JP2014148481A - Method for manufacturing alkylene carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing alkylene glycol, capable of reacting alkylene oxide, carbon dioxide and water to form alkylene glycol and efficiently stably carbonating the alkylene oxide and hydrolyzing alkylene carbonate for a long period of time.SOLUTION: The method for manufacturing alkylene glycol comprises: forming alkylene carbonate by carbonating alkylene oxide; and performing reaction for carbonating the alkylene oxide using two or more reactors connected in-series when forming the alkylene glycol by hydrolyzing the alkylene carbonate in the presence of alkali metal carbonate. The temperature of the first reactor is 70°C or more and 100°C or less.

Description

  The present invention relates to a method for producing an alkylene glycol in which an alkylene oxide is produced by reacting an alkylene oxide with carbon dioxide and water. Specifically, the present invention relates to a process for producing alkylene glycol by producing alkylene carbonate by carbonated alkylene oxide and hydrolyzing it in the presence of an alkali metal carbonate to produce alkylene glycol. It is about. According to the present invention, alkylene carbonate carbonateation and alkylene carbonate hydrolysis can be carried out efficiently and stably over a long period of time.

Alkylene glycol is used as a raw material for polyurethane, unsaturated polyester resin and antifreeze. In particular, ethylene glycol is an organic compound useful as a raw material for polyester fibers.
Ethylene glycol can be produced by adding ethylene oxide and water in the absence of a catalyst. However, when ethylene glycol is produced by this method, a large excess of water is used to suppress by-products such as diethylene glycol, triethylene glycol, and polyethylene glycol, so that a great deal of energy is required for water removal. There is a problem.

  As a method for solving this problem, a method for producing ethylene glycol by reacting water and ethylene oxide in the presence of carbon dioxide has been proposed. In this method, ethylene oxide and carbon dioxide are reacted in the presence of a catalyst to produce ethylene carbonate (hereinafter sometimes referred to as “carbonation step”), and the produced ethylene carbonate is reacted in the presence of an alkali metal carbonate. The reaction is carried out in two stages in which ethylene glycol is produced by hydrolysis (hereinafter sometimes referred to as “hydrolysis step”). In this method, since diethylene glycol, triethylene glycol, or the like is hardly generated as a by-product, the amount of water used for hydrolysis can be reduced.

  In the case of producing ethylene glycol by this method, when taking out the alkylene glycol generated after hydrolysis and circulating the residual liquid to the carbonation step, in order to prevent the activity decrease due to chlorination of the carbonated catalyst due to long-term reaction, A method of regenerating a catalyst by adding iodide or bromide to a carbonated catalyst solution and precipitating and removing chloride in an organic solvent is disclosed (Patent Document 1). Also disclosed is a method of removing a liquid containing chlorine ions in order to prevent alkali metal carbonate from becoming a chloride due to a long-term reaction, reducing the activity of the hydrolysis catalyst, and leaving unreacted alkylene carbonate remaining. (Patent Document 2).

  However, in order to efficiently and stably carry out alkylene carbonate carbonateation and alkylene carbonate hydrolysis over a long period of time, further improvement of the production method has been demanded.

JP 2004-292384 A International Publication WO2011 / 136127

  The present invention has been made in view of the above-mentioned present situation. An alkylene carbonate is produced by carbonated alkylene oxide, and an alkylene glycol is produced by hydrolyzing it in the presence of an alkali metal carbonate. It is an object of the present invention to provide a method for producing an alkylene glycol according to the present invention, which can efficiently and stably carry out alkylene carbonate carbonateation and alkylene carbonate hydrolysis for a long period of time.

  The present inventor has intensively studied to solve the above problems. As a result, when alkylene glycol is produced by hydrolyzing alkylene carbonate produced by carbonated alkylene oxide in the presence of an alkali metal carbonate, two or more reactions to carbonate the alkylene oxide are performed. It has been found that the above-mentioned problem can be solved when the temperature of the first reactor is set to 70 ° C. or higher and 100 ° C. or lower when the reaction is performed using a series reactor.

