JPH04198141A - Continuous production of dialkyl carbonate and diols - Google Patents

Abstract

PURPOSE:To obtain the title compound from a cyclic carbonate and an aliphatic monoalcohol in high yield, in high selectivity and continuously by carrying out reaction in the presence of a catalyst at plural plates of continuous multi- stage column and simultaneously taking out a low-boiling product by distillation. CONSTITUTION:In continuously producing a dialkyl carbonate and a diol by reacting a cyclic carbonate with an aliphatic monoalcohol in the presence of a catalyst, the cyclic carbonate and the aliphatic monoalcohol are continuously fed (1 and 2) to a continuous multi-stage distillation column 5, brought into contact with the catalyst laid at plural plates in the distillation column 5 to carry out reaction, a low-boiling product among the objective compounds formed by the reaction is taken out (3) in a gaseous state by distillation from the distillation column 5, a high-boiling product is continuously extracted (4) in a liquid state from the bottom of the column to successively give the objective compound at high reaction rate, in high reaction ratio, in high yield and in high selectivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for continuously producing dialkyl carbonates and diols by reacting cyclic carbonates and aliphatic monoalcohols.

[Conventional technology]

Several proposals have been made regarding methods for producing dialkyl carbonates and diols from the reaction of cyclic carbonates and aliphatic monoalcohols, most of which involve catalysts. Such catalysts include, for example, alkali metals or basic compounds containing alkali metals [U.S. Pat.
Publication No. 4-48715 (U.S. Patent No. 4.181.676)
(specification)], tertiary aliphatic amine [JP-A-51-122
No. 025 (U.S. Pat. No. 4,062.884)], thallium compounds [JP-A-54-48716 (U.S. Pat. No. 4,307,032)], tin alkoxides (JP-A-54-48716 (U.S. Pat. No. 4,307,032)) Publication No. 54-63023), zinc,
Aluminum and titanium alkoxides (Japanese Patent Application Laid-open No. 1983-
148726), a composite catalyst consisting of a Lewis acid and a nitrogen-containing organic base (Japanese Unexamined Patent Publication No. 55-64550), a phosphine compound (Japanese Unexamined Patent Publication No. 55-6455), 4
class bosphonium salt (Japanese Unexamined Patent Publication No. 1983-1.0144)
, cyclic amidine (JP-A-59-106436),
Compounds of zirconium, titanium and tin [JP-A-63-4
No. 1432 (U.S. Pat. No. 4,661.609)], a solid strongly basic anion exchanger containing 44th-class ammonium (Japanese Patent Application Laid-open No. 63-238043), a tertiary amine or quaternary ammonium group A solid catalyst selected from ion exchange resins containing ion exchange resins, strongly acidic or weakly acidic ion exchange resins, silicates of alkali metals or alkaline earth metals impregnated in silica, and ammonium exchange olides No. 31737 (U.S. Pat. No. 4.69)
1.041)), a homogeneous catalyst selected from tertiary phosphine, tertiary arsine, tertiary stibine, divalent sulfur or selenium compounds (US Pat. No. 4.734.518), etc. Proposed.

Furthermore, three reaction methods have been proposed so far. These three reaction methods are used in the most typical reaction example, a method for producing dimethyl carbonate and ethylene glycol from ethylene carbonate and methanol.

That is, the first method is a complete batch method in which ethylene carbonate, methanol, and a catalyst are charged into an autoclave, which is a batch reaction vessel, and the reaction is carried out under pressure at a reaction temperature higher than the boiling point of methanol for a predetermined reaction time. [U.S. Pat. No. 3.64]
2.858 specification, JP-A-54-48715 (
U.S. Patent No. 4,181,676), Japanese Patent Application Laid-open No. 1983
-63023, JP 54-148726, JP 55-64550, JP 55-645
No. 5, JP-A-56-10144].

The second method uses an apparatus in which a distillation column is provided above a reaction vessel, and ethylene carbonate, methanol, and a catalyst are charged into the reaction vessel and the reaction is allowed to proceed by heating to a predetermined temperature. In this case, the dimethyl carbonate and methanol formed form the lowest azeotrope (boiling point 63°C/760 mmt(g), so this azeotrope is equal to methanol (boiling point 64,6°C/760 mmt(g)).
mmHg). In this system, a distillation column is provided to separate the azeotrope and methanol. That is, the dimethyl carbonate vapor and methanol vapor evaporated from the reaction vessel are separated into azeotrope vapor and liquid methanol while ascending the distillation column, and the azeotrope vapor is distilled off from the top of the distillation column. , liquid methanol flows down and is returned to the reaction vessel for reaction. Also, in this method, is methanol added continuously or in batches to the reaction vessel in order to supplement the methanol that is distilled out by azeotroping with the dimethyl carbonate that is produced? In this method, the reaction proceeds only in a hatch-type reactor in which a catalyst, ethylene carbonate, and methanol are present. Therefore, the reaction is carried out in a batch manner, and is carried out under reflux for a long period of time, from 3 to 20 hours.

