CA2077196C - Process for the continuous preparation of dialkyl carbonates - Google Patents
Process for the continuous preparation of dialkyl carbonates Download PDFInfo
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- CA2077196C CA2077196C CA002077196A CA2077196A CA2077196C CA 2077196 C CA2077196 C CA 2077196C CA 002077196 A CA002077196 A CA 002077196A CA 2077196 A CA2077196 A CA 2077196A CA 2077196 C CA2077196 C CA 2077196C
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- carbonate
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- transesterification
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
- C07C69/96—Esters of carbonic or haloformic acids
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C68/00—Preparation of esters of carbonic or haloformic acids
- C07C68/06—Preparation of esters of carbonic or haloformic acids from organic carbonates
- C07C68/065—Preparation of esters of carbonic or haloformic acids from organic carbonates from alkylene carbonates
Abstract
Dialkyl carbonates can be prepared in a continuous manner by transesterification of ethylene carbonate or propylene carbonate with alcohols in the presence of a catalyst in a column equipped with packing or baffles, by passing the reactants in countercurrent such that the ethylene carbonate or propylene carbonate are metered into the upper part of the column and the alcohol is metered into the lower part of the column and the catalyst is arranged as a fixed bed in the column or is also metered into the upper part of the column in solution or suspension, the dialkyl carbonate formed, if appropriate as a mixture with alcohol, being removed at the top of the column and the ethylene glycol or propylene glycol formed from the ethylene carbonate or propylene carbonate being removed at the toot of the column, if appropriate together with the catalyst.
Description
Process for the Continuous Preparation of Dialkyl Carbonates BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a continuous process for the preparation of dialkyl carbonates by trans-esterification of ethylene carbonate or propylene carbonate with C1-C4-alcohols in the presence of a catalyst, the starting substances being passed in countercurrent to one another.
1. FIELD OF THE INVENTION
The present invention relates to a continuous process for the preparation of dialkyl carbonates by trans-esterification of ethylene carbonate or propylene carbonate with C1-C4-alcohols in the presence of a catalyst, the starting substances being passed in countercurrent to one another.
2. DESCRIPTION OF THE RELATED ART
It is known that ethylene glycol carbonate and propylene glycol carbonate (glycol carbonates) can be reacted with alcohols in the presence of catalysts to give dialkyl carbonates and ethylene glycol (EG) or propylene glycol.
Although these reactions can proceed with a high select-ivity, the processes have a number of disadvantages in their procedure. As a rule, the transesterification proceeds relatively slowly under normal pressure, so t'~at the use of elevated temperature, often above the bon ing point of the alcohol employed, is recommended, w~i4'~
results in the process being carried out in pres~u=
vessels (German published patent application 2 740 243 -EP 1082; and German publish°d patent application 2 740 X51 =
EP 1083).
In this process, the reaction usually proceeds only unti' equilibrium is established in the transesterification reaction. After removal from the pressure container, the reaction mixture must be removed from the catalyst very quickly, for example by flash distillation, so that the starting compounds are not reformed in a reversal of the formation reaction, for example when the alcohol of low boiling point distils off. During removal from the catalyst by distillation, the glycol carbonate still in equilibrium can decompose into carbon dioxide and into polyglycols and is therefore unavailable for further transesterification, the yield being reduced, and all the by-products mentioned interfere with the working up.
However, even if this removal of the catalyst is effected satisfactorily, further distillations must still be carried out. Thus, it is first necessary to separate high boiling components (glycols and glycol carbonates) from the low-boiling components (alcohols and dialkyl carbonates).
However, distillative purification of ethylene glycol, which must have a high purity for example for the preparation of polyesters, to remove incompletely reacted ethylene glycol carbonate, which in turn is preferably employed for the preparation of dialkyl carbonates, is not possible without restriction since both compounds form an azeotrope. A
similar difficulty is found when methanol, which is the preferred alcoholic component, has to be separated off from the dimethyl carbonate (DMC) formed. These compounds also form an azeotrope, which can be distilled into its separate components only in a cumbersome manner (EP 894 dated March 7, 1979 and literature cited therein).
SUMMARY OF THE INVENTION
In spite of diverse attempts at a solution, there was therefore an urgent need for the various difficulties mentioned to be effectively overcome. It has now been found, surprisingly, that the disadvantages mentioned in the transesterification of glycol carbonates with _ 2 _ 2~°~~1~6 alcohols to give dialkyl carbonates can be eliminated if the transesterificatian is carried out in a column with the starting substances in countercurrent to one another;
this process can be carried out under unexpectedly mild conditions.
The invention therefore relates to a process for the preparation of dialkyl carbonates of the formula (R~p)aCp (1) in which R1 denotes straight-chain or branched C1-C4-alkyl, by transesterification of ethylene carbonate or propylene carbonate with 3-80 mol, preferably 4-20 mol, particular-ly preferably 6-16 mol, of alcohols of the formula R~OH ( I ~ ) in which R1 has the above meaning, per mole of ethylene carbonate or propylene carbonate in the presence of catalysts, which is characterised in that the transesterification is carried out in a column equipped with packing or baffles at temperatur~a in the range of 60-160°C, preferably 60-150°C, particularly Le A 28 516 - 3 -preferably 55-1:i0°C, and the reactants are passed in countercurrent such that the ethylene carbonate or propylene carbonate are metered into the upper part of the column and the alcohol is metered into the lower part of the column and the catalyst is arranged as a fixed bed in the column or is also metered into the upper part of the calum: in solution or suspension, the dialkyl carbonate farmed, if appragriate as a mixture with alcohol, being removed at the top of the column and the ethylene glycol or propylene glycol formed from the ethylene carbonate or propylene carbonate being removed at the foot of the column, if appropriate together with the catalyst.
In spite of the mild conditions, complete transesterific atian of the glycol carbonate to the dialkyl carbonate is achieved in this process, so that first of all the distillation of the glycol carbonate azeatrape into its separate components .is dispensed with, since the glycol can already be removed at the foot of the column in a state free from glycol carbonate. The otherwise customary rapid separation of the reaction mixture from the catalyst is consequently superfluous, since the dialkyl carbonates are removed at the top of the column and are thus separated from the glycol and from the catalyst, and reversal of the reaction to give the starting substances is no longer possible. Moreover, in the case of a transesterification with methanol, which is preferably employed, as the alcohol, the column can be operated so that not only the expected azeatrope of methanol (about Le A 29 516 - 4 20'~~1~~
70 $) and dimethyl carbonate (about 30 $) but also a mixture which contains considerably more dimethyl carbonate than corresponds to the azeotrope is obtained at the tap of the column. In the case of methanol, it is therefore even possible to carry out the transesterifica-tian such that instead of pure methanol, mixtures of methanol and dimethyl carbonate, which may be obtained in other processes, are employed as the starting material in the transesterification according to the invention with glycol carbonate without a prior difficult separation.
This is also possible of course when alcohols other than methanol are used, As a result of being able to use mixtures of alcohols and dialkyl carbonates instead of the pure alcahols far the transesterification, the often difficult and energy--intensive separation of the mix-tures, a predominant number of which are azeotropes, is no longer necessary. The alcohol and the dialkyl carbonate in such mixtures have the s.3me alkyl radical, which means that undesirable, complicated reaction mixtures having different alkyl radicals are avoided.
The solution to the object described is distinguished by its simplicity and its straightforwardness.
In the si.zaplest case, the column to be employed is an isothermally heated tube filled with the customary packing to.be used for distillations, into the top of which the catalyst solution and the glycol carbonate are introduced. The alcohol to be used is sent from the bottom in vapour form in countercurrent to this mixture.
he A 28 516 - 5 -20~~196 The transesterification steps proceed surprisingly rapidly in the tube, so that considerable amounts of dialkyl carbonate pass over at the top even in a relatively short column of this simple design.
However, the column can also comprise, at the lower end, a stripping part which operates at a higher temperature and in which substantial to complete separation of the alcohol from the glycol trickling down, and recycling into the transesteri.fication region of the column takes place.
The column can furthermore have, in the upper part, a rectifying part which operates at a lower temperature, in order to bring the separation of gaseous alcohol and dialkyl carbonate from higher-boiling components, such as, for example, glycol and glycol carbonate, to comple-tion and in this way to remove a high-strength or pure mixture of alcohol and dialkyl carbonate at the column top.
Energy can be supplied via the alcohol introduced into the column in vapour form and/or via the bottom evaporat-or. The alcohol may also be metered in in liquid farm, in which case energy must be supplied via the bottom evaporator. Tn the first case, a widening of the column diameter in the middle part of the column, in whidh the majority of the transesterification proceeds, t~ four times that of the other parts may be of advantage. In the second case, the evaporation enthalpy for the alcohol he A 28 516 - 6 -must be transported through the stripping part and leads to a high loading with gas and liquid here. This results in a widening of the column in the stripping part in order to guarantee the separations envisaged in that part. The widening and length of the stripping part depend on the column baffles chosen in the stipping part, and these can be designed by the expert.
Since two molecules of alcohol are replaced by one molecule of dialkyl carbonate in the course of the transesterification in the gas phase, a reduction in cross-section by not more than a factor of 2 may be advantageous to keep the speed of the gas constant in the middle part of the column.
The column can thus either be heated isothermally or, preferably, be equipped with one or more temperature zones which differ from the main part, resulting in a temperature gradient with values which increase from the top downwards.
