CA1097693A - Process for the production of ethylene glycol - Google Patents
Process for the production of ethylene glycolInfo
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- CA1097693A CA1097693A CA296,049A CA296049A CA1097693A CA 1097693 A CA1097693 A CA 1097693A CA 296049 A CA296049 A CA 296049A CA 1097693 A CA1097693 A CA 1097693A
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Abstract
ABSTRACT OF THE DISCLOSURE
PROCESS FOR THE PRODUCTION OF ETHYLENE GLYCOL
A cyclic process for producing ethylene glycol comprising the steps of:
(1) contacting formaldehyde with a synthesis gas comprising carbon monoxide and hydrogen in the presence of a catalytic amount of hydrogen fluoride under conditions effective to deplete carbon monoxide from the synthesis gas and produce glycolic acid and diglycolic acid;
(2) contacting the acid product of step (1) with ethylene glycol, diethylene glycol, or mixtures thereof under conditions effective to produce ethylene glycol glycolate and diglycolate, diethylene glycol glycolate and diglycolate, or mixtures thereof;
(3) removing residual carbon monoxide from the carbon monoxide depleted synthesis gas of step (1) thereby producing a hydrogen-rich gas;
(4) contacting the glycolate and diglycolate product of step (2) with the hydrogen-rich gas mixture of step (3) under conditions effective to produce ethylene glycol, diethylene glycol, or mixtures thereof; and (5) recycling from step (4) to step (2) an amount of the glycol product effective to esterify substantially all the acid product present in the reaction zone of step (2).
PROCESS FOR THE PRODUCTION OF ETHYLENE GLYCOL
A cyclic process for producing ethylene glycol comprising the steps of:
(1) contacting formaldehyde with a synthesis gas comprising carbon monoxide and hydrogen in the presence of a catalytic amount of hydrogen fluoride under conditions effective to deplete carbon monoxide from the synthesis gas and produce glycolic acid and diglycolic acid;
(2) contacting the acid product of step (1) with ethylene glycol, diethylene glycol, or mixtures thereof under conditions effective to produce ethylene glycol glycolate and diglycolate, diethylene glycol glycolate and diglycolate, or mixtures thereof;
(3) removing residual carbon monoxide from the carbon monoxide depleted synthesis gas of step (1) thereby producing a hydrogen-rich gas;
(4) contacting the glycolate and diglycolate product of step (2) with the hydrogen-rich gas mixture of step (3) under conditions effective to produce ethylene glycol, diethylene glycol, or mixtures thereof; and (5) recycling from step (4) to step (2) an amount of the glycol product effective to esterify substantially all the acid product present in the reaction zone of step (2).
Description
3~976~3 ~ sAcKG~ouND OE THE INV~NTION
2 The process of this invention ccncerns ~he production
3 of ethylene glyccl fIcm formaldehyde and a synthesis gas
4 COmpLisiDg carbon ~cnoxide and hydrogen. ~ore particularly, this invention provides a multiple-step process for producing ethylene 6 glycol. The princiEal steps involve (1) production of glycolic 7 and diglycolic acids and simultaneous separation of carbon 8 monoxide and hydrcgen iD synthesis gas, (2) esterification of the 9 acid product, and (3) Leduction of the esters. In addition to the integrated reaction steps~ the process utilizes specific 11 recycling steps tc enhance the efficiency of the esterification 12 and hydrogenation reactions.
13 Commonly assigned U.S. Patent 3,911,003 granted october 14 7, 1975 describes an imEroved p~ccess for producing glycolic acid and diglycolic acid from formaldehyde and carbon monoxide 16 employing a hydrogen fluoride catalyst~ According to the 17 disclosure, in cas~s where the glycolic acid product is intended 18 as a feedstock in the production of ethylene glycolr ~he acid is 19 esterified with methanol and then catalytically hydrog nated to produce ethylene glycol. While the chemistry of this procedure 21 is satisfactory, it has been found that the ec~nomics of ~he 22 proc~ss presents a prcbIem for large scale cQmmeLcial ~`
23 explcitation. The substantial cost of methanol esterification 24 and hydrogenatioD is not entirely offset by the improved ylelds and reaction rates oktained through the use cf a hydrogen 26 fluoride catalyst.
