JPH072735A - Production of isopropyl acetate - Google Patents

Abstract

PURPOSE:To obtain isopropyl acetate from crude propylene and acetic acid by a liquid phase reaction; firstly separating a low-boiling point component from a pressurized crude reaction solution, secondly separating the objective material, thereafter separating the unreacted material and a high-boiling point component and recycling the unreacted material to the reaction. CONSTITUTION:High purity isopropyl acetate is obtained by the following processes. A catalyst consisting of acidic ion exchange resin is placed in a reaction vessel 1 and an impurity-containing propylene and acetic acid are supplied to the reaction vessel 1. The pressurized reactional solution obtained by the reaction in the reaction vessel 1 is depressurized in a flush tank 2 to separate into a vapor phase and a liquid phase. The vapor phase is cooled in a condenser 3 and the condensate is mixed, in a tank 4, with the liquid phase obtained above. The mixed crude reactional solution is introduced into the first distillation tower 5, a low-boiling point component is condensed and removed and the remainder is treated in the third distillation tower 7 to obtain the objective product of isopropyl acetate. The remainder of the third distillation tower 7 is further treated in the fourth distillation tower 8 and a mixture consisting of unreacted acetic acid and sec-butyl acetate is taken out by side cut and returned to the reaction. The bottom of the fourth distillation tower 8 is removed from the reaction system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides a highly pure compound obtained by reacting propylene containing impurities with acetic acid in the liquid phase in the presence of an acidic ion exchange resin catalyst and continuously purifying the resulting crude isopropyl acetate. To a method for producing isopropyl acetate. High-purity isopropyl acetate produced by the production method of the present invention is a useful substance as a solvent, a fragrance, or the like.

[0002]

2. Description of the Related Art A method for synthesizing isopropyl acetate by reacting acetic acid with propylene in the presence of an acidic ion exchange resin catalyst is known (JP-A-4-169552), and isopropyl acetate can be obtained by an industrial method. In the process, it is known that unreacted acetic acid is recycled to improve the yield of over-all (hydrocarbon).
Bon Processing, April 1975; HYDOCA
RBON PROCESSING APRIL 197
5). As a method for producing isopropyl acetate, it is known that it can be synthesized by reacting acetic acid and propylene in a liquid phase under an acidic catalyst. Also,
It is also known to use crude propylene as propylene.

[0003]

However, when the crude propylene as described above is used, a trace amount of water contained in the raw propylene and acetic acid as raw materials and a trace amount generated by the reaction of acetic anhydride to form acetic anhydride. Water reacts with propylene to produce isopropyl alcohol (IP
A; boiling point 82 ° C.) and the like. Further, it contains saturated hydrocarbons and olefins having 4 carbon atoms as impurities. The olefins having 4 carbon atoms in these impurities react with propylene and acetic acid to produce olefins having 7 carbon atoms and acetic acid esters having 6 or more carbon atoms as by-products. These by-products have a boiling point close to that of isopropyl acetate or acetic acid, and thus are difficult to separate. Therefore, in the case of a simple continuous distillation column combination, the number of stages of the distillation column becomes large, which causes an increase in equipment cost or a large loss rate of isopropyl acetate. Such facts are very problematic and unrealistic for industrial processes. Therefore, a method for producing high-purity isopropyl acetate using crude propylene has been desired.

[0004]

In order to solve the above-mentioned problems, the inventors of the present invention have proposed a process for industrially producing isopropyl acetate from crude propylene and acetic acid by a liquid phase reaction. , The low boiling point component is concentrated and separated in the first distillation column, then the product isopropyl acetate is obtained in the third distillation column, the unreacted acetic acid and the high boiling point component are separated in the fourth distillation column, and the unreacted acetic acid is used in the reaction step. It is intended to provide a manufacturing method that goes through a series of refining processes for recycling.