The packing or ordered fillings to be used are those which are customary per se for distillations, such as are described, for example, in Ullmann's Encyclopadie der Techn. Chemie (Ullmann's Encyclopaedia of Industrial Chemistry), 4th Edition, Volume 2, page 528 et seq. Examples which may be mentioned are: RaschigT"" or Pall ringsTM, Berl-, Intalex- or torus-saddlesT"", and interpacking bodies of various materials, such as glass, stoneware, porcelain, carbon, high-grade steel or plastic, which can be processed in a woven fabric- or mesh-like manner, especially if metal is used. Packing and ordered fillings which have a large surface area and good wetting i properties as well as an adequate residence time of the liquid are preferred. These are, for example, Pall- and Novolax-rings", Berl-saddles", BX-packingTM, Montz-PakT"", Mellapak~', MelladurTM, KerapakT'" and CY-packingsTM.
However, not only packed columns but also those having fixed baffles are suitable for the process according to the invention. Of these, those having bubble or valve trays with high residence times coupled with a good mass transfer are preferred.
However, other tray columns are'also generally suitable, for example those having perforated, bubble, valve, tunnel and centrifugal trays, which can in turn be present in various embodiments.
The column is operated such that a solution of the catalyst in the glycol carbonate employed, or also in the glycol on which this is based or also in the alcohol to be employed or also in another suitable inert solvent foreign to the system, is metered into the upper half, preferably into the upper third. In the case where a catalyst which is insoluble in the reactants is employed, this can also be employed as a mixture with the packing mentioned or as a heap poured onto the column trays _ g _ installed. The glycol carbonate is likewise introduced into the upper region, preferably into the upper third of the column; it preferably has a temperature the same as that prevailing at this point in the column. The alcohol, as a rule in vapour form, is. metered into the lower half of the column, preferably above any stripping zone present.
The dialkyl carbonate is removed at the top of the column, preferably after passing through a rectifying zone, and is condensed. Tn general, it still contains portions of the alcohol in the system. A glycol which is of high-percent strength if the conditions have been set carefully is discharged from the bottom of the column, and can be separated Pram the catalyst and impurities in Z5 a purifying distillation.
The molar ratio in the column varies from 3-30 mol.
preferably 4-20 mol, particularly preferably 6-16 mnl, of alcohol per mol of ethylene carbonate or propylene carbonate.
The temperature in the column is 60-160°C, preferably 60--150°C, particularly preferably 65-130°C. A temperature gradient which is to be applied in a preferred manner lies in the stated temperature range and rises from the top of the column to the bottom of the column.
As a rule, the reaction of the process according to the invention is carried out under normal pressure. However, Le A 28 516 - 9 -20"~'~~.96 it is also possible to carry out the reaction under a slightly increased pressure of up to about 3 bar, prefer-ably up to 2 bar, or under a reduced pressure of down to 50 mbar, preferably down to 100 mbar, particularly preferably down to 200 mbar. In a manner known to the expert, by deviating from normal pressure it may become possible to influence the azeotrope to be remaved, for example, at the top.
The space/time loading of the column is 0.1-3 g of the total amount of reaction participants per ml of effective column volume per hour, preferably 0.2-2.5 g/ml/hour, particularly preferably 0.3-2.0 g/ml/houx; the effective column volume here is that of the packing or the volume in which fixed baffles are located. Catalysts which are suitable for the process according to the invention are knawn in the literature.
Such catalysts are, for example, hydrides, oxides, hydroxides, alcoholates, amides or salts of alkali metals, such as lithium, sodium, potassium, rubidium and caesium, preferably of lithium, sodium and potassium, particularly preferably of sodium and potassium (US-3 642 858, US-3 803 201 and EP 1082). xn the case where the alcoholates are employed, according to the invention these can also be formed in situ by using the elemental alkali metals and the alcohol to be reacted according to the invention. Salts of the alkali metals can be those of organic or inorganic acids, such as of acetic acid, propionic acid, butyric acid, benzoic acid, Le A 28 516 - 10 ~'4'~'~196 stearic acid or carbonic acid (carbonates or bicarbon-ates), of hydrochloric acid, hydrobromic or hydriodic acid, nitra.c acid, sulphuric acid, hydrofluoric acid, phosphoric acid, hydrocyanic acid, thiocyanic acid, boric S acid, stannic acid, C1-C4-stannonic acids or antimony acids. Preferred possible compounds of the alkali metals are the oxides, hydroxides, alcoholates, acetates, propionates, benzoates, carbonates and bicarbonates, and hydroxides, alcoholates, acetates, benzoates or carbon aces are particularly preferably employed.
Such alkali metal compounds (farmed in situ, if appropri ate, from the free alkali metals) are employed in amounts of 0.001 to 2 $ by weight, preferably 0.005 to 0.9 $ by weight, particularly preferably 0.01 to 0.5 ~ by weight, based on the reaction mixture to be reacted.
It is possible, according to the invention, to add substances which, if appropriate, complex such alkali metal compounds (EP 274 953). Examples which may be mentioned are crown ethers, such as dibenzo-18-crown-6, polyethylene glycols or bicyclic nitrogen-containing cryptands.
Such complexing agents are employed in amounts of 0.1 to 200 mol ~, preferably 1 to 100 moi ~, based on the alkali metal compound.
Suitable catalysts for the process according to 'the invention are furthermore thallium-I and thallium-lII
Le A 28 516 - 11 compounds, such as the oxides, hydroxides, carbonates, acetates, bromides, chlorides, fluorides, formates, nitrates, cyanates, stearates, naphthenates, benzoates, cyclohexylphosphonates and hexahydrobenzoates, cyclo-pentadienylthallium, thallium methylate and thallium ethylate, preferably T1-(I) oxide, T1-(I) hydroxide, T1-(I) carbonate, T1-(T) acetate, T1-(TIT) acetate, T1-(I) fluoride, T1-(I) formats, T1-(I) nitrate, T1-(I) naphthenate and T1-(I) methylate (EP 1083). The amounts of thallium catalyst are not particularly critical. They are in general 0.0001-ZO ~ by weight, preferably 0.001-1 ~ by weight, based on the total reaction mixture.
Nitrogen-containing bases can furthermore be employed as 15~ catalysts in the process according to the invention (US-4 062 884). Examples which may be mentioned are secondary or tertiary amines, such as triethylamine, tributylamine, methyldibenzylamine, di.znethylcyclohexyl-amine and 'the like.
The amounts of nitrogen-containing bases employed accord-ing to the invention are from 0.01 to 10 'k by weight, preferably from 0.1 to 5 ~ by weight, particularly preferably from 0.1 to 1 ~ by weight, based on the total reaction mixture.
Heterogeneous catalyst systems can furthermore be employed in the process according to the invention (US 4 062 884r US 4 691 041, .TA 63/238 043 and Le A 28 516 - 12 -.
EP 298 167j. Such systems are, for example, ion exchanger resins with functional groups from tertiary amines, quaternary ammonium groups, examples of counter-ions which may be mentioned being hydroxide, chloride or hydrogen sulphate, sulphonic acid groups or carboxyl groups, for both of which hydrogen, alkali metals or alkaline earth metals may be mentioned as examples of counter-fans. These functional groups can be banded to the polymer either directly or via inert 1p chains. Alkali metal silicates or alkaline earth metal silicates, .impregnated on silicon dioxide supports, and ammonium exchanged zeolites may furthermore be mentioned.
According to the invention, these heterogeneous catalysts are preferably employed in stationary form, but it is also possible for them to be used, for example, as a fine powder in suspension. In the stationary form, the cata-lysts can be employed, far example, instead of the packing described or as a mixture with this.
Catalysts which can furthermore be employed according to the invention are compounds from the group comprising phasphines, stibines, arsines and divalent sulphur and selenium compounds as well as opium salts thereof (EP 180 387 and US ~ 734 518). The following may be mentioned as examples: tributylphasphine, ~triphenyl-phasphine, diphenylphosphine, 1,3-bis-(diphenylphos-phino)propane, triphenylarsine, trimethylarsi.ne, tri-butylarsine, 1,2-bis-(diphenylarsino)ethane, triphenyl-stibine, Biphenyl sulphide, Biphenyl disulphide, Biphenyl Le A 28 516 - 13 -selenide, tetraphenylphosphonium halide (C1, Br or I), tetraphenylarsonium halide (C1, Br or I), triphenyl-sulphonium halide (Cl or Br) and the like.
The amounts of this catalyst.group employed according to the invention are in the range .f.ram 0.1 to 10 ~ by weight, preferably from 0.1 to 5 ~ by weight, particu-larly preferably in the range from 0.1 to 2 ~ by weight, based on the total reaction mixture.
Complexes or salts of tin, titanium ar zirconium can 1U furthermore be employed according to the invention (US 4 661 609). Examples of such systems are butylstan-none acid, tin methoxide, dimethyltin, dibutyltin oxide, dibutyltin dilaurate, tributyltin hydride, tributyltin chloride, tin(II) ethylhexanoates, zirconium alkoxides (methyl, ethyl ar butyl), zirconium(IV) halides (F, C1, Br or I), zirconium nitrates, zirconium acetylacetonate, titanium alkoxides (methyl, ethyl ar isopropyl), titanium acetate, titanium acetylacetonate and the like.
The amounts which can be employed according to the invention are 0.1 to 10 ~ by weight, preferably 1 to 5 by weight, based on the total mixture.
Bifunctional catalysts of the formula ~~a~b)m' ~BcYa~n ( III ) can furthermore be employed in the process according to Le A 28 516 - 1,~
the invention. In these bifunctional catalysts, the molar ratio of the two components in square brackets is expressed by the indices m and n. These indices can assume, independently of one another, values of 0.001-1, preferably 0.01-1, particularly preferably 0.05-1 and especially preferably 0.1-1. Within the square brackets are neutral salts of in each case one ration and one anion. The indices a and b independently of one another represent integers from 1-5; the indices c and d inde-pendently of one another denote integers from 1-3, where the valency requirements of the rations and anions for the formation of such neutral salts are to be met.