27 Accordingly~ it remains desirable ta provide an 28 e~fective process fpr pre~pari~g ethylene glycol from formaldehyde 29 and a synthesis gas comErising carbon monoxide and hydrogen~
~7Çi~3 1 SU~MARY OF TH~ INVENTION
2 It has ncw ke6n found that a prccess for preparing 3 ethylene glycol wbich comprises the steps of (1) contacting 4 formaldehyde and a synthesis gas comprising carhon monoxide aDd hydrcgen in the presence of hydrcgen fluoride under conditions 6 effective to depl~te carbon monoxide from the synthesis gas and 7 simultaneously fcr~ glycolic and dig~ycolic acids; (2) contacting 8~ the acid product cf ste~ (1) with ethylene glycol, diethylene 9 glyccl, or mixt~r~s thereof under conditions effective to produce ethylene glycol glycolate and diglycolate, diethylene glycol 11 glycolate and diglycolate, or mixtures thereof; (3) removing 12 residual carbon mcDoxide from the carbon moncxide depleted 13 synthesis gas o step ~1) tc Eroduce a hydrogen-rich gas; (4) 14 contacting the glycola~e and diglycolate product of step (23 ~ith the hydrogen-rich gas mixture of step (3) under conditions 16 effective to prod~c~ ethylene glycol or diethylene glycol~ and 17 (5) recycling a pcrtion of the glycol product from step (4~ to 18 step (2) economically achieves high yields of ethylene glycol.
The several features of the prese~t process will become 21 more readily appar~nt from the following detailed description of 22 the invention taken in conjunction ~ith the accompanying ~i~ures.
23 Figure 1 ilIustrat~s in flow-sheet form a preferred embodime~t of 24 the process of thiC iDvention. Figure 2 illustrates a preferred product distillatioll scheme.
26 ~=~, c =~ ~
27 The present invention ~rovides an economical cyclic 28 proc~ss for prod~cing high yields of ethylene glycol at improved 29 production rates. lhe process utilizes a carefully selected sequence of reactiolns employiDg particular reac~ants and reaction 31 conditions, as well as recycle to achieve eccnomical productioD
32 ~ rates and yields.
7~
1 In the first step, a reaction zone is charged with 2 formaldehyde, a synthesis gas co~prising carbon monoxide and 3 hydrogen, and hydrogen fluoride. The reacticn zone is maintained 4 under conditions ~hich are effective to form diglycolic and glycclic acids, otber~ise known as oxydiacetic and hydroxyacetic 6 acids respectively.
7 Reaction conditions suitable fcr the production of 8 glycolic acid include a temperature of from about 0C to about 9 100C, preferable 0C tc about 80C, and a synthesis gas partial pres~ure ~etween abcut 10 Esig and about 4000 psig. Preferably 11 the reaction is carried out in the presence of water, for example 12 up tc a~out 25 ~eight percent of water based on the total ~eight 13 of formaldehyde, ~ater and hydrogen fluoride catalyst. ~he 14 presence of water increases the production of glycolic acid and decreases ihe production of diglycolic acid. In a particularly 16 preferred embodim~nt cf the process of this invention the 17 temperature in th~ reaction zone i~ maintained between 20C and 18 60C and the synth~-cic gas partial pressure is maintained bet~een - -19 10 and 3000 psigO lypically the total Eressure is not appreciably above the carbo~ monoxide and hydrogen partial , 21 pressures, carban ~onaxide and hydrogen being by far t~e most 22volatile of the r~actants and prcducts. Usually the total ~ - -23 pressure is about 1 tc 19 peIcent higher than the carbon monoxide 24 a~d bydrogen partial Eressures.
