KR100250773B1 - Maximizing process efficiency for producing unsaturated carboxylic acid esters with its new apparatus - Google Patents

Abstract

PURPOSE: A process for producing unsaturated carboxylic esters is provided to achieve maximum catalyst utility by conversion of Flow Mode, forward direction of equilibrium reaction by smooth water-separation and easy operation at vacuum working process by continuously reacting unsaturated carboxylic acid and aliphatic alcohol having C1-C12. CONSTITUTION: A process for producing unsaturated carboxylic esters comprises continuously reacting unsaturated carboxylic acid and aliphatic alcohol having C1-C12 under a strong acidic cation-exchanging resin catalyst. The process consists of a first step of flowing a reactant solution upward a catalyst layer in a reactor filled with the catalyst as a fixed layer by using lower filer; a second step of supplying heat to react and to remove moisture by circulating the reactant solution passing through the reactor; a third step of transporting water content generated at the esterification process into water-separating column in azeotropic state of the water and alcohol; a fourth step of condensing a gas produced from the separating column in a condenser then passing it through a decanter; and a fifth step of refluxing organic layer alone or in a mixture with the alcohol supplied to the water-separating column.

Description

Maximizing Efficiency of Unsaturated Carboxylic Acid Ester Production Process and Its New Apparatus

The present invention is an improved method for producing unsaturated carboxylic acid esters and a novel production apparatus thereof (Patent Application No. 94-12614), which is a novel method for maximizing esterification conversion while retaining the advantages of conventional reactors. The present invention relates to a manufacturing process for maximizing the production efficiency of unsaturated carboxylic acid esters and a novel production apparatus thereof.

The existing reactor (Patent Application No. 94-12614) applied to the esterification reaction is a typical catalytic fixed bed reactor in which the circulation direction of the reaction liquid flows from top to bottom. The reactor takes an indirect heating method in which a part of the reaction liquid is forcedly circulated while supplying heat for the reaction through a heat exchanger installed next to the reactor. This separates the reaction part from the heating part and supplies the heat required for the reaction liquid to reach the reaction temperature, thereby making it difficult to operate the vacuum in Japanese Patent Laid-Open Publication No. 49-54326, the physical properties of the catalyst derived from Japanese Patent Laid-Open Publication No. 63-017844. The problem of the reaction process, such as a damage problem and catalyst damage by direct heating of Unexamined-Japanese-Patent No. 62-39150, is solved. In addition, it has advantages such as utility cost reduction due to efficient heat transfer, maintaining high conversion rate of the reaction in the form of a catalyst fixed bed reactor, and operating cost by reducing investment cost and power consumption.

The present invention for maximizing efficiency is aimed at maximizing the efficiency of the reactor while maintaining the advantages of the existing reactor. The concept of the efficiency maximization reactor devised in the present invention is basically due to the conversion of the flow mode, thereby maximizing the catalyst utilization efficiency, the forwarding of the equilibrium reaction due to the smooth water separation, and the ease of operation during the decompression operation. It has several fundamental advantages over conventional reactors.

Japanese Laid-Open Patent Publication No. 56-20544 mentioned a form in which the reaction liquid is sent from the bottom up in a resin catalyst fixed bed reaction system. However, by taking the direct heating form, the catalyst is damaged by heat and polymerization due to overheating and (meth) acrylic acid. Has disadvantages such as discharge to water separation tower.

The present invention provides a method for producing a corresponding unsaturated carboxylic acid ester by continuously reacting an unsaturated carboxylic acid with an aliphatic alcohol having 1 to 12 carbon atoms under a strong acid cation exchange resin catalyst, the catalyst by flow mode conversion. Disclosed are a new process for maximizing the efficiency of the new carboxylic acid esters and a new manufacturing apparatus thereof, which can achieve the maximum utilization efficiency, the normalization of the equilibrium reaction due to the smooth water separation, and the ease of operation in the decompression operation.

1 is a schematic diagram illustrating the main apparatus and process of the reactor of the present invention.

* Explanation of symbols for main parts of the drawings

1 catalytic reactor 2: catalyst layer in the reactor

3: filter in the reactor (catalyst holder) 4: water separation tower

5: heat exchanger 6: secondary water separation vacuum

7: circulation pump 1 8: circulation pump 2

9: condenser 10: decanter

Hereinafter will be described with respect to the maximization of the efficiency of the conventional reactor, the production process and the device for maximizing the efficiency of the unsaturated carboxylic acid esters shown in the drawings.