Furthermore, in (ITI), A denotes the ration of a metal which belongs to the third period and group IIa, to the fourth period and group IIa, IVa-VIIIa, Ib or IIb, to the fifth period and group IIa, IVa-VIIa, IIb or IVb or to the sixth period and group IIa-VIa of the Periodic Table of the Elements in the short-period form.
The expert can see the metals suitable for ration A from the usual pxesentations of the Periodic Table of the Elements (Mendeleev) in the short--period form. A is Le A 28 516 ~ 15 -2 0'~'~ 19 ~
preferably the ration of one of the metals Mg, Ca, Sr, Ba, Zn, Cu, Mn, Co, Ni, Fe, Cr, Mo, W, Ti, Zr, Sn, Hf, ~7 or Ta, preferably the canon of one of the metals Mg, Ca, Zn, Co, Ni, Mn, Cu or Sn. In addition to the non-com-plexed canons of the metals mentioned, cationic oxo complexes of the metals mentioned are also possible, such as, fox oxam,ple, titanyl Ti0''~' and chromyl Cr02t".
The anion X belonging to the ration A is that of an inorganic or organic acid. Such an inorganic or organic :10 acid can be monobasic or dibasic or tribasic. Such acids and their anions are known to the expert. Examples of anions of monobasic inorganic or organic acids are:
fluoride, bromide, chloride, iodide, nitrate, the anion of an alkanecarboxylic acid having 1-lz C atoms and benzoate; examples of anions of dibasic inorganic or organic acids are: sulphate, oxalate, succinate, fumar-ate, maleate, phthalate and others; examples of tribasic inorganic or organic anions are: phosphate or citrate.
Preferred anions X in the catalyst of the formula (IIIj are: fluoride, chloride, bromide, iodide, sulphate, nitrate, phosphate, formate, acetate, propionate, oxal-ate, butyrate, citrate, succinate, famerete, maleate, benzoate, phthalate, decanoate, stearate, palmitate and laurate. Particularly preferred anions X are: chloride, bromide, iodide, acetate, laurate, stearate, palmit~te, decanoate, nitrate and sulphate.
A suitable ration B in the catalysts of the formula (IIIj is one from the group comprising alkali metal rations or Le A 28 516 - 16 --alkaline earth metal cations, quaternary ammonium, phosphonium, arsonium or stibonium canons and ternary sulphonium cations.
Alkali and alkaline earth metal cations which may be mentioned here are: the lithium, sodium, potassium, rubidium, caesium, magnesium, calcium, strontium and barium canon, praferably the alkali metal canons mentioned, particularly ,preferably the sodium and the potassium catian.
Suitable rations B are preferably those of the formulae:
R ~ ~1 ~ R3 R2 ~ ~ Rs Q (tv) s '~ cv) or Rs Ra Ra wherein Q1 represents N, P, As or Sb and R2, R3, R" and RS independently of one another are _ straight°chain or branched C1°CI8°alkyl or C7-Cla°
aralkyl, and one of the radicals R2°RS can also be Cs°Ciz°ar'Yl .
Le A 28 516 ° 17 B is particularly preferably a ration of the formula Rz R3 /~
Q (VI) ~5 ~ ~l wherein QZ represents D1 or 1', preferably N.
In the context of the formulae (TV) and (V1), the radi-call R~z, R~3, R~4 and RCS, which independently of one another denote straight--chain or branched C1-G1~-alkyl or C,-Ce-aralkyl, and one of the radicals R~ to >~ can also be phenyl., especially preferably replace the radicals Rz, R3, R" and RS respectively. Furthermore, the radicals R22 R~ , R~ and Ft~, which independently of one another denote Cl-CB-alkyl or benzyl, and one of the radicals R22 to R2s can also be phenyl, especially preferably replace~the radicals Rlz, R1', Rl" and R'S respectively.
Straight-chain or branched C1-Cle-alkyl is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, dodecyl, hexadecyl or octadecyl, Preferred aJ.kyl has 1-12 C atoans, and particularly preferred alkyl his 1-8 C atoms.
Le A 28 516 - 18 ~
C~-C12-Aralkyl is, for example, benzyl, phenylethyl, phenylpropyl, naphthylmethyl or naphthyl-ethyl; preferred aralkyl is benzyl or phenylethyl, and especially preferred aralkyl is benzyl.
C6-C12-Aryl is, for example, phenyl, naphthyl or biphenylyl, preferably phenyl.
The anion Y in the catalyst of the formula (III) is a halide ion, such as fluoride, chloride, bromide or iodide, preferably bromide or iodide, particularly preferably iodide. However, it can also have the meaning of other anions mentioned under X, if the anion X, in the specific case, is bromide or iodide.
The bifunctional catalyst of the formula (III) is em-ployed in an amount of 0.005-5 $ by weight, preferably 0.01-3 $ by weight, particularly preferably 0.01-1 $ by weight, based on the total transesterification mixture.
These amounts of catalyst in some cases differ from the amounts mentioned in the literature. It is particularly surprising that relatively high concentrations of the active catalysts based on alkali metal compounds can be employed in the process according to the invention without the evolutions of COZ, which reduce the yield and impede the reaction procedure, and the formation of polyols occurring, as is known, for example, from German published patent application 2 740 243, in the literature ~i~~d therein and from German published patent application 2 740 251.
2o~~l~s This is also a surprising feature of the process according to the invention.
Examples 1-7 A solution of the catalyst TCOH in ethylene glycol and the starting substance ethylene glycol carbonate were metered separately, about 10 cm below the upper and of the column, into an isothermally thermostatical:Ly controlled column packed with Raschig rings of glass and having a length of 250 cm and a diameter of 30 mm. Methanol in vapour farm, which was fed in as a vapour about 30 cm above the lower end of the column, was passed in counter-current to this stream. A mixture of methanol and dimethyl carbonate was removed at the top of the column, which operated without a rectifying part, and ethylene glycol, which, where appropriate, still contained minor amounts of ethylene glycol carbonate and alcohol, was removed at the lower end, which had no stripping part.
The following Table 1 shows some examples of the trans-esterificatian process according to the invention and the results thereof. These were determined after constant conditions and ratios had been established in the column.
Since neither a stripping nor a rectifying paxt were present, the bottom product still contained methanol and, where appropriate, small amounts of dimethyl carbonate, and the distillate still contained traces of ethylene glycol or ethylene glycol carbonate.
Le A 28 516 - 20 -~o~~~o~
Example 8 The process of Examples 1 to 7 was repeated, and instead of methanol, a stream of ethanol in vapour form was fed in about 30 cm above the lower end of the column. The result is shown in the following Table 2.
Le A 28 X16 - 21 -O s.Y1 N N n N n o c0 .~-s Q
N t!1 ~ M M -1 N .C
CL N OW ..C
UP cf' ~ ' V O d~ ~
lt? 1D N -1W d->
G
O i~
'rt d-, M N V1 n CO r.i .-1 4-~
+~ . . . . . .
O
U
O (.~ o .-~ a. ~ 0 LO o uP
W
M
v .~
O
Q
b N
N
W U'1 M e3' ~l' M [J1 N n W
CL
O
Q . . . . . .
O w w-I
O
(U
dP ~t1 ~!1 M (3~
W M M .la .A
W
ca a .~1 r., .-r ~i ~
b .N
~
.~
m .O .-1 Ch C~ p l~ G) N N
t0 W
.1.1 \ M i.t1 N 10 ap I~
d' ~ N d' M M M N
i O
.1r O
W
ro ''~; ~'-1 M n ~
u~ rn .-i $
i O ' 4a ~
U ~
--1 ' b O
N U
ri s gyp' M +~
dA n t'~ N M
A cr b ~
~
..1 .1,d O
' 'C~
~ O
O'~
~
~
~+.~
~ ;a'MU N N O
b1 ~
~
O
~
r-I
00 f-1 M L;
O
fl) ~
O
'at ~ w c ~ a''V
r. ~ u~ a ~
u~ ~
c d p, ~
.-O
V
~
.>~ rt1 W .,.I
b p N rn u1 t~ o ~ ~
o ' M r1 ~
M tA
~
hr tT . ~ rn ~ ~ H
t~ c N
;
Tf N
G
m .
~
.
N
~r ~.. OOpGO J ~ b ~U pooonoo co eo O
O
f~
U
N ~ A ~ a .
x oc~ooo o~a~ ' O .C M 1D L~ LO O (y O Q
. tn (U
~
O \ M t0 C91 4p M r~1lD
O N O O
~, r-1 (0 h M 10 6p ~T
U N
..-~ r'~'Y
O
t~ M .. ~
U
tra n '~' V !~ 'd M (y cr r-i rmi dv U sn o ..-r ~ a .-a'~ ' ~
.-i ~r O
~
.-I
.~
of ::e .fir" r1 N 6!7 O N e-1O 47 O b ~o O
a o O
(a7 Nr1 ~ N N U N II
f91 Ii II
II
O
x H ~
.-1 N M er s~ c~ ~
u1 .~f'~.
~,O'' W
L,~ A ae ~~
m6 v -._-.L'.
4-, N yJ .7-J
x ~
tv Q N C
+~ dP N '.-I .-1 G.7 U _ C
'U w cn C C
O O 'C7 U U
U
f-1 (,W p G N N
a, ~w N ro N a rn c~, w o . r~ a~ a~
+~ o o., .o .A
o to ~ w W cW M ,-I ~-~ '-1 W
A.1 r-1 r-1 ,1-~ r!