In this method, one product, dimethyl carbonate, is continuously extracted from the reaction system, but the other product, ethylene glycol, is mixed with unreacted ethylene carbonate in the presence of a catalyst. It will stay for a while. In order to suppress side reactions caused by long-term residence of ethylene glycol and ethylene carbonate and prevent a decrease in selectivity, a large excess of methanol is used relative to the ethylene carbonate charged in batches to the reaction vessel. In fact, in the methods proposed so far, 14 moles (U.S. Pat. 1-311054)
, 22 mol [JP-A-51-122025 (U.S. Patent No. 4.062.884)], 23 mol [JP-A-54-48716 (U.S. Pat. No. 4,307.0)]
(No. 32 specification)] a large excess of methanol was used.

The third method is to continuously supply a mixed solution of ethylene carbonate and methanol to a tubular reactor maintained at a predetermined reaction temperature, and from the other outlet unreacted ethylene carbonate and methanol and the product dimethyl carbonate. This is a continuous reaction method in which a reaction mixture containing ethylene glycol and ethylene glycol is continuously extracted in liquid form. Two methods are used depending on the texture of the catalyst used. That is, a method in which a homogeneous catalyst is passed through a tubular reactor together with a mixed solution of ethylene carbonate and methanol, and after the reaction, the catalyst is decomposed from the reaction mixture.
41432 (U.S. Pat. No. 4,661.609), U.S. Pat. No. 4.734.518] and
Method using a heterogeneous catalyst fixed in a tubular reactor [JP-A-63-238043, JP-A-64-31
No. 737 (U.S. Pat. No. 4,691,041). Since the reaction of ethylene carbonate and methanol to produce dimethyl carbonate and ethylene glycol is an equilibrium reaction, in this continuous flow reaction method using a tubular reactor, the reaction rate of ethylene carbonate is determined by the charging composition ratio and reaction temperature. It is impossible to increase the reaction rate above the equilibrium rate. For example, Japanese Patent Application Laid-Open No. 63-41432 (U.S. Patent No. 4.661.
According to Example 1 of No. 609), in a flow reaction at 130° C. using raw materials with a molar molar ratio of methanol/ethylene carbonate of 4/1, the conversion rate of ethylene carbonate is 25%.

This means that it is necessary to separate and recover a large amount of ethylene carbonate and methanol remaining unreacted in the reaction mixture and recirculate it to the reactor.
The method of the '1737 publication (U.S. Pat. No. 4,691,041) uses extensive equipment for separation, purification, recovery, and recycling.

As described above, the methods proposed so far for producing dialkyl carbonates and diols from cyclic carbonates and aliphatic monoalcohols are (1) complete batch reaction method (2) reaction with a distillation column installed at the top. There are three methods: Basochi reaction method using a pot (3) and liquid flow reaction method using a tubular reactor, but in all cases, the reaction time (or the residence time when the reaction liquid is in contact with the catalyst) is long. thing [(1)
and (2+), the need to use large amounts of aliphatic alcohols ((2)), and the need to separate, recover, and recycle large amounts of unreacted raw materials with low reaction rates ((3)). ): ].Furthermore, no method for continuously producing dialkyl carbonate and diols with high reaction rate, high yield, and high selectivity has been proposed so far.

[Invention or problem to be solved]

Without these drawbacks of the methods proposed so far, dialkyl carbonates and diols can be produced continuously at a high reaction rate, with high reaction rate, high yield, and high selectivity. The purpose is to provide a method to do so.

[Failure to solve the problem]

As a result of extensive studies, the present inventors discovered that an excellent method is to carry out the reaction in multiple stages in a continuous multi-stage distillation column and simultaneously extract low-boiling products by distillation. Based on this, the present invention was completed.

That is, the present invention allows a cyclic carbonate to react with an aliphatic monoalcohol in the presence of a catalyst to continuously produce a dialkyl carbonate and a diol. Continuously supplied into a continuous multi-stage distillation column and brought into contact with a catalyst present in multiple stages in the distillation column, the reaction is carried out, and at the same time, among the dialkyl carbonates and diols produced by the reaction, low-boiling point Provided is a method for continuously producing dialkyl carbonates and diols, characterized in that the product is continuously extracted in gaseous form from the distillation column by distillation, and the high boiling point product is continuously extracted in liquid form from the bottom of the column. It is.

The method of the present invention exhibits high reaction rate, high yield, and high selectivity in a short reaction time compared to the conventional method, that is, the batch reaction method using a reaction vessel equipped with a distillation column at the top. This seems to be due to the following reasons.

