CA1305173C - Process for production of ethylene glycol and dimethyl carbonate - Google Patents

Abstract

PROCESS FOR PRODUCTION OF ETHYLENE
GLYCOL AND DIMETHYL CARBONATE
(D#80,532-F) ABSTRACT
A process is disclosed for the preparation of ethylene glycol and dimethyl carbonate by reacting methanol and ethylene carbonate in the presence of a series of heterogenous catalyst systems including ion exchange resins with tertiary amine, quaternary ammonium, sulfonic acid and carboxylic acid functional groups, alkali and alkaline earth silicates impregnated into silica and ammonium exchanged zeoIites.

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Description

~3~ 3 PROCESS FOR PRODUCTION OF ETHYLENE
GLYCOL AND DI~ETHYL CARBONATE
(D#80,532-F) This invention concerns an improved process for prepar-ing ethylene glycol and dimethyl carbonate by the transesterification reaction of ethylene carbonate and methanol in the presence of several classes of heterogenous catalysts, including macroreticular and gel type ion exchange resins with tertiary amine functional groups, ion exchange resins with ~uaternary ammonium functional groups, ion exchange resins with sulfonic acid groups, ion exchange resins with carboxylic acid functional groups, alkali and alkaline earth silicates on silica, and ammonium exchanged zeolites. The invention is particularly advantageous in that substantially fewer moles of methanol are needed in the methanol-ethylene carbonate feedstock per mole of dimethyl carbonate produced.

BACKGROUND O~ THE INVENTION
Generally the prior art reports that the transesterification of aliphatic hydroxy compounds with carbonic acid, aliphatic diesters and aromatic diester~ occurs readily in the presence of a basic catalyst and is a convenient method of synthesis of higher carbonates.
Several references deal with the transesterification of glycol carbonates using an aliphatic alcohol. Most demonstrate the use of methanol and ethylene carbonate.

~l~ ~

~3~5~3 There is taught in U. 5. Patent No. 3,803,201 a process for making dimethyl carbonate by methanolysis of alkylene carbonate wherein the improvement comprises removing the dimethyl carbonate from the reaction mixture during the reaction by distilling a mixture of methanol and dimethyl carbonate from the reaction mixture.
U. S. Patent No. 4,307,032 discloses a process for the preparation of a dialkylcarbonate by contacting a glycol carbonate of a 1,2-diol with 2 to 4 carbon atoms with a selected alcohol to form the corresponding carbonate of said alcohol at a temperature of between 50 and 250C, in the presence of an improved catalyst which is a thallium compound, so that the reaction can take place under milder conditions. Thallium is however expensive and very toxic.
In another process disclosed in U. S. Patent No. 4,181,676 there is taught a method for preparation of dialkyl carbonate by contacting a glycol carbonate of a 1,2-~iol having 2 to 4 carbon atoms with a selected group of alcohols at an elevat-ed temperature in the presence of an alkali metal or alkali metal compound wherein the improvement comprises employing less than 0.01 percent by weight of alkali metal or alkali metal compound based on the weight of the reaction mixture.
It is known that alkyl carbonates of the type ROCOOR
can be obtained from alcohols and cyclic carbonates corresponding to the above formula through a transesterification reaction in ~3~ 73 the presence of alkali alcoholates or hydrates; however, moderate amounts of inorganic compounds are produced by these reactions which must be removed by methods which may unfavorably affect the general economy of the process.
In U. S. Patent 4,062 9 884 this problem was addressed and it was found that dialkylcarbonates can be prepared by reacting alcohols with cyclic carbonates in the presence of organic bases, which makes it unnecessary to remove inorganic compounds and allows the catalyst to be totally recovered by means of simple distillation. The preferred organic base is a tertiary aliphatic amine.
U. S. Patent 4,349,486 teaches a monocarbonate transesterification process comprising contacting a beta-fluoroaliphatic carbonate, a compound selected from the class of monohydroxy aliphatic alcohols, monohydroxy phenols and ortho-positioned dihyroxy aromatic compounds in the presence of a base. This invention claims to greatly reduce undesirable side reactions and only small amounts of carbonic acid-aliphatic-aromatic mixed diester is associated with the isolated aromatic monocarbonate reaction.
The Gilpin and Emmons Patent, referred to above, dis cusses problems associated with the separation of the methanol, dimethyl carbonate azeotrope and teaches one solution, wherein dimethyl carbonate is isolated from the azeotrope by a ~3~5~

