CA1241347A - Purification of ethylene glycol derived from ethylene carbonate - Google Patents
Purification of ethylene glycol derived from ethylene carbonateInfo
- Publication number
- CA1241347A CA1241347A CA000480995A CA480995A CA1241347A CA 1241347 A CA1241347 A CA 1241347A CA 000480995 A CA000480995 A CA 000480995A CA 480995 A CA480995 A CA 480995A CA 1241347 A CA1241347 A CA 1241347A
- Authority
- CA
- Canada
- Prior art keywords
- ethylene glycol
- ethylene
- ethylene carbonate
- boiling fraction
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
- C07C31/18—Polyhydroxylic acyclic alcohols
- C07C31/20—Dihydroxylic alcohols
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S203/00—Distillation: processes, separatory
- Y10S203/06—Reactor-distillation
Abstract
PURIFICATION OF ETHYLENE GLYCOL DERIVED FROM
ETHYLENE CARBONATE
INVENTOR
MITCHELL BECKER
HOWARD M. SACHS
ABSTRACT
Ethylene glycol is purified, particularly for fiber-grade applications, by removal of the residual ethylene carbonate from which the glycol was derived.
The effluent from a reactor in which ethylene carbonate is hydrolyzed to ethylene glycol is distilled to produce a lower-boiling fraction comprising ethylene glycol and water and a higher-boiling fraction comprising ethylene glycol, higher glycols, and concentrated in hydrolysis catalyst. The higher-boiling fraction is recirculated to reflux against the lower-boiling product, thereby reducing the ethylene carbonate content of the ethylene glycol to very low levels suitable for fiber-grade applications.
ETHYLENE CARBONATE
INVENTOR
MITCHELL BECKER
HOWARD M. SACHS
ABSTRACT
Ethylene glycol is purified, particularly for fiber-grade applications, by removal of the residual ethylene carbonate from which the glycol was derived.
The effluent from a reactor in which ethylene carbonate is hydrolyzed to ethylene glycol is distilled to produce a lower-boiling fraction comprising ethylene glycol and water and a higher-boiling fraction comprising ethylene glycol, higher glycols, and concentrated in hydrolysis catalyst. The higher-boiling fraction is recirculated to reflux against the lower-boiling product, thereby reducing the ethylene carbonate content of the ethylene glycol to very low levels suitable for fiber-grade applications.
Description
PURIFICATION OF ETHYLENE GLYCOL DERIVED FROM
ETHYLENE CARBONATE
This invention relates generally to the produc-tion of fiber-grade ethylene glycol. More specifically, it relates to the purification of ethylene glycol derived from ethylene carbonate.
The conventional process Eor hydrolysis of ethylene oxide to glycols employs a large excess of water and no catalyst.
In recent years preparation of ethylene glycol from ethylene carbonate has received attention since reduced utility costs and lower make of higher glycols are possible, compared with direct hydration of ethylene oxide. Ethylene carbonate may be made by the reaction of ethylene oxide with carbon dioxide in the presence of a number of potential catalysts, for example organic ammonium, phosphonium, sulfonium, and antimony halides, as disclosed in Canadian Application Serial No. 416,748 filed December 1, 1982. Ethylene carbonate so produced may be hydrolyzed by adding a suitable amount of water and using the same catalysts mentioned above, or others, such as potassium carbonate disclosed in U.S. 4,117,250 or alumina disclosed in Japanese published application 57-314542 published January 25, 1982.
A number of patents have described a one-step process by which ethylene oxide is hydrolyzed to ethylene glycol under carbon dioxide pressure and using a cata-lyst. U.S. 3,629,343 is an earlY disclosure of this type, but there have been many others, such as U.S.
4,160,116. It is suggested in the patents that ethylene carbonate is formed as an intermediate in the hydrolysis of ethylene oxide, but the data supplied reports only high yields of e-thylene glycol and the desired low yields of higher glycols. Presumably if it is an intermediate, SOMt`' ethylene carbonate could be present in the ethy:Lene glycol product.
;/~ 1267
ETHYLENE CARBONATE
This invention relates generally to the produc-tion of fiber-grade ethylene glycol. More specifically, it relates to the purification of ethylene glycol derived from ethylene carbonate.
The conventional process Eor hydrolysis of ethylene oxide to glycols employs a large excess of water and no catalyst.
In recent years preparation of ethylene glycol from ethylene carbonate has received attention since reduced utility costs and lower make of higher glycols are possible, compared with direct hydration of ethylene oxide. Ethylene carbonate may be made by the reaction of ethylene oxide with carbon dioxide in the presence of a number of potential catalysts, for example organic ammonium, phosphonium, sulfonium, and antimony halides, as disclosed in Canadian Application Serial No. 416,748 filed December 1, 1982. Ethylene carbonate so produced may be hydrolyzed by adding a suitable amount of water and using the same catalysts mentioned above, or others, such as potassium carbonate disclosed in U.S. 4,117,250 or alumina disclosed in Japanese published application 57-314542 published January 25, 1982.