The reactor unit is mainly composed of catalytic reactor (1), water separation tower (4), heat exchanger (5), secondary water separation vacuum (6), circulation pumps (7, 8), condenser (9) and decanter (10). It consists of).

Reactor (1) having an outer wall is filled with a cation exchange resin catalyst (2) in the form of a fixed bed, the heat of the reaction liquid through the heat exchanger (5) located outside the reactor (1) to the heat required for reaction and water separation Indirect heating is supplied. That is, the direct heat transfer medium is a reaction liquid which circulates between the heat exchanger 5 and the insulated secondary water separation vacuum 6 while flowing the catalyst layer 2 in the reactor 1 from the bottom up.

Unsaturated carboxylic acid and C1-C12 (aliphatic) alcohol enter the bottom of the reactor through feedstock line 11. The raw material introduced into the reactor is in contact with the catalyst through the filter (3) and the esterification reaction proceeds, at which time the reaction solution takes the method of flowing the ion exchange resin catalyst layer (2) from the bottom up. The filter 3 in the reactor serves to support the catalyst 2 in the reactor 1 while separating the catalyst and the reaction liquid.

Moisture in the product produced by the esterification reaction is naturally transported to the water separation tower 4 through the pipe 12 in azeotropic form with the corresponding (aliphatic) alcohol and ester, so that moisture in the reaction system is primarily at the top of the reactor. .

Gases from the water separation column are liquefied through the condenser (9), and after passing through the decanter (10), the organic layer is separated through the pipe (19) alone or with (aliphatic) alcohol supplied to the water separation column (4). It is refluxed to the tower 4 to prevent the discharge of acid from the reactor 1 to the water separation tower (4). Part of the water layer is used to leave the reaction system through the pipe 20 to be transferred to the separation / purification system and the other part of the water layer is treated in the water treatment process.

Other reaction products and unreacted materials are sent to the heat exchanger 5 via a circulation pump 2. The heat exchanger 5 takes the form of a typical shell and tube, and the heat medium or steam flows into the shell side 17 and flows out 18 to supply the circulating fluid with heat required for the reaction. The reaction liquid obtained sufficient heat from the heat exchanger (5) is decanted from the liquid and gas in the secondary water separation vacuum (6) so that the gaseous phase is separated from the water separation tower (4) with the gas from the top of the reactor through the pipe (14). ), The liquid is circulated at a high speed through the pipe 15 through the circulation pump 1 to the bottom of the reactor, and some of them are separated from the reaction system through the pipe 21 as a product of the reaction process of the present invention. Transferred to the refinery.

In addition, a polymerization inhibitor is introduced into the lower part of the heat exchanger 5 having the highest fear of overheating, and a small amount of synergistic air is supplied through the pipe 16, and if necessary, a small amount of the raw material pipe 11 is provided. Air can be added.

The efficiency maximization reactor having such a conversion flow mode accepts the advantages of the existing reactor as it is, but has advantages such as the most essential catalytic reaction, equilibrium reaction and operability compared to the conventional flow mode. The following is a description of each major advantage of the present invention compared to conventional reactors.

[Maximum Catalyst Utilization Efficiency by Conversion of Flow Mode]

In general, in the Nth-order catalytic reaction (except for the autocatalytic reaction flow), the plug flow mode (Recycle Ratio = 0) obtained by placing the catalyst on a fixed bed is compared to the mixed flow mode (Recycle Ratio = ∞) obtained by physically fluidizing the catalyst. In the case of the continuous process of introducing the same flow rate, the unit conversion rate is known to be high. This is due to the characteristics of each flow mode, and in this catalytic reaction, the PFR (Plug Flow Reactor) side is advantageously applied than the CSTR (Continuous Stirred Tank Reactor), and it is interpreted that the target conversion rate can be obtained with a small amount of catalyst.