combination of low temperature crystallization and fractional distillation.
In the art there are also discussions of the transesterification reaction and the general acid-base catalysis of such systems~ For example, in J. Am. Chem. Soc. 96(a) 2924-9 (1974), Hine and Kluppel discuss enthalpies for the reactions of esters, such as trimethyl orthoformate, triethyl ortAoformate, tetramethyl orthocarbonate etc. with excess 65~
tetrahydrofuran-35% water in the presence of acid at 25 to give the corresponding simple esters and methanol or ethanol.
Enthalpies of formation are calculated. It is found that the marked stabilization that accompanies the attachment of several alkoxy groups to the same saturated carbon atom may be illustrated by the disproportionation of dimethyl ether to tetramethyl orthocarbonate and methane.
In another article in the J. Org. Chem. 49(b) 1122-1125 (1984) Cella and Bacon discuss the results of their work. Among other things, they found that the alkylation of alkali metal bicarbonate and carbonate salts with alkyl halides in dipolar aprotic solvents and phase-transfer catalysts produces alkyl carbonates in good yields. The major limitation of this method is the failure of activated aryl halides or electronegatively substituted alkyl halides to produce carbonates due to the facility with which the intermediate alkoxy carbonate salts decompose.

~3~ Y3 6~626-189 Disadvantages of the methods discussed above include in many cases the fact that it is necessary to use a large amoun~ of methanol feedstock relati.ve to the amount of dimethyl ~arbonate produced. Also, in many cases alkali metal halides are coproduced and these present disposal problems.
It would be a substantlal advance in the art to devise an efficient process for coproducing dimethyl carbonate and ethylene glycol which required only ca. 2~5 moles of methanol per mole of dimethyl carbonate produced. THe dimethyl carbonate produced by this novel process could be used as a gasoline extender.
SUMMARY OF_THE INVENTION
This invention concerns a process for the simultaneous production of ethylene glycol and dimethyl carbonate from ethylene carbonate and methanol which comprises reacting ethylene carbonate and methanol in the presence o~ several classes of heterogeneous catalyst inaluding lon exchange resins with quaternary ammoniu~ functional groups, ion exchange resins with sulfonic acid groupings, ion exchange resins with carboxyllc acid C

~3~5~1L73 functional groups, alkali and alkallne earth silicates on silica, and ammonium exchanged zeolites, at a temperature of fro~ 0C to 150C and an operative pressure of 0 to 5000 psig, until the desired products are formed.

- Sa -B

~3~ 73 A particular advantage of these systems over the prior art is that lower molar concentrations of methanol are required in the methanol-ethylene carbonate feed in order to produce an equilibrium concentration of ethylene carbonate.
Other advantages to using the heterogeneous catalysts of this invention include.
1) The high rates of the transesterification reaction achieved with these catalysts.

2) The ease with which the catalyst can be removed from the reaction products.

3) The lack of color bodies produced in the ester products.

4) The economic advantages of recycling the recovered solid catalyst for reuse in further transesterification.

5) The lack of corrosion of metal equipment.

DRAWINGS
Figure 1 is a schematic illustration of the preferred process of the invention using a block diagram layout.

DETAILED DESCRIPTION OF THE INVENTION
In the narrower and more preferred practice of this invention dimethylcarbonate and ethylene glycol are prepared ~3~5~