A number of patents have described a one-step process by which ethylene oxide is hydrolyzed to ethylene glycol under carbon dioxide pressure and using a cata-lyst. U.S. 3,629,343 is an earlY disclosure of this type, but there have been many others, such as U.S.
4,160,116. It is suggested in the patents that ethylene carbonate is formed as an intermediate in the hydrolysis of ethylene oxide, but the data supplied reports only high yields of e-thylene glycol and the desired low yields of higher glycols. Presumably if it is an intermediate, SOMt`' ethylene carbonate could be present in the ethy:Lene glycol product.
;/~ 1267
-2-Two step processes are disclosed for example in U.S. 4,314,945 (carbonation) and U.S. 4,117,250 (hydrolysis), and U.S. 4,400,559 and U.S. Patent No. 4,508,927. Hydrolysis of ethylene carbonate also is disclosed in Japanese published application 56-139432 published October 30, 1981.
As shown in U.S. 4,117,250 preparation of fiber-grade ethylene glycol requires care to assure that critical product specifications are met. One concern would be the amount of ethylene carbonate in the ethvlene glycol. Although no specific limit is known to have been established, it is clear that the presence of ethylene carbonate, which can decompose to form ethylene oxide and carbon dioxide, should be avoided. It has been found that, despite the high percentage yields of ethylene glycol obtained, that the effluent from the hydrolysis reactor will contain a significant amount of unhydrolyzed ethylene carbonate. It is the purpose of the method to be disclosed to reduce the residual ethylene carbonate in the ethylene glycol to an amount suitable for fiber-grade production.
The atmospheric pressure boiling points of ethylene carbonate (238c) and ethylene glycol (197c) suggest that they could be separated by distillation.
However, it is known that an azeotrope exists which makes it difficult to make the separation. When high con-centrations of ethylene glycol relative to ethylene carbonate are present the azeotrope, having a lower boiling point, would tend to move overhead and be found in the bulk of the ethylene glycol taken as an overhead product. Consequently separation of small amounts of ethylene carbonate from ethylene glycol by distillation is quite difficult. It has been achieved in the method of the present invention.
Summary of the Invention It has been found that purification of ethylene glycol derived from ethylene carbonate requires special
As shown in U.S. 4,117,250 preparation of fiber-grade ethylene glycol requires care to assure that critical product specifications are met. One concern would be the amount of ethylene carbonate in the ethvlene glycol. Although no specific limit is known to have been established, it is clear that the presence of ethylene carbonate, which can decompose to form ethylene oxide and carbon dioxide, should be avoided. It has been found that, despite the high percentage yields of ethylene glycol obtained, that the effluent from the hydrolysis reactor will contain a significant amount of unhydrolyzed ethylene carbonate. It is the purpose of the method to be disclosed to reduce the residual ethylene carbonate in the ethylene glycol to an amount suitable for fiber-grade production.
The atmospheric pressure boiling points of ethylene carbonate (238c) and ethylene glycol (197c) suggest that they could be separated by distillation.
However, it is known that an azeotrope exists which makes it difficult to make the separation. When high con-centrations of ethylene glycol relative to ethylene carbonate are present the azeotrope, having a lower boiling point, would tend to move overhead and be found in the bulk of the ethylene glycol taken as an overhead product. Consequently separation of small amounts of ethylene carbonate from ethylene glycol by distillation is quite difficult. It has been achieved in the method of the present invention.
Summary of the Invention It has been found that purification of ethylene glycol derived from ethylene carbonate requires special
-3~
treatment to reduce the ethylene carbonate to the desired level. While the hydrolysis reactor effluen-t Jay contain up to about 5 wt. ethylene carbonate based on ethylene glycol, typically about 0.5 to 2 wt.%, it is desirable to remove this ethylene carbonate to the lowest possible level, generally below 0.05 wt.~ basecl on ethylene glycol, preferably below 0.03 wt.%.
According to the method of the invention this is done by completing the hydrolysis of ethylene carbonate to ethylene glycol. The hydrolysis reactor effluent comprising ethylene glycol, higher glycols, catalyst, and unreacted water and ethylene carbonate is distilled to produce a lower-boiling fraction comprising ethylene glycol and water and a higher-boiling traction comprising catalyst, ethylene glycol, and higher glycols. A portion of the higher-boiling fraction is recirculated to the distillation equipment as a reflux against vapors of the lower-boiling fraction to complete the hydrolysis of ethylene carbonate.
The invention therefore relates to a process for reducing the ethylene carbonate content of ethylene glycol produced by hydrolysis of ethylene carbonate in the presence of a catalyst comprising: (a) distilling in a vapor-liquid contacting means the effluent of said hydroly-sis comprising ethylene glycol, higher glycols, catalyst, and unreacted ethylene carbonate and withdrawing as a lower-boiling fraction a stream comprising substantially only ethylene glycol and water and as a higher-boiling fraction a liquid stream comprising substantially only hydrolysis cata-lyst, ethylene glycol, and higher glycol; (b) recirculating a sufficient amount of said higher-boiling fraction of (a) through said vapor-liquid contacting means as reflux against said lower-boiling fraction of (a) to reduce the ethylene carbonate content of said lower-boiling fraction to below about 0.05 wt. percent; (c) recirculating the remaillinCT
portion of said h:igher-boiling fraction -to said hydrolysis reaction.