_~ N .1.~ ,i) N N
.Q O ro \ r1 ''1 rh'1 Cl~ M
~ ~ f~
O
+.i W W
Ca .
O ~ ,.
W p C
:, da N p~ . ro O
A
N N .r-i ~
~
a, t x7 G
~ ro ~ O
-1 Q tT'~-~
N d ~
Q
Q,-r 1 ~
~
A dP N N N ~ r-1 H .r.~
W
r1 O U '-1 ~-'~ U
v ,~ W ro .,~ ro ~
~
~
.4 Ov ~ 1.~ N N p .,.
ro \ cr IC N r1 N
CT ~ :, H N.=, '~N f1, Q
N U o U
[-~o .~ .N
ro G
.n N
x ro 0o U Q1 u1 W rr M ,-r ro r-~
o s~ n U O U
,~r.fd '~
r-! N r-1 <T ro <T
U
x .~ co ~Dro o \ C.' ra r-1 G', U x ~ N ' ~ o ' ~
~
~
~a~ro~
x a~~~
~ ~ ~b~~
x o W W ~ ~ I! Ii It II
N
x H O ~
,T. oo .a ~
. W A ~
Le 2B516 - 23 -A
2077.~9~
Example 9 44 g of EGC and 0.06 g of KOH (dissolved in 3 g of EG) were introduced per hour onto the top of a column, having a diameter of 28 mm and a length of 120 cm, which was packed with a packing of wire mesh fabric (diameter 3 mm), temperature-controlled at 80°C and additionally equipped at the lower end with a 40 cm long stripping part heated to 100°C, and 120 g of hot MeOH vapour, at 100°C, were blown .i.nto the column from the bottom, directly above the stripping part.
When equilibrium had been established in the column, a mixture of 68.4 ~ of MeOH and 31.6 ~ of DMC was obtained at the top and a mixture which contained. 81.0 ~ of EG, 18.9 $ of MeOH and 0.1 ~ of EGC was discharged from 'the bottom.
Example 10 When 88 g of EGC, 240 g of MeOH and 0.12 g of KOH, dissolved in 6 g of EG, were metered per hour into the column from Example 9, a top product of 60.6 $ of MeOH
and 39.4 ~ of DMC and a bottom groduct of 71.5 ~ of EG, 21.8 ~ of MeOH and 5.8 ~ of EGC were obtained in the stationary state.
When the temperature in the stripping part was increasad by 10°, the content of EGC in the bottom product was reduced to 0.5 ~.
Le A 28 516 - 24 -These examples first of all show how surprisingly smoothly and rapidly the transesterification proceeds with more than 99 $ selectivity under mild conditions of 70-100° without applying pressure (in this context, compare Example 9 of EP 1082 or Example 6 and the comparison examples o:f EP 10$3 with the present examples).
'rhe transesterification can .furthermore be controlled so that the bottom product virtually no longer contains EGC, that is to say separation of the EG/EGC azeotrope is spared (see Examples 1, 6, 9, 11, 12 and 13), which was not possible according to the prior art.
Finally, a top product which contains more DMC than corresponds to the MeOH/DMC azeotrope can be obtained (Examples 1, 4, 5, 6 and 8), and instead of MeOH, the azeotrope of MeOH and DMC can be employed, considerable additional transesterification taking place (Example 6:
in addition to that metered ,in, about a further 1.6 mol of DMC are formed).
Examples 11-13 The educt ethylene carbonate and, separately, a solution of the catalyst KOH in ethylene glycol were metered into the upper end of a 10-tray, isothermally heated bubble tray column having a length of 68 cm and a diameter of 5 cm. At the lower end of the column; methanol in vapour form was passed in countercurrent to the stream flowing Le A 28 516 - 25 -20'~'~19~
down. A vigreux column having a length of 15 cm and a diameter of 3.5 cm was mounted as a separating unit on the top of the bubble tray column, above the metering unit. A 30 cm long separating part having a diameter of 3.5 cm, packed with 4 x ~ mm glass Raschig rings, was located at the lower end. The top stream was removed at the top of the Vigreux separating column, and tho bottom product stream was removed at the lower end of the stripping part. The following table shows some examples of the process accarding to the invention. The compositions were determined after constant conditions had been established.
Le A 28 516 - 26 -~~'~7196 w x a o ~
0 0 . . .
~ ~ O
U
>~
'L9 W
O w ~
~aw s~
N
N
O
.G
~-t O w-i .t~
'd'M U1 i-1O
r-r ~ U te ~ O
~-i U
W .7 r n rn O
h . o G
I
p U
N
ri O
u1 rnop N
N '-Ir-I ~
~
W
~ ~)O
It is known that ethylene glycol carbonate and propylene glycol carbonate (glycol carbonates) can be reacted with alcohols in the presence of catalysts to give dialkyl carbonates and ethylene glycol (EG) or propylene glycol.
Although these reactions can proceed with a high select-ivity, the processes have a number of disadvantages in their procedure. As a rule, the transesterification proceeds relatively slowly under normal pressure, so t'~at the use of elevated temperature, often above the bon ing point of the alcohol employed, is recommended, w~i4'~
results in the process being carried out in pres~u=
vessels (German published patent application 2 740 243 -EP 1082; and German publish°d patent application 2 740 X51 =
EP 1083).
In this process, the reaction usually proceeds only unti' equilibrium is established in the transesterification reaction. After removal from the pressure container, the reaction mixture must be removed from the catalyst very quickly, for example by flash distillation, so that the starting compounds are not reformed in a reversal of the formation reaction, for example when the alcohol of low boiling point distils off. During removal from the catalyst by distillation, the glycol carbonate still in equilibrium can decompose into carbon dioxide and into polyglycols and is therefore unavailable for further transesterification, the yield being reduced, and all the by-products mentioned interfere with the working up.
However, even if this removal of the catalyst is effected satisfactorily, further distillations must still be carried out. Thus, it is first necessary to separate high boiling components (glycols and glycol carbonates) from the low-boiling components (alcohols and dialkyl carbonates).
However, distillative purification of ethylene glycol, which must have a high purity for example for the preparation of polyesters, to remove incompletely reacted ethylene glycol carbonate, which in turn is preferably employed for the preparation of dialkyl carbonates, is not possible without restriction since both compounds form an azeotrope. A
similar difficulty is found when methanol, which is the preferred alcoholic component, has to be separated off from the dimethyl carbonate (DMC) formed. These compounds also form an azeotrope, which can be distilled into its separate components only in a cumbersome manner (EP 894 dated March 7, 1979 and literature cited therein).
SUMMARY OF THE INVENTION
In spite of diverse attempts at a solution, there was therefore an urgent need for the various difficulties mentioned to be effectively overcome. It has now been found, surprisingly, that the disadvantages mentioned in the transesterification of glycol carbonates with _ 2 _ 2~°~~1~6 alcohols to give dialkyl carbonates can be eliminated if the transesterificatian is carried out in a column with the starting substances in countercurrent to one another;
this process can be carried out under unexpectedly mild conditions.
The invention therefore relates to a process for the preparation of dialkyl carbonates of the formula (R~p)aCp (1) in which R1 denotes straight-chain or branched C1-C4-alkyl, by transesterification of ethylene carbonate or propylene carbonate with 3-80 mol, preferably 4-20 mol, particular-ly preferably 6-16 mol, of alcohols of the formula R~OH ( I ~ ) in which R1 has the above meaning, per mole of ethylene carbonate or propylene carbonate in the presence of catalysts, which is characterised in that the transesterification is carried out in a column equipped with packing or baffles at temperatur~a in the range of 60-160°C, preferably 60-150°C, particularly Le A 28 516 - 3 -preferably 55-1:i0°C, and the reactants are passed in countercurrent such that the ethylene carbonate or propylene carbonate are metered into the upper part of the column and the alcohol is metered into the lower part of the column and the catalyst is arranged as a fixed bed in the column or is also metered into the upper part of the calum: in solution or suspension, the dialkyl carbonate farmed, if appragriate as a mixture with alcohol, being removed at the top of the column and the ethylene glycol or propylene glycol formed from the ethylene carbonate or propylene carbonate being removed at the foot of the column, if appropriate together with the catalyst.
In spite of the mild conditions, complete transesterific atian of the glycol carbonate to the dialkyl carbonate is achieved in this process, so that first of all the distillation of the glycol carbonate azeatrape into its separate components .is dispensed with, since the glycol can already be removed at the foot of the column in a state free from glycol carbonate. The otherwise customary rapid separation of the reaction mixture from the catalyst is consequently superfluous, since the dialkyl carbonates are removed at the top of the column and are thus separated from the glycol and from the catalyst, and reversal of the reaction to give the starting substances is no longer possible. Moreover, in the case of a transesterification with methanol, which is preferably employed, as the alcohol, the column can be operated so that not only the expected azeatrope of methanol (about Le A 29 516 - 4 20'~~1~~
70 $) and dimethyl carbonate (about 30 $) but also a mixture which contains considerably more dimethyl carbonate than corresponds to the azeotrope is obtained at the tap of the column. In the case of methanol, it is therefore even possible to carry out the transesterifica-tian such that instead of pure methanol, mixtures of methanol and dimethyl carbonate, which may be obtained in other processes, are employed as the starting material in the transesterification according to the invention with glycol carbonate without a prior difficult separation.