simultaneously by a transesterîfication process which comprises reacting ethylene carbonate and methanol in the presence of an ion exchange resin with tertiary amine functional groups, at a temperature of at least 50C and a pressure of at least 50 psig until the desired products are formed.
Starting materials employed in the process are an alcohol and an alkylene carbonate. Alcohols which work in the process of this invention include the monohydric alcohols con-taining one to 10 carbon atoms, including methanol, ethanol, isopropanol and isobutanol. Methanol is the preferred alcohol.
Alkalene carbonates which will work in the process of this invention include the carbonate derivatives of 1,2-diols containing two to 10 carbon atoms per molecule, including ethylene carbonate, 1,2-propylene carbonate and 1,2-butanediol carbonate. Ethylene carbonate is the preferred alkylene carbonate feedstock for this process. The preferred starting materials are represented in Figure 1. Recovery of the desired ethylene glycol and dimethyl carbonate can generally be carried out by distillation and crystallization.
More specifically, methanol and ethylene carbonate are fed into the transesterification reactor "A" in Figure 1 in streams adjusted to maintain a mole ratio of methanol to ethylene carbonate o~ between 1:2 and 1:5. The reactor is maintained at a temperature of from 0C to lSGC and a pressure of 0-5000 psig, and the methanol and ethylene carbonate are passed over a ~3~73 heterogeneous catalyst, producing as effluents methanol, dimethyl carbonate, ethylene glycol and ethylene carbonate. These efflu-ents are channeled to a distillation tower, designated "B", where the methanol and dimethyl carbonate are rem~ved as "overhead".
This "overhead" fraction is sent to a second distillation tower, designated "C", wherein the overhead is distilled at about 10 atm to recover pure dimethyl carbonate as a "bottoms" product and methanol as an "overhead" product. The methanol is recycled to the first reactor "A", and the dimethyl carbonate is sent to storage. The bottoms from Tower "B" are sent to a fourth tower, designed as "D", and distilled ak about 100 mm Hg wherein an overhead comprising an azeotrope of ethylene carbonate and ethylene glycol is produced and passed over a second catalyst bed, which catalyzes the addition of stoichiometric amounts of water to the ethylene carbonate in the azeotrope. This bed, designated as reactor "E" produces substantial quantities of ethylene glycol. The bottoms from "D", largely ethylene carbonate, are recycled to reactor "A".
This process is further described INFRA.
Figure I shows that in Tower "C", the methanol, dimethyl carbonate azeotrope, produced in the ester exchange reactor "A", is separated, and the dimethyl carbonate is isolated in essentially pure form.
The heterogeneous catalyst systems suitable for the practice of this invention generally comprise an insoluble acid ~3~73 ~86~6-189 or base. At least six classes of he~erogeneous catalysts have been found effective for the desired simultaneous production of e~hylene ylycol and dimethyl carbonate. They include:
l) The first class of catalysts for the practice of ~his invention is certaln ammonium exchanged zeolites.
Particularly effective are ammonlum exchanged Y-zeolites, such as the ammonium form of LZY-62, LZY-72 and LZY-82 marketed by Union Carbide.
2) A second class of suitable hekerogeneous catalysts is the ion exchange resins with strongly basic functional gxoups, such as the quaternary ammonlum and phosphonium functional group.
In such resins the quaternary ammonium ``- 13~

function is bonded to an organic polymer backbone, eithex direetly, or through one or more carbon atoms. The quaternary ammonium function may, for example, be the trimethylammonium hydroxide base, or the trimethylammonium chloride or trimethylammonium bromide groups bonded tG a polystyrene backbone, that may be cross-linked with divinylben~ene. Examples of suitable resins of this elass inelude the commercially available Amberlyst A-26 and A-27, Dowex 1 x 2-100 and Amberlite IRA-904, IRA-410 and IRA-400 ~OH) resins, as well as Amberlite IRA-458.

3) A third class of suitable eatalysts is the ion exehange resins with strongly acidic cation exchange. These inelude the gel type or maeroreticular ion exchange resins with sulfonic acid functional groups, wherein the sulfonic acid func-tion is bonded direetly or indireetly to an organie polymer baekbone. Examples of sueh resins inelude the Amberlyst~ 15 and XN-1010, Amberlite IR-118, Dowex 50 x 2-100 and 5 x 8-100, XL-383 and -386, plus Bio Rad AG50W-X2 and Ambersep 252H.

4) Also effeetive are weakly aeidie ion exehange resins that may, for example, eontain the earboxylie acid fune-tion. Here the polymer baekbone of the resin may contain acrylie acid, methaerylic acid and styrene polymer units, and the earboxylic acid groups may be present as the free acid, or as the ~3~5~ 68626-189 corresponding alkali or alkaline earth metal salt. 5uitable examples include Amberlite~ IRP-64, IRC-8~ and IRC-72~
5) A fifth type of suitable catalysts is a class of heterogeneous catalysts compris:ing alkali and alkaline earth silicates i~pregnated into silica. Suitable examples include the lithium, sodium, potassium and calcium æilicates impregnated in~o silica beads. A ~ypical preparation of such a catalyst is illustrated in Example A.
During the cosynthesis of ethylene glycol and dimethyl carbonate by the reaction of ethylene carbonate with methanol~ a large excess o~ methanol is normally employed in the prior art.
Usually the inltial molar ratio of methanol to ethylene carbonate is in the ran~e of 5 or greater, and preferably at least 10.