The reaction of the present invention involves converting a cyclic carbonate (A) and an aliphatic monoalcohol (B) into a dialkyl carbonate (C
) and diols (D) are produced - This is an equilibrium reaction represented by (I) (A) (B) (C) (D). [Here, R1 represents a divalent group +CH2- (m is an integer of 2 to 6), and one or more hydrogens thereof may be substituted with an alkyl group or aryl group having 1 to 10 carbon atoms.

Further, R2 represents a monovalent aliphatic group having 1 to 12 carbon atoms, and one or more hydrogen atoms thereof may be substituted with an alkyl group or an alkyl group having 1 to 10 carbon atoms. ] Since this reaction normally proceeds in the liquid phase, in order to increase the reaction rate, it is necessary to generate low-boiling point products from the reaction solution among the dialkyl carbonates and diols produced as a result of the reaction. Do you need to remove it as quickly as possible?

However, the reaction rate described in the prior art using a reaction vessel equipped with a distillation column at the top was unable to increase the reaction rate.

The reason for this is that there is a gas-liquid field that is limited only to the reaction site or the part of the reaction vessel where the catalyst is present, and that the reaction by-products produced by the reaction are evaporated from the liquid in the reaction vessel to the gas phase. This is because the area is small.

On the other hand, in the method of the present invention, the catalyst is present in a wide range of multiple stages in the continuous multistage distillation column, and the reaction can proceed in this wide range. In this region, the supplied reaction liquid repeatedly comes into contact with vapor rising from below, and while distilling, it flows down without reacting. At this time, the low boiling point reaction product evaporates from the reaction liquid into the vapor phase. As a result, the concentration distribution of each component inside the continuous multi-stage distillation column has a distribution in which the concentration of high-boiling products in the reaction liquid gradually increases from the feed section to the bottom of the column, and in the vapor phase from the bottom of the column to the top of the column. The concentration of low-boiling products gradually increases over time.

Considering any position in the reaction region, the reaction liquid is considered to be in a state approaching an equilibrium composition as a result of the reaction, and the vapor phase is also considered to have a composition approaching a vapor-liquid equilibrium state with respect to the reaction liquid.

Therefore, if the reaction solution remains in this position, the reaction will not proceed any further, or in fact, the reaction solution will flow down and make gas-liquid contact with the vapor phase with a low concentration of low-boiling reaction products. It is possible to further advance the reaction to increase the concentration of the high boiling point reaction product in the reaction solution.

Therefore, it is considered that the reason why the method of the present invention has superior effects compared to conventional methods is mainly due to the following points.

(2) Compared to reaction formats such as reaction vessels equipped with distillation columns, the gas-liquid interfacial area can be increased, and as a result, mass transfer of low-boiling reaction products to the vapor phase becomes easier.

■High-boiling raw materials in the reaction liquid in the continuous multi-stage distillation column repeatedly come into gas-liquid contact with the vapor containing low-boiling raw materials rising from below, and then flow down without reacting.

Therefore, it is possible to increase the reaction rate of raw materials even though it is a continuous type (conventional reaction types such as reaction vessels equipped with distillation columns cannot be used continuously to increase the reaction rate of raw materials). (usually difficult).

(2) The reaction can be almost completed while the reaction solution flows down the continuous multi-stage distillation column. Since the residence time of the reaction solution in the distillation column is shorter than when a batch type reaction vessel is used, there are fewer side reactions and the selectivity of the desired product can be increased.

■As the steam rises through the continuous multi-stage distillation column,
It rises while repeating gas-liquid contact with the descending liquid.

Therefore, the thermal energy of the steam is effectively utilized.

The continuous multi-stage distillation column used in the present invention is a distillation column having two or more theoretical plates for distillation, and may be a distillation column as long as continuous distillation is possible. . Such continuous multi-stage distillation columns include, for example, plate column types using trays such as bubble bell trays, perforated plate trays, valve trays, and countercurrent trays, as well as those using Raschig rings, Lessing rings, Paul rings, Berl saddles, and inter-stage distillation columns. Usually, there are packed tower types filled with various packing materials such as Rox saddle, Dickson backing, McMahon backing, Helipak, Sulsar packing, Melapak, etc.
Any type of column used as a continuous tray distillation column can also be used. Furthermore, a distillation column having both a multi-stage section and a section filled with packing material is also preferably used. Furthermore, when a solid catalyst is used, a packed column type distillation column in which the solid catalyst is used as part or all of the packing is also preferably used.

The cyclic carbonate used as a raw material in the present invention is a compound represented by (A) above, and includes, for example, alkylene carbonates such as ethylene carbonate and propylene carbonate, 1,3-dioxacyclohebut-2-one is preferably used, and ethylene carbonate and propylene carbonate are particularly preferably used from the viewpoint of easy availability.