That is, according to the present invention, "In a method for producing isopropyl acetate from propylene containing impurities and acetic acid, (a) the pressurized reaction liquid obtained in the reaction system is separated into a gas phase and a liquid phase, (B) The separated gas phase is cooled to be separated into a non-condensate and a condensate, and (c) the condensate is mixed with the above liquid phase to give a reaction crude liquid, and the reaction crude liquid is fed to the first distillation column. Guide,
The top liquid and the bottom liquid are separated, (d) the top liquid of the first distillation column is guided to the second distillation column, and the top liquid of the second distillation column is discharged to the outside of the system. The bottom liquid of the second distillation column is returned to an appropriate stage of the first distillation column, (f) the bottom liquid of the first distillation column is introduced into the third distillation column, and the top liquid of the third distillation column is highly pure. Isopropyl acetate was distilled off, (g) the bottom liquid of the third distillation column was introduced into the fourth distillation column, and the top liquid of the azeotropic composition was distilled from the top of the fourth distillation column, mainly acetic acid and sec- The mixture consisting of butyl acetate is side-cut and returned to the reaction system,
(H) A method for producing high-purity isopropyl acetate, characterized in that the bottom liquid of the fourth distillation column is discharged to the outside of the system ”.

An embodiment for carrying out the method for producing high-purity isopropyl acetate (hereinafter referred to as IPAC) of the present invention is shown in FIG. 1 and will be described based on this. In FIG. 1, 1 is a reactor, 2 is a flash tank, 3 is a condenser, 4 is a tank, 5 is a first distillation column, 6 is a second distillation column, and 7
Indicates a third distillation column, 8 indicates a fourth distillation column, and arrows indicate the flow direction of a mixture of liquids or gases indicated by alphabets flowing in each part.

In the production method of the present invention, first, propylene containing impurities and acetic acid are reacted in the liquid phase in the presence of a catalyst. In the present invention, a hydrocarbon mixture containing about 20% by weight or more of propylene can be used as propylene containing impurities. As such a hydrocarbon mixture, propylene obtained by catalytically cracking petroleum such as naphtha is used. It is possible to use a crude propylene which is a by-product when isobutene is produced by dehydrogenating a fraction containing 3 carbon atoms or isobutane.

The water content in acetic acid is preferably less than 0.1%. The catalyst used in the IPAC synthesis reaction may be a general catalyst used in this type of reaction and does not need to be a special catalyst. Generally, an acidic catalyst such as an acidic ion exchange resin is used, and synthesis can be performed by a liquid phase reaction, a gas phase reaction and a gas-liquid mixed phase reaction. TECHNICAL FIELD The present invention relates to a process for producing a high-purity IPAC by a continuous treatment from a reaction crude liquid under pressure in a reaction in a liquid phase.
In the purification process of the present invention, either normal pressure or increased pressure can be applied.

In the present invention, the molar ratio of acetic acid and propylene in the raw material feed liquid (P) is in the range of 1.0 to 2.0,
It is preferable to supply both acetic acid and propylene in a liquid state and in a cocurrent flow to a continuous flow type fixed bed reactor filled with an acidic ion exchange resin catalyst for reaction. The pressure in the reactor may be a pressure sufficient to keep the reaction system in a liquid phase, for example, 15 to 100 kg / cm ² , and more preferably 15
It can be appropriately selected from the range of up to 50 kg / cm ² . The temperature at the entrance of the catalyst phase is maintained at 70 to 120 ° C. for reaction. The pressurized IPAC reaction crude liquid reacted in this way is
It is manufactured by a continuous purification method according to the flow shown in FIG.

For example, the pressurized reaction crude liquid (A) in a pressurized state that exits the reactor 1 (temperature 70 to 120 ° C., pressure 15 to 100)
The pressure of kg / cm ² ) is first released in the flash tank 2 and returned to normal pressure. At this time, it is separated into a liquid phase (D) and a gas phase (B). Since IPAC is present in the gas phase (B), it is cooled using condenser-3 to minimize IPAC loss due to flash. When propylene containing an inert gas is used, the amount of the inert gas is large, so that the pressure loss is large. At this time, the temperature of the refrigerant used is preferably 20 ° C. or lower. The condensed liquid (C) containing IPAC condensed by the condenser-3 is mixed with the liquid phase (D) of the flash tank 2 in the tank 4, and the mixed liquid (E) is fed continuously to the first distillation column 5. To be done.