25Among otber factors; the economic success of the 26 process of this inventicn is attributable to the high yields of 27 glycolic acid resulting from the use of a catalyst comprising 28 hydrogen fluoride tc promote the reaction of formaldehyde and 29 carbon mo~oxide, at moderate temperatures and precsu~es. An important feature cf this process is that ~y using a catalyst 31 comprising HF, prescuIes are sufficiently low that ra~ synthesis
13 Commonly assigned U.S. Patent 3,911,003 granted october 14 7, 1975 describes an imEroved p~ccess for producing glycolic acid and diglycolic acid from formaldehyde and carbon monoxide 16 employing a hydrogen fluoride catalyst~ According to the 17 disclosure, in cas~s where the glycolic acid product is intended 18 as a feedstock in the production of ethylene glycolr ~he acid is 19 esterified with methanol and then catalytically hydrog nated to produce ethylene glycol. While the chemistry of this procedure 21 is satisfactory, it has been found that the ec~nomics of ~he 22 proc~ss presents a prcbIem for large scale cQmmeLcial ~`
23 explcitation. The substantial cost of methanol esterification 24 and hydrogenatioD is not entirely offset by the improved ylelds and reaction rates oktained through the use cf a hydrogen 26 fluoride catalyst.
27 Accordingly~ it remains desirable ta provide an 28 e~fective process fpr pre~pari~g ethylene glycol from formaldehyde 29 and a synthesis gas comErising carbon monoxide and hydrogen~
~7Çi~3 1 SU~MARY OF TH~ INVENTION
2 It has ncw ke6n found that a prccess for preparing 3 ethylene glycol wbich comprises the steps of (1) contacting 4 formaldehyde and a synthesis gas comprising carhon monoxide aDd hydrcgen in the presence of hydrcgen fluoride under conditions 6 effective to depl~te carbon monoxide from the synthesis gas and 7 simultaneously fcr~ glycolic and dig~ycolic acids; (2) contacting 8~ the acid product cf ste~ (1) with ethylene glycol, diethylene 9 glyccl, or mixt~r~s thereof under conditions effective to produce ethylene glycol glycolate and diglycolate, diethylene glycol 11 glycolate and diglycolate, or mixtures thereof; (3) removing 12 residual carbon mcDoxide from the carbon moncxide depleted 13 synthesis gas o step ~1) tc Eroduce a hydrogen-rich gas; (4) 14 contacting the glycola~e and diglycolate product of step (23 ~ith the hydrogen-rich gas mixture of step (3) under conditions 16 effective to prod~c~ ethylene glycol or diethylene glycol~ and 17 (5) recycling a pcrtion of the glycol product from step (4~ to 18 step (2) economically achieves high yields of ethylene glycol.
The several features of the prese~t process will become 21 more readily appar~nt from the following detailed description of 22 the invention taken in conjunction ~ith the accompanying ~i~ures.
23 Figure 1 ilIustrat~s in flow-sheet form a preferred embodime~t of 24 the process of thiC iDvention. Figure 2 illustrates a preferred product distillatioll scheme.
26 ~=~, c =~ ~
27 The present invention ~rovides an economical cyclic 28 proc~ss for prod~cing high yields of ethylene glycol at improved 29 production rates. lhe process utilizes a carefully selected sequence of reactiolns employiDg particular reac~ants and reaction 31 conditions, as well as recycle to achieve eccnomical productioD
32 ~ rates and yields.
7~
1 In the first step, a reaction zone is charged with 2 formaldehyde, a synthesis gas co~prising carbon monoxide and 3 hydrogen, and hydrogen fluoride. The reacticn zone is maintained 4 under conditions ~hich are effective to form diglycolic and glycclic acids, otber~ise known as oxydiacetic and hydroxyacetic 6 acids respectively.