The other raw material, aliphatic monoalcohols, is a compound represented by (B), for example,
Methanol, ethanol, propatool (each isomer),
Allyl alcohol, butanol (each isomer), 3-buten-1-ol, amyl alcohol (each isomer), hexyl alcohol (each isomer), heptyl alcohol (each isomer), octyl alcohol (each isomer), Nonyl alcohol (each isomer), decyl alcohol (each isomer)
, undecyl alcohol (each isomer), dodecyl alcohol (each isomer), cyclopentanol, cyclohexanol, cycloheptatool, cycloofnol, methylcyclopentanol (each isomer), ethylcyclopentanol (each isomer) ), methylcyclohexanol (each isomer), ethylcyclohexanol (each isomer), dimethylcyclohexanol (each isomer), diethylcyclohexanol (each isomer), phenylcyclohexanol (each isomer), pentyl alcohol , phenethyl alcohol (all isomers), phenylpropanol (all isomers), etc. Furthermore, in these aliphatic monoalcohols, halogens, lower alkoxy groups, cyano groups, alkoxycarbonyl groups, aryloxycarbonyl groups, It may be substituted with a substituent such as an acyloxy group or a nitro group.

Among these aliphatic monoalcohols, alcohols having 1 to 6 carbon atoms are preferably used, and particularly preferred are methanol, ethanol, propatool (
Each isomer) and butanol (each isomer) are alcohols having 1 to 4 carbon atoms.

In the present invention, the catalyst must be present in multiple stages of a continuous multi-stage distillation column having two or more theoretical stages, and the feature of the present invention is that in the multiple stages where the catalyst is present, cyclic carbonate and aliphatic monoalcohol The object of the present invention is to carry out a reactive distillation method in which the reaction is allowed to proceed by bringing the products into contact with each other, and at the same time, low-boiling products are extracted in gaseous form by distillation.

What method can be used to present a catalyst in multiple stages of such a continuous multi-stage distillation column? For example, in the case of a homogeneous catalyst that dissolves in the reaction liquid under the reaction conditions, the distillation The catalyst can be present in the reaction system by continuously feeding the catalyst into the column, or in the case of a heterogeneous catalyst that does not dissolve in the reaction liquid under the reaction conditions, solids may be present in the distillation column. By arranging a catalyst, it is possible to make the catalyst exist in the reaction system, or there may be a method in which these are used in combination.

When the homogeneous catalyst is continuously supplied to the distillation column, it may be supplied at the same time as the raw material, or it may be supplied at a different position from the raw material. Further, the catalyst may be supplied from the bottom of the column to a position having at least two or more theoretical plates. However, since the reaction actually proceeds in the distillation column in the area below the catalyst supply position, it is preferable to supply the catalyst to the area between the top of the column and the raw material supply position. In addition, when using a heterogeneous solid catalyst, the catalyst can be packed in the necessary amount at any position in the distillation column, and it is good to have at least two theoretical plates in the bed where the catalyst is present. . The area in the distillation column where no catalyst is present functions only as a normal distillation column, such as concentrating the reaction product.

This solid catalyst also has the effect of filling the distillation column.

As the catalyst used in the present invention, various known catalysts can be used. For example, alkali metals and alkaline earth metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, etc.: hydrides and hydroxides of alkali metals and alkaline earth metals;
Basic compounds such as alkoxides, alkoxides, amidides, etc. Basic compounds such as carbonates, bicarbonates, and organic acid salts of alkali metals and alkaline earth metals; triethylamine, tributylamine, trihexyl Tertiary amines such as amines and benzyldiethylamine; N-alkylpyrrole, N-alkylindole,
Oxazole, N-alkylimidazole, N-alkylpyrazole, oxadiazole, pyridine, alkylpyridine, quinoline, alkylquinoline, isoquinoline, alkylisoquinoline, acridine, alkylacridine, phenanthroline, alkylphenanthroline,
Nitrogen-containing heteroaromatic compounds such as pyrimidine, alkylpyrimidine, pyrazine, alkylpyrazine, l-riazine, and alkyltriazine; diazabicycloundecene (D
BU), cyclic amidines such as diazabicyclononene (DBN): thallium oxide, thallium halide, thallium hydroxide, thallium carbonate, thallium nitrate, thallium sulfate,
Thallium compounds such as organic acid salts of thallium, nitributylmethoxytin, tributylethoxytin, dibutyldimethoxytin, diethyljethoxytin, dibutylethylenediethoxytin, dibutylphenoxytin, diphenylmethoxytin, dibutyltin acetate, tributyltin chloride, Tin compounds such as tin 2-ethylhexanoate, zinc compounds such as dimethoxyzinc, jetoxyzinc, ethylenedioxyzinc, dibutoxyzinc; aluminum compounds such as aluminum trimethoxide, aluminum triisopropoxide, aluminum trimethoxide, etc. Types: Titanium compounds such as tetramethoxytitanium, tetraethoquinotitanium, tetrabutoxytitanium, dichlorodimethoxytitanium, tetraisopropoxytitanium, titanium acetate, titanium acetylacetonate; trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, Phosphorus compounds such as tributylmethylphosphonium halide, trioctylbutylphosphonium halide, and triphenylmethylphosphonium halide; zirconium compounds such as zirconium halides, zirconium acetylacetonate, zirconium alkoxide, and zirconium acetate; lead and compounds containing lead; For example, PbO1Pb
Lead oxides such as O2, pb, o, etc; PbS, Pb
Lead sulfides such as 2S3 and PbS2; Pb(OH)2
, Pb30□(OH)2, Pb2[PbO□(OH)2
1. Lead hydroxides such as Pb20(OH)2.

