SG185059A1

SG185059A1 - Method for producing alkylene carbonate and/or alkylene glycol

Info

Publication number: SG185059A1
Application number: SG2012079554A
Authority: SG
Inventors: Masahiko Yamagishi; Takayoshi Ono
Original assignee: Mitsubishi Chem Corp
Priority date: 2010-04-28
Filing date: 2011-04-21
Publication date: 2012-12-28
Also published as: BR112012027617B1; KR20160039307A; BR112012027617A2; KR101663347B1; TWI511947B; WO2011136127A1; JP5725019B2; TW201141820A; KR20130056242A; CN102858727A; CN102858727B; KR101671155B1; JPWO2011136127A1

Abstract

METHOD FOR PRODUCING ALKYLENE CARBONATE AND/oR ALKYLENE GLYCOLA asitlyn 44y; Fixpdilc-Lng aLkyler4e carbEhatn end/or aEkylebe alycol is providsd, sompriaino a aeacdial step of reacting alkylena okida, water, &mica:tan dioxido in tha preasnut of a catalyst and an alkali metal. caxbenate to prate alkvlete carbonate dud/or alkylenn glycol, and a catalyst circulation atcp of ixavexing ethylene carbonate or alkyleno glyeel frcm a reaction liquid obtalsexi in the reaction step to cixtulete A eatalyat Livid containing the catalyst to the regactim ntep, an object off .0,40cai is to pthvith anch a prodactihn meth:xi that any precipitate is not act-mutated in a reaction system while aaihtaining the hytnolysis rate, and the ccerationcan beperforwed. tably for a long period of duet The method (xavnisee a etw oE ramoving an alkali rental chloride originating EITKEE the alkali metal cathonate =stained in the reaction liquid, or cillorine,ion originating fixAu ti-16 aeral entoride No suitable figure

Description

DESCRIPTION

METHOD FOR PRODUCING ALKYLENE CARBONATE AND/OR

ALKYLENE GLYCOL

Field of the Invention:

[0001]

The present invention relates to a method for producing alkylene carbonate and/or alkylene glycol wherein alkylene oxide and carbon dioxide are reacted in the presence of a catalyst and an alkali metal carbonate to produce alkylene carbonate, and the alkylene carbonate contained in a reaction liquid is further "hydrolyzed to produce alkylene glycol. : * Description of the Related Art:

[0002]

Ethylene glycol is produced on a large scale by means of a

CT method in which ethylene oxide and water are directly reacted with each other to perform the hydrolysis. However, in the case of this method, it is necessary to use water which is in a large excess amount as compared with the stoichiometric amount with respect to ethylene glycol in order to control the byproduction of, for example, diethylene glycol and triethylene glycol when the hydrolysis is performed. For this reason, it is necessary that an aqueous solution of produced ethylene glycol should be distilled to perform dehydration in a large excess amount. A problem arises such that a great deal of energy is required to obtain purified ethylene glycol.

[0003]

A method, in which ethylene glycol is produced by reacting water and ethylene oxide in the presence of carbon dioxide, has been proposed as a method for solving this problem. The reaction thereof is carried out at two stages such that ethylene carbonate is produced by reacting ethylene oxide and carbon dioxide (hereinafter referred "to as “carbonation step"), and then ethylene glycol is produced by ’ hydrolyzing ethylene carbonate (hereinafter referred to as "hydrolysis step™). In the hydrolysis of ethylene carbonate, for exanple, diethylene glycol and triethylene glycol are scarcely byproduced. Therefore, the hydrolysis can be performed with water which is in a slightly excess amount as compared with the - stoichiometric amount, It is possible to greatly decrease the cost : required for the dehydration of the agueocus solution of produced ethylene glycol. Carbon dioxide is produced when ethylene carbonate is hydrolyzed. Therefore, this carbon dioxide is circulated and . used. Further, it is also possible to produce ethylene carbonate by extracting ethylene carbonate produced as an intermediate in this method.

[0004] *

The method as described above has been such a problem that the activity of the catalyst is reduced in the carbonation step. The following methods have been disclosed as countermeasures thereof.

That is, a method has been disclosed (Patent Document 1), in which the reduction of the activity of the carbonation catalyst is avoided such that a condensation liquid (condensate), which is accompanied with carbon dioxide released in the hydrolysis step, is returned to the carbonation step. Further, a method has been disclosed (Patent

Document 2), in which the catalyst is reproduced or regenerated by : adding an iodide or a bromide to a catalyst liquid so that a chloride is sedimented or precipitated in an organic solvent and the chloride is removed, because it has been found out that the cause of the reduction of the activity of the catalyst in the carbonation step is the chlorination of the catalyst. However, no disclosure has been hitherto provided about the reduction of the activity of the catalyst in the hydrolysis step and about any method for avoiding the activity reduction. [Prior Arts] : [Patent Pocument:]

[0005] [Patent Document 1] Japanese Patent Application Laid-open No. 2000- 143563 . [Patent Document 2] Japanese Patent Application Laid-open No. 2004- 292384 ’

SUMMARY OF THE INVENTION

[0006]

The present invention resides in a method for producing alkylene carbonate and/or alkylene glycol comprising a reaction step of reacting alkylene oxide, water, and carbon dioxide in the presence of a catalyst and an alkali metal carbonate to produce alkylene carbonate and/or alkylene glycol, a recovering step of recovering . alkylene carbonate and/or alkylene glycol from a reaction liquid obtained in the reaction step, and : a catalyst circulation step of circulating a catalyst liquid containing the catalyst to the reaction step, an object of which is " to provide such a production method that precipitate is not : accumulated in a reaction system while maintaining the hydrolysis rate, and the operation can be performed stably for a long period of time.