C

3L3~ 3 This preferred ratio range is illustrated b~ U. S. Pat-ent 3,803~201 11974). In the practice of this invention, by contrast, the initial molar ratio of methanol to ethylene carbonate is preferably 2 to 5. Such a range of molar ratios is illustrated by the accompanying examples.
Potential advantages to operating at this lower methanol-to ethylene carbonate molar ratio include the lower levels of methanol required to be recycled after the transesterification step in a process scheme such as described in Figure l.
Ethylene glycol-dimethyl carbonate synthesis using the classes of heterogeneous catalysts described SUPRA can be con-ducted at reaction temperatures in the range from 0 to 150C.
The preferred operating temperature range is 60-l20C.
The reaction can be conducted under atmospheric pressure. A pressure reactor is n vertheless required in the case of low-boiling point components if the reaction is to be carried out in the upper temperature range and in the liquid phase. The pressure is not critical. In general the reaction is allowed to proceed under the autogenous pressure of the reactants. However, the reaction can also be carried out under elevated pressure, for example, under an inert atmosphere. A
pressure of zero to 5000 psig is appropriate here. An operating pressure of greater than 50 psig is preferred.

~3~73 The residence time for the ethylene carbonate and methanol reactants in the transesterification reactor ("A" in Figure 1) may vary over a wide range according to the temperature of reaction, the molar ratios of carbonate/alcohol feedstocks, etc. Using the heterogeneous catalysts of this invention, the necessary residence time in the reactor may range ~rom 0.1 hours to 10 hours, although it may be extended beyond 1~ hours without danger of additional by-products being formeda The preferred residence time is in the range of 0.5 to ~ hours.
l`he desired products of this process according to the invention are ethylene glycol and dimethyl carbonate.
By-products include diethylene glycol and dimethyl ether.
Products have been identified in this work by gas chromatography ~gc), NMR, IR and GCIR or a combination of these techniques. Analyses have, for the most part, been by g.c.; all temperatures are in degrees centigrade and all pressures in pounds per square inch gauge.
The following examples illustrate the novel process of this invention. The examples are only For illustrating tha invention and are not considered to be limiting:

EXAMPLE I
This example illustrates the cosynthesis of ethylene glycol and dimethyl carbonate using, as the heterogeneous 5 ~73 catalyst, a weakly basic ion exchange resin containing tertiary amine functional groups.
The synthesis was conducted in a tubular reactor (0.625" ~ia.; 29" long), constructed of 316 stainless steel, operated upflow and mounted in a furnace, controllable to ~ 1.0C
and fitted with pumps allowing flow control of <~ 1 ml/min. The reactor was also fitted with a pressure regulating ~e~ice and equipment for monitoring temperature r pressure and flow rate.
The reactor was charged at the beginning of the experi-ment with 100 cc of a weakly basic, macroreticular, ion exchange resin with N,N-dimethylamine functional groups bonded to a polystyrene polymer (Rohm and Haas Amberlyst A-21). A screen and glass beads were placed at the top and bottom of the reactor to ensure the resin would remain in the middle portion.
The catalyst bed was first conditioned by washing with methanol (lO0 cc/hr., 100C) for 40 hours. A solution of methanol (1185g, 37.0 mole) plus ethylene carbonate (815g, 9.3 mole) was then pumped through the catalyst bed at 100 cclhr., while the reactor was held at 80C, at a total pressure of 100 psig. Samples of the product liquid were taken periodically and material after three hours running time typically showea the following composition:

~L3~5:~73 Dimethyl carbonate = 4.76%
Ethylene glycol = 1.86%
Methanol ~ 60.7%
Ethylene carbonate = 24.72 EXAMPLES II-X
A series of ethylene glycol-dimethyl carbonate syntheses were conducted using the reactor, procedures and weakly basic ion exchange resin of Example I. In these examples the operating temperature was raised to 100C; the liquid hourly space velocity (LHSV) and total operating pressure (psig) were varied independently. The results are shown in Table I. It may be noted that:
1~ In Examples II and III, operating at a space velocity of 0.7-1:15, at 100C and 100 psig, produces close to an equilibrium mixture of dimethyl carbonate and ethylene glycol. In these examples the concentration of dimethyl carbonate in the crude product liquid exceeds 19~, while the concentration of ethylene glycol coproduct reaches 11~6 .