  That is, the first gist of the present invention is to produce alkylene glycol by reacting alkylene oxide with carbon dioxide and water to produce alkylene glycol, wherein the alkylene glycol is produced by carbonated alkylene oxide. Produced by hydrolyzing the alkylene carbonate in the presence of an alkali metal carbonate, and the reaction for carbonated the alkylene oxide is carried out using two or more series reactors, the first reactor The temperature is 70 ° C. or higher and 100 ° C. or lower. The second gist of the present invention resides in the method for producing alkylene glycol described in the first gist, wherein the alkylene oxide contains a chlorine compound. The third gist of the present invention is the method for producing alkylene glycol according to the first or second gist, wherein after the hydrolysis, the produced alkylene glycol is taken out and the remaining liquid is circulated to the carbonation step. It exists in the manufacturing method of alkylene glycol characterized by the above-mentioned. A fourth aspect of the present invention is the process for producing alkylene glycol according to any one of the first to third aspects, wherein the two or more series reactors include two or more bubble columns and a plug flow. The present invention resides in a process for producing alkylene glycol, wherein a plug flow reactor is connected in series after the bubble column.

  According to the present invention, high-purity alkylene glycol can be efficiently produced at low cost and stably for a long period of time by a simple method.

Hereinafter, embodiments of the method for producing alkylene glycol of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and the like, and may be arbitrarily set within the scope of the present invention. It can be changed and implemented.
The method for producing alkylene glycol of the present invention is a method for producing alkylene glycol by reacting alkylene oxide with carbon dioxide and water. Specifically, in the method for producing alkylene glycol of the present invention, alkylene carbonate is produced by carbonated alkylene oxide, and alkylene glycol is produced by hydrolyzing it in the presence of an alkali metal carbonate. Here, the carbonation reaction is carried out using two or more series reactors, and the temperature of the first reactor is 70 ° C. or more and 100 ° C. or less.

In the method for producing alkylene glycol of the present invention, the carbonation and hydrolysis may be carried out in the same reactor even if the carbonate is reacted with a carbonate reactor and then hydrolyzed with the reactor for hydrolysis. Chemical conversion and hydrolysis may be performed. Further, since the method for producing alkylene glycol of the present invention can efficiently perform carbonateation and hydrolysis for a long period of time stably, the method for producing alkylene glycol of the present invention is preferably applied to continuous operation, It is particularly preferable to apply to continuous operation for one year or more.

(1) Carbonation step The carbonation step is a step of producing alkylene carbonate by reacting alkylene oxide and carbon dioxide in the presence of a catalyst.
Catalysts used in the carbonation step (sometimes referred to as “carbonation catalysts”) include alkali metal bromides or iodides, alkaline earth metal halides, alkylamines, quaternary ammonium salts, organotins, germaniums, What is necessary is just to use suitably selecting from well-known carbonation catalysts, such as a tellurium compound and halogenated organic phosphonium salt. Of these, quaternary phosphonium salts are preferable, and quaternary phosphonium iodides or quaternary phosphonium bromides are more preferable. Specifically, triphenylmethylphosphonium iodide, triphenylpropylphosphonium iodide, triphenylbenzylphosphonium iodide, tributylmethylphosphonium iodide, and the like are particularly preferable. The carbonated catalyst is preferably supplied to the carbonated reaction system in an amount of 0.001 to 0.05 times mol of alkylene oxide.

  In the carbonation step according to the present invention, an alkali metal carbonate is preferably present from the viewpoint of the production efficiency of alkylene glycol. The alkali metal carbonate can be present by adding the alkali metal carbonate to the reaction system in the carbonation step. The alkali metal carbonate is preferably sodium carbonate or potassium carbonate. Further, if it exists as a carbonate in the reaction system, it may be added as a hydroxide or bicarbonate. In the case where an alkali metal carbonate is present in the carbonation step, the alkali metal carbonate has a molar ratio of 0.01 to 1 with respect to a carbonated catalyst such as a quaternary phosphonium iodide from the viewpoint of easily maintaining the hydrolysis rate. It is preferable to make it exist. That is, when the hydrolysis rate decreases due to a long-term reaction or the like, it is preferable to add the alkali metal carbonate so as to have the above concentration.