[0007]

In order to achieve the object as described above, the present . inventors have firstly investigated the cause of the reduction of the activity of the hydrolysis catalyst. As a result, it has been found that potassium carbonate, which exists in the reaction system, is changed to potassium chloride as the reaction proceeds, and the velocity or rate of the hydrolysis reaction of ethylene carbonate is } consequently decreased or lowered, In particular; the cause of the decrease in the velocity of the hydrolysis reaction is considered as follows. ‘That is, chloro-hydrocarbon is used as a selectivity regulating agent in a step of producing ethylene oxide as a raw material. A trace amount of the chloro-hydrocarbon is mixed into the step of producing ethylene glycol or ethylene carbonate, and the chloro-hydrocarbon is further decomposed to provide chlorine ion. In this way, potassium carbonate contained in the reaction liquid is converted into potassium chloride, and the velocily of the hydrolysis reaction of ethylene carbonate is lowered little by little.

[0008]

Further, it has been revealed that the organochlorine compound stays at a high concentration of 80 to 420 ppm in a condensation liquid (condensate) cbtained when excessive carbon dioxide recovered in the carbonation step or carbon dioxide released from the hydrolysis reactor is ccoled.

[0009]

That is, the following fact has been found out, The organochlorine campound, which is the cause of the deceleration of the hydrolysis reaction, is concentrated in the liguid obtained by condensing the gas containing carbon dioxide released from the carbonation reactor or the hydrolysis reactor. Because of the recovery of the liquid, the organochlorine compound is gradually accumulated in the process, and the accumlated organochlorine compound is gradually decomposed, and potassium carbonate, which is used as the hydrolysis catalyst, is neutralized by chlorine ion. In view of the above, when the liquid, which contains the organochlorine compound, is bled to the outside of the system, it has been surprisingly found that the chlorination of the hydrolysis catalyst can be avoided, and it is possible to avoid the reduction of the activity of the hydrolysis catalyst.

[0010] - . Ethylene glycol is contained in an amount of about 5% to 30% in the condensation liquid of carbon dioxide released in the carbonation step or. from the hydrolysis reactor. When the chlorine ion {organochlorine compound) is bled, a problem arises such that ethylene glycol is also bled simultaneously. However, it has been revealed that the organochlorine compound can be separated by distillation frem ethylene glycol without causing any decomposition when the organochlorine compound is subjected to the distillation under a cendition in which potassium carbonate is absent.

[0011] i

Based on the knowledge as described above, the present inventors have found that the operation can be performed for a long period of time without accumulating any precipitate in the reaction system while maintaining the hydrolysis rate, by performing the reaction while removing the alkali metal chloride originating from the alkali metal carbonate contained in the reaction liquid or removing the chlorine ion originating from the alkali metal chloride.

[0012] :

That is, the present invention has the following features. (1) A method for producing alkylene carbonate and/or alkylene : glycol, comprising: : a reaction step of reacting alkylene oxide, water, and carbon dioxide in the presence of a catalyst and an alkali metal carbonate to produce alkylene carbonate and/or alkylene glycol, a recovering step of recovering alkylene carbonate and/or alkylene glycol from a reaction liquid obtained in the reaction step, and a catalyst circulation step of cireulating.a liquid containing the catalyst to the reaction step, said method further comprising: : a step of removing an alkali metal chloride originating from the alkali metal carbonate contained in the reaction liquid, and/or : chlorine ion originating from the alkali metal chloride. {2) The method according to (1), wherein the step of removing the alkali metal chloride originating From the alkali metal carbonate contained in the reaction liquid comprises exlracting a part or a total amount of the reaction liquid containing the catalyst obtained in the reaction step to distill and separate at least a part of alkylene glycol contained in the reaction liquid, and removing solid precipitated in the distillation separation operation, and : said catalyst circulating step comprises circulating a residual liquid obtained by removing solid precipitated in the distillation separation operation, to the reaction step.

(3) The method according to (1), wherein the step of removing the alkali metal chloride originating from the alkali metal carbonate contained jn the reaction liquid comprises extracting a part or a total amount of the reaction liquid containing the catalyst in the reaction step to distill and separate at least a part of alkylene glycol ‘contained in the extractec reaction liquid, and removing .solid precipitated in the distillation separation operation, and said catalyst circulating step comprises circulating the catalyst separated from a residual liquid ¢btained by removing solid precipitated in the distillation separation, to the reaction step.

(4) The method according to (2) or (3), wherein the precipitated solid is removed at not less than 80°C.

(5) The method according to (1), wherein: ‘

the reaction step comprises a carbonation step of reacting alkylene oxide and carbon dioxide in the presence of the catalyst and the alkali metal carbonate to produce alkyleme carbonate, and a . hydrolysis step of hydrolyzing alkylene carbonate contained in a reaction liquid of the carbonation step to produce alkylene glycol, and said step of removing chlorine ion originating from the alkali

. metal chloride camprises a condensation step of cooling a gas containing carbon dioxide released in the carbenation step and/or the hydrolysis step; and a step of discharging a condensation liquid obtained in the condensation step so that the catalyst liquid, which is circulated to the reaction step in the catalyst circulation step, hag the ratio of an alkalinity with respect to the catalyst concentration of not less than 0.03 mol/mol. (6) The method according to (5), wherein the condensation . liquid obtained in the step of removing chlorine ion is further dehydrated and distilled to remove water and an organochlorine compound contained therein, and then the resultant liquid is circulated to the reaction step. (7) The method according to (6), wherein said organochlorine compound is ethylene chlorohydrin. (B) The method according to any one of (5) to (7), wherein the condensation liquid is circulated to a place which is disposed at a hydrolysis reaction liquid supply stage or stages located thereover of a distillation tower for distilling and separating water contained in a hydrolysis reaction Liquid obtained in the hydrolysis step. (9) The method according to any one of (1) to (8B), wherein . the alkali metal carbonate is additionally added to the reaction . step. : {10} The method according to arly one of (1) to (2), wherein . alkylene carbonate is ethylene carbonate, and alkylene glycol is ethylene glycol.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]

Fig. 1 shows a graph illustrating a relationship between the number of operation days and the ratio of the alkalinity

(concentration of OH group of the hydrolysis catalyst contained in a ] catalyst liouid) with respect to the catalyst concentration in the catalyst liquid circulated to a carbonation step, in a reaction system in which a condensation liquid obtained in a hydrolysis step is discharged to the outside of the reaction system.