However, in the esterification reaction dealing with the present invention, the equilibrium reaction as well as the catalytic reaction acts as an important factor of the overall reaction. Therefore, the optimal reactor for the esterification reaction should be designed to maximize the catalytic reaction by maximizing the properties of the PFR while maximizing the water removal and the whole reaction toward the forward reaction. Existing reactor is based on catalytic reaction superior to CSTR by maintaining PFR Flow Mode, and partially satisfies the conditions for inducing forward reaction by recycling the reaction solution once to remove moisture per single loop, but from top to bottom Due to the flow mode in the direction, contact between the catalyst and the reaction solution becomes inefficient, which may cause problems such as axial, radial distribution, and channeling.

Therefore, in this efficiency maximization reactor, the flooded bed type, which sends the reaction solution from the bottom up, maximizes the contact between the catalyst and the reaction solution and minimizes the channeling. This is the most fundamental difference from the existing reactor. This type of upflow mode is not suitable for extreme pressurization due to the capacity and economical issues of the compressor, but it is the best flow mode when using the catalyst fixed bed reactor to which atmospheric pressure and depressurization are applied like this esterification process. It should be set in consideration of.

[Forwarding Equilibrium Reaction Due to Smooth Water Separation]

In the esterification reaction, acid and alcohol are catalyzed under reduced pressure to produce water and ester. At this time, the generated water has an upward driving force to boil. In the existing reactor, a forced circulation method that physically obstructs this flow of water generated in the catalyst bed and pushes it downward is forced. Getting drunk. This circulating method of circulating the reaction liquid in the reverse direction with the driving reaction of water is one of the obstacles to inefficient water separation. In the factory site, the vacuum is applied at the top of the water separation tower, so when the upflow mode is taken, the driving force of the gas in the reactor connected to the water separation tower is the same as the direction of the vacuum at the top of the tower, so that water can be moistened more smoothly. It eliminates the effect of forcibly lowering the gas driving force upward in the downflow mode, and the operation is much smoother and the moisture removal is maximized to maximize the forward equilibrium reaction. This is based on the forward relationship between the driving force of the water and the flow mode, and applied / applied the principle of reboiling installed at the bottom of the distillation column in the factory.

[Easy operation during decompression operation]

One of the indispensable conditions at the factory production site is ease of operation. As described above, if the reaction liquid is forcedly circulated to the reactor under reduced pressure in the existing down flow mode after considering the optimum circulation ratio of the existing invention reactor, a pressure drop between the head of the liquid passing through the catalyst bed and the suction side of the circulating pump is generated. There is a big risk that Vapor Pocket will be formed. In particular, when such a vapor pocket is formed in the lower part of the reactor, the desired flow rate cannot be recycled, and this causes an abnormal influence on the overall reaction kinetics. This problem is fundamentally solved when using the upflow mode derived from the present invention. In other words, when converting the flow mode to Upflow, which is the direction for maximizing efficiency, it is possible to eliminate the possibility of Vapor Pocket, which may occur in the lower part of the reactor, and thus, it is possible to send the circulated amount of the reaction solution at the desired optimum flow rate.

Example 1

In Example 1, an experiment was performed while flowing the reaction liquid from the bottom of the catalyst layer with the apparatus described in FIG. 1 and the configuration and operation of the present invention to obtain a flow mode conversion comparison result with the existing reactor.

The experiment was carried out on the butyl acrylate reaction process, and the Amberlyst 39 strongly acid cation exchange resin catalyst of Rohm & Haas was used as the butyl acrylate synthesis continuous process catalyst.

The reactor used in the experiment was a 3.5L reactor made of glass and filled with a 2.0L resin catalyst by wet volume. After the catalyst was used, the catalyst was washed with 60% butyl acrylate, 30% acrylic acid, and 10% butanol to remove water from the catalyst. The experiment was carried out through the catalyst pretreatment.

As the reaction conditions of the experiment performed, 1.3L of a reaction solution having a molar ratio (BuOH: AA) of butanol and acrylic acid (1.2) was introduced into the reactor, followed by the first instant of water from the water separation tower while maintaining the catalyst temperature in the reactor at 72 ° C. From was considered as reaction time. The volume ratio of the reaction solution and the wet resin catalyst was 0.65.