The first distillation column 5 is a column installed for the purpose of removing low boiling point components. As the low boiling point component, isopropyl alcohol (IPA), isopropyl ether (IP)
E), an olefin having 7 carbon atoms and the like are main components. Of these low-boiling components, the olefin having 7 carbon atoms is a peculiar impurity produced by the reaction of the olefin having 4 carbon atoms, which is one of the impurities in propylene, with propylene under this reaction condition. The product is the major cause of the decrease in the purity of IPAC as a product. In addition, isopropyl alcohol (IPA) and isopropyl ether (IPE) are produced by the reaction of propylene with water (water in propylene or acetic acid, water generated when acetic acid is condensed by acetic acid condensation). To do.

Therefore, in the first distillation column 5, the purity is 99.9.
The above low boiling point components and IPAC are separated with the goal of obtaining about 10% of product IPAC. The operating conditions of the first distillation column 5 are such that the concentration of the low boiling point component in the column low liquid containing IPAC and unreacted acetic acid is below the specified specifications, but the boiling points of the IPAC and the olefin having 7 carbon atoms are It is difficult to separate because it is close. Therefore, a large amount of IPAC is distilled in the distillate in addition to the above low boiling point components. If the distillate is discarded as it is, the loss of entrained IPAC becomes large and the acquisition rate of the product IPAC deteriorates.

Therefore, when only the first distillation column 5 is used as a method of removing low boiling point components, the loss of entrained IPAC becomes large, so the overhead liquid (F) of the first distillation column 5 is fed to the second distillation column 6. Charge and concentrate low-boiling components. In the bottom liquid (H) of the second distillation column 6, IPAC and some low-boiling-point components remain, but this is a multiple-effect system in which it is returned to an appropriate stage of the first distillation. By adopting this method, entrainment loss of IPAC is greatly reduced. Further, in the second distillation column 6, the amount of the treated liquid is about 1/20 of that of the first distillation, so the column diameter may be 1/3 or less, which does not burden the facility cost. The concentrated top liquid of the second distillation column is taken out of the system.

Next, the bottom liquid (I) of the first distillation column is charged into the third distillation column 7. Here, I from the top of the tower as a product
Obtain PAC (J). From the bottom liquid (K), acetic acid and sec-
Butyl acetate (hereinafter referred to as SBAC), a high boiling point component, and the like are obtained, and charged into the fourth distillation column 8. The fourth distillation column 8 is intended to remove the high boiling point components and recover unreacted acetic acid. Liquid charged to the fourth distillation column 8 (K)
Is unreacted acetic acid, a high boiling point substance and SBAC, and S
BAC is produced by reacting an olefin having 4 carbon atoms, which is an impurity in propylene gas, with acetic acid. SB
Although AC has a boiling point close to that of acetic acid and is difficult to separate, it has been confirmed that AC decomposes into an olefin having 4 carbon atoms and acetic acid. From this, it was found that SBAC becomes an equilibrium composition in the reaction step and does not increase, and therefore, the separation of SBAC does not have to be particularly considered in the present production step.

The high boiling point component is an olefin having 9 carbon atoms, which is a trimer of propylene. Since the olefin having 9 carbon atoms is azeotroped with acetic acid, the olefin having 9 carbon atoms and acetic acid cannot be separated by the method of distilling acetic acid from the top of the tower and removing the high boiling point component from the bottom of the tower. Since this recovered acetic acid is recycled for use in the reaction system, an olefin having 9 carbon atoms accumulates in the reaction system and the purification system. Recycling such acetic acid containing an olefin into the reaction system may increase the amount of by-products and adversely affect the catalyst.

Further, even in the refining system, a treatment for intermittently separating a high-concentration olefin having 9 carbon atoms is required, which makes operation control in the continuous refining system difficult. Therefore, by utilizing the azeotropic property, olefin having 9 carbon atoms and acetic acid are distilled out in an azeotropic composition from the top of the column, a high boiling point component (N) is removed from the bottom of the column, and acetic acid is side-cut to obtain high purity. Acetic acid can be recovered. In addition, the loss of acetic acid is only the azeotrope content with the olefin having 9 carbon atoms, and a small amount of loss is sufficient.