- 3a -The concentration of the catalyst in the recirculating liquid is much higer than in the hydrolysis reactor and may be about 10 to 50 wt. percent of the liquid. In a preferred embodiment the hydrolysis reactor eEfluent is fed into the middle of a vapor-liquid contacting tower, where it joins the recirculating higher-boiling fraction. Alternatively, the reactor effluent is flashed and the liquid portion included in the recirculating liquid. In another embodiment, the lower-boiling fraction leaving the vapor-liquid contactor is condensed and a portion of the liquid obtained is returned to the contactor as supplementary reflux. Typically, the contactor will be operated at sub-atmospheric pressure, e.g. about 200 mm Hg absolute to one atmosphere as determined by the desired temperature, generally about 150-225C preferably about 170 to 210C.
treatment to reduce the ethylene carbonate to the desired level. While the hydrolysis reactor effluen-t Jay contain up to about 5 wt. ethylene carbonate based on ethylene glycol, typically about 0.5 to 2 wt.%, it is desirable to remove this ethylene carbonate to the lowest possible level, generally below 0.05 wt.~ basecl on ethylene glycol, preferably below 0.03 wt.%.
According to the method of the invention this is done by completing the hydrolysis of ethylene carbonate to ethylene glycol. The hydrolysis reactor effluent comprising ethylene glycol, higher glycols, catalyst, and unreacted water and ethylene carbonate is distilled to produce a lower-boiling fraction comprising ethylene glycol and water and a higher-boiling traction comprising catalyst, ethylene glycol, and higher glycols. A portion of the higher-boiling fraction is recirculated to the distillation equipment as a reflux against vapors of the lower-boiling fraction to complete the hydrolysis of ethylene carbonate.
The invention therefore relates to a process for reducing the ethylene carbonate content of ethylene glycol produced by hydrolysis of ethylene carbonate in the presence of a catalyst comprising: (a) distilling in a vapor-liquid contacting means the effluent of said hydroly-sis comprising ethylene glycol, higher glycols, catalyst, and unreacted ethylene carbonate and withdrawing as a lower-boiling fraction a stream comprising substantially only ethylene glycol and water and as a higher-boiling fraction a liquid stream comprising substantially only hydrolysis cata-lyst, ethylene glycol, and higher glycol; (b) recirculating a sufficient amount of said higher-boiling fraction of (a) through said vapor-liquid contacting means as reflux against said lower-boiling fraction of (a) to reduce the ethylene carbonate content of said lower-boiling fraction to below about 0.05 wt. percent; (c) recirculating the remaillinCT
portion of said h:igher-boiling fraction -to said hydrolysis reaction.
- 3a -The concentration of the catalyst in the recirculating liquid is much higer than in the hydrolysis reactor and may be about 10 to 50 wt. percent of the liquid. In a preferred embodiment the hydrolysis reactor eEfluent is fed into the middle of a vapor-liquid contacting tower, where it joins the recirculating higher-boiling fraction. Alternatively, the reactor effluent is flashed and the liquid portion included in the recirculating liquid. In another embodiment, the lower-boiling fraction leaving the vapor-liquid contactor is condensed and a portion of the liquid obtained is returned to the contactor as supplementary reflux. Typically, the contactor will be operated at sub-atmospheric pressure, e.g. about 200 mm Hg absolute to one atmosphere as determined by the desired temperature, generally about 150-225C preferably about 170 to 210C.
-4~
Brlef Descr on of the ~ra~ings The sole figure illustrates embodiments of the invention.
Descri~tlon of the Preferred Embodiments For descriptions of the hydrolysis of ethylene carbonate to ethylene glycol, reference may be made to patents and patent applications mentioned earlier. It is feasible to carry out the process of the invention on the effluent of a one-step process whereby ethylene oxide is hydrolyzed under carbon dioxide pressure in the presence of a catalyst. Preferably, ethylene carbonate will be prepared from ethylene oxide separately and then reacted with a small excess of water at above ambient tempera-tures and pressures in the presence of a suitable amount of a hydrolysis catalyst. Although theoretically a 1/1 ratio could be used, some additional water is usually recommended in the art. More specifically, about 1.1 to 3 mols of water will be employed for each mol of ethylene carbonateO The temperature may be from about 150 to 200C., preferably 170 to 185C., while the pressure may be from 7 to 12 bar, preferably 8 to 10 bar. Various catalysts may be used such as organic ammonium, phos-phonium, sulfonium, or antimony halides, but many others have been suggested in the art and these are not intended to be excluded from the process of the invention by their not having been specifically mentioned here. Organic phosphonium halides are preferred since they can be used for preparing both carbonate and glycol in the presence of water. The amount of the catalyst may be from 0.1 to
Brlef Descr on of the ~ra~ings The sole figure illustrates embodiments of the invention.