  The carbonation reaction according to the present invention is carried out using two or more series reactors. The reactor used for carbonation can be carried out using any apparatus as long as the alkylene oxide is carbonated, but a bubble column is preferred. In addition, the temperature of the reactor can be determined by removing at least a part of the reaction liquid from the reaction tower using a bubble tower having a conduit having a heat exchanger for heat removal or heating and a circulation pump. Then, it is preferable to control by circulating in the reaction tower. Here, it is preferable that raw material alkylene oxide, carbon dioxide, and a carbonation catalyst are continuously supplied from the bottom of the column to continuously react. When the hydrolysis step is also performed in the carbonation step, it is preferable to continuously supply alkali metal carbonate and water from the tower bottom. Moreover, it is also preferable to perform a carbonation reaction using the reactor provided with the ejector type nozzle (Unexamined-Japanese-Patent No. 11-269110). The carbonation reaction according to the present invention is preferably performed using a bubble column group in which two bubble columns are connected in series, but even if the carbonate reaction is performed by connecting three or more bubble columns in series. good. The number of reactors for carrying out the carbonation reaction according to the present invention is preferably large from the viewpoint of easily reaching a high reaction rate even if the total residence time is short. On the other hand, from the viewpoint of the construction cost of the reactor. Is preferably less. Therefore, it is preferably 2 to 4 groups, more preferably 2 to 3 groups, and most preferably 2 groups.

In addition, a plug flow reactor (tubular reactor) is placed after the bubble column to allow the alkylene oxide to react efficiently and completely, and the alkylene oxide remaining in the reaction solution after the reaction is reacted in the bubble column. It is preferable to make it. The number of reactors for performing the carbonation reaction according to the present invention when using a plug flow reactor is most preferably the number of the above preferred reactors plus one plug flow reactor. preferable. That is, the carbonation step according to the present invention uses two or more bubble columns and a plug flow reactor, and uses a reactor in which a plug flow reactor is connected in series after the two or more bubble columns. It is preferable to carry out.

In the carbonation reaction according to the present invention, the temperature of the first reactor is set to 70 ° C. or higher and 100 ° C. or lower. Moreover, it is preferable that a minimum is 80 degreeC, and it is especially preferable that it is 85 degreeC. The upper limit is preferably 95 ° C, particularly preferably 90 ° C.
In the method for producing alkylene glycol of the present invention, by setting the temperature of the first reactor in the carbonation reaction to be in the above range, the reason for being able to carry out the carbonation and hydrolysis efficiently and stably for a long period of time is as follows. Is estimated as follows. That is, it is considered that when the temperature of the first reactor is higher than the lower limit, the carbonation reaction easily proceeds, and when the temperature is lower than the upper limit, a by-product is hardly generated. With regard to the upper limit, it is conceivable that the alkali metal carbonate reacts with an impurity such as a chlorine compound in the reaction due to the alkylene oxide as the raw material. Here, when the reaction temperature is high, the carbonation reaction rate becomes faster relative to the dissolution rate of carbon dioxide in the reaction solution, the amount of dissolved carbon dioxide decreases, the pH of the reaction solution increases, and chlorine It is considered that impurities such as compounds are decomposed and easily react with the alkali metal carbonate. Conversely, when the reaction temperature is low, the carbonation reaction rate is relatively slow relative to the dissolution rate of carbon dioxide in the reaction solution, and it is considered that impurity decomposition is not likely to occur due to the pH of the reaction solution being lowered. . As data supporting this assumption, in the examples described later, in the examples where the first reactor was in the above temperature range and in the comparative examples outside the above range, the residue obtained by taking out the alkylene glycol produced after hydrolysis was removed. When the liquid is circulated to the carbonation step and reacted for one year, the chlorine ion concentration in the circulating liquid shows lower data in the examples.