This is also possible of course when alcohols other than methanol are used, As a result of being able to use mixtures of alcohols and dialkyl carbonates instead of the pure alcahols far the transesterification, the often difficult and energy--intensive separation of the mix-tures, a predominant number of which are azeotropes, is no longer necessary. The alcohol and the dialkyl carbonate in such mixtures have the s.3me alkyl radical, which means that undesirable, complicated reaction mixtures having different alkyl radicals are avoided.
The solution to the object described is distinguished by its simplicity and its straightforwardness.
In the si.zaplest case, the column to be employed is an isothermally heated tube filled with the customary packing to.be used for distillations, into the top of which the catalyst solution and the glycol carbonate are introduced. The alcohol to be used is sent from the bottom in vapour form in countercurrent to this mixture.
he A 28 516 - 5 -20~~196 The transesterification steps proceed surprisingly rapidly in the tube, so that considerable amounts of dialkyl carbonate pass over at the top even in a relatively short column of this simple design.
However, the column can also comprise, at the lower end, a stripping part which operates at a higher temperature and in which substantial to complete separation of the alcohol from the glycol trickling down, and recycling into the transesteri.fication region of the column takes place.
The column can furthermore have, in the upper part, a rectifying part which operates at a lower temperature, in order to bring the separation of gaseous alcohol and dialkyl carbonate from higher-boiling components, such as, for example, glycol and glycol carbonate, to comple-tion and in this way to remove a high-strength or pure mixture of alcohol and dialkyl carbonate at the column top.
Energy can be supplied via the alcohol introduced into the column in vapour form and/or via the bottom evaporat-or. The alcohol may also be metered in in liquid farm, in which case energy must be supplied via the bottom evaporator. Tn the first case, a widening of the column diameter in the middle part of the column, in whidh the majority of the transesterification proceeds, t~ four times that of the other parts may be of advantage. In the second case, the evaporation enthalpy for the alcohol he A 28 516 - 6 -must be transported through the stripping part and leads to a high loading with gas and liquid here. This results in a widening of the column in the stripping part in order to guarantee the separations envisaged in that part. The widening and length of the stripping part depend on the column baffles chosen in the stipping part, and these can be designed by the expert.
Since two molecules of alcohol are replaced by one molecule of dialkyl carbonate in the course of the transesterification in the gas phase, a reduction in cross-section by not more than a factor of 2 may be advantageous to keep the speed of the gas constant in the middle part of the column.
The column can thus either be heated isothermally or, preferably, be equipped with one or more temperature zones which differ from the main part, resulting in a temperature gradient with values which increase from the top downwards.
The packing or ordered fillings to be used are those which are customary per se for distillations, such as are described, for example, in Ullmann's Encyclopadie der Techn. Chemie (Ullmann's Encyclopaedia of Industrial Chemistry), 4th Edition, Volume 2, page 528 et seq. Examples which may be mentioned are: RaschigT"" or Pall ringsTM, Berl-, Intalex- or torus-saddlesT"", and interpacking bodies of various materials, such as glass, stoneware, porcelain, carbon, high-grade steel or plastic, which can be processed in a woven fabric- or mesh-like manner, especially if metal is used. Packing and ordered fillings which have a large surface area and good wetting i properties as well as an adequate residence time of the liquid are preferred. These are, for example, Pall- and Novolax-rings", Berl-saddles", BX-packingTM, Montz-PakT"", Mellapak~', MelladurTM, KerapakT'" and CY-packingsTM.
However, not only packed columns but also those having fixed baffles are suitable for the process according to the invention. Of these, those having bubble or valve trays with high residence times coupled with a good mass transfer are preferred.
However, other tray columns are'also generally suitable, for example those having perforated, bubble, valve, tunnel and centrifugal trays, which can in turn be present in various embodiments.
The column is operated such that a solution of the catalyst in the glycol carbonate employed, or also in the glycol on which this is based or also in the alcohol to be employed or also in another suitable inert solvent foreign to the system, is metered into the upper half, preferably into the upper third. In the case where a catalyst which is insoluble in the reactants is employed, this can also be employed as a mixture with the packing mentioned or as a heap poured onto the column trays _ g _ installed. The glycol carbonate is likewise introduced into the upper region, preferably into the upper third of the column; it preferably has a temperature the same as that prevailing at this point in the column. The alcohol, as a rule in vapour form, is. metered into the lower half of the column, preferably above any stripping zone present.
The dialkyl carbonate is removed at the top of the column, preferably after passing through a rectifying zone, and is condensed. Tn general, it still contains portions of the alcohol in the system. A glycol which is of high-percent strength if the conditions have been set carefully is discharged from the bottom of the column, and can be separated Pram the catalyst and impurities in Z5 a purifying distillation.
The molar ratio in the column varies from 3-30 mol.
preferably 4-20 mol, particularly preferably 6-16 mnl, of alcohol per mol of ethylene carbonate or propylene carbonate.
The temperature in the column is 60-160°C, preferably 60--150°C, particularly preferably 65-130°C. A temperature gradient which is to be applied in a preferred manner lies in the stated temperature range and rises from the top of the column to the bottom of the column.
As a rule, the reaction of the process according to the invention is carried out under normal pressure. However, Le A 28 516 - 9 -20"~'~~.96 it is also possible to carry out the reaction under a slightly increased pressure of up to about 3 bar, prefer-ably up to 2 bar, or under a reduced pressure of down to 50 mbar, preferably down to 100 mbar, particularly preferably down to 200 mbar. In a manner known to the expert, by deviating from normal pressure it may become possible to influence the azeotrope to be remaved, for example, at the top.
The space/time loading of the column is 0.1-3 g of the total amount of reaction participants per ml of effective column volume per hour, preferably 0.2-2.5 g/ml/hour, particularly preferably 0.3-2.0 g/ml/houx; the effective column volume here is that of the packing or the volume in which fixed baffles are located. Catalysts which are suitable for the process according to the invention are knawn in the literature.
Such catalysts are, for example, hydrides, oxides, hydroxides, alcoholates, amides or salts of alkali metals, such as lithium, sodium, potassium, rubidium and caesium, preferably of lithium, sodium and potassium, particularly preferably of sodium and potassium (US-3 642 858, US-3 803 201 and EP 1082). xn the case where the alcoholates are employed, according to the invention these can also be formed in situ by using the elemental alkali metals and the alcohol to be reacted according to the invention. Salts of the alkali metals can be those of organic or inorganic acids, such as of acetic acid, propionic acid, butyric acid, benzoic acid, Le A 28 516 - 10 ~'4'~'~196 stearic acid or carbonic acid (carbonates or bicarbon-ates), of hydrochloric acid, hydrobromic or hydriodic acid, nitra.c acid, sulphuric acid, hydrofluoric acid, phosphoric acid, hydrocyanic acid, thiocyanic acid, boric S acid, stannic acid, C1-C4-stannonic acids or antimony acids. Preferred possible compounds of the alkali metals are the oxides, hydroxides, alcoholates, acetates, propionates, benzoates, carbonates and bicarbonates, and hydroxides, alcoholates, acetates, benzoates or carbon aces are particularly preferably employed.
Such alkali metal compounds (farmed in situ, if appropri ate, from the free alkali metals) are employed in amounts of 0.001 to 2 $ by weight, preferably 0.005 to 0.9 $ by weight, particularly preferably 0.01 to 0.5 ~ by weight, based on the reaction mixture to be reacted.
It is possible, according to the invention, to add substances which, if appropriate, complex such alkali metal compounds (EP 274 953). Examples which may be mentioned are crown ethers, such as dibenzo-18-crown-6, polyethylene glycols or bicyclic nitrogen-containing cryptands.
Such complexing agents are employed in amounts of 0.1 to 200 mol ~, preferably 1 to 100 moi ~, based on the alkali metal compound.
Suitable catalysts for the process according to 'the invention are furthermore thallium-I and thallium-lII
Le A 28 516 - 11 compounds, such as the oxides, hydroxides, carbonates, acetates, bromides, chlorides, fluorides, formates, nitrates, cyanates, stearates, naphthenates, benzoates, cyclohexylphosphonates and hexahydrobenzoates, cyclo-pentadienylthallium, thallium methylate and thallium ethylate, preferably T1-(I) oxide, T1-(I) hydroxide, T1-(I) carbonate, T1-(T) acetate, T1-(TIT) acetate, T1-(I) fluoride, T1-(I) formats, T1-(I) nitrate, T1-(I) naphthenate and T1-(I) methylate (EP 1083). The amounts of thallium catalyst are not particularly critical. They are in general 0.0001-ZO ~ by weight, preferably 0.001-1 ~ by weight, based on the total reaction mixture.
Nitrogen-containing bases can furthermore be employed as 15~ catalysts in the process according to the invention (US-4 062 884). Examples which may be mentioned are secondary or tertiary amines, such as triethylamine, tributylamine, methyldibenzylamine, di.znethylcyclohexyl-amine and 'the like.
The amounts of nitrogen-containing bases employed accord-ing to the invention are from 0.01 to 10 'k by weight, preferably from 0.1 to 5 ~ by weight, particularly preferably from 0.1 to 1 ~ by weight, based on the total reaction mixture.
Heterogeneous catalyst systems can furthermore be employed in the process according to the invention (US 4 062 884r US 4 691 041, .TA 63/238 043 and Le A 28 516 - 12 -.
EP 298 167j. Such systems are, for example, ion exchanger resins with functional groups from tertiary amines, quaternary ammonium groups, examples of counter-ions which may be mentioned being hydroxide, chloride or hydrogen sulphate, sulphonic acid groups or carboxyl groups, for both of which hydrogen, alkali metals or alkaline earth metals may be mentioned as examples of counter-fans. These functional groups can be banded to the polymer either directly or via inert 1p chains. Alkali metal silicates or alkaline earth metal silicates, .impregnated on silicon dioxide supports, and ammonium exchanged zeolites may furthermore be mentioned.