7 Reaction conditions suitable fcr the production of 8 glycolic acid include a temperature of from about 0C to about 9 100C, preferable 0C tc about 80C, and a synthesis gas partial pres~ure ~etween abcut 10 Esig and about 4000 psig. Preferably 11 the reaction is carried out in the presence of water, for example 12 up tc a~out 25 ~eight percent of water based on the total ~eight 13 of formaldehyde, ~ater and hydrogen fluoride catalyst. ~he 14 presence of water increases the production of glycolic acid and decreases ihe production of diglycolic acid. In a particularly 16 preferred embodim~nt cf the process of this invention the 17 temperature in th~ reaction zone i~ maintained between 20C and 18 60C and the synth~-cic gas partial pressure is maintained bet~een - -19 10 and 3000 psigO lypically the total Eressure is not appreciably above the carbo~ monoxide and hydrogen partial , 21 pressures, carban ~onaxide and hydrogen being by far t~e most 22volatile of the r~actants and prcducts. Usually the total ~ - -23 pressure is about 1 tc 19 peIcent higher than the carbon monoxide 24 a~d bydrogen partial Eressures.
25Among otber factors; the economic success of the 26 process of this inventicn is attributable to the high yields of 27 glycolic acid resulting from the use of a catalyst comprising 28 hydrogen fluoride tc promote the reaction of formaldehyde and 29 carbon mo~oxide, at moderate temperatures and precsu~es. An important feature cf this process is that ~y using a catalyst 31 comprising HF, prescuIes are sufficiently low that ra~ synthesis
- 5 -.
6~3 gas having a hydrogen to carbon monoxide molar ratio of about 2:1 can be practically employed. While hydrogen fluoride, per se, is oE course a satisfactory catalyst, other catalysts comprising hydrogen fluoride are also satisfactory. For example, commonly assigned United States Patent Serial No. 4,016,208 describes suitable catalysts comprising hydrogen fluoride and non-inter-fering constituents such as metal salts like copper oxides, silver oxide, nickel oxide and halogen acids such as HBr, HCl and HI.
HBF4 is a particularly preferred constituent.
In the presence of hydrogen fluoride, the reaction to produce glycolic acid is surprisingly rapid. The rate of reaction is so high that even at moderate temperatures in the range of 20C to 60C the reaction is completed in relatively short reaction times. The low reaction temperatures which may be employed in the initial stage of the process of this inven-tion minimize reactor corrosion, such that stainless steel re-actors are satisfactory. At higher temperatures more expensive materials such as Monel,* Hastelloy* alloys or titanium are required.
Preferably, the ratio of condensed reactants and cata-lyst is maintained such that in excess of 0.5 mol of hydrogen fluoride are present pex mol of formaldehyde. Suitable hydrogen fluoride to formaldehyde mol ratios range from 1:2 to about 4:1, preferabIy 7:3. Expressed on a weight basis the overall ratio of reactants is suitably from about 5 to about 65 percent formal-dehyde and from about 40 to about 95 percent catalyst with a partial pressure of carbon monoxide ranging from about lO to about 4000 psig. More preferable ranges are from 5 to about 40 percent formaldehyde and 45 to about 85 percent catalyst. The rate of reaction is most rapid at the higher proportions of catalyst in the reaction mixture.
* Trade marks i ~
1 The syntbecic gas stream to the reaction zone ca~ be 2 passed either concurren-tly or countercurrently to the 3 formaldehyde stream. In a preferred embodiment the synthesis gas 4 is passed countercurr~ntly to the formaldehyde and catalyst so that the carbon mcncxide is reacted out of the upward-flowing 6 stream and a purified hydlogen-rich stream of reduced carbon
HBF4 is a particularly preferred constituent.
In the presence of hydrogen fluoride, the reaction to produce glycolic acid is surprisingly rapid. The rate of reaction is so high that even at moderate temperatures in the range of 20C to 60C the reaction is completed in relatively short reaction times. The low reaction temperatures which may be employed in the initial stage of the process of this inven-tion minimize reactor corrosion, such that stainless steel re-actors are satisfactory. At higher temperatures more expensive materials such as Monel,* Hastelloy* alloys or titanium are required.