  Further, the temperature of the second and subsequent reactors in the carbonation reaction according to the present invention is preferably high in terms of the conversion rate of alkylene oxide, but is preferably low in terms of the fact that the decomposition of the carbonation catalyst hardly occurs. Therefore, the lower limit is preferably 135 ° C., more preferably 140 ° C., the upper limit is preferably 160 ° C., and more preferably 155 ° C.

  The pressure during the reaction is preferably a high pressure from the viewpoint of high carbon dioxide solubility, but is preferably a low pressure from the viewpoint that the required power of the compressor may be small. Therefore, it is preferably 0.5 MPa or more, more preferably 1.0 MPa or more, and on the other hand, it is preferably 5.0 MPa or less, and more preferably 3.0 MPa or less.

  As the raw material alkylene oxide, ethylene oxide, propylene oxide or the like is used. The purity of the alkylene oxide is preferably high from the viewpoint of easily obtaining high-purity alkylene glycol by the method for producing alkylene glycol of the present invention, but is preferably low-purity from the viewpoint of the price of the alkylene oxide. As the raw material alkylene oxide, specifically, ethylene oxide produced by a gas phase oxidation reaction of ethylene can be used. When ethylene oxide is produced by this method, chlorohydrocarbon is usually used as a selectivity control agent. However, in the method for producing alkylene glycol of the present invention, chlorine compounds such as chlorohydrocarbon are included for the reasons described above. The alkylene oxide containing a chlorine compound is preferable because it is considered that an excellent effect is obtained even when the alkylene oxide used is used as a raw material.

The amount of carbon dioxide used in the carbonation step is preferably 0.1 to 5.0 moles relative to the alkylene oxide.
In the carbonation step according to the present invention, due to the presence of water, a part of the produced alkylene carbonate is hydrolyzed to alkylene glycol. The hydrolysis reaction proceeds easily even in the presence of equimolar or less carbon dioxide relative to the alkylene oxide. When the alkylene carbonate is also hydrolyzed in the carbonation step, the amount of water relative to the alkylene oxide is usually preferably 1.0 to 10 moles relative to the alkylene oxide.

  The conversion rate of alkylene oxide in the carbonation step according to the present invention is preferably high for safety. That is, in the carbonation step, a gas containing carbon dioxide is usually distilled, but since the unreacted alkylene oxide is contained in the gas, it is preferable to compress it and circulate it in the reaction step. Here, the lower the concentration of alkylene oxide in the gas, the higher the safety when compressing the gas. Therefore, the conversion rate of alkylene oxide is preferably 95% or more, and more preferably 99% or more.

  Further, in the carbonation step according to the present invention, the conversion rate from the alkylene carbonate to the alkylene glycol is preferably high in terms of easily reducing the load of the hydrolysis step, but is low when extracted as the alkylene carbonate. preferable. Moreover, since the hydrolysis reaction of alkylene carbonate is an endothermic reaction, it is preferable that the amount of the heat medium necessary for maintaining the temperature in the carbonation step is small and the energy loss is also low. Therefore, the conversion rate of the alkylene carbonate is preferably 10% or more, more preferably 30% or more, and on the other hand, it is preferably 90% or less, more preferably 80% or less. .

  In the method for producing alkylene glycol of the present invention, as described above, alkylene glycol may be produced in the carbonation step, or the reaction solution obtained in the carbonation step is sent to the hydrolysis step, and in the carbonation step. The produced alkylene carbonate may be hydrolyzed to produce alkylene glycol. Moreover, you may collect | recover alkylene carbonate from some reaction liquids obtained at the carbonation process, and send a residual liquid to a hydrolysis process.

(2) Hydrolysis step The hydrolysis step is a step of hydrolyzing the alkylene carbonate produced in the carbonation step in the presence of an alkali metal carbonate to produce alkylene glycol.
The temperature at which the hydrolysis reaction is carried out is preferably a high temperature in terms of the reaction rate, but a low temperature is preferable in terms of the quality of the produced alkylene glycol. Therefore, it is preferable to carry out at 100 to 180 ° C. Although the pressure at the time of performing a hydrolysis reaction will be arbitrary if it is below the boiling point of a reaction liquid, Usually, it is normal-pressure -2.1 Mpa. In terms of the ease of the hydrolysis reaction, the reaction temperature is preferably increased and the pressure is preferably decreased as the reaction proceeds.