According to the invention, these heterogeneous catalysts are preferably employed in stationary form, but it is also possible for them to be used, for example, as a fine powder in suspension. In the stationary form, the cata-lysts can be employed, far example, instead of the packing described or as a mixture with this.
Catalysts which can furthermore be employed according to the invention are compounds from the group comprising phasphines, stibines, arsines and divalent sulphur and selenium compounds as well as opium salts thereof (EP 180 387 and US ~ 734 518). The following may be mentioned as examples: tributylphasphine, ~triphenyl-phasphine, diphenylphosphine, 1,3-bis-(diphenylphos-phino)propane, triphenylarsine, trimethylarsi.ne, tri-butylarsine, 1,2-bis-(diphenylarsino)ethane, triphenyl-stibine, Biphenyl sulphide, Biphenyl disulphide, Biphenyl Le A 28 516 - 13 -selenide, tetraphenylphosphonium halide (C1, Br or I), tetraphenylarsonium halide (C1, Br or I), triphenyl-sulphonium halide (Cl or Br) and the like.
The amounts of this catalyst.group employed according to the invention are in the range .f.ram 0.1 to 10 ~ by weight, preferably from 0.1 to 5 ~ by weight, particu-larly preferably in the range from 0.1 to 2 ~ by weight, based on the total reaction mixture.
Complexes or salts of tin, titanium ar zirconium can 1U furthermore be employed according to the invention (US 4 661 609). Examples of such systems are butylstan-none acid, tin methoxide, dimethyltin, dibutyltin oxide, dibutyltin dilaurate, tributyltin hydride, tributyltin chloride, tin(II) ethylhexanoates, zirconium alkoxides (methyl, ethyl ar butyl), zirconium(IV) halides (F, C1, Br or I), zirconium nitrates, zirconium acetylacetonate, titanium alkoxides (methyl, ethyl ar isopropyl), titanium acetate, titanium acetylacetonate and the like.
The amounts which can be employed according to the invention are 0.1 to 10 ~ by weight, preferably 1 to 5 by weight, based on the total mixture.
Bifunctional catalysts of the formula ~~a~b)m' ~BcYa~n ( III ) can furthermore be employed in the process according to Le A 28 516 - 1,~
the invention. In these bifunctional catalysts, the molar ratio of the two components in square brackets is expressed by the indices m and n. These indices can assume, independently of one another, values of 0.001-1, preferably 0.01-1, particularly preferably 0.05-1 and especially preferably 0.1-1. Within the square brackets are neutral salts of in each case one ration and one anion. The indices a and b independently of one another represent integers from 1-5; the indices c and d inde-pendently of one another denote integers from 1-3, where the valency requirements of the rations and anions for the formation of such neutral salts are to be met.
Furthermore, in (ITI), A denotes the ration of a metal which belongs to the third period and group IIa, to the fourth period and group IIa, IVa-VIIIa, Ib or IIb, to the fifth period and group IIa, IVa-VIIa, IIb or IVb or to the sixth period and group IIa-VIa of the Periodic Table of the Elements in the short-period form.
The expert can see the metals suitable for ration A from the usual pxesentations of the Periodic Table of the Elements (Mendeleev) in the short--period form. A is Le A 28 516 ~ 15 -2 0'~'~ 19 ~
preferably the ration of one of the metals Mg, Ca, Sr, Ba, Zn, Cu, Mn, Co, Ni, Fe, Cr, Mo, W, Ti, Zr, Sn, Hf, ~7 or Ta, preferably the canon of one of the metals Mg, Ca, Zn, Co, Ni, Mn, Cu or Sn. In addition to the non-com-plexed canons of the metals mentioned, cationic oxo complexes of the metals mentioned are also possible, such as, fox oxam,ple, titanyl Ti0''~' and chromyl Cr02t".
The anion X belonging to the ration A is that of an inorganic or organic acid. Such an inorganic or organic :10 acid can be monobasic or dibasic or tribasic. Such acids and their anions are known to the expert. Examples of anions of monobasic inorganic or organic acids are:
fluoride, bromide, chloride, iodide, nitrate, the anion of an alkanecarboxylic acid having 1-lz C atoms and benzoate; examples of anions of dibasic inorganic or organic acids are: sulphate, oxalate, succinate, fumar-ate, maleate, phthalate and others; examples of tribasic inorganic or organic anions are: phosphate or citrate.
Preferred anions X in the catalyst of the formula (IIIj are: fluoride, chloride, bromide, iodide, sulphate, nitrate, phosphate, formate, acetate, propionate, oxal-ate, butyrate, citrate, succinate, famerete, maleate, benzoate, phthalate, decanoate, stearate, palmitate and laurate. Particularly preferred anions X are: chloride, bromide, iodide, acetate, laurate, stearate, palmit~te, decanoate, nitrate and sulphate.
A suitable ration B in the catalysts of the formula (IIIj is one from the group comprising alkali metal rations or Le A 28 516 - 16 --alkaline earth metal cations, quaternary ammonium, phosphonium, arsonium or stibonium canons and ternary sulphonium cations.
Alkali and alkaline earth metal cations which may be mentioned here are: the lithium, sodium, potassium, rubidium, caesium, magnesium, calcium, strontium and barium canon, praferably the alkali metal canons mentioned, particularly ,preferably the sodium and the potassium catian.
Suitable rations B are preferably those of the formulae:
R ~ ~1 ~ R3 R2 ~ ~ Rs Q (tv) s '~ cv) or Rs Ra Ra wherein Q1 represents N, P, As or Sb and R2, R3, R" and RS independently of one another are _ straight°chain or branched C1°CI8°alkyl or C7-Cla°
aralkyl, and one of the radicals R2°RS can also be Cs°Ciz°ar'Yl .
Le A 28 516 ° 17 B is particularly preferably a ration of the formula Rz R3 /~
Q (VI) ~5 ~ ~l wherein QZ represents D1 or 1', preferably N.
In the context of the formulae (TV) and (V1), the radi-call R~z, R~3, R~4 and RCS, which independently of one another denote straight--chain or branched C1-G1~-alkyl or C,-Ce-aralkyl, and one of the radicals R~ to >~ can also be phenyl., especially preferably replace the radicals Rz, R3, R" and RS respectively. Furthermore, the radicals R22 R~ , R~ and Ft~, which independently of one another denote Cl-CB-alkyl or benzyl, and one of the radicals R22 to R2s can also be phenyl, especially preferably replace~the radicals Rlz, R1', Rl" and R'S respectively.
Straight-chain or branched C1-Cle-alkyl is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, dodecyl, hexadecyl or octadecyl, Preferred aJ.kyl has 1-12 C atoans, and particularly preferred alkyl his 1-8 C atoms.
Le A 28 516 - 18 ~
C~-C12-Aralkyl is, for example, benzyl, phenylethyl, phenylpropyl, naphthylmethyl or naphthyl-ethyl; preferred aralkyl is benzyl or phenylethyl, and especially preferred aralkyl is benzyl.
C6-C12-Aryl is, for example, phenyl, naphthyl or biphenylyl, preferably phenyl.
The anion Y in the catalyst of the formula (III) is a halide ion, such as fluoride, chloride, bromide or iodide, preferably bromide or iodide, particularly preferably iodide. However, it can also have the meaning of other anions mentioned under X, if the anion X, in the specific case, is bromide or iodide.
The bifunctional catalyst of the formula (III) is em-ployed in an amount of 0.005-5 $ by weight, preferably 0.01-3 $ by weight, particularly preferably 0.01-1 $ by weight, based on the total transesterification mixture.
These amounts of catalyst in some cases differ from the amounts mentioned in the literature. It is particularly surprising that relatively high concentrations of the active catalysts based on alkali metal compounds can be employed in the process according to the invention without the evolutions of COZ, which reduce the yield and impede the reaction procedure, and the formation of polyols occurring, as is known, for example, from German published patent application 2 740 243, in the literature ~i~~d therein and from German published patent application 2 740 251.
2o~~l~s This is also a surprising feature of the process according to the invention.
Examples 1-7 A solution of the catalyst TCOH in ethylene glycol and the starting substance ethylene glycol carbonate were metered separately, about 10 cm below the upper and of the column, into an isothermally thermostatical:Ly controlled column packed with Raschig rings of glass and having a length of 250 cm and a diameter of 30 mm. Methanol in vapour farm, which was fed in as a vapour about 30 cm above the lower end of the column, was passed in counter-current to this stream. A mixture of methanol and dimethyl carbonate was removed at the top of the column, which operated without a rectifying part, and ethylene glycol, which, where appropriate, still contained minor amounts of ethylene glycol carbonate and alcohol, was removed at the lower end, which had no stripping part.
The following Table 1 shows some examples of the trans-esterificatian process according to the invention and the results thereof. These were determined after constant conditions and ratios had been established in the column.
Since neither a stripping nor a rectifying paxt were present, the bottom product still contained methanol and, where appropriate, small amounts of dimethyl carbonate, and the distillate still contained traces of ethylene glycol or ethylene glycol carbonate.
Le A 28 516 - 20 -~o~~~o~
Example 8 The process of Examples 1 to 7 was repeated, and instead of methanol, a stream of ethanol in vapour form was fed in about 30 cm above the lower end of the column. The result is shown in the following Table 2.