The present invention will be described below with reference to specific examples, but the present invention is not limited thereto. Here, the composition of propylene used in the following examples is such that propylene is 76.1% by weight, propane is 22.0% by weight, and the balance is mainly olefins having 4 carbon atoms. Further, the molar ratio refers to a molar ratio of acetic acid to propylene, which is LHSV.
Is based on the amount of acetic acid supplied.

Example 1 The reactor 1 (cylindrical tube type) shown in FIG. 1 was filled with an acidic ion exchange resin as a catalyst, and propylene containing impurities and acetic acid were supplied to the reactor 1.
A raw material feed stream (P) consisting of acetic acid and propylene containing impurities is fed to the reactor 1 and reacted in the catalyst layer,
The reaction mixture was cooled via a heat exchanger (not shown) and part of it was circulated.

The circulating stream was combined with the feed stream (P).
A feed stream of LHSV 1.0 and a propylene molar ratio of 1.4 was passed through this reactor 1 at a reaction pressure of 40 kg / cm ² .
The pressure-applied pressurized reaction crude liquid thus obtained was depressurized in the flash tank 2 and separated into a gas phase (non-condensed component) and a liquid phase (condensed component). Non-condensed component is condenser
It was cooled to 10 ° C. at 3, IPAC was condensed, and the condensed components from the flash tank were mixed in the tank 4. At this point, the composition of the reaction crude liquid (E) was IPAC 71%, acetic acid 2
It was 5% and other 4%.

This reaction crude liquid (E) was sent to the first distillation column 5. The first distillation column 5 was composed of 20 stages of a concentration section and 20 stages of a recovery section, and under this condition of a reflux ratio of 30, IPA, IPE, and an olefin having 7 carbon atoms were cut to a bottom spec of about 500 ppm. This bottom liquid was sent to the third distillation column 7. The composition of the distillate of the first distillation column 5 is IPAC8.
3%, low boiling point components containing IPA, IPE, olefin having 7 carbon atoms 16%, and water 1%. If this distillate is discarded as it is, the loss of IPAC corresponds to 7% of the charged liquid, so the distillate was sent to the second distillation column 6 to further concentrate the low boiling point components.

The second distillation column 6 has 20 stages of concentration section and 20 recovery section.
The low boiling point component was concentrated to about 70% at a reflux ratio of 30. Since the low-boiling point component was mixed in the bottom liquid, it was returned to the first distillation column 5. By adopting such a multiple utility system, the loss of IPAC could be reduced to 0.7% of the amount charged. The bottom liquid of the first distillation column 5 was sent to the third distillation column 7. The third distillation column 7 was composed of 40 stages of concentration section and 20 stages of recovery section, and the product IPAC was distilled from the top of the column at a reflux ratio of 1. The obtained IPAC had a purity of 99.9%.
Next, the bottom liquid of the third distillation column 7 was sent to the fourth distillation column 8.

The acetic acid recovery and the high boiling point component removal in the fourth distillation column 8 were carried out in the concentration section 20 stages and the recovery section 20 stages. Here, since the olefin having 9 carbon atoms and the acetic acid are azeotropically distilled, the azeotrope of the acetic acid and the olefin having 9 carbon atoms is distilled from the top of the column, and the high-boiling component is removed from the bottom of the column. It was collected by side cut and recycled to the reaction system. By this acetic acid recovery method, the loss of acetic acid was 0.8% based on the charged amount.

Example 2 As crude propylene containing impurities, 60.0% by weight of propylene, 28.0% by weight of propane, and 3% by weight of a residue containing an olefin having 4 carbon atoms were used as crude propylene. The same procedure as in Example 1 was performed. The composition of the reaction crude liquid after the pressure was released was IPAC 71%, acetic acid 25% and other 4%. The purity of IPAC obtained by purifying under the same conditions as in Example 1 was 9
It was 9.9%. Even if the purity of the raw material crude propylene was lowered, the by-products did not change and the product quality was not affected.