Fig. 2 shows a graph illustrating a relationship between the number of operation days and the chlorine ion concentration with respect to potassium contained in a catalyst liquid circulated to a carbonation step in a reaction system in which a condensation liquid obtainad in a hydrolysis step is discharged to the outside of the reaction system.

Fig. 3 shows a graph illustrating a relationship between the . number of operation days and the chlorine ion concentration with respect to potassium contained in a catalyst liquid circulated to a carbonation step in a reaction system in which a condensation liquid . : obtained in a hydrolysis step is not discharged to the outside of the reaction system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014]

The present invention will be explained in detail below. ‘ However, the present invention is not limited to embodiments and examples described below. The present invention can be carried out while arbitrarily changing within a range without deviating from the gist or essential characteristics of the present invention.

[0015] : The present invention relates to a method for producing :

alkylene carbonate and/or alkylene glycol comprising a reaction step of reacting alkylene oxide, water, and carbon dioxide in the presence of a catalyst and an alkali metal carbonate to produce alkylene carbonate and/or alkylene glycol, a recovering step of recovering alkylene carbonate and/or alkylene glycol from a reaction liquid obtained in the reaction step, and ' a catalyst circulation step of circulating a catalyst liquid containing the catalyst to the reaction step, the method further comprising a step of removing an alkali metal chloride originating from the alkali metal carbonate contained in the reaction liquid, ox chlorine ion originating fram the alkali metal chloride.

[0016]

The reaction step, which is referred to in the present invention, means both of the "carbonation step of producing alkylene carbonate” and the "hydrolysis step of further hydrolyzing alkylene carbonate contained in the reaction liquid after the carbonation step”. The carbonation step and the hydrolysis step will be explained below. However, the present invention is not limited to the reaction system in which the carbonation step and the hydrolysis ' step are performed separately, and these steps may be performed in a game reactor.

[0017] (1) Carbonation step

The catalyst for the carbonation step (this catalyst is referred to herein as "carbonation catalyst™ in some cases) may be used while being appropriately selected from known ones including, . for example, bromides or iodides of alkali metals, halides of alkaline earth metals, alkylamines, quaternary ammonium salts, organic stannum, germanium, or tellurium compounds, and halogenated organic phosphonium salts. In particular, quaternary phosphonium "iodide or bromide is preferably used. Specifically, there are exemplified, for example, triphenylmethylphosphonium iodide, triphenylpropylphosphonium iodide, triphenylbenzylphosphonitm iodide, and tributylmethylphosphonium iodide, It is preferable that the carbonation catalyst as described above is supplied to the reaction system so that the carbonation catalyst exists 0.001 to 0.05 time mole (mole ratio) with respect to alkylene oxide.

[0018]

Tn the carbonation step, it is also possible to similtaneously perform the hydrolysis reaction as described later as well as the carbonation reaction. When the hydrolysis reaction is performed simultaneously, the alkali metal carbonate is allowed to co-exist as the hydrolysis catalyst in the reaction system. Specifically, for exarple, a hydroxide, a carbonate, or a bicarbonate of scdium or potassium, preferably potassium may be added to the carbonation step.

Even when any alkali metal compound is added, the compound exists as a carbonate in the reaction system. In this case, the carbonate of alkali metal, preferably potassium carbonate is preferably allowed to exist to provide a mole ratio of 0.01 to 1.0 with respect to the carbonation catalyst including, for example, quaternary phosphonium sodide. "It is also preferable that the alkali metal carbonate is additionally added to the reaction system in order to maintain the concentration as described above.

[0019]

The method of the present invention comprises the step of removing an alkali metal chloride originating frem the alkali metal carbonate, or chlorine ion originating from the alkali metal chloride from the reaction system.

[0020] : } For example, ethylene oxide or propylene oxide 1s used as alkylene oxide which is the raw material. Purified alkylene oxide having a high purity may be used as alkylene oxide or any crude preparation may be used as alkylene oxide, but usually alkylene oxide contains trace amount of chloride compound such as chloro- hydrocarbon. Specifically, for example, in the case of ethylene oxide, it is possible to use crude ethylene oxide having a low purity containing water obtained from a step of producing ethylene oxide as described in WO 2004/056794. Tn a preferred embodiment of the present invention, alkylene carbonate, which is to be produced, is ethylene carbonate. .

[0021] ’ Tn the carbonation step, alkylene oxide is converted into not only alkylene carbonate but also alkylene glycol depending on the presence of water. Therefore, the reaction proceeds with ease even in the case of a supply amount of carbon dioxide of not more than an equimolar amount with respect to alkylene oxide. When the hydrolysis step is performed simultaneously, it is preferable that the amount of water is usually about 1.0 to 10 times mole with respect to alkylene . oxide. As for carbon dioxide, a sufficient effect is obtained in an amount of not more than an equimolar amount with respect to alkylene oxide. However, any strict restriction is not necessary in relation to the amount ratio thereof. The amount is preferably not less than 0.1 time mole and hot mere than 5.0 times mole.

[0022] : The reaction temperature of the carbonation step is usually 50 to 200°C. However, the reaction is preferably performed at 100°C to 170°C. The reaction pressure is usually 0.5 to 5.0 MPa. However, the reaction is preferably performed at 1.0 to 3.0 MPa.

[0023]

The carbonation reaction can be performed by using any arbitrary apparatus, However, it is preferable that the carbonation - reaction is performed by using a bubble tower. For example, a bubble tower, which has a liquid circulating conduit provided with a heat- removing heat exchanger and a circulating pump at intermediate positions, is used so that the reaction licuid contained in the tower ig cirenlated via the liquid circulating conduit, and the reactlon temperature is controlled thereby. BAlkylene oxide as the raw material, carbon dioxide, the catalyst, and optionally water are continuously supplied from the tower bottom to perform the reaction - continuously. It is also preferable to use a reactor which is ~ provided with an ejector type nozzle as disclosed in Japanese Patent

Application Laid-open No. 11-269110. Tt is inefficient to completely react alkylene oxide in the bubble tower. Therefore, it is also preferable that a tube type reactor is arranged al the back of (downstream from) the bubble tower to further react alkylene oxide contained in the liquid.