  The amount of water present at the time of the hydrolysis reaction is sufficient if it is an equimolar amount or more with respect to the alkylene carbonate, but it is possible to supply an extra amount that evaporates with carbon dioxide as the hydrolysis reaction proceeds. preferable. Specifically, it is usually preferable to supply 10 times mol or less, preferably 1 to 5 times mol for the alkylene oxide. The method for supplying water may be any of supplying the whole amount by a carbonation reaction or adding in a hydrolysis step. Moreover, when adding at a hydrolysis process, you may divide and supply in multiple times with progress of reaction. In the case of a continuous reaction, water may be supplied as a liquid or water vapor. Further, the water evaporated together with the carbon dioxide generated along with the hydrolysis of the alkylene carbonate may be condensed and returned to the reactor.

  The reactor that performs the hydrolysis step is not particularly limited as long as the alkylene carbonate produced in the carbonation step can be hydrolyzed into alkylene glycol, but carbon dioxide is usually generated as the hydrolysis reaction proceeds. Use a reactor equipped with equipment that can remove the carbon dioxide. Further, since the hydrolysis reaction is an endothermic reaction, it is preferable to include a heat exchanger for heating. When a heat exchanger is provided, the heat exchanger may be installed in the reactor, or a part of the reaction solution is withdrawn from the reactor and heated and then returned to the reactor. It may be installed. The hydrolysis reaction may be carried out in a single reactor, but in order to maintain a high conversion rate of alkylene carbonate, a partition is provided inside the reactor to control the flow of liquid, or a plurality of reactors. It is preferable to react using

  The kind and amount of alkali metal carbonate used in the hydrolysis step are as described above. That is, when an alkali metal carbonate is used in the carbonation step, the alkali metal carbonate contained in the reaction solution after the carbonation step can be used as it is. Moreover, when the alkali metal carbonate in a hydrolysis process is less than the said density | concentration, it is preferable to add so that it may become the said density | concentration.

(3) Dehydration process The alkylene glycol produced | generated in the carbonation process and hydrolysis process based on this invention can be refine | purified by a well-known method. The purification of alkylene glycol is usually carried out by distillation. Specifically, it is preferable to remove water by distillation under reduced pressure. Here, the liquid from which water has been removed by distillation usually contains alkylene glycol, dialkylene glycol, other high-boiling components, a carbonation catalyst, and the like.

(4) Catalyst separation and circulation process The liquid dehydrated by distillation is preferably supplied to a flushing tank to vaporize high boiling components such as alkylene glycol and dialkylene glycol and take out. Further, in the method for producing alkylene glycol of the present invention, the produced alkylene glycol and dialkylene glycol are taken out, and the remaining high-boiling components such as alkylene glycol and dialkylene glycol, a carbonated catalyst and a hydrolysis catalyst are contained. Is preferably recycled to the carbonation step. Further, a part of the liquid containing the carbonated catalyst may be bleed. Further, the carbonated catalyst may be recovered from the bleed liquid and supplied to the carbonated reactor. It is preferable to use an apparatus equipped with a reboiler as the evaporation apparatus to supply energy necessary for evaporation and control the evaporation amount.

(5) Purification step The high-boiling components such as alkylene glycol and dialkylene glycol taken out as described above are appropriately purified by a known method. Specifically, for example, distillation separation can be performed under reduced pressure, and alkylene glycol can be obtained as the top component.
By the method for producing alkylene glycol of the present invention, carbonation and hydrolysis can be carried out efficiently and stably over a long period of time. Specifically, the process for producing alkylene glycol of the present invention enables continuous operation for one year or more.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by a following example, unless the summary is exceeded.
[Raw material]
In both Example 1 and Comparative Example 1, ethylene oxide produced by subjecting ethylene to a gas phase oxidation reaction using chlorohydrocarbon as a selectivity regulator was used as a raw material.