2~ In Examples VIII-X (in comparison with Example II
etc.), total pressure appears to have little effect upon the product composition.

~3~ 173 TABLE I
Effect of Conditions on Carbonate Exchange Reactiona'b'C
_ Temp. Press~ ~ d,e % d,e ~ d,e % d,e Example lHSV C psig MeOH EG EC DMC
II 1.15 100 100 54.0 11.0 13.2 19.1 III 0.7 100 100 53.4 11.4 13.6 19.6 IV 1.7 100 100 57.1 8.0 17.9 15.1 V 2.0 100 100 58.7 6.8 18.6 14.1 VI 4.25 100 100 57.8 6.2 21.8 8.4 VII 2.2 100 60 61.6 7.8 13.0 15.0 VIII 1.0 100 500 54.0 11.3 13.2 19.2 IX 1.0 100 1000 53.6 11.2 13.4 19.3 X 1.0 100 2000 53.7 11.2 13.4 19~ 2 aFeed = 4.0 mole methanol per mole of ethylene carbonate bCatalyst = Rohm and Haas A21 resin conditioned for 40.0 hours prior to experiment.
CAll work done in an upflow mode; see Example I for detailed description of reactor and procedure.
dResults determined by G.C., given in area percent eMeOH = methanol; EG = ethylene glycol; EC = ethylene carbonate;
DMC = dimethyl carbonate - 16~

~3C~ 3 EXAMPLES XI
This example illustrates the cosynthesis of ethylene glycol and dimethyl carbonate where the heterogeneous catalyst i5 another weakly basic ion exchange resin containing the tertiary amine functional group.
Using the reactor and procedures of Example I, the catalyst bed is comprised of 100 cc of a weakly basic, gel type, ion exchange resin with N,N-dimethylamine functional groups bonded indirectly to an acrylic acid polymer (Rohm and Haas ~merlite~ IRA-68). After conditioning the catalyst bed by washing with methanol (100 cc/hr., 100C) for 40 hr., a solution of methanol (1185g, 37.00 mole) plus ethylene carbonate (815g, 9.3 mole) was pumped through the bed at 100 cc/hr., while the reactor was held at 50C (for 4 hr.), 80C (for 20 hr.) and 100C
(for 5 hr.). The total pressure in the reactor was maintained at 100 psig throughout this experiment. Samples of the product liquid were taken periodically at all three reaction temperatures, typical product compositions were as follows:
At 50C: Dimethyl carbonate = 0.2%
Ethylene glycol = 0.1%
Methanol = 59.4%
Ethylene carbonate = 39.4%
At 80C: Dimethyl carbonate = 16.5%
Ethylene glycol = 11.2%
Methanol = 47.2%
Ethylene carbonate = 23.9%

~3~S~73 At 100C: Dimethyl carbonate = 21.8%
Ethylene glycol = 15.5~
Methanol = 43.3%
Ethylene carbonate = 18.7%

It may be noted that in this example, operating the transesterification reaction at 100C, with the IRA-68 ion exchange xesin, the concentration of dimethyl carbonate in the crude product liquid is 21.8%, while the concentration of ethylene glycol coproduct is 15.5~.

EXAMPLE XII
This example illustrates the cosynthesis of ethylene glycol and dimethyl carbonate using another weakly basic ion exchange resin containing the tertiary amine functional group and a phenolic matrix structure.
Following the procedures of Example I, the catalyst bed, comprising 100 cc of Duolite~ S-761, is pretreated with methanol at 100C and then fed a standard solution of methanol (37.0 mole) plus ethylene carbonate (9.3 mole) at a pump rate of 100 cc~hr., while the reactor is held at 80C and 100 psig.
Samples of the liquid product were taken periodically, material after 3 hours running time typically showed the following compo-sition:

..
, ~5~l~3 Dimethyl carbonate = 6.0 Ethylene glycol = 5.6 Methanol = 71.4 Ethylene carbonate = 5.6%

EXAMPLES XI I I-XI.IX
In this series, representative examples of five addi-tional classes of heterogeneous catalysts were evaluated for the production of dimethyl carbonate and ethylene glycol. The reactor and procedures were as described in Example I. The results are shown in Tables II through V.
It may be noted that dimethyl carbonate - ethylene glycol cosynthesis from ethylene carbonate and methanol has been demonstrated with the following classes of catalysts.
1) Ion exchange resins with strongly basic functional groups, such as the quaternary ammonium functional group. This is illustrated in Table II by Exam-ples XIII through XXV for the Amberlyst A-26 and A-27, Dowex 1 x 2-100 and Amberlite IRA-904, IRA-410 and IRA-400(OH) resins over the temperature range 60-120C.