[0024] in this embodiment, the reaction liquid, which is obtained in the carbonation step, is fed to the hydrolysis step. However, a part } or a total amount of the reaction liquid may be fod to the step of producing alkylene carbonate to recover alkylene carbonate depending on circumstances. The remaining reaction liquid after the recovery of alkylene carbonate is combined with the remaining liquid obtained in the carbonation step, and the conbined liouid is fed to the hydrolysis step.

[0025] (2) Hydrolysis step

Tt is advantageous that the hydrolysis reaction is performed at a high temperature in view of the reaction rate. However, if the temperature is excessively high, the.guality of alkylene glycol may pe lowered. Therefore, it is preferable that the hydrolysis reaction ig usually performed at 100 to 180°C. The reaction pressure is . } arbitrary within a range not more than the boiling point of the . liquid. However, it is preferable that the hydrolysis reaction is usually performed at a pressure ranging fram the atmospheric pressure (normal pressure) to 2.1 MPa. It is also preferable that the hydrolysis is accelerated by raising the reaction temperature and/or lowering the reaction pressure as the hydrolysis proceeds.

[0028] :

Tt is sufficient that the amount of water with respect to the reaction liquid cbtained from the carbonation step is not less than an equimolar amount with respect to alkylene carbonate contained : therein. However, it is preferable that water is added in an extra amount in consideration of water accompanied with carbon dioxide gas as the hydrolysis proceeds. It is preferable that the reaction is performed with water usually in an amount of not more than 10 times mole and preferably 1 to 5 times mole with respect to alkylene oxide used as the raw material. The water is added, for example, by a method in which water is collectively added at first in the carbonation step, a method in which water is additionally added in the hydrolysis step, a method in which water is added several times in a divided manner as the reaction proceeds in the hydrolysis step, and a method in which water is supplied with steam. However, any one of the methods as described above may be used.

[0027] :

The reactor, which is used for the hydrolysis step, is not specifically limited. However, it is necessary to remove carbon dioxide gas which is produced as the reaction proceeds. Further, it is preferable to provide a heat exchanger for performing the heating in order to avoid the decrease in temperature, because the reaction ig an endothermic reaction. There can be used'a method in which the } heat exchanger is installed at the inside of the reactor, or a method in which a part of the liquid is extracted to perform the heating . with the heat exchanger installed at the outside and then is returned to the reactor again. As for the reactor, the reaction may be performed with one reactor. However, in order to maintain a high degree of conversion of alkylene carbonate, there can be used a method in which a partition is provided at the inside of the reactor "to control the flow of the liquid, or a method in which a plurality of reactors are used to perform the reaction.

The catalyst which is used in the carbonation step can be used : in the hydrolysis step as it is. If the hydrolysis rate is to insufficient, the catalyst may be additionally added in the hydrolysis step.

[0028] : (3) Recovering step (Dehydration step)

Alkylene glycol, which is produced by the hydrolysis, can be separated and obtained from the reaction liquid by means of any known method. Usually, the dehydration step is firstly performed, in which the distillation, preferably the distillation under the reduced pressure is performed in a distillation apparatus so that water is separated. After that, crude alkylene glycol is obtained, which is ’ camposed of, for example, alkylene glycol, dialkylene glycol, other high boiling point components, and the carbonation catalyst.

[0029] . (4) Catalyst separation step, catalyst circulation step

The liquid, which contains the catalyst in the reaction step, . is circulated to any one of stages of the reaction step after separating the catalyst by means of an appropriate method. In the pregent invention, the step, in which the liouid containing the catalyst is circulated to the reaction step, is referred to herein as reatalyst circulation step”. The step of separating the catalyst, which is referred to herein as "catalyst separation step”, may be . : performed before the catalyst circulation step.

For example, the liquid containing the catalyst, which is subjected to the catalyst separation step, is obtained from the reaction step performed after the carbonation step-

Specifically, the following catalyst separation and circulation steps can be performed when the liquid containing the catalyst obtained in the hydrolysis step is used. That is, the reaction : liquid obtained in the hydrolysis step is dehydrated as described in (3). After that, the reaction liquid is supplied to a flashing tank to vaporize (evaporate) and separate almost all of alkylene glycol and high boiling point compounds including dialkylene glycol. The liquid, which contains remaining alkylene glycol and high boiling point compounds including dialkylene glycol and the catalyst, is recovered, and the liquid is circulated as the catalyst liquid to the reaction step. In this procedure, it is preferable that the catalyst liquid is circulated to the carbonation step. It is preferable that the catalyst is separated as described above at a reduced pressure in order to facilitate the evaporation of, for example, alkylene glycol and dialkylene glycol. Bn evaporation apparatus, which is provided with a reboiler, is used so that the energy required for the evaporation is supplemented and the amount of evaporation is controlled.

[0030] (5) Step of removing alkali metal chloride originating from alkali netal carbonate

The method of the present invention includes the step of removing the chloride (referred. to herein as “alkali metal chloride” in same cases) formed by neutralizing the alkali metal carbonate used . as the hydrolysis catalyst. ‘The method for removing the alkali metal chloride originating from the alkali metal carbonate as described above may be any method in which the alkali metal chloride existing in the reaction system can be removed. However, the following method is preferably adopted. That is, any reaction liquid of the reaction step of the present invention is extracted to remove the alkali metal chloride contained in the reaction liquid, and then the reaction liquid in which alkali metal chloride has been removed is circulated to any stage of the reaction step of the present invention. In the method of the present invention, inorganic bromide or inorganic iodide may ke added for removing chloride compound derived from carbonation catalyst, but inorganic bromide or inorganic iodide may not be added.