Preferably, the ratio of condensed reactants and cata-lyst is maintained such that in excess of 0.5 mol of hydrogen fluoride are present pex mol of formaldehyde. Suitable hydrogen fluoride to formaldehyde mol ratios range from 1:2 to about 4:1, preferabIy 7:3. Expressed on a weight basis the overall ratio of reactants is suitably from about 5 to about 65 percent formal-dehyde and from about 40 to about 95 percent catalyst with a partial pressure of carbon monoxide ranging from about lO to about 4000 psig. More preferable ranges are from 5 to about 40 percent formaldehyde and 45 to about 85 percent catalyst. The rate of reaction is most rapid at the higher proportions of catalyst in the reaction mixture.
* Trade marks i ~
1 The syntbecic gas stream to the reaction zone ca~ be 2 passed either concurren-tly or countercurrently to the 3 formaldehyde stream. In a preferred embodiment the synthesis gas 4 is passed countercurr~ntly to the formaldehyde and catalyst so that the carbon mcncxide is reacted out of the upward-flowing 6 stream and a purified hydlogen-rich stream of reduced carbon
7 mono~ide content ic cbtained. In accordance witb the cyclic
8 nature of the process the carbon monoxide depleted stream is used
9 in the subsequent hydrogenation described in detail hereinafter.
Crude glycolic acid and diglycolic acid are recovered 11 from the first reacticn zone. The crude acid contains 12 catalyst which is ~referably removed prior to esterification and 13 recycled to the first reaction zone. The boiling point of 14 hydrogen fluoride is 19.7C at one atmosphere, which is considerably lower than that of diglycolic or glycolic acid.
16 Thus, the hydrogen fluoride catalyst is readily separated by 17 distillation and r~cycled tc the reaction zone.
18 According tc the present process the purified acid 19 product is esterifi~d with ethylene glycol, diethylene glycol, or a ~i~ture of the twa and hydrogenated to Eroduce ethylene glycol r 21 and diéthylene glycol. U.S~ Patent 2~28~44~ granted June 9, 22 1942 describes tbe esterificaticn and hydrogenation of glycolic 23 acid. It has been found that prior to esterification it is 24 deslrable to dehydrat~ the glycolic acid by heating to a teloperature of from about 120C to about 200C, preferable frcm 26 abGut 150~C to abcot 180C under 0.1 to 0. 2 atmospheric pressure.
27 ~ Glycclic acid poss~sses characteristics of bcth a carboxylic acid 28 and an alcohol and is accordingly capable of formi~g linear 29 esters by reactioD ~etween an alcohol grcup of one molecule and the carboxyl grouE of another ~ith the simultaneous formation cf 31 water ~hich is re~cved. These esters may tak~ the form of 1 monoglycolide or polyglycolides. Nany of the glycolides of 2 glycolic acid are solids at normal temperatures and pressures.
3 However, they are soluble in hot ethylene glycol. As used 4 herein~fter the term "anhydrous glycolic acid" includes the various dehydrated forms of the acid, and in particular a mixture 6 of glycolic acid and polyglycolides.
7 Following dehydration, the anhydrous glycolic acid is 8 contacted with ethylene glycol or diethylene glycol under 9 conditions effective to produce the glycolate esters. Preferably complete esterification is achieved by adding hot ethylene or 11 diethylene glycol and removing watar formed during esterification 12 until substantially all the car~oxyl groups of the anhydrous acid 13 are esterified. Suitable conditions for esterification include 14 at temperature of from about 150C to about 250C, preferably from about 170C to about 220C, and a pressure of from about 0 16 psig to about 100 psig, preferably from about 0 psig to about 50 17 psig.
18 The glycol employed during esterification ~s preferably 19 obtained as a recycled portion of the crude glycol product. The~ -following reaction sequence illustrates that in theory 1 mol of 21 ethylene glycol will combine with 1 mol of anhydro~s glycolic 22 acid to produce 2 mols of ethylene glycol, a fraction of which .
23 may be recycled to the es~erification step and the remainder 24 recovsred as product. In practice, it is desirable to recycle sufficient ethylene glycol to insure a molar excess of alcohol 26 during esterification. Suitable mol ratios of glycol to acid 27 during esterification vary from about 1.5:1 to about 10:1, 28 pFc~erably from about 2:1 to about 6~
. . ' .