The temperature of the reactor was measured by installing a glass thermowell inside the reactor to measure the Axial temperature profile of the catalyst layer. In the reactor used in the present invention, it was found that the temperature profile of the catalyst layer was a constant temperature operation showing a nearly constant tendency. Considering the thermodynamic phenomenon of the butyl acrylate formation reaction, it is known to be accompanied by a slight exotherm, but it was analyzed that it does not have a significant effect on the catalyst bed constant temperature operation of the reactor. In addition, it was visually confirmed that the reaction solution reached the boiling state while passing through the heat exchanger.

The produced water was continuously removed from the water separation tower, and the reaction solution was continuously recycled, and a semibatch-type execution method was performed in which some of the water was sampled over time. The pressure on the water separation tower tower connected to the reactor was 135 Torr, and the total semibatch reaction time was 300 minutes. The reaction solution circulated at the bottom of the reactor was sampled and analyzed at 30 minute intervals.

During the water removal and reaction experiment, PT (Phenothiazine), a polymerization inhibitor of amines dissolved in 70% butanol and 30% butyl acrylate solution, was introduced into the reactor so that the total amount of the reaction solution was 3000 ppm or more. Continuously flowed into the bottom of the heat exchanger.

This experiment focused on the conversion of acrylic acid and the conversion rates based on acrylic acid were 79%, 86%, 88% and 92% at 90, 120, 150 and 180 minutes for each batch of reaction time.

As mentioned earlier, there were no operational difficulties due to the formation of Vapor Pocket at the bottom of the reactor.

Example 2

In the present Example 2, the apparatus used in Example 1, such as a reactor and a heat exchanger, was used as it was, while the preparation of the reaction solution and the amount of catalyst, reaction conditions, the manner of carrying out the reaction, and the administration of the polymerization inhibitor were also the same. Increased the validity of However, the conditions and apparatus different from those of Example 1 are different from those of using the water separation vacuum used in Example 1, and the improved manufacturing method of unsaturated carboxylic acid esters and the new manufacturing apparatus thereof (Patent Application No. 94-12614). As mentioned in the present invention, the reaction solution was circulated while flowing down from above the catalyst bed.

The experimental results were 72%, 78%, 85%, and 87% of acrylic acid conversion at 90, 120, and 180 minutes of reaction batch time.

In the depressurization operation, some vapor pockets were formed intermittently between the catalyst bed and the bottom of the reactor. As a result of examining the flow of the reaction liquid at the lower end of the catalyst bed, it was observed that the fluid passed through the catalyst bed as a channeling phenomenon. This shows the localization phenomenon between the reaction solution and the catalyst bed.

Claims (9)

A method for producing a corresponding unsaturated carboxylic acid ester by continuously reacting an unsaturated carboxylic acid with an aliphatic alcohol having 1 to 12 carbon atoms under a strong acid cationic resin catalyst, wherein a) an outer wall is insulated, and a cation is used by using a lower filter. Allowing the reaction liquid to flow from the bottom to the top in the reactor in which the exchange resin catalyst is filled in a fixed bed shape; b) circulating the reaction liquid passing through the reactor through a heat exchanger to supply heat for reaction and water removal; c) transferring the water produced by the esterification reaction to the water separation tower while azeotropic with the aliphatic alcohol and the ester; d) condensing gases from the water separation column in a condenser and passing through a decanter; And e) refluxing the organic layer alone or together with the aliphatic alcohol supplied in the water separation column to the water separation tower, and removing the water layer from the reaction system. The process of claim 1, wherein the reaction solution exiting the heat exchanger is subjected to secondary water separation using an insulated water separation vacuum to drive the esterification reaction to the forward reaction. The method according to claim 1 or 2, wherein the unsaturated carboxylic acid is acrylic acid and methacrylic acid. The method of Claim 1 or 2 using 100-5000 ppm amine polymerization inhibitor based on the total weight of reaction liquid. The method according to claim 1 or 2, wherein air is supplied to the heat exchanger and the reactor bottom to prevent polymerization. The method of Claim 1 or 2 whose reaction temperature is 50-150 degreeC. The method according to claim 1 or 2, wherein the reaction pressure is 10 to 1500 Torr. The method according to claim 1 or 2, wherein the molar ratio of unsaturated carboxylic acid to aliphatic alcohol is 1: 0.5 to 2.0. The method of claim 4 wherein air is supplied to the bottom of the heat exchanger and reactor to prevent polymerization.

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