Alphabet (A) in FIG.
(P) shows a mixture of liquid or gas flowing in each position, and the composition of each mixture in Example 1 and Example 2 is as follows. (A) IPAC, acetic acid, propylene, IPA, IPE,
C7 olefin, C9 olefin, acetic ester, propane, etc .; (B) Propylene, inert gas, IPAC, IPA, I
PE, olefins having 7 carbon atoms; (C) IPAC, IPA, IPE, olefins having 7 carbon atoms; (D) IPAC, acetic acid, IPA, IPE, olefin having 7 carbon atoms, olefin having 9 carbon atoms, acetic ester (E) IPAC, acetic acid, IPA, IPE, olefin having 7 carbon atoms, olefin having 9 carbon atoms, acetate ester, etc .; (F) IPAC, IPA, IPE, olefin having 7 carbon atoms, etc .; (G) IPAC, (H) IPAC, olefin having 7 carbon atoms, etc .; (I) IPAC, acetic acid, olefin having 9 carbon atoms, acetic ester, etc .; (J) IPAC; (K) IPAC, Acetic acid, SBAC, C9 olefin, acetic acid ester, etc .; (L) C9 olefin, acetic acid, IPAC, etc .; (M) Acetic acid, BAC such; (N) high-boiling components; (O) propylene, inert gas; (P) is a feed stream of acetic acid and propylene as a raw material. The raw material crude propylene used in Examples 1 and 2 was obtained by thermally decomposing naphtha.

Example 3 As propylene containing impurities, propylene 58.0% by weight, propane 28.0% by weight, carbon dioxide gas 7% by weight, methane 2% by weight, isobutane 3% by weight and other olefins having 4 carbon atoms. 2% by weight
Example 1 was repeated except that the crude propylene consisting of was used.

The raw material crude propylene used in Example 3 was obtained as a by-product in the process for producing isobutene by dehydrogenating isobutane. The composition of the reaction crude liquid after the pressure was released was IPAC 70%, acetic acid 26% and other 4%. The purity of IPAC obtained by purifying under the same conditions as in Example 1 was 99.9%. Even if the origin of propylene containing impurities was changed, there was almost no change in the by-products, and the quality of the product was not affected.

[0027]

According to the production method of the present invention, a fraction having 3 carbon atoms containing propylene, which is obtained by catalytically cracking petroleum such as naphtha, is used as a by-product in the production step of isobutene by dehydrogenation of crude propylene or isobutane. Since crude propylene obtained as a living organism can be used as propylene containing impurities, IPAC of high purity, for example, about 99.9% can be continuously produced at low cost without increasing equipment cost. It is possible to manufacture well. Moreover, it is possible to recycle and reuse the unreacted substance without purifying it.

[Brief description of drawings]

FIG. 1 is a first process of producing isopropyl acetate according to the present invention.
It is a figure which shows an example.

[Explanation of symbols]

 1 Reactor 2 Flash Tank 3 Condenser 4 Tank 5 First Distillation Tower 6 Second Distillation Tower 7 Third Distillation Tower 8 Fourth Distillation Tower

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Tokumoto 3-35-1, Okubo, Konan-ku, Yokohama, Kanagawa Prefecture (72) Inventor Kazuo Sakamoto 4--14, Kurihara Chuo, Zama City, Kanagawa Prefecture

Claims (1)

[Claims] 1. A method for producing isopropyl acetate from propylene containing impurities and acetic acid, wherein the pressurized reaction solution obtained in (a) the reaction system is separated into a gas phase and a liquid phase, and (b)
The separated gas phase is cooled to separate into non-condensate and condensate,
(C) The condensate is mixed with the above liquid phase to give a reaction crude liquid, and this reaction crude liquid is introduced into a first distillation column and separated into a top liquid and a bottom liquid, and (d) a first distillation column. Leading the top liquid of the to the second distillation column,
The top liquid of the second distillation column is discharged to the outside of the system, (e) the bottom liquid of the second distillation column is returned to an appropriate stage of the first distillation column, and (f) the bottom liquid of the first distillation column is It is led to the third distillation column, high-purity isopropyl acetate is distilled off as the top liquid of the third distillation column, (g) the bottom liquid of the third distillation column is led to the fourth distillation column, and the column of the fourth distillation column is introduced. The azeotropic composition top liquid is distilled from the top, a mixture mainly composed of acetic acid and sec-butyl acetate is side-cut and returned to the reaction system, and (h) the bottom liquid of the fourth distillation column is removed from the system. A method for producing high-purity isopropyl acetate, which comprises discharging into high purity.