetate refining tower for refining, preferably after being preheated (for example, to 75-85° C.) and then enters the tert-butyl acetate refining tower for refining, and tert-butyl acetate with a higher boiling point is extracted from the side line of the tert-butyl acetate refining tower; (F) Alcohol recovery: The materials including tert-butyl alcohol, C8 hydrocarbons, water and tert-butyl acetate from the top reflux tank of the deacidification tower and the ester refining tower enter the alcohol recovery tower to recover alcohol. The azeotrope formed by tert-butyl alcohol, C8 hydrocarbons and water is produced from the top of the tower, and tert-butyl alcohol is produced from the side line.

7. The method according to claim 6, characterized in that A small amount of a mixture of tert-butyl alcohol and tert-butyl acetate is discharged from the bottom of the alcohol recovery tower.

8. The method according to claim 6 or 7, characterized in that: The total amount of the polymerization inhibitor tert-butyl alcohol added is 10±2 wt % of the amount of acetic acid added.

9. A device for preparing tert-butyl acetate, comprising an acetic acid desalting tank (2), a filter (6), a precooler (7), an esterification reactor (8), a light component removal tower (11), a deacetic acid removal tower (20), a product refining tower (30), and an alcohol recovery tower (40) connected in sequence. The light component removal tower (11), the acetic acid removal tower (20), the product refining tower (30) and the alcohol recovery tower (40) each comprise a tower top condenser, a reflux tank, a tower bottom reboiler, a feed inlet, a tower top reflux and a tower bottom discharge port, and the acetic acid removal tower (20), the product refining tower (30) and the alcohol recovery tower (40) each have a tower side line discharge port. The acetic acid feed pipeline is connected to the acetic acid desalting tank (2), the isobutylene feed pipeline is connected to the dehydrator (4), the outlets of the acetic acid desalting tank (2) and the dehydrator (4) are connected to the filter (6), the precooler (7) and the esterification reactor (8) in sequence, and the outlet of the esterification reactor (8) is connected to the light component removal tower (11). The bottom discharge port of the light component removal tower (11) is connected to the feed port of the deacetylating tower (20) through a pipeline; the top discharge port of the deacetylating tower (20) is connected to the top reflux tank of the deacetylating tower (20) through a pipeline; the discharge port of the top reflux tank of the deacetylating tower (20) is connected to the feed port of the alcohol recovery tower (40) through a pipeline; the bottom discharge port of the deacetylating tower (20) is connected to the feed port of the desalting tank (2) through the bottom discharge pipeline of the deacetylating tower; the upper discharge port of the deacetylating tower is connected to the product refining tower (30) through the upper side line (26) of the deacetylating tower; the upper side line (26) of the deacetylating tower is preferably provided with a preheating The top discharge port of the product refining tower (30) is connected to the top reflux tank of the product refining tower through a pipeline, the discharge port of the top reflux tank of the product refining tower is connected to the feed port of the alcohol recovery tower (40) through the outlet pipeline of the product refining tower reflux tank, and the side line (37) of the product refining tower is connected to the product intermediate tank; the top discharge port of the alcohol recovery tower (40) is connected to the top reflux tank of the alcohol recovery tower through a pipeline, the discharge port of the top reflux tank of the alcohol recovery tower is connected to the mixed material tank through the outlet pipeline of the alcohol recovery tower reflux tank, and the side line (49) of the alcohol recovery tower is connected to the filter (6) through the filter feed pipeline.

10. The device according to claim 9, characterized in that The discharge pipeline of the alcohol recovery tower kettle is connected to the mixing material tank.

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