Na2Pb02, K2PbOz, Na2Pb02,
Namarites such as KHPbO7; Na2PbO*
, Na2H2PbO+ , K2PbO3, K2[Pb
(OH)6], K4PbQ4, Ca2Pb04, C
PbCO3,2PbC0
3. Lead carbonates and their basic salts such as Pb(OH)2; Pb(OCH3)2, (CH30)Pb(OP
h) Alkoxyleads such as , Pb(OPh)2; Aryloxyleads: Pb(OCOCH3)2, Pb(O
COCH3).

Lead salts of organic acids such as PtJ(OCOCH3)2, PbO, 3H20, and their carbonates and basic salts; Bu4P
b, Ph4Pb, BusPbC1! , PflaPb
Br, Ph5Pb (or Ph2PbO), Bu3
Organic lead compounds such as PbOH and Ph2PbO (Bu is a butyl group, Ph is a phenyl group); Pb-N
a, Pb-Ca, Pb-Ba, Pb-3n,
Lead alloys such as Pb-3b; lead minerals such as boenite and sennenite, and hydrates of these lead compounds; anion exchange resins containing tertiary amine groups, ion exchange resins containing amide groups Ion exchangers such as resins, ion exchange resins having at least one exchange group of sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups, and solid strongly basic anion exchangers having quaternary ammonium groups as exchange groups. ;
Solid inorganic compounds such as silica, silica-alumina, silica-magnesia, aluminosilicate, gallium silicate, various zeolites, various metal-exchanged zeolites, and ammonium-exchanged zeolites are used.

As the solid contact, a solid strongly basic anion exchanger having a quaternary ammonium group as an exchange group is particularly preferably used. Examples include basic anion exchange resins, cellulose strongly basic anion exchangers having quaternary ammonium groups as exchange groups, and strongly basic anion exchangers supported on inorganic carriers having quaternary ammonium groups as exchange groups.

As the strong basic anion exchange resin having a quaternary ammonium group as an exchange group, for example, a styrene-based strong basic anion exchange resin is preferably used. A styrene-based strongly basic anion exchange resin is a strong basic anion exchange resin that has a copolymer of styrene and divinylbenzene as a base material and has a quaternary ammonium (I type or ■ type) as an exchange group.For example, It is schematically shown by the following formula.

○ ○ OO○ CH3CO2, HCO2, IO*, BrO3, CzC
At least one anion selected from h is used, preferably cz, Br, HCO3, C
At least one anion selected from O3 is used. Also, regarding the structure of the resin matrix, can either gel type or macroreticular type (MR type) be used?
The MR type is particularly preferred because of its high organic solvent resistance.

As a cellulose strongly basic anion exchanger having a quaternary ammonium group as an exchange group, for example, -QC)12cf (JR3X0) obtained by trialkylaminoethylating some or all of the H groups of cellulose, Examples include cellulose having an exchange group.R represents an alkyl group, usually methyl, ethyl, propyl,
Butyl is used, preferably methyl or ethyl.

Moreover, X is as described above.

The strongly basic anion exchanger supported on an inorganic carrier having a quaternary ammonium group as an exchange group, which can be used in the present invention, is a quaternary Ammonium group-0 (
CH2). It means the one into which yiR3Xo is introduced. However, R, and X are as described above. n is usually an integer of 1 to 6, preferably n=2. Inorganic carriers include silica, alumina, silica alumina, titania,
It is possible to use silica, alumina, silica alumina, and particularly preferably silica. Any method can be used to modify the surface hydroxyl groups of the inorganic carrier.