Descri~tlon of the Preferred Embodiments For descriptions of the hydrolysis of ethylene carbonate to ethylene glycol, reference may be made to patents and patent applications mentioned earlier. It is feasible to carry out the process of the invention on the effluent of a one-step process whereby ethylene oxide is hydrolyzed under carbon dioxide pressure in the presence of a catalyst. Preferably, ethylene carbonate will be prepared from ethylene oxide separately and then reacted with a small excess of water at above ambient tempera-tures and pressures in the presence of a suitable amount of a hydrolysis catalyst. Although theoretically a 1/1 ratio could be used, some additional water is usually recommended in the art. More specifically, about 1.1 to 3 mols of water will be employed for each mol of ethylene carbonateO The temperature may be from about 150 to 200C., preferably 170 to 185C., while the pressure may be from 7 to 12 bar, preferably 8 to 10 bar. Various catalysts may be used such as organic ammonium, phos-phonium, sulfonium, or antimony halides, but many others have been suggested in the art and these are not intended to be excluded from the process of the invention by their not having been specifically mentioned here. Organic phosphonium halides are preferred since they can be used for preparing both carbonate and glycol in the presence of water. The amount of the catalyst may be from 0.1 to
5 wt. based on the reactants, preferably 0.5 to 3~, but it will be understood by those skilled in the art that the amount of catalyst used will be aEfected by the type of compound selected. The reaction will be carrlecl out in a suitable vessel, such as the plug-flow or con-tinuou~ly mixed reactors suggested by the art, oralternatively other types such as compartmented, staged reactors. The size of the vessel will be determined by various Eactors, such as the holdup-time, disengagement o the carbon dioxide produced, type ox mixing employed and the like.
After the reaction has been carried out the product mixture will be withdrawn and refined to produce purified ethylene glycol, by removing water, catalyst, unreac~ed ethylene carbonate and higher glycols. How-ever the ethylene carbonate is particularly difficult to remove since it forms a low-boiling azeotrope with ethylene glycol. Various methods might be considered for merely removing unreacted ethylene carbonate, such as decomposing ethylene carbonate to ethylene oxide or providing additional residence time in the hydrolyzer.
These methods are considered less attractive than the process of the invention. Completely hydrolyzing the ethylene carbonate has the advantage of producing addi-tional ethylene glycol and the present method was found to effect the substantially complete removal of ethylene carbonate.
Sufficient separation of ethylene glycol from the higher glycols and the catalyst can be made by merely heating and flashing at a lower pressure the hydrolysis reactor effluent, as will be seen. However, with such simple processing, the ethylene carbonate content of the product ethylene glycol may be as high as 1%, while less than 0.05~ is desired. It has been found that by using higher temperatures than are needed to separate ethylene glycol and by contacting the product ethylene glycol in the vapor phase with a high concentration of catalyst that the ethylene carbonate content may be substantially reduced, as will be seen in the following examples.
SIMPLE PLASH
The e~1uent of a hydrolysis reactor containinq 70 wt. % ethylene glycol, 3 wt. ethy}ene carbonate, J
3~7 0.7 wt,. % catalyst (methyl triphenyl phosphon$um iodide), ~4 we. watery and 2 wt. higher glycol3 was fed to a ample flash at temperature of 170~C. and 250 mm Hg.
The h was tarried out irk a 200 ml vessel supplied 5 with 290 gm/hr of liquid effluent. The vapor produced contained 74 wt. ethylene glyco}s, 0.3 wt. S ethylene ~arbonate~ end 25 we water. The liquid ~:ontalned 61 wt. g ethylene glycol, û.04 wt. % ethylene carbonate? 20 wt. S higher glyco7~ and 19 wt. % catalyst end could be 10 recycled to the hydrolysis reactor or reuse after purging any ret ma)ce of h$gher qlycols. The level of ethylene carbonate is considered undesirably high for polymer product ion .
EXAMPI.E 2 11$ EC I RCU LAT IOII O r C A~L~'S'r SOI.UTI ON
An Old~rshaw* column containing twenty 3~ diam-ever eve l:rays way installed aboYe the flash chamber used in Example 1. Instead of returning the flashed catalystcontaining liquid to 'che hydrolysis rector, the 20 liquid was introduced to the upper tray and permitted to flow downward in counter~urr~nt contact with the vapor produced by the slash of the feed l iquid . When the recirculation was 3~3 parts for each part of feed. The ethylene carbonate in the product ethylene glycol was 25 found to be 0.08 wt~ S. and when the recirculation was in~rea~ed to 8.2 parts for each part of feed the ethylene carbonate content wa 0.14 wt. I. In this mode of opera-tion, recirculation reduced the ethylene carbonate in the product, although an optimum recirculation rate appeared to exist.
I= .
Using the equipment of Example 2 the location of the feed is changed to enter it the midpoint of the fractionating tray, that i , at tray 10 of 20, instead of at the flash chamber below the trays. Under the * Trademark _7~ l d conditions of Examples 1 and 2 the recirculation rate to tray 20 is varied and the ethylene carbonate in the ethylene glycol is measured, with the following results.