[0031]

As for the reaction liquid to be extracted, at first, it is preferable that the concentration of the alkali metal chloride is not more than 2% by weight, especially from 0.1% by weight to 1% by weight. If the concentration of the alkali metal chloride contained in the extracted reaction liquid is excessively high, then the chloride itself is precipitated, and any choke trouble is caused, which is not preferred. The reaction liquid, which is subjected to removal of alkali metal chloride, may be any reaction liquid obtained after the carbonation step. However, there is exemplified the reaction liquid of the hydrolysis step during the continuous operation, the reaction liquid obtained from the hydrolysis step, or the liquid (referred to herein as “catalyst liquid” in some cases) obtained by removing alkylene glycol and water fram the reaction "liquid obtained from the hydrolysis step.

[0032]

The reaction liquid may be extracted either continuously or intermittently. The total amount of the reaction liquid may be extracted. However, when a part of the reaction liquid is extracted,

"then the amount of the reaction liquid to be treated is small, and the treatment is performed with ease. } [0033] ] The method for removing the alkali metal chloride from the reaction liquid may be any known method. Specifically, there are exemplified a method in which at least a part of alkylene glycol contained in the reaction liquid obtained as described above is distilled and separated and solid matter (solid content) precipitated in the distillation separation process is removed, and a method in which an ion exchange resin is used. A method camprising removing ‘ the solid matter precipitated when alkylene glycol and high boiling . point components contained in the reaction liquid are evaporated and recovered will be explained below.

[0034]

At first, the extracted reaction liquid is subjected to a step of distilling and separating at least a part of alkylene glycol contained in the obtained reaction liquid (hereinafter referred to as "distillation step" in some cases). The distillation step is carried out until the concentration of the alkali metal chloride in the liquid is not less than 0.5%, preferably not less than 1%, and more preferably not less than 28. In the distillation separation step, alkylene glycol is distilled and separated. However, high boiling point components including dialkylene glycol and trialkylene glycol may also be separated in order that the concentration of the alkali metal chloride contained in the reaction liquid is within the range as described above.

[0035]

Specifically, the following distillation methed is available.

That is, the distillation is performed at a reduced pressure, specifically at a pressure of not more than 500 torr and preferably 30 to 200 torr at such a temperature that the catalyst is not deteriorated, specifically at 120 to 200°C and preferably 120 to 180°C. A distillation apparatus, which is provided with a reboiler, is used so that the energy required for the evaporation is supplemented and the amount of evaporation is controlled.

[0036]

When at least alkylene glycol is distilled and separated, the high boiling point compounds are optionally distilled and separated, to and the ONGENELEEA of the alkali metal chloride exceeds 0.5% by weight in the liquid, the alkali metal chloride is precipitated although the situation depends on the compositions of components other than the alkali metal chloride. The solid matter, which comprises the precipitated alkali metal chloride, is separated from the solution part. As for the separation method, the separation can be performed by means of any method including, for example, the filtration separation, the centrifugal separation, and the precipitation separation.

[0037] : Specifically, when the precipitation separation is performed, for example, by the aid of a precipitation tank, the solubility is generally small when the temperature is low, ‘and the removing effect is enhanced. However, in the method of the present invention, if the cooling is excessively performed, then the viscosity of the catalyst solution as the solution part is increased, and the flowability or fluidity disappears. Therefore, it is preferable to perform heating : or heat-retention so that the handling is performed preferably at a temperature of not less than 80°C and more preferably not less than 90°C and not wore than 180°C. The precipitation tank may be installed distinctly from the evaporation apparatus. However, it is preferable that the distillation apparatus and the precipitation tank may be integrated into one unit, and the reaction liquid, which is heated by the heat exchanger, is directly flashed into the precipitation tank fram the middle stage or the upper portion.

[0038] } The alkali metal chloride, which is the sedimented or precipitated solid matter, is preferably treated, for example, by means of a method in which the alkali metal chloride is recovered as the solid after performing the solid-liquid separation, or a method in which the residual liquid existing in the precipitation tank is extracted through a drain line and then the remaining alkali metal chloride is dissolved in a solvent followed by being subjected to : detoxication treatment; or the alkali metal chloride is extracted as the solid ag it is through a menhole followed by being subjected to detoxication treatment. The solution part, which is separated and recovered as .described above, can be supplied as the liquid containing the catalyst subjected to the catalyst separation step as . described above to the reactor, preferably the reactor of the carbonation step, and the solution part can be used as the catalyst (catalyst circulation step). As for the catalyst liquid which is the solution part after the removal of the solid matter, only the catalyst can be further separated and recovered therefrom and can be provided to the catalyst circulation step as well. The method for recovering the catalyst is exemplified by a method described in

Japanese Patent No. 4273802. oo . [0039] (6) Step of removing chlorine ion originating from alkali metal chloride

The method of the present invention comprises a step of removing, from the reaction system, the chlorine ‘ion originating from : the alkali metal chloride formed by neutralizing the alkali metal carbonate allowed to exist as the hydrolysis catalyst. Any method for removing the chlorine ion originating from the alkali metal chloride as described above is available provided that the chlorine ion, which exists in the reaction — can be removed by the method. Preferably, the method has the following feature. That is, the condensation liquid (condensate) is discharged to the outside of the system as described below so that the catalyst lionid, which is circulated to the reaction step, has an alkalinity (concentration of

OH group of the hydrolysis catalyst contained in a catalyst liquid) of not less than 0.03 mol/mol with respect to the catalyst concentration. If the alkalinity of the catalyst licuid is not more ‘ than 0.03 mol/mol with respect to the catalyst concentration, the hydrolysis rate is lowered, which makes it industrially disadvantageous as a method for producing alkylene carbonate and/or alkylene glycol. The alkalinity of the catalyst liquid is adjusted to be not less than 0,03 mol/mol with respect to the catalyst concentration. More preferably, the alkalinity is adjusted to be not . less then 0.05 mol/mol with respect to the catalyst concenlration.

The alkalinity can be measured by means of any known method.

Specifically, the measurement can be carried out for the catalyst liquid by performing the titration with acid.

Furthermore, the condensation liquid may be discharged to the outside of the system when the molar ratio of the chlorine ion contained in the catalyst liquid is less than 3 with respect to the contained alkali metal.