[Measurement method of chloride ion concentration]
Chlorine ion concentration was measured by precipitation titration analysis.

(1) Carbonation process Carbonate pressurized with carbon dioxide at 2.0 MPa, a first bubble column (90 ° C.), a second bubble column (150 ° C.), and a plug flow reactor connected in series in this order. By supplying 78 parts by weight of an aqueous ethylene oxide solution (60% by weight), 5 parts by weight of tributylmethylphosphonium iodide and 0.8 parts by weight of potassium carbonate / hour to the hydrogenation reactor, ethylene carbonate and ethylene glycol were obtained. A liquid containing was obtained. In this reaction, the conversion of ethylene oxide was 99%. The ethylene oxide concentration at the outlet of the plug flow reactor was 10 ppm by weight or less by gas chromatography.

(2) Hydrolysis step The reaction solution obtained in the carbonation step is supplied to a first hydrolysis reactor at 1.8 MPa and 150 ° C. to carry out a hydrolysis reaction of ethylene carbonate, followed by 0.2 MPa, 150 The remaining ethylene carbonate was hydrolyzed in a second hydrolysis reactor at 0 ° C. to obtain a liquid after the hydrolysis step. As a result of analyzing this liquid by gas chromatography, ethylene glycol was 70% by weight and ethylene carbonate was not detected (the detection limit of ethylene carbonate by gas chromatography was 0.5 ppm).

(3) Dehydration step The liquid obtained in the hydrolysis step was distilled under reduced pressure using a distillation column at a tower bottom of 140 ° C. and 80 torr to obtain a liquid dehydrated from the tower bottom. Ethylene glycol was evaporated from this solution using a vacuum evaporator at 140 ° C. and 60 torr.
(4) Catalyst separation and circulation step The catalyst-concentrated liquid was recovered from the bottom of the evaporator (13 parts by weight / hour) and recycled to the carbonation step to reuse the catalyst.

(5) Purification step The liquid obtained from the top of the evaporator was introduced into a distillation column and distilled at a column top pressure of 50 torr and a column bottom temperature of 160 ° C. to obtain ethylene glycol from the column top.
Although continuous operation was continued for one year, both the carbonation reaction and the hydrolysis reaction were able to continue without problems. Moreover, the accumulation | storage rate of the chlorine ion calculated | required from the chlorine ion density | concentration in the circulating liquid after one year operation was 27 ppm / day.

[Comparative Example 1]
In Example 1, continuous operation was performed in the same manner as in Example 1 except that the temperature of the first bubble column in the carbonation step was set to 118 ° C. However, since ethylene carbonate was detected at the outlet of the hydrolysis reactor after 9 months of operation, a decrease in hydrolysis rate was confirmed, so a hydrolysis catalyst was added. The accumulation rate of chloride ions determined from the chloride ion concentration in the circulating fluid after continuous operation for one year was 95 ppm / day.

  From the above Examples, it was confirmed that the carbonate production of alkylene oxide and the hydrolysis of alkylene carbonate could be efficiently and stably performed for a long period of time by the method for producing alkylene glycol of the present invention.

Claims (4)

  In the method for producing alkylene glycol, wherein alkylene oxide is produced by reacting alkylene oxide with carbon dioxide and water, the alkylene glycol is produced by carbonated alkylene oxide, and the presence of alkali metal carbonate The reaction is carried out under hydrolysis and the carbonate reaction of the alkylene oxide is carried out using two or more serial reactors, and the temperature of the first reactor is 70 ° C. or higher and 100 ° C. or lower. A process for producing an alkylene glycol, characterized in that   The method for producing alkylene glycol according to claim 1, wherein the alkylene oxide contains a chlorine compound.   The method for producing alkylene glycol according to claim 1 or 2, wherein after the hydrolysis, the produced alkylene glycol is taken out and the remaining liquid is circulated to the carbonate step. Method.   The method for producing alkylene glycol according to any one of claims 1 to 3, wherein the two or more series reactors are two or more bubble columns and a plug flow reactor, A process for producing an alkylene glycol, wherein the plug flow reactors are connected in series later.