TABLE I
FlashRecirc. Ethylene Temp.Ratio Carbonate (EC) (C.)(wt.ptu) in Product (wt.~) 1702.9 0.09 1707.3 o~oa 190 0 1.0 1902.~ 0.06 1904.5 < 0O03 1907.4 < 0.03 Comparing the results at 1709C. with Exampl2 2 it will be seen that high recirculation rates did not increase the ethylene carbonate content of the ethylene glycol~ when the feud entered at the tenth tray instead of below in the flash chamber.
Further improvement was obtained by increasing the flash temperature to 190C. so that with sufficient recirculation the ethylene carbonate content of the ethylene glycol was reduced below 300 ppm, whereupon it was no longer detectible.
The sole figure illustrates practical embodi ments of the process of the invention. Feed from the hydrolysis reactor (not shown) containing 70 wt.
ethylene glycol, 3 wt. ethylene carbonate, 2~ wt.
water, and 2 wt. higher glycols, and 0.7 wt. catalyst at a temperature of 170C. and sufficient pressure to maintain it in the liquid phase is heated to 190C. (10) (optional) and flashed to a pressure of 680 mmHg as it .'..'J~
enters a 20 tray distillation column (12) at tray 10.
Ethylene carbonate, catalyst, and some ethylene glycol move downward in the column as they join the recirculat-ing liquid passing down from the trays above. The liquid at the bottom of the column contains 61 wt. ethylene glycol, 0.04 wt. % ethylene carbonate, 20 wt. % higher glycols, and 19 wt. catalyst. A reboiler (13) provides vapor to contact the liquid passing down over the trays.
A l portion of this liquid is withdrawn for return to the hydrolysis reactor. The remainder, 4.5 parts or each part of hydrolysis reactor effluent, is cooled (15) recirculated via line 14 to tray 10 to contact the ethylene glycol and water vapors rising through the column and complete the hydrolysis of ethylene carbonate.
The vapor withdrawn overhead via line 16 is cooled (18) subsequently further distilled (not shown) to produce fiber-grade ethylene glycol contains 0.02 we. ethylene carbonate, 73 wt. % ethylene glycol, 25 wt. water, and 2 wt. % higher glycols, In an alternative operation, a portion of the overhead vapor is condensed and returned (20) to the column as a reflux. In still another operation, the feed to the column is flashed and the vapor fed to the column while the liquid is fed to the tower bottoms.
The distillation column will be operated at temperatures in excess of about 150C, preferably at or above the temperature of the hydrolysis reactor, generally about 150- - 225C particularly about 170 to 2tOC. The operating pressure will be adjusted to suit the desired temperature and thus would usually be sub-atmospheric, probably in the range of about 200 mm Hg absolute to one atmosphere.
After the reaction has been carried out the product mixture will be withdrawn and refined to produce purified ethylene glycol, by removing water, catalyst, unreac~ed ethylene carbonate and higher glycols. How-ever the ethylene carbonate is particularly difficult to remove since it forms a low-boiling azeotrope with ethylene glycol. Various methods might be considered for merely removing unreacted ethylene carbonate, such as decomposing ethylene carbonate to ethylene oxide or providing additional residence time in the hydrolyzer.
These methods are considered less attractive than the process of the invention. Completely hydrolyzing the ethylene carbonate has the advantage of producing addi-tional ethylene glycol and the present method was found to effect the substantially complete removal of ethylene carbonate.
Sufficient separation of ethylene glycol from the higher glycols and the catalyst can be made by merely heating and flashing at a lower pressure the hydrolysis reactor effluent, as will be seen. However, with such simple processing, the ethylene carbonate content of the product ethylene glycol may be as high as 1%, while less than 0.05~ is desired. It has been found that by using higher temperatures than are needed to separate ethylene glycol and by contacting the product ethylene glycol in the vapor phase with a high concentration of catalyst that the ethylene carbonate content may be substantially reduced, as will be seen in the following examples.
SIMPLE PLASH
The e~1uent of a hydrolysis reactor containinq 70 wt. % ethylene glycol, 3 wt. ethy}ene carbonate, J
3~7 0.7 wt,. % catalyst (methyl triphenyl phosphon$um iodide), ~4 we. watery and 2 wt. higher glycol3 was fed to a ample flash at temperature of 170~C. and 250 mm Hg.
The h was tarried out irk a 200 ml vessel supplied 5 with 290 gm/hr of liquid effluent. The vapor produced contained 74 wt. ethylene glyco}s, 0.3 wt. S ethylene ~arbonate~ end 25 we water. The liquid ~:ontalned 61 wt. g ethylene glycol, û.04 wt. % ethylene carbonate? 20 wt. S higher glyco7~ and 19 wt. % catalyst end could be 10 recycled to the hydrolysis reactor or reuse after purging any ret ma)ce of h$gher qlycols. The level of ethylene carbonate is considered undesirably high for polymer product ion .