For example, inorganic carrier and amino alcohol HO (CH2)
. After aminoalkoxylating NR2 by proceeding with a dehydration reaction in the presence of a base catalyst, halogenated alkyl RX'(X' represents a halogen, usually Cβ, Br
, I, etc.) to react with some (CH2)
. yR, xQ group. Furthermore, by performing anion exchange, a quaternary ammonium group-0 (CH2) having the desired anion X0 and stomach R3X0 are obtained. Also,
In the case of n=2, the inorganic support is treated with N,N-dialkylaziridine to form N,N-dialkylaminoethoxylate into -0CH2CH2NR2 group, and then -0CH2CH2 back R3X0 group is converted by the above-mentioned method. Ru.

A commercially available solid strong basic anion exchanger having a quaternary ammonium group as an exchange group can also be used. In that case, it may be used as a catalyst after performing ion exchange with a desired anion species as a pretreatment.

It also consists of macroreticular and gel-type organic polymers to which a heterocyclic group containing at least one nitrogen atom is bonded, or an inorganic carrier to which a heterocyclic group containing at least one nitrogen atom is bonded. Solid catalysts are also preferably used.

In carrying out the present invention, if the raw materials, cyclic carbonate and aliphatic monoalcohol, are supplied to the complex stage in which a catalyst is present in a continuous multi-stage distillation column, the cyclic carbonate and aliphatic monoalcohol can be fed to any stage of the continuous multistage distillation column. It can be supplied continuously from several inlets. The raw material is continuously fed to the distillation column as a liquid, gas, or a mixture of liquid and gas. In addition to supplying the raw material to the continuous multistage distillation column in this manner, it is also a preferred method to additionally supply a gaseous raw material to the lower part of the distillation column intermittently or continuously. Among cyclic carbonates and aliphatic monoalcohols, raw materials with higher boiling points are continuously supplied to the distillation column in a liquid or gas-liquid mixed state to a stage above the stage where the catalyst is present, and raw materials with lower boiling points are continuously supplied to the distillation column. A method of continuously supplying it in gaseous form to the lower part of the distillation column is also a preferred method. In this case, it does not matter if the high boiling point raw material supplied from the upper part contains the low boiling point raw material.

These feedstocks may contain product dialkyl carbonates or diols, but since this reaction is reversible, if the concentration of these products is too high, the reaction rate of the raw materials will decrease. This is not preferable because it lowers the

The quantitative ratio of cyclic carbonate and aliphatic monoalcohols supplied to the continuous multi-stage distillation column may vary depending on the type and amount of catalyst and the reaction conditions. The monoalcohols are preferably supplied in a molar ratio of 0.01 to 1000 times. In order to increase the reaction rate of the cyclic carbonate, it is preferable to supply the aliphatic monoalcohol in an excess amount of two times the mole or more; however, if too much excess is used, the size of the apparatus may need to be increased. In this sense, it is particularly preferable to use 2 to 20 times the molar amount of the aliphatic monoalcohol.

In the present invention, a cyclic carbonate and an aliphatic monoalcohol are reacted in the presence of a catalyst in multiple stages in a multi-stage continuous distillation column to produce a dialkyl carbonate and a diol, or one of these products is , the lower boiling point product is continuously withdrawn from the distillation column in gaseous form. In this case, the gaseous effluent may be a low-boiling product alone or a mixture with aliphatic monoalcohols and/or cyclic carbonates, or may also contain small amounts of high-boiling products.

The outlet for extracting gaseous substances containing low-boiling products from a continuous multi-stage distillation column can be provided at any position other than the bottom of the column, but the concentration of low-boiling products in the vapor phase usually varies depending on the column. It increases towards the top. Therefore, it is preferable to provide the gaseous substance extraction port between the raw material supply position and the top of the column or at the top of the column, and it is more preferable to provide the outlet at the top of the column. The gaseous components extracted in this manner may be liquefied by cooling or the like, and a portion thereof may be returned to the upper part of the distillation column, a so-called reflux operation. When the reflux ratio is increased by this reflux operation, the efficiency of distilling the low-boiling point products into the vapor phase increases, so that the concentration of the low-boiling point products in the extracted gas component can be increased. However, if the reflux ratio is increased too much, the required thermal energy will increase, which is not preferable. Therefore, the reflux ratio is usually 0 to 10, preferably 0 to 5.
is used.

Among the dialkyl carbonates and diols produced by the method of the present invention, high-boiling point products are continuously extracted in liquid form from the lower part of the continuous multi-stage distillation column. In this case, the liquid extract may be a high-boiling point product alone, a mixture with an aliphatic monoalcohol and/or a cyclic carbonate, or it may contain a small amount of a low-boiling point product. . If a high boiling point catalyst is used which can be dissolved in the reaction liquid under the reaction conditions, this liquid effluent also contains this catalyst. An outlet for withdrawing a liquid material containing high-boiling products from the continuous multi-stage distillation column is provided at the bottom of the column, particularly preferably at the bottom of the column. The liquid substance extracted in this way may be returned to the lower part of the distillation column in the form of a gas or a gas-liquid mixture by heating a part of it in a reboiler.