Le A 28 X16 - 21 -O s.Y1 N N n N n o c0 .~-s Q
N t!1 ~ M M -1 N .C
CL N OW ..C
UP cf' ~ ' V O d~ ~
lt? 1D N -1W d->
G
O i~
'rt d-, M N V1 n CO r.i .-1 4-~
+~ . . . . . .
O
U
O (.~ o .-~ a. ~ 0 LO o uP
W
M
v .~
O
Q
b N
N
W U'1 M e3' ~l' M [J1 N n W
CL
O
Q . . . . . .
O w w-I
O
(U
dP ~t1 ~!1 M (3~
W M M .la .A
W
ca a .~1 r., .-r ~i ~
b .N
~
.~
m .O .-1 Ch C~ p l~ G) N N
t0 W
.1.1 \ M i.t1 N 10 ap I~
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Le 2B516 - 23 -A
2077.~9~
Example 9 44 g of EGC and 0.06 g of KOH (dissolved in 3 g of EG) were introduced per hour onto the top of a column, having a diameter of 28 mm and a length of 120 cm, which was packed with a packing of wire mesh fabric (diameter 3 mm), temperature-controlled at 80°C and additionally equipped at the lower end with a 40 cm long stripping part heated to 100°C, and 120 g of hot MeOH vapour, at 100°C, were blown .i.nto the column from the bottom, directly above the stripping part.
When equilibrium had been established in the column, a mixture of 68.4 ~ of MeOH and 31.6 ~ of DMC was obtained at the top and a mixture which contained. 81.0 ~ of EG, 18.9 $ of MeOH and 0.1 ~ of EGC was discharged from 'the bottom.
Example 10 When 88 g of EGC, 240 g of MeOH and 0.12 g of KOH, dissolved in 6 g of EG, were metered per hour into the column from Example 9, a top product of 60.6 $ of MeOH
and 39.4 ~ of DMC and a bottom groduct of 71.5 ~ of EG, 21.8 ~ of MeOH and 5.8 ~ of EGC were obtained in the stationary state.
When the temperature in the stripping part was increasad by 10°, the content of EGC in the bottom product was reduced to 0.5 ~.
Le A 28 516 - 24 -These examples first of all show how surprisingly smoothly and rapidly the transesterification proceeds with more than 99 $ selectivity under mild conditions of 70-100° without applying pressure (in this context, compare Example 9 of EP 1082 or Example 6 and the comparison examples o:f EP 10$3 with the present examples).
'rhe transesterification can .furthermore be controlled so that the bottom product virtually no longer contains EGC, that is to say separation of the EG/EGC azeotrope is spared (see Examples 1, 6, 9, 11, 12 and 13), which was not possible according to the prior art.
Finally, a top product which contains more DMC than corresponds to the MeOH/DMC azeotrope can be obtained (Examples 1, 4, 5, 6 and 8), and instead of MeOH, the azeotrope of MeOH and DMC can be employed, considerable additional transesterification taking place (Example 6:
in addition to that metered ,in, about a further 1.6 mol of DMC are formed).
Examples 11-13 The educt ethylene carbonate and, separately, a solution of the catalyst KOH in ethylene glycol were metered into the upper end of a 10-tray, isothermally heated bubble tray column having a length of 68 cm and a diameter of 5 cm. At the lower end of the column; methanol in vapour form was passed in countercurrent to the stream flowing Le A 28 516 - 25 -20'~'~19~
down. A vigreux column having a length of 15 cm and a diameter of 3.5 cm was mounted as a separating unit on the top of the bubble tray column, above the metering unit. A 30 cm long separating part having a diameter of 3.5 cm, packed with 4 x ~ mm glass Raschig rings, was located at the lower end. The top stream was removed at the top of the Vigreux separating column, and tho bottom product stream was removed at the lower end of the stripping part. The following table shows some examples of the process accarding to the invention. The compositions were determined after constant conditions had been established.
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Claims (13)
1. A process for the preparation of a dialkyl carbonate of the Formula (R1O)2CO (I) in which R1 denotes straight-chain or branched C1-C4-alkyl, by transesterification of ethylene carbonate or propylene carbonate with 3-30 mole of an alcohol of the formula R1OH (II) in which R1 has the above meaning, per mol of ethylene carbonate or propylene carbonate in the presence of catalysts, wherein the transesterification is carried out in a column equipped with peeking or baffles at temperatures in the range of 60-160°C and the reactants, are passed in countercurrent such that the ethylene carbonate or propylene carbonate are metered into the upper part of the column and the alcohol is metered into the lower part of the column and the catalyst is arranged as a fixed bed in the column or is also metered into the upper part of the column in solution or suspension, the dialkyl carbonate formed, if appropriate as a mixture with alcohol, being removed at the top of the column and the ethylene glycol or propylene glycol formed from the ethylene carbonate or propylene carbonate being removed at the foot of the column, if appropriate together with the catalyst.
2. The process of claim 1, wherein 4-20 mols of the alcohol are employed per mol of ethylene carbonate or propylene carbonate.
3. The process of claim 2, wherein 6-16 mols of alcohol are employed per mol of ethylene carbonate or propylene carbonate.
4. The process of claim 1, 2 or 3, wherein the transesterification is carried out at 60-150°C.
5. The process of claim 4, wherein the transesterification is carried out at 65-130°C.
6. The process of any one of claims 1 to 5, wherein the alcohol is methanol.
7. The process of any one of claims 1 to 5, wherein the alcohol is ethanol.
8. The process of any one of claims 1 to 7, wherein the column has a space/time loading of 0.1-3 g/ml/hour, based on the total amount of reaction participants.
9. The process of claim 8, wherein the space/time loading is 0.2-2.5 g/ml/hour.
10. The process of claim 9, wherein the space/time loading is 0.3-2.0 g/ml/hour.
11. The process of any one of claims 1 to 10, wherein instead of the pure alcohol, an alcohol/dialkyl carbonate mixture in which the alcohol and the dialkyl carbonate have the same alkyl radical is employed as the alcohol.
12. The process of any one of claims 1 to 11, wherein the column has a temperature gradient with values in the stated range which increase from the top downwards.
13. The process of any one of claims 1 to 12, wherein the middle part of the column is widened to up to four times the diameter of the remaining part of the column.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4129316.9 | 1991-09-03 | ||
| DE4129316A DE4129316A1 (en) | 1991-09-03 | 1991-09-03 | METHOD FOR THE CONTINUOUS PRODUCTION OF DIALKYL CARBONATES |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2077196A1 CA2077196A1 (en) | 1993-03-04 |
| CA2077196C true CA2077196C (en) | 2004-04-27 |
Family
ID=6439785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002077196A Expired - Fee Related CA2077196C (en) | 1991-09-03 | 1992-08-31 | Process for the continuous preparation of dialkyl carbonates |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5231212A (en) |
| EP (1) | EP0530615B1 (en) |
| JP (1) | JPH05213830A (en) |
| KR (1) | KR100232029B1 (en) |
| CA (1) | CA2077196C (en) |
| DE (2) | DE4129316A1 (en) |
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|---|---|---|---|---|
| DE4216121A1 (en) * | 1992-05-15 | 1993-11-18 | Bayer Ag | Process for the continuous production of dialkyl carbonates |
| US5436362A (en) * | 1992-11-20 | 1995-07-25 | Chiyoda Corporation | Method of producing dialkylcarbonate |
| US5487392A (en) * | 1993-11-15 | 1996-01-30 | Haaga; John R. | Biopxy system with hemostatic insert |
| CN1049212C (en) * | 1994-06-24 | 2000-02-09 | 华东理工大学 | Improved synthetic method of dialkyl carbonate |
| US5498743A (en) * | 1994-10-20 | 1996-03-12 | Mobil Oil Corp. | Process for producing dialkylcarbonates |
| US5489703A (en) * | 1995-05-19 | 1996-02-06 | Amoco Corporation | Reaction extraction of alkyl carbonate |
| ES2174126T3 (en) * | 1995-12-22 | 2002-11-01 | Asahi Chemical Ind | METHOD FOR CONTINUOUS PRODUCTION OF DIALQUIL CARBONATE AND DIOLES. |
| DE19623508C2 (en) * | 1996-06-13 | 1998-08-20 | Henkel Kgaa | Process for the preparation of dialkyl carbonates |
| TW568898B (en) * | 1998-06-10 | 2004-01-01 | Asahi Chemical Ind | Method for continuously producing a dialkyl carbonate and a diol |
| US5902894A (en) | 1998-08-26 | 1999-05-11 | Catalytic Distillation Technologies | Process for making dialkyl carbonates |
| ES2291190T3 (en) | 1999-03-03 | 2008-03-01 | Asahi Kasei Chemicals Corporation | METHOD TO CONTINUOUSLY PRODUCE A DIALQUYL CARBONATE AND A DIOL. |