2) Ion exchange resins with strongly acidic cation exchange. This is illustrated in Table III for resins with the sulphonic acid functional groups 13~ 3 by Æxamples XXVI through XXXVIII for Amberlyst 15 and XN-1010, Amberlite IR-118, Dowex 50 x 2-100 and 5 x 8-100, XL-383 and -386, plus Bio Rad~
AG 50W-X2 and Ambersep 252H at temperatures to 140C.

3) Weakly acidic ion exchange resins containing, for example, the carboxylic acid function. This i5 illustrated in Table IV by Examples XXXIX through XLIII for Amberlite IRC-72, IRC-84 and IRP-64.

4) Alkali and alkaline earth silicates impregnated into silica. This class of catalyst is illustrated by Examp~e XLIV and through XLVI in Table V.

5) Ammonium exchanged zeolites. This class of catalyst is illustrated in Table V by Examples XLVII through XLIX.

.

~3~S~73 TABLE IIa EFF~r OF CA'rALYST STRUCToRE UPON THE ME'~HANOLr HYLENE CARBONATE ~XC~N OE RE~CTION -STRONGLY ~ASIC RESIN CATALYSTS
Temp. Product Composition (%)b Example Catalyst Supplier lC) LMSV MeOH EG EC DMC
XIII Amberlyst A-26 Rahm &60 1.1 53.25.9 32.2 8.4 Eaas XIV Amherlyst A-26 Rohn &90 1.1 47.611.4 24.7 16.0 Haas XV Amberlyst A-26 Rohm &110 1.1 44.115.1 19.4 21.1 Haas XVI Amberlyst ~-27 Rohm &100 1.0 52.93.4 30.7 4.3 Haas XVII DGwex 1 x 2-100 Dow 60 1.0 55.22.2 31.4 3.1 XVIII Dcwex 1 x 2-100 Dcw 80 1.0 51.94.1 36.6 5.4 XIX Dowex 1 x 2-100 Dow 100 1.0 48.59.1 27.8 12.8 XX Amberlite IR~-904 Rohm &100 1.0 57.10.5 40.7 0.7 Haas XXI Amberlite IRA-904 Rohm &120 1.0 51.95.2 34.4 7.1 Haas XXII Amberlite IRA-400(OH) Rohm & 60 1.052.1 5.533.0 7.7 Haas XXIII Amberlite IRA-400(0H) Ro~m & 80 1.044.4 1303 22.8 18.5 Haas xxrv A~berlite IR~-400(0~) Rohm & 100 1.041.7 16.7 23.7 23.7 Haas XXV Amberlite IRA-410 Rohm &100 1.0 46.910.6 26.3 14.6 Haas Cperating conditions as per Example I.
b~eOH, me~hanol EG, ethylene glycol; EC, ethylene carbonate, DMC, dimethyl carbonate, results determined byrG. C., given in weight percent.

'7;~

TABLE III
EFFECT OF CArrALYST STRUCTURE UPON I~E MEr~L~NOLr RT~YLENE CARBONATE EXCH~N OE REACTION
Sr~RONGLY ACIDIC RESIN CATALYSTS
rremp. Product Composition (%?b Example Catalyst Supplier ~C~ LHSV M~OH EG EC DMC
XXVI Amberlyst 15 Rohm &120 1.0 45.53.6 15.2 7.9 Haas XXVII ~mberlyst XN-1010 Rohm &100 1.0 53O47.0 23.7 8.9 Haas XXVIII Pmberlyst IR-118 Rohm &100 1.0 47.911.324.8 13.8 Haas XXIX Dowex 50 x 2-100 Dow 100 1.0 48.610.826.3 13.5 XXX Dowex 5 x 8-100 Dow 100 1.0 47.012.923.9 15.0 XXXI Dowex 5 x 8-100 Dow 120 1.0 43.121.715.3 16.4 XXXII Dowex 5 x 8-100 Dow 140 1.0 44.432.6 3.4 4.4 XXXIII X1r383 Rohm & 90 1.058.1 8.7 27.4 4.5 Haas XXXIV XL-386 Rohm &90 1.0 58.37.6 28.1 3.9 ~aas XXXV Bio Rad AG-50W~X2 Bio Rad 100 1.049.7 10.1 24.8 13.9 XXXVI k~bersep 252H Rohm &100 1.0 49.39.9 28.6 11.0 Haas XXXVII Ambersep 252H Rohm &120 1.3 46.017.320.4 13.6 Haas XXXVIII Ambersep 252H Rohm &140 1.0 44.631.2 3.1 5.5 Haas Operating conditions as per Example I.
Designation as per Table II.