In a particularly preferred embodiment of the present invention, the cyclic carbonate is ethylene carbonate or propylene carbonate, and the aliphatic monoalcohol is an aliphatic monoalcohol having 1 carbon atom.
~4 lower alcohols methanol, ethanol,
Using propatool (each isomer), allyl alcohol, butanol (each isomer), the corresponding dialkyl carbonate dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diallyl carbonate,
This is the case when dibutyl carbonate and ethylene glycol or propylene glycol are produced. In these cases, ethylene carbonate or propylene carbonate, which has a high line point among the raw materials, is introduced in liquid form into the distillation column from an inlet installed between the trays of the continuous multi-stage distillation column and the top of the column where the catalyst is present. A lower aliphatic monoalcohol, which is a low-boiling point raw material, is continuously supplied in gaseous form into the distillation column from the bottom of the column. The dialkyl carbonate, which is a low boiling point product produced by the reaction, is continuously extracted in gaseous form from the top of the continuous multi-stage distillation column.
The high-boiling products ethylene glycol or propylene glycol are continuously withdrawn in liquid form from the bottom of the distillation column.

The amount of catalyst used in the present invention varies depending on the type of catalyst used, or when the catalyst is continuously fed to the reaction zone of a continuous multi-stage distillation column, the amount of catalyst used in the present invention varies depending on the type of catalyst used, or when the catalyst is continuously fed to the reaction zone of a continuous multi-stage distillation column, the amount of catalyst used in the present invention varies depending on the type of catalyst used. It is usually used in an amount of 0.0001 to 50% by weight, expressed as a percentage of the total weight. In addition, when the solid catalyst is installed and used in a continuous multi-stage distillation column, 0.01 to 7
A catalyst amount of 5% by volume is preferably used.

In the present invention, since the reaction mainly occurs in multiple stages of a continuous multi-stage distillation column in which a catalyst is present, the amount of reaction product produced usually depends on the amount of hold-up liquid in the distillation column. In other words, when using distillation columns having the same column height and the same column diameter, a distillation column with a large amount of bold-up liquid is preferable in the sense that the residence time of the reaction liquid, that is, the reaction time can be relatively long. However, if the amount of hold-up liquid is too large, the residence time becomes long, making it easier for side reactions to proceed and flooding to occur. Therefore, although the amount of hold-up liquid in the distillation column used in the present invention may vary depending on the distillation conditions and the type of distillation column, it is usually expressed as the volume ratio of the amount of hold-up liquid to the empty column volume of the continuous multi-stage distillation column. 0.005～
It is done at 0.75.

In addition, in the present invention, the average residence time of the reaction liquid in the continuous multi-stage distillation column varies depending on the reaction conditions, the type and internal structure of the multi-stage continuous distillation column (for example, the types of trays and packing materials), or is usually 0. .001 to 50 hours, preferably 0.01 to 50 hours
It is 10 hours, more preferably 0.05 to 5 hours.

The reaction temperature is the temperature within the continuous multi-stage distillation column, and varies depending on the type of raw materials used and reaction pressure, but is usually 0 to 350°C.
'C1 is preferably in the range of 20 to 200'C. In addition, the reaction pressure may be reduced pressure, normal pressure, or increased pressure.
It is usually 0.00001 to 200 kg/cm2.

In the present invention, it is not always necessary to use a solvent, or a suitable inert solvent may be used for the purpose of facilitating the reaction operation, such as ethers, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated Aliphatic hydrocarbons, halogenated aromatic hydrocarbons, etc. can be used as the reaction solvent.

In addition, an inert gas such as nitrogen, helium, or argon may be allowed to coexist in the reaction system as a substance inert to the reaction, or the lower part of the continuous multistage distillation column may be used to accelerate the distillation of low-boiling products produced. Alternatively, the above-mentioned inert gas or a low-boiling organic compound inert to the reaction may be introduced in gaseous form.

〔Example〕

EXAMPLES Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to these examples.

Example 1 Dimethyl carbonate-1 and ethylene glycol were continuously produced from ethylene carbonate and methanol using a packed column type continuous multistage distillation apparatus with an inner diameter of 2 cm and a length of 1 m as shown in Fig. 1. The reaction was carried out.

As a catalyst and filler, an anion exchange resin with a quaternary ammonium group as an exchange group (Dowex@MSA-1゜CZ
The mold) was ion-exchanged with a 2N Na2COa aqueous solution, washed repeatedly with pure water, and then replaced with dry methanol, which was packed into the distillation column to a height of about 60 cm. There are approximately 10 cm above and below this catalyst.
The container was filled with stainless steel Dixon packing having a height of 3rr+m in diameter.