[0040]

Tf the molar ratio of the chlorine ion concentration is not

Jess than 3 with respect to the contained alkali metal, then the ‘ ‘alkali metal, which is added as the hydrolysis catalyst, is neutralized, and the alkali metal does not fuhiction as the hydrolysis catalyst, which is not preferred. The molar ratio of the chlorine ion in the catalyst liquid to be circulated is less than 3, ’ preferably less than 2, and most preferably less than 1 with respect to the contained alkali metal. The chlorine ion concentration in the catalyst liquid to be circulated can be measured by means of any ordinarily usable method including, for example, the sedimetry or precipitation titration and the ion chromatograph.

When the amount of discharge of the condensation liquid, which provides the above described range of the molar ratio, can be recognized as an empirical value, a suitable amount may be discharged without menitoring the chlorine ion concentration in the catalyst licuid to be circulated. Co

[0041]

When the method for removing the chlorine ion originating from the alkali metal chloride described above is carried out, the method for producing alkylene carbonate and/or alkylene glycol includes a condensation step of cooling the gas containing carbon dioxide released in the carbonation step and/or the hydrolysis step described above.

When the chlorine ion is removed in the carbonation step, the gaseous phase portion of the reactor is cooled to recover the condensation liquid which is extracted and discharged. The total amount of the condensation liquid may be discharged, or alternatively, a part of the liquid may be discharged in an amount which is sufficient so that the alkalinity in the catalyst liquid to be circulated to the reaction step is not less than 0.03 mol/mol with respect to the catalyst concentration. Alkylene oxide, which is the raw material, is contained in the condensation liquid in’addition to the chlorine ion (organochlorine compound). Therefore, the liquid may be discharged as a solution containing the chlorine ion (organochlorine compound) after alkylene oxide is recovered, if necessary.

[0042]

When the chlorine ion (organochlorine compound) is removed in the hydrolysis step, carbon dioxide gas, which is produced as the hydrolysis proceeds, is cooled to condense water vepor or steam accarpanied with carbon dioxide gas, and thus the chlorine ion : (organochlorine compound) is recovered in the condensation liquid.

Accordingly, the total amount of the condensation liquid, or a certain amount of the condensation liquid, which is sufficient to allow the alkalinity of the catalyst liquid circulated to the reaction step to be not less than 0.03 mol/mol with respect to the :

catalyst concentration, is extracted to the outside of the reaction system. .

[0043]

The amount of accumulation of the chlorine ion is small at the initial stage of the operation, and the alkalinity of the catalyst liquid is not less than 0,03 mol/mol with respect to the catalyst concentration. Therefore, the liquid may be returned as it is to the hydrolysis reactor. The condensation liquid may be extracted after : the chlorine jon is accumilated. However, it is preferable that the condensation liquid is extracted beforehand in order to avoid the accumuzlation of the chlorine ion. It is preferable that the extraction is carried out continuously or intermittently while adjusting the extraction amount and while monitoring the situation of the hydrolysis reaction and/or the chlorine ion concentration in the : catalyst liquid. The remaining liquid after extracting and discharging park of the condensation liquid to the outside of the . reaction system can be circulated to the carbonation step and/or the hydrolysis step.

[0044]

The condensation liquid, which is extracted to the outside of the reaction system, may be discarded as a drain as it is or after performing detoxication treatment, if necessary. However, it is preferable that the condensation liquid is recovered to the process so that alkylene glycol is recovered ag a product, because the condensation liquid contains organic compound including, for example, alkylene glycol. In order that the chlorine ion {organochlorine compound) is prevented from being returned as chlorine to the process when the discharged liquid is recovered, it is preferable that the dehydration distillation is performed beforehand to distill and separate the organochlorine compound together with water, and then alkylene glycol is recovered.

[0045]

Another method for removing the chlorine ion is also usable,

That ig, the condensation liquid is supplied to a place which is disposed at a hydrolysis reaction liquid supply stage or stages located thereover of the distillation tower in the dehydration step . described above so that the chlorine ion (organochlorine compound) is . discharged from a tower top together with water. The reaction licuid, which comes from the hydrolysis step, contains the hydrolysis catalyst. Therefore, if the condensation liquid is supplied to any stage lower than the supply stage, there is such a possibility that the chlorine ion (organochlorine compound) may be reacted with the hydrolysis catalyst to behave as chlorine which consequently neutralizes the hydrolysis catalyst. In order to avoid such an inconvenience, it is necessary that .thé condensation liquid should be supplied to the stage disposed over the supply stage of the hydrolysis reaction liquid to avoid any contact with the hydrolysis catalyst.

[0046] h Supplament of catalyst

Tn order to continue the operation while further maintaining the hydrolysis rate in the wemstlon step of the present invention, the alkali metal carbonate, which is initially added as the hydrolysis catalyst, can be also supplanted to the reaction step.

It is preferable that the alkali metal carbonate, preferably potassium carbonate is added in such an amount that molar ratio thereof with respect to the carbonation catalyst such as quaternary phosphoniun iodide or the like is maintained within 0.01 to 1.0. 2s for the method for adding the carbonate, solid may be directly introduced. However, such a method is effective that the carbonate is added by being dissolved in water or the carbonate is added by being dissolved in alkylene glycol, in view of the handling. The alkali metal carbonate may be added continuously. However, the operation can be continued without causing any problem by means of such a method that an appropriate amount of the alkali metal } carbonate is additionally added when the reaction rate is lowered, while monitoring the situation of the hydrolysis reaction.

[0047] . when halcgen such as iodine or bromine derived from the carbonation catalyst and/or the catalyst itself is/are removed in an } | accampanied manner with the removal of chlorine, it is preferable that the carbonation catalyst and/or hydrolysis catalyst is/are additionally added, or hydrogen halide such as hydrogen iodide, hydrogen bromide or the like, which corresponds to the catalyst having been used, is added depending on the situation.

[0048] (8) purification of alkylene carbonate and alkylene glycol

Crude alkylene carbonate and/or crude alkylene glycol, which is/are thus produced and recovered, can be purified in accordance with usable any known method, if necessary.

EXAMPLES

[0049]

The present invention will be explained more specifically by referring to Examples. However, the present invention is not limited to Examples described below without: deviating from the gist or essential characteristics thereof.