| US6365767B1 (en) | 1999-05-28 | 2002-04-02 | Exxonmobil Chemical Patents Inc. | Process for co-production of dialkyl carbonate and alkanediol |
| US6207850B1 (en) | 1999-11-03 | 2001-03-27 | Mobil Oil Corporation | Process for co-production of dialkyl carbonate and alkanediol |
| US6407279B1 (en) | 1999-11-19 | 2002-06-18 | Exxonmobil Chemical Patents Inc. | Integrated process for preparing dialkyl carbonates and diols |
| US6162940A (en) * | 1999-12-14 | 2000-12-19 | Mobil Oil Corporation | Process for co-production of dialkyl carbonate and alkanediol |
| US6342623B1 (en) | 2000-02-04 | 2002-01-29 | Exxonmobil Chemical Patents Inc. | Process for co-production of dialkyl carbonate and alkanediol |
| US6166240A (en) * | 2000-02-22 | 2000-12-26 | Mobil Oil Corporation | Process for co-production of dialkyl carbonate and alkanediol |
| DE10140846A1 (en) * | 2001-08-21 | 2003-03-06 | Cognis Deutschland Gmbh | Process for the preparation of dialkyl carbonates |
| US6620959B1 (en) | 2002-04-16 | 2003-09-16 | Exxonmobil Chemical Patents Inc. | Process for the production of unsymmetric and/or symmetric dialkyl carbonates and diols |
| CA2560101A1 (en) | 2004-06-17 | 2005-12-29 | Asahi Kasei Chemicals Corporation | Method for producing a dialkyl carbonate and a diol |
| BRPI0512550B1 (en) * | 2004-06-25 | 2015-09-08 | Asahi Kasei Chemicals Corp | process for the production of aromatic carbonate and aromatic carbonate |
| EA009715B1 (en) | 2004-07-13 | 2008-02-28 | Асахи Касеи Кемикалз Корпорейшн | Industrial process for producing aromatic carbonate |
| CN101006045B (en) | 2004-08-25 | 2010-12-01 | 旭化成化学株式会社 | Process for producing high-purity diphenyl carbonate on commercial scale |
| KR100898536B1 (en) | 2004-10-14 | 2009-05-20 | 아사히 가세이 케미칼즈 가부시키가이샤 | Process for production of high-purity diaryl carbonate |
| CN101268030B (en) | 2005-09-20 | 2011-05-11 | 旭化成化学株式会社 | Process for production of dialkyl carbonate and diol |
| WO2007060894A1 (en) | 2005-11-25 | 2007-05-31 | Asahi Kasei Chemicals Corporation | Process for industrial production of dialkyl carbonates and diols |
| BRPI0618799A2 (en) * | 2005-11-25 | 2016-08-30 | Asahi Kasei Chemicals Corp | process for industrially producing a dialkyl carbonate and a diol |
| WO2007069462A1 (en) * | 2005-12-12 | 2007-06-21 | Asahi Kasei Chemicals Corporation | Process for production of dialkyl carbonate and diol in industrial scale |
| TWI308911B (en) * | 2005-12-13 | 2009-04-21 | Asahi Kasei Chemcials Corp | Process for industrially producing dialkyl carbonate and diol |
| TW200732291A (en) * | 2005-12-14 | 2007-09-01 | Asahi Kasei Chemicals Corp | Process for production of dialkyl carbonate and diol in industrial scale and with high yield |
| BRPI0620082A2 (en) * | 2005-12-19 | 2016-11-16 | Asahi Kasei Chemicals Corp | process for the production of a high purity diphenyl carbonate on an industrial scale, and a high purity diphenyl carbonate |
| TWI314549B (en) | 2005-12-26 | 2009-09-11 | Asahi Kasei Chemicals Corp | Industrial process for separating out dialkyl carbonate |
| TW200738601A (en) * | 2005-12-27 | 2007-10-16 | Asahi Kasei Chemicals Corp | Industrial process for production of dialkyl carbonate and diol |
| TWI334410B (en) | 2006-01-10 | 2010-12-11 | Asahi Kasei Chemicals Corp | Industrial process for production of high-purity diol |
| TWI327998B (en) | 2006-01-26 | 2010-08-01 | Asahi Kasei Chemicals Corp | Industrial process for production of diol |
| TW200738602A (en) * | 2006-02-01 | 2007-10-16 | Asahi Kasei Chemicals Corp | Industrial process for producing high-purity diol |
| TWI382979B (en) * | 2006-02-22 | 2013-01-21 | Shell Int Research | Process for the production of alkylene carbonate and use of alkylene carbonate thus produced in the manufacture of an alkane diol and a dialkyl carbonate |
| TW200740731A (en) * | 2006-02-22 | 2007-11-01 | Shell Int Research | Process for the preparation of alkanediol |
| TW200740749A (en) * | 2006-02-22 | 2007-11-01 | Shell Int Research | Process for the preparation of an alkanediol and a dialkyl carbonate |
| TWI378087B (en) * | 2006-02-22 | 2012-12-01 | Shell Int Research | Process for the preparation of an alkanediol and a dialkyl carbonate |
| TWI383976B (en) | 2006-02-22 | 2013-02-01 | Shell Int Research | Process for the production of dialkyl carbonate and alkanediol |
| TWI387584B (en) * | 2006-03-13 | 2013-03-01 | Shell Int Research | Process for the production of alkylene carbonate and use of alkylene carbonate thus produced in the manufacture of an alkane diol and a dialkyl carbonate |
| TWI385144B (en) * | 2006-06-13 | 2013-02-11 | Shell Int Research | Glycol separation and purification |
| TWI430981B (en) * | 2006-12-04 | 2014-03-21 | Shell Int Research | Process for the preparation of alkylene glycol |
| RU2464267C2 (en) * | 2007-04-23 | 2012-10-20 | Шелл Интернэшнл Рисерч Маатсхаппий Б.В. | Method of producing 1,2-alkylene carbonate |
| US7851645B2 (en) * | 2008-02-11 | 2010-12-14 | Catalytic Distillation Technologies | Process for continuous production of organic carbonates or organic carbamates and solid catalysts therefore |
| US8110698B2 (en) * | 2008-02-11 | 2012-02-07 | Shell Oil Company | Process for producing diphenyl carbonate |
| TWI457317B (en) * | 2008-05-20 | 2014-10-21 | Shell Int Research | Process for the production of alkylene carbonate |
| DE102009053370A1 (en) | 2009-11-14 | 2011-05-19 | Bayer Materialscience Ag | Process for the purification of dialkyl carbonates |
| DE102010006657A1 (en) | 2010-02-03 | 2011-08-04 | Bayer MaterialScience AG, 51373 | Process for the preparation of dialkyl carbonates |
| US9249082B2 (en) * | 2010-02-09 | 2016-02-02 | King Abdulaziz City for Science and Technology (KACST) | Synthesis of dimethyl carbonate from carbon dioxide and methanol |
| DE102010042937A1 (en) | 2010-10-08 | 2012-04-12 | Bayer Materialscience Aktiengesellschaft | Process for the preparation of diaryl carbonates from dialkyl carbonates |
| DE102010042934A1 (en) | 2010-10-26 | 2012-04-26 | Bayer Materialscience Aktiengesellschaft | Process for the continuous production of dialkyl carbonate |
| DE102010042936A1 (en) | 2010-10-26 | 2012-04-26 | Bayer Materialscience Aktiengesellschaft | Process for the continuous production of dialkyl carbonate |
| EP2650278A1 (en) | 2012-04-11 | 2013-10-16 | Bayer MaterialScience AG | Method for manufacturing diaryl carbonates from dialkyl carbonates |
| JP2016501855A (en) | 2012-11-21 | 2016-01-21 | バイエル・マテリアルサイエンス・アクチェンゲゼルシャフトＢａｙｅｒ ＭａｔｅｒｉａｌＳｃｉｅｎｃｅ ＡＧ | Method for producing dialkyl carbonate |
| US9656943B2 (en) | 2015-10-20 | 2017-05-23 | Chang Chun Plastics Co. Ltd. | Process for producing dimethyl carbonate |
| US10131620B2 (en) | 2015-10-20 | 2018-11-20 | Chang Chun Plastics Co., Ltd. | Process for producing dimethyl carbonate |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3803201A (en) * | 1971-02-22 | 1974-04-09 | Dow Chemical Co | Synthesis of dimethyl carbonate |
| DE2737265A1 (en) * | 1977-08-18 | 1979-03-01 | Bayer Ag | PROCESS FOR SEPARATION OF DIMETHYLCARBONATE FROM ITS AZEOTROP WITH METHANOL |
| DE2740251A1 (en) * | 1977-09-07 | 1979-03-22 | Bayer Ag | PROCESS FOR THE PRODUCTION OF DIALKYLCARBONATES |
| DE2740243A1 (en) * | 1977-09-07 | 1979-03-15 | Bayer Ag | PROCESS FOR THE PRODUCTION OF DIALKYLCARBONATES |
| US4691041A (en) * | 1986-01-03 | 1987-09-01 | Texaco Inc. | Process for production of ethylene glycol and dimethyl carbonate |
-
1991
- 1991-09-03 DE DE4129316A patent/DE4129316A1/en not_active Withdrawn
-
1992
- 1992-08-21 EP EP92114286A patent/EP0530615B1/en not_active Expired - Lifetime
- 1992-08-21 DE DE59204056T patent/DE59204056D1/en not_active Expired - Lifetime
- 1992-08-26 US US07/936,182 patent/US5231212A/en not_active Expired - Lifetime
- 1992-08-27 JP JP4250427A patent/JPH05213830A/en active Pending
- 1992-08-31 CA CA002077196A patent/CA2077196C/en not_active Expired - Fee Related
- 1992-09-01 KR KR1019920015814A patent/KR100232029B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE4129316A1 (en) | 1993-03-04 |
| KR100232029B1 (en) | 1999-12-01 |
| KR930005962A (en) | 1993-04-20 |
| EP0530615A2 (en) | 1993-03-10 |
| US5231212A (en) | 1993-07-27 |
| DE59204056D1 (en) | 1995-11-23 |
| EP0530615B1 (en) | 1995-10-18 |
| CA2077196A1 (en) | 1993-03-04 |
| JPH05213830A (en) | 1993-08-24 |
| EP0530615A3 (en) | 1993-06-16 |
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