EXAMPI.E 2 11$ EC I RCU LAT IOII O r C A~L~'S'r SOI.UTI ON
An Old~rshaw* column containing twenty 3~ diam-ever eve l:rays way installed aboYe the flash chamber used in Example 1. Instead of returning the flashed catalystcontaining liquid to 'che hydrolysis rector, the 20 liquid was introduced to the upper tray and permitted to flow downward in counter~urr~nt contact with the vapor produced by the slash of the feed l iquid . When the recirculation was 3~3 parts for each part of feed. The ethylene carbonate in the product ethylene glycol was 25 found to be 0.08 wt~ S. and when the recirculation was in~rea~ed to 8.2 parts for each part of feed the ethylene carbonate content wa 0.14 wt. I. In this mode of opera-tion, recirculation reduced the ethylene carbonate in the product, although an optimum recirculation rate appeared to exist.
I= .
Using the equipment of Example 2 the location of the feed is changed to enter it the midpoint of the fractionating tray, that i , at tray 10 of 20, instead of at the flash chamber below the trays. Under the * Trademark _7~ l d conditions of Examples 1 and 2 the recirculation rate to tray 20 is varied and the ethylene carbonate in the ethylene glycol is measured, with the following results.
TABLE I
FlashRecirc. Ethylene Temp.Ratio Carbonate (EC) (C.)(wt.ptu) in Product (wt.~) 1702.9 0.09 1707.3 o~oa 190 0 1.0 1902.~ 0.06 1904.5 < 0O03 1907.4 < 0.03 Comparing the results at 1709C. with Exampl2 2 it will be seen that high recirculation rates did not increase the ethylene carbonate content of the ethylene glycol~ when the feud entered at the tenth tray instead of below in the flash chamber.
Further improvement was obtained by increasing the flash temperature to 190C. so that with sufficient recirculation the ethylene carbonate content of the ethylene glycol was reduced below 300 ppm, whereupon it was no longer detectible.
The sole figure illustrates practical embodi ments of the process of the invention. Feed from the hydrolysis reactor (not shown) containing 70 wt.
ethylene glycol, 3 wt. ethylene carbonate, 2~ wt.
water, and 2 wt. higher glycols, and 0.7 wt. catalyst at a temperature of 170C. and sufficient pressure to maintain it in the liquid phase is heated to 190C. (10) (optional) and flashed to a pressure of 680 mmHg as it .'..'J~
enters a 20 tray distillation column (12) at tray 10.
Ethylene carbonate, catalyst, and some ethylene glycol move downward in the column as they join the recirculat-ing liquid passing down from the trays above. The liquid at the bottom of the column contains 61 wt. ethylene glycol, 0.04 wt. % ethylene carbonate, 20 wt. % higher glycols, and 19 wt. catalyst. A reboiler (13) provides vapor to contact the liquid passing down over the trays.
A l portion of this liquid is withdrawn for return to the hydrolysis reactor. The remainder, 4.5 parts or each part of hydrolysis reactor effluent, is cooled (15) recirculated via line 14 to tray 10 to contact the ethylene glycol and water vapors rising through the column and complete the hydrolysis of ethylene carbonate.
The vapor withdrawn overhead via line 16 is cooled (18) subsequently further distilled (not shown) to produce fiber-grade ethylene glycol contains 0.02 we. ethylene carbonate, 73 wt. % ethylene glycol, 25 wt. water, and 2 wt. % higher glycols, In an alternative operation, a portion of the overhead vapor is condensed and returned (20) to the column as a reflux. In still another operation, the feed to the column is flashed and the vapor fed to the column while the liquid is fed to the tower bottoms.
The distillation column will be operated at temperatures in excess of about 150C, preferably at or above the temperature of the hydrolysis reactor, generally about 150- - 225C particularly about 170 to 2tOC. The operating pressure will be adjusted to suit the desired temperature and thus would usually be sub-atmospheric, probably in the range of about 200 mm Hg absolute to one atmosphere.
Claims (5)
1. A process for reducing the ethylene car-bonate content of ethylene glycol produced by hydrolysis of ethylene carbonate in the presence of a catalyst comprising:
(a) distilling in a vapor-liquid contacting means the effluent of said hydrolysis comprising ethylene glycol, higher glycols, catalyst, and unreacted ethylene carbonate and withdrawing as a lower-boiling fraction a stream comprising substantially only ethylene glycol and water and as a higher-boiling fraction a liquid stream comprising substantially only hydrolysis catalyst, ethylene glycol, and higher glycols;
(b) recirculating a sufficient amount of said higher-boiling fraction of (a) through said vapor-liquid contacting means as reflux against said lower-boiling fraction of (a) to reduce the ethylene carbonate content of said lower-boiling fraction to below about 0.05 wt.
percent;
(c) recirculating the remaining portion of said higher-boiling fraction to said hydrolysis reaction.
(a) distilling in a vapor-liquid contacting means the effluent of said hydrolysis comprising ethylene glycol, higher glycols, catalyst, and unreacted ethylene carbonate and withdrawing as a lower-boiling fraction a stream comprising substantially only ethylene glycol and water and as a higher-boiling fraction a liquid stream comprising substantially only hydrolysis catalyst, ethylene glycol, and higher glycols;
(b) recirculating a sufficient amount of said higher-boiling fraction of (a) through said vapor-liquid contacting means as reflux against said lower-boiling fraction of (a) to reduce the ethylene carbonate content of said lower-boiling fraction to below about 0.05 wt.
percent;
(c) recirculating the remaining portion of said higher-boiling fraction to said hydrolysis reaction.