~L3~5~7~3 rA~[E ~7a ~ECT OF CArrALYST Sr~UCTURE UPON rrHE MErHANOLr WE~KLY ACIDIC RESINS
Temp. Product Composition (~)b Example Cataly~st Supplier (~C~ LHSV MeOH h'G EC D~C
XXXIX ~mberlite IRP-64 Rohm & 100 1.0 58.30.1 40.6 0.1 Haas XL Amkerlite IRC-84 R~hm & 100 1.0 60.90.1 38.6 Haas XII Amberlite IR~-84 Rohm & 140 1.0 56.00O3 42.9 0.2 Haas XLII Amberlite IRC-72 Rohm & 100 1.0 51.98.6 26.7 12.3 ~as XIIII Amberlite IRC-72 Rohm & 120 1.0 46.313.4 21.0 18.7 Haas aOperating conditions as per EXample I.
bDesi~nation as per Table II.

~3~ 73 TABLE V
EYFECT OF CATALYST STRUCTURE UPON THE MEI~ OL, El~LENE CARBONATE EXCHANOE ~rION -TREAI~D SILIQ AMD ZEOLITE CAT~LYSTS
Temp. Product Cc~position ~)b EXample Catalyst ~C) LHSVMeOH EG EC DMC
XIIV NaSiO3 on Silica 80 1.0 43.512.3 28.214.7 XLV KHSi205 on Silica 125 1.0 54.5 3.336.9 4.5 XLVI LiSiO3 on Silica 125 1.0 55.1 1.7 31.92.7 XLVII Zeolite LZY-62, N~14 Form 100 1.0 44.4 3.747.9 2.1 XLVIII Zeolite LZY-72, NH4 Form 100 1.0 47.4 2.946.3 2.0 XLIX Zeolite LZY-82, NH4 Form 100 1.0 49.4 3.142.1 3.3 Operating conditions as per Example I.
bDesignation as per Table II.
CFor synthesis procedure; See Example A.
~repare by procedure similar to Example A.

~24-~3(~!5~3 EXAMPLE A
This example illustrates the preparation of the sodium silicate on silica catalyst employed in Table V, Example XLIV, for dimethyl carbonate-ethylene glycol cosynthesis.
Silica pellets (180g, 3.0 mole, 3/16" Dia., 3/16" high) were soaked with water glass (400 cc, 32% Conc. of sodium silicate) for 40 hours. The pellets were then filtered off, spread on a stainless steel tray where they had no contact with each othex, and calcined at Ca. 550C. for 24 hours. The resul-tant material was then sieved to a 20 mesh screen. The weight of the pellets was 123g.
Analyses of the pellets by atomic absorption showed a sodium content of 4.8~.