A reaction liquid of a carbonation step, which contained ethylene carbonate and ethylene glycol (EG), was obtained by : supplying 5 parts by weight/Hr of tributylmethylphosphonium iodide, 0.8 part by weight/Hr of potassium carbonate, and 78 parts by weight /Hr of an ethylene oxide aqueous solution as a raw material (60% by weight) to a carbonation reaction portion including a carbonation reactor which was at 100°C, which had a residence time of : 1 hour, and which was pressurized with carbon dioxide at 2.0 MPa. [00511 : (2) Hydrolysis step . The reaction liquid, which was obtained from the carbonation step, was transferred to a hydrolysis reaction portion including a hydrolysis reactor which had a temperature of 150°C, which had a pressure of 0.5 MPa, and which had a residence time of 2 hours so ’ that contained ethylene carbonate was hydrolyzed, thereby 87.5 parts by weight/Hr of a hydrolysis step reaction liquid containing the catalyst and ethylene glycol was obtained,

[0052] :

(3) Purification

The reaction liquid, which was ebtained from the hydrolysis step, was distilled with a reduced pressure distillation tower at 80 torr having a temperature of 140°C at the tower bottom to obtain a dehydrated Liquid from the tower bottom. Most part of ethylene glycol contained therein was further evaporated with a reduced pressure evaporator operated at 140°C and 60 torr, and 13 parts by weight/Hr of a catalyst liquid, in which the catalyst was concentrated, were recovered From a bottom portion of the evaporator.

The recovered catalyst liquid was circulated to and used in the carbonation reactor.

When the operation was continued, the hydrolysis reaction became insufficient. Therefore, the operation was continued while adding potassium carbonate.

The reaction liquid was extracted from the hydrolysis step in which the operation was continued for 3 months. 100 parts of the } reaction liquid were charged into an evaporator made of glass to perform the distillation separation operation for ethylene glycol.

The pressure was 30 torr, and the heating was performed by heating an oil bath to 170°C.

[0053]

When 5 parts of ethylene glycol contained in the reaction liquid were distilled out, it was confirmed that potassium chloride . was precipitated on a surface of a bottam flask of the evaporator. :

The evaporation operation was further continued. The evaporation

Co operation was stopped when a liquid, which contained a main component of 46 parts of ethylenc glycol, was distilled out. It was confirmed that potassium chloride was sedimented or precipitated at the bottom of the flask. In this situation, a part of the liquid containing the catalyst was extracted from the supernatant portion, and the part of the liquid was used as a reproduced or regenerated catalyst solution from which potassium chloride had been removed. The carbonation step and the hydrolysis step were performad in the same manner as described above. As a result, the operation was successfully further continued without causing any problem in both of the carbonation reaction and the hydrolysis reactien. .

[0054]

Comparative Example 1

The operation was continued in the same manner as in Example 1 except that potassium chloride was not removed from the catalyst liquid in Example 1. As a result, potassium chloride was precipitated in the catalyst liquid, it was difficult to circulate . the catalyst liquid, and the operation was stopped.

[0055]

Example 2 (1) Carbonation step }

A reaction liquid of a carbonation step, which contained ethylene carbonate and ethylene glycol (EG), was obtained such that 5 parts by weight/Hr of tributylmethylphosphonium iodide, 0.8 part by weight/Hr of potassium carbonate, and 78 parts by weight/Hr of an ethylene oxide agueous solution as a raw material (60% by weight) were supplied to a carbonation reaction portion including a carbonation reactor which was at 100°C, which had a residence time of . 1 hour, and which was pressurized with carbon dioxide at 2.0 MPa.

[0056] (2) Hydrolysis step .

The reaction liquid, which was obtained from the carbonation step, was used to perform the hydrolysis reaction of ethylene carbonate with a first hydrolysis reactor which had a temperature of 150° and which had a pressure of 1.8 MPa, and any remaining ethylene carbonate was thereafter hydrolyzed with a second hydrolysis reactor which had a temperature of 150°C and which had a pressure of 0.2 MPa to obtain 87.5 parts by weight/Hr of a hydrolysis step reaction liquid containing the catalyst and ethylene glycol. Carbon dioxide gas, which was produced in accordance with the hydrolysis, was cooled with a heat exchanger. Water, which was accompanied with carbon - dioxide gas, was condensed, and then water was returned to the . hydrolysis reactor to continue the reaction.

[0057] {3} Dehydration/chlorine ion removing step

The reaction liquid, which was obtained from the hydrolysis step, was dehydrated and distilled with a reduced pressure distillation tower al 80 torr having a temperature of 140°C at the tower bottom to cbtain a dehydrated liquid from the tower bottom, and the liquid was further applied to a reduced pressure evaporator operated at 140°C and 60 torr so that a greater part of ethylene glycol was evaporated thereby. 13 parts by weight/Hr of the catalyst liquid, in which the catalyst was concentrated, were recovered from a bottom portion of the evaporator, The recovered catalyst liquid was used as the catalyst, and the recovered catalyst liquid was circulated to the first hydrolysis reactor.

[0058]

Carbon dioxide gas, which was produced in the first hydrolysis reactor, was cooled after continuing the operation as described above , to analyze the condensation liquid (condensate) of water vapor or steam accompanied with carbon dioxide gas. As a result, 167 ppm of ethylene chlorohydrin, 273 ppm of chloromethyl dioxolane, and 17.2% . by weight of ethylene glycol were contained in the condensation liquid, Accordingly, the continuous extraction was started for the total amount of the condensation liguid.

[0059]

The operation was carried out for 100 days. The evaluation was performed by using the alkalinity as the index of the hydrolysis rate. The alkalinity was measured by titrating, with acid, the number of moles of OH group to serve as the hydrolysis catalyst contained in the catalyst liquid circulated to the carbonation step. ' In order to eliminate the influence to be exerted hy the change of the catalyst concentration in the catalyst liquid, the value obtained by dividing the alkalinity value by the number of moles of tributylmethylphosphonium iodide as a catalyst. An cbtained result : is shown in Fig. 1. As shown in Fig. 1, any decrease in the reaction rate of the hydrolysis reaction was not cbserved, The alkalinity of "the catalyst liquid was maintained to be not less than 0.03 mol/mol . with respect to the catalyst concentration.