2. The process of claim 1 wherein the amount of hydrolysis catalyst in said recirculating liquid fraction is about 10 to 50 percent.
3. The process of claim 1 wherein said lower-boiling fraction of (a) is condensed and a portion of the condensate is returned to said vapor-liquid contacting means as supplemental reflux.
4. The process of claim 1 wherein said hydro-lysis efflent is flashed into liquid and vapor portions and the vapor portion fed to the vapor-liquid contacting means and the liquid portion fed into the higher-boiling product.
5. The process of claim 1 wherein said effluent is flashed at a temperature of from 150° to 225°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/608,639 US4519875A (en) | 1984-05-09 | 1984-05-09 | Purification of ethylene glycol derived from ethylene carbonate |
| US608,639 | 1984-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1241347A true CA1241347A (en) | 1988-08-30 |
Family
ID=24437362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000480995A Expired CA1241347A (en) | 1984-05-09 | 1985-05-08 | Purification of ethylene glycol derived from ethylene carbonate |
Country Status (16)
| Country | Link |
|---|---|
| US (1) | US4519875A (en) |
| EP (1) | EP0161111B1 (en) |
| JP (1) | JPS60239429A (en) |
| KR (1) | KR920003774B1 (en) |
| AU (1) | AU570108B2 (en) |
| BG (1) | BG51039A3 (en) |
| BR (1) | BR8502190A (en) |
| CA (1) | CA1241347A (en) |
| DD (1) | DD232483A5 (en) |
| DE (1) | DE3574369D1 (en) |
| ES (1) | ES8607895A1 (en) |
| IN (1) | IN163264B (en) |
| RO (1) | RO91716A (en) |
| SU (1) | SU1604153A3 (en) |
| YU (1) | YU45715B (en) |
| ZA (1) | ZA853523B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4691041A (en) * | 1986-01-03 | 1987-09-01 | Texaco Inc. | Process for production of ethylene glycol and dimethyl carbonate |
| US4830712A (en) * | 1987-09-29 | 1989-05-16 | Union Carbide Corporation | Process for refining ethylene glycol |
| US5080871A (en) * | 1989-03-10 | 1992-01-14 | Chemical Research & Licensing Company | Apparatus for alkylation of organic aromatic compounds |
| US5019669A (en) * | 1989-03-10 | 1991-05-28 | Chemical Research & Licensing Company | Alkylation of organic aromatic compounds |
| US5118872A (en) * | 1989-03-10 | 1992-06-02 | Chemical Research & Licensing Company | Process for conducting heterogeneous chemical reactions |
| US5672780A (en) * | 1995-08-11 | 1997-09-30 | Eastman Kodak Company | Purification of ethylene glycol recovered from polyester resins |
| US6156160A (en) * | 1998-10-07 | 2000-12-05 | Huntsman Petrochemical Corporation | Alkylene carbonate process |
| AU1819599A (en) | 1998-10-07 | 2000-04-26 | Huntsman Petrochemical Corporation | Process for the preparation of alkylene carbonate |
| US6258962B1 (en) | 1999-06-14 | 2001-07-10 | Mobil Oil Corp. | Process for producing alkylene carbonates |
| US6407279B1 (en) | 1999-11-19 | 2002-06-18 | Exxonmobil Chemical Patents Inc. | Integrated process for preparing dialkyl carbonates and diols |
| JP5282366B2 (en) * | 2006-03-20 | 2013-09-04 | 三菱化学株式会社 | Method for purifying ethylene carbonate, method for producing purified ethylene carbonate, and ethylene carbonate |
| KR101378819B1 (en) * | 2006-03-20 | 2014-03-28 | 츠키시마기카이가부시키가이샤 | Method of purifying ethylene carbonate, process for producing purified ethylene carbonate and ethylene carbonate |
| CN103193594B (en) * | 2012-01-10 | 2015-01-07 | 中国石油化工股份有限公司 | Method for separating ethylene glycol and 1, 2-butanediol |
| KR20200139734A (en) | 2018-04-30 | 2020-12-14 | 사이언티픽 디자인 컴파니 인코포레이티드 | Epoxylation process using concentrated ethylene oxide solution |
| WO2019213032A1 (en) | 2018-04-30 | 2019-11-07 | Scientific Design Company, Inc. | Method for improving the manufacture of ethylene glycol |
| EP3788028A4 (en) | 2018-04-30 | 2022-03-16 | Scientific Design Company, Inc. | Process for preparing ethylene glycol |
| CN112041292A (en) | 2018-04-30 | 2020-12-04 | 科学设计有限公司 | Recycle process for the production of ethylene glycol |