EXAMPLE L
A process description based on experimental data and literature data is shown in Figure I. Figure I describes the system using a block diagram layout. In this process, methanol and ethylene carbonate are fed into the transesterification reactor "A" at such a rate that the space velocity is 1.2. The various streams are adjusted such that the total reactor input is maintained at a mole ratio of 4/1 (methanol/ethylene carbonate = 4/1). The reactor is maintained at 100C and 100 p6ig. The catalyst is an ion exchange resin (Rohm and Haas Amberlyst A-21) used as the free base and kept in the ~3~S~73 reactor by use of appropriate porous plugs. The reactor efflu-ent, consisting of methanol (54.0%), dimethyl carbonate ~19.1~), ethylene glycol (11.0%) and ethylene carbonate (13.2%) is sent to distillation tower l'B" where the methanol and dimethyl carbonate are removed. The overhead consisting of methanol (72%) and dimethyl carbonate (28%) is sent to distillation tower "C" where the components are distilled at 10 atm. to recover pure dimethyl carbonate, as a bottoms product while methanol is taken overhead and is 95~ pure. This stream i5 recycled to reactor "A". The bottoms from tower "B" are sent to tower "D" where they are distilled at 110 mm Hg. The overhead consists of the azeotrope of ethylene carbonate and ethylene glycol. Vapor liquid equilibrium data indicates this material will be a about 5-6%
ethylene carbonate. This material is passed over another resin bed "E" (Amberlyst ~ A-21, same as above) after combining with 2 equivalents of water per mole of ethylene carbonate. This reactor "E" is also operated at a space velocity of 1.2 and maintained at 100C. The effluent is ethylene glycol (98.9%) having a small amount of water (1.1~) and is sent to purifica-tion. The residue bottoms from tower "D" is largely ethylene carbonate and is recycled to reactor "A", thereby completing the system.

Claims (10)

1. A process for producing ethylene glycol and dimethyl carbonate by reacting ethylene carbonate and methanol in the presence of a heterogeneous catalyst selected from the group consisting of ion exchange resins with quaternary ammonium functional groups, ion exchange resins with sulfonic acid functional groups, ion exchange resins with the carboxylic acid functional groups, alkali and alkaline earth silicates impregnated into silica, and ammonium exchanged zeolites, at a temperature of 0° to 150°C until the desired products are formed.

2. The process of Claim 1 wherein the initial molar ratio of methanol to ethylene carbonate is in the range of 2 to 5.

3. The process of Claim 1 wherein the operating pressure is between 0 and 5000 psig.

4. The process of Claim 1 for simultaneously produc-ing dimethyl carbonate and ethylene glycol further comprising:
feeding methanol and ethylene carbonate into a transesterification reactor in streams adjusted to maintain a mole ratio of methanol to ethylene carbonate of between 2:1 and

5:1, maintaining the reactor at a temperature of from 60° to 120°C and a pressure of at least 50 psig, passing said methanol and ethylene carbonate over an ion exchange resin in said reactor, producing as effluents methanol, dimethyl carbonate, ethylene glycol and ethylene carbonate, wherein said effluents are channeled to a distillation tower, removing the methanol and dimethyl carbonate as an overhead fraction, sending said overhead to a second distillation tower, while sending the bottoms to a third distillation tower, distilling said overhead in the second distillation tower at 10 atm to recover pure dimethyl carbonate as a bottoms product, removing methanol as an overhead product, recycling said "overhead" methanol to said first reactor, distilling said bottoms from the first tower at ca 100 mm Hg in the third tower, to produce an overhead comprising an azeotrope of ethylene carbonate and ethylene glycol and a residue which is recycled to the first reactor, and passing said overhead over a second resin bed with sufficient water to produce ethylene glycol.

5. The process of any one of claims 1 to 4, wherein the catalyst is an ion exchange resin with quaternary ammonium functional groups selected from the group consisting of the Amberlyst ? A-26 and A-27, Dowex 1 x 2-100 and Amberlite ? IRA-904, IRA-410 and IRA-400 (OH) resins.

6. The process of any one of claims 1 to 4, wherein the catalyst is an ion exchange resin with sulfonic acid functional groups selected from the group consisting of the Amberlyst ? 15 and XN-1010, Amberlite ? IR-118, Dowex ? 50 x 2-100 and 5 x 8-100, XL-383 and-386, plus Bio Rad ? AG50 W-X2 and Ambersep 252H
resins.

7. The process of any one of claims 1 to 4, wherein the catalyst is an ion exchange resin with carboxylic acid functional groups selected from the group consisting of Amberlite ? IRP-64, IRC-84 and IRC-72.

8. The process of any one of claims 1 to 4 wherein the catalyst is an alkali and alkaline earth silicate impregnated into silica selected from the group consisting of sodium silicate, potassium silicate and lithium silicate.

9. The process of any one of claims 1 to 4 wherein the catalyst is an ammonium exchanged Y-zeolite.

10. The process of any one of claims 1 to 4 wherein the catalyst is an ammonium exchanged zeolite selected from the group consisting of LZY-62, LZY-72 and LZY-82.