[0060]

Further, the concentration of chlorine ion and the concentration of potassium contained in the catalyst liquid were ‘ measured, ICP (Inductively Coupled Plasma) emission spectrochemical analysis method was adopted as the method for measuring potassium.

Sedimetry or precipitation titration amalysis method was adopted as the method for measuring chlorine ion. Obtained results are shown in . Table 1 and Fig. 2. As is clear from Table 1 and Fig, 2, the concentration of chlorine ion contained in the catalyst licuid was less than 3 in molar ratio with respect to the concentration of alkali metal. :

[0061]

Table 1 days

I 0.146 0.152 1.04 0.145 1.02 21 0.158 27 41 0.133 0.163 1.23 48 0.177 55 62 0.117 1.32 69 0.104 1.38 7 TT 0.00 78 0.123 85 92 _ 29 0.13¢ 0.214 1.57 0.211 1,53

[0062] .

Example 3 :

Distillation was performed in a distillation tower having a theoretical plate number of 8 together with the hydrolysis reaction liquid and the condensation liguid extracted in Example 2 as described above. Ethylene chlorohydrin and chloromethyl dioxolane were distilled out together with water from the tower top, and ethylene glycol containing no organochlorine compound was recovered from the tower bottom of the distillation tower.

[0063] :

Comparative Example 2

Ethylene glycol was produced in the same manner as in Example 2 except that the condensation liquid of water vapor or steam accompanied with carbon dioxide gas obtained by cooling carbon dioxide gas produced in the first hydrolysis reactor was supplied as it was to the hydrolysis step. The operation was continued for 230 days, and the alkalinity of the hydrolysis catalyst contained in the catalyst liquid to be circulated to the carbonation step was measured in the same manner as in Example 2. The result 1s shown in Fig. 3.

Ag is clear fram Fig. 3, the alkalinity of the hydrolysis catalyst was decreased, and the reaction rate of the hydrolysis reaction was gradually slowed down. The degree of conversion of ethylene carbonate was lowered to 98.8% from the foregoing value of not less than 99.9%.

INDUSTRIAL APPLICABILITY Co

[0064]

Aecording to the present invention, a method for producing alkylene carbonate and/or alkylene glycol, in which the reduction of the catalyst is avoided in the hydrolysis step, any precipitate is not accumulated in the reaction system while maintaining the hydrolysis rate, and the operation can be perfommed stably for a long period of time, is provided. When this method is adopted, alkylene carbonate and/or alkylene glycol can be efficiently produced with little loss.

Claims

CLATMS

1. A method for producing alkylene carbonate and/or alkylene glycol, comprising: a reaction step of reacting alkylene oxide, water, and carbon dioxide in the presence of a catalyst and an alkali metal carbonate to produce alkylene carbonate and/or alkylene glycol, a recovering step of recovering alkylene carbonate and/or alkylene glycol from a reaction liquid obtained in the reaction step, and - a catalyst circulation step of circulating a liquid containing the catalyst to the reaction step, } said method further comprising: a step of removing an alkali metal chloride originating from the alkali metal carbonate contained in the reaction liquid, and/or chlorine ion eorigineting from the alkali metal chloride.

2. The method according to claim 1, wherein the step of removing the alkali metal chloride originating fram the alkali metal carbonate contained in the reaction liquid comprises extracting a part or a total amount of the reaction liquid containing the catalyst cbtained in the reaction step to distill and separate at least a part of alkylene glycol contained in the reaction liquid, and removing solid precipitated in the distillation separation operation, and ’ said catalyst circulating step camprises circulating a residual liquid obtained by removing Solid precipitated in the distillation separation operaticn, to the reaction step.

3. The method according to claim 1, wherein the step of removing the alkali metal chloride originating from the alkali metal carbonate contained in the reaction liquid comprises extracting a part or a.total amount of the reaction liquid containing the catalyst in the reaction step to distill and separate at least a part of alkylene glycol contained in the extracted reaction liquid, and : removing solid precipitated in the distillation separation operation, and sald catalyst circulating step comprises circulating the catalyst separated from a residual liquid obtained by removing solid precipitated in the distillation separation, to the reaction step.

4. The method according to claim 2 or 3, wherein the precipitated solid is removed at not less than 80°C.

5. The method according to claim 1, wherein: the reaction step comprises a carbonation step of reacting alkylene oxide and carbon dioxide in the presence of the catalyst and the alkali metal carbonate to produce alkylene carbonate, and a nydralysis step of hydrolyzing alkylene carbonate contained in a . reaction liquid of the carbonation step to produce alkylene glycol, and said step of removing chlorine ion originating from the alkali metal chloride comprises a condensation step of cooling a gas containing carbon dioxide released in the carbonation step and/or the hydrolysis step; and a step of discharging a condensation liguid obtained in the condensation step so that the catalyst liquid, which is circulated to the reaction step in the catalyst circulation step,

has the ratio of an alkalinity with respect to the catalyst concentration of not less than 0.03 mol/mol.

6. The method according to claim 5, wherein the condensation liquid obtained in the step of removing chlorine lon is further dehydrated and distilled to remove water and an organochlorine compound contained therein, and then the resultant liquid is : circulated to the reaction step.

: 7. The method according to claim 6, whersin said organochlorine compound is ethylene chlorohydrin.

8. The method according to any one of claims 5 to 7, wherein the condensation liguid is circulated to a place which is disposed at a hydrolysis reaction liquid supply stage or stages located thereover of a distillation tower for distilling and separating water contained in a hydrolysis reaction liquid obtained in the hydrolysis step.

9. The method according to any one of claims 1 to 8, wherein the alkali metal carbonate is additionally added to the reaction step.

10. The method according to any one of claims 1 to 9, wherein bo alkylene carbonate is ethylene carbonate, and alkylene glycol is ethylene glycol. :