Family Cites Families (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3629343A (en) * | 1968-10-11 | 1971-12-21 | Vnii Neftekhim Protsessov | Process for the production of alkylene glycols |
| US3809724A (en) * | 1971-09-08 | 1974-05-07 | Halcon International Inc | Preparation and recovery of alkylene glycols |
| US4057471A (en) * | 1975-09-12 | 1977-11-08 | Halcon International, Inc. | Recovery of alkylene glycols |
| US4021311A (en) * | 1975-09-12 | 1977-05-03 | Halcon International, Inc. | Recovery of alkylene glycols by azeotropic distillation with 1,2,3-trimethyl benzene |
| US4117250A (en) * | 1977-12-22 | 1978-09-26 | Union Carbide Corporation | Continuous process for producing alkylene glycols from alkylene carbonates |
| US4314945A (en) * | 1977-12-22 | 1982-02-09 | Union Carbide Corporation | Alkylene carbonate process |
| US4160116A (en) * | 1978-08-28 | 1979-07-03 | Showa Denko K.K. | Process for the production of alkylene glycols |
| GB2048698B (en) * | 1979-05-11 | 1983-03-30 | Eardley D | Rapid response distillation method and apparatus for use therein |
| CA1121389A (en) * | 1979-05-24 | 1982-04-06 | Hiroshi Odanaka | Process for the production of alkylene glycols |
| JPS5690029A (en) * | 1979-12-24 | 1981-07-21 | Nippon Shokubai Kagaku Kogyo Co Ltd | Preparation of high-purity alkylene glycol |
| JPS5692228A (en) * | 1979-12-27 | 1981-07-25 | Nippon Shokubai Kagaku Kogyo Co Ltd | Preparation of high-purity alkylene glycol |
| JPS56118024A (en) * | 1980-02-22 | 1981-09-16 | Nippon Shokubai Kagaku Kogyo Co Ltd | Preparation of high-purity alkylene glycol |
| JPS56139432A (en) * | 1980-04-03 | 1981-10-30 | Showa Denko Kk | Preparation of alkylene glycol by hydrolysis of alkylene carbonate |
| JPS6058897B2 (en) * | 1980-06-30 | 1985-12-23 | 株式会社日本触媒 | Method for producing alkylene glycol |
| JPS6055042B2 (en) * | 1981-12-25 | 1985-12-03 | 株式会社日本触媒 | Method for producing alkylene glycol |
| US4400559A (en) * | 1982-06-14 | 1983-08-23 | The Halcon Sd Group, Inc. | Process for preparing ethylene glycol |
| JPS5913741A (en) * | 1982-07-14 | 1984-01-24 | Mitsubishi Petrochem Co Ltd | Preparation of high purity ethylene glycol |
-
1984
- 1984-05-09 US US06/608,639 patent/US4519875A/en not_active Expired - Fee Related
-
1985
- 1985-04-23 IN IN348/DEL/85A patent/IN163264B/en unknown
- 1985-04-26 AU AU41722/85A patent/AU570108B2/en not_active Ceased
- 1985-05-06 KR KR1019850003064A patent/KR920003774B1/en active IP Right Grant
- 1985-05-07 DD DD85276072A patent/DD232483A5/en not_active IP Right Cessation
- 1985-05-07 DE DE8585303219T patent/DE3574369D1/en not_active Expired
- 1985-05-07 EP EP85303219A patent/EP0161111B1/en not_active Expired
- 1985-05-08 BG BG70145A patent/BG51039A3/en unknown
- 1985-05-08 YU YU76385A patent/YU45715B/en unknown
- 1985-05-08 CA CA000480995A patent/CA1241347A/en not_active Expired
- 1985-05-08 BR BR8502190A patent/BR8502190A/en unknown
- 1985-05-08 RO RO85118650A patent/RO91716A/en unknown
- 1985-05-08 JP JP60097677A patent/JPS60239429A/en active Pending
- 1985-05-08 SU SU853896549A patent/SU1604153A3/en active
- 1985-05-09 ZA ZA853523A patent/ZA853523B/en unknown
- 1985-05-09 ES ES542970A patent/ES8607895A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0161111B1 (en) | 1989-11-23 |
| ZA853523B (en) | 1986-12-30 |
| DE3574369D1 (en) | 1989-12-28 |
| IN163264B (en) | 1988-08-27 |
| RO91716A (en) | 1987-05-15 |
| JPS60239429A (en) | 1985-11-28 |
| KR850008656A (en) | 1985-12-21 |
| YU76385A (en) | 1987-12-31 |
| AU570108B2 (en) | 1988-03-03 |
| EP0161111A3 (en) | 1987-04-01 |
| US4519875A (en) | 1985-05-28 |
| AU4172285A (en) | 1985-11-14 |
| DD232483A5 (en) | 1986-01-29 |
| BG51039A3 (en) | 1993-01-15 |
| YU45715B (en) | 1992-07-20 |
| ES8607895A1 (en) | 1986-06-01 |
| KR920003774B1 (en) | 1992-05-14 |
| BR8502190A (en) | 1986-01-07 |
| EP0161111A2 (en) | 1985-11-13 |
| ES542970A0 (en) | 1986-06-01 |
| SU1604153A3 (en) | 1990-10-30 |
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