81.6g/methanol vapor from the lower part of the tower raw material inlet 2
A mixture of ethylene carbonate and methanol (weight ratio: ethylene carbonate/methanol = 5/1) heated to 7°C was introduced at a rate of 26.4 g/hr from the raw material inlet 1 at the bottom of the column. The temperature inside the column was about 78°C at the bottom of the column and about 65°C at the top of the column.

The gaseous components extracted from the top gas extraction port 3 are cooled and liquefied, and are continuously extracted at a rate of 77.2 g/hr.
It was continuously extracted at a rate of 8 g/hr. After reaching a steady state, the liquid condensed from the gas components extracted from the top of the column contains dimethyl carbonate (29 weight 96) and methanol (96 weight).
71% by weight).

In addition, the liquid components extracted from the bottom of the tower were ethylene glycol (50% by weight, 96% by weight), methanol (49.5% by weight),
) and high-boiling by-products (0.5 wt. 96), no ethylene carbonate was detected. This result shows that the reaction rate of ethylene carbonate is 100%, and the yield and selectivity of dimethyl carbonate are 99.5%.
, the yield and selectivity of ethylene glycol are 99.5%. By this method, dimethyl carbonate and ethylene glycol were produced continuously,
After 200 to 400 hours, the results were similar to those of Habo.

Example 2 The same method as Example J was performed except that propylene carbonate was used instead of ethylene carbonate. As a result,
Dimethyl carbonate (28.5% by weight) as top component
) and methanol (71.5% by weight),
In addition, a mixture of propylene glycol (55.1% by weight) and methanol (44.3% by weight) containing a trace amount (0.6% by weight) of high-boiling byproducts was continuously obtained as a bottom component.

The reaction rate of propylene carbonate is 100%, the yield and selectivity of dimethyl carbonate are 99.4%, and the yield and selectivity of propylene glycol are 99.4%.
It was 96.

Example 3 Dimethyl carbonate and ethylene glycol were continuously produced from ethylene carbonate and methanol using a continuous multi-stage distillation apparatus consisting of an old-style distillation column having 30 stages as shown in Figure 2. The reaction was carried out.

A mixture of ethyne carbonate and methanol (weight ratio: ethylene carbonate/methanol 2/J) containing lead acetate (200 ppm) as a catalyst was heated to 70°C, and 143. It was introduced continuously at a rate of 7 g/hr. Additionally, 356.3 g/hr of methanol was continuously introduced from the inlet 2 at the bottom of the column. The bottom component is heated in the reboiler 6, and a part of it is continuously extracted from the liquid component extraction port 4.

The gaseous components extracted from the top gas extraction port 3 were cooled and liquefied and extracted continuously at a rate of 365.7 g/hr, and the bottom liquid was continuously extracted at a rate of 134.3 g/hr. . After reaching a steady state, the liquid condensed from the gas components extracted from the top of the column is dimethyl carbonate (29% by weight).
and methanol (71% by weight).

In addition, in 134.3 g of the bottom liquid extracted from the bottom of the tower,
It contained 72.9 g of ethylene glycol, 1-1.05 g of ethylene carbonate, 0.8 g of high-boiling by-products, and 59.5 g of methanol. The results show that the reaction rate of ethylene carbonate was 99%, the yield and selectivity of dimethyl carbonate were 99.2%, and the yield and selectivity of ethylene glycol were 99%.

〔Effect of the invention〕

By the method of the present invention, dialkyl carbonates and diols can be continuously produced from cyclic carbonates and aliphatic alcohols in high yield and high selectivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a packed column type continuous multi-stage distillation apparatus,
FIG. 2 is a schematic diagram of an old series continuous multi-stage distillation apparatus. 1: High boiling point raw material inlet 2: Low boiling point raw material inlet 3: Low boiling point reaction product outlet 4, high boiling point reaction product outlet 5, plate tower 6: Rewheeler patent applicant Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] (1) When reacting a cyclic carbonate and an aliphatic monoalcohol in the presence of a catalyst to continuously produce a dialkyl carbonate and a diol, the cyclic carbonate and the aliphatic monoalcohol are continuously produced in multiple stages. The reaction is carried out by continuously feeding into the distillation column and bringing it into contact with the catalyst present in multiple stages in the distillation column. At the same time, among the dialkyl carbonates and diols produced by the reaction, low boiling point products are 1. A method for continuously producing dialkyl carbonates and diols, characterized in that a gaseous product is continuously extracted from the distillation column by distillation, and a high-boiling product is continuously extracted in a liquid form from the bottom of the column.