7~3 o 2 COO~L + HOC~I2CII2O~I IIOCII2-C-O-CII2-C~I2O~I + l52 2 2 ) ¦ 2 110C~2CI~ o~l ) 1 Having prepared the ester, the next step in the 2 process, which is alsc illustrated by the reaction sequence 3 depicted above, com~rises hydrogenating the ester to produce 4 glycol. The liquid phase hydrogenation can ke conducted at S temp~ratures from about 150~C to about 300~C, preferably from 6 about 200C to a~cut 250C and ~ressures from about 500 psig to~
7 about 5000 psig, pleferably from about 1000 psig to about 2000 8 psig. Considerable latitude in the temperature of hydrogenation ; ~ 9 lS possible depending upo~ the use and chcice of hydrogenation ~
~10 catalyst. Metals and metal oxid~s are tbe pre~erable catalysts~ -.
11~ Typical metal oxide catalysts include, for example, copper 02ide-~
~12 ~chromlum ox1de, OI copper o~ide i~ combination with the o~ide of ~13 ~ ~ maqnesium, barium, scdium, nlcke1, sllver, 1lthlum, potass1um, 14~ cesium, zinc, cobalt and the like or mixtures tbereof~ A
preferred catalyst comprises cobalt~metal~in combinatio~ vith l6~ zlnc and copper o~xld~s.
17 ~ As previous~ly~noted, the carbon monoxide-depleted ~;18~ hydrcgen-rich streaw from the~ first~ reaction~ 20~ne provides a l9~ ready~source of~hydroge~for the~ester hydrogenation reaction.
20~ However,~ carbon moDoxide~ lS a polson in ester hydrogenation 21 reactions. Carbo~ mono~ide can ~e removed by any of the ~nown , ~
~ 2Z~ me~hods. A common method is to react carbon monoxide with some - : :, : . .
23 of t~e hydrogen~ to fcIm~ methane over kno~n commercial catalysts,-2 4 ~ usually nickel on an ine~r~t oxide or kieselguhr support. The , 9 _ , ::
.
6~3 hydrogen may also be purified by adsorption of the impurities in cyclic adsorption processes, or by cryogenic separation. Accord-ingly, the carbon monoxide-depleted stream is preferably passed to a hydrogenation vessel in order to convert remaining carbon monoxide to methane. ~ny of the conventional hydrogenation catalysts can be employed for this purpose. United States Patent 3,930,812 granted January 6, 1976, describes a typical hydrogen-ation of carbon oxides to methane.
The carbon monoxide depleted stream from the first reaction zone also contains some hydrogen fluoride catalyst. The catalyst may be removed by known methods. For example, catalyst may be removed by adsorption on NaF pellets to give a complex, from which the catalyst may be recovered for reuse.
Following hydrogenation, the ethylene glycol product is purified, for example by distillation to produce a refined com-mercial grade ethylene glycol.
The following Example is intended to further illustrate practice of the present invention. The example is not intended to limit the scope of the inventlon, inasmuch as various modifi-catlons and alternative embodiments of the principals of the invention will be readily apparent to those of ordinary skill in the art.
EXAMPLE
This Example illustrates a material balance for pro-ducing 200,000,000 lb/yr of~ethylene glycol according to a preferred embodiment of the present cyclic process. Referring to Figure 1, carbonylation reactor 1 is charged through line 2 with 12,960 lb/hr formaIdehyde, 3884 lb/hr water and 570 lb/hr hydrogen fluoride; and through line 3 with synthesis gas com-30 prising 14,056 lb/hr carbon monoxide and 3092 lb/hr hydrogen.
Crude glycolic acid and diglycolic acid are recovered 11 from the first reacticn zone. The crude acid contains 12 catalyst which is ~referably removed prior to esterification and 13 recycled to the first reaction zone. The boiling point of 14 hydrogen fluoride is 19.7C at one atmosphere, which is considerably lower than that of diglycolic or glycolic acid.
16 Thus, the hydrogen fluoride catalyst is readily separated by 17 distillation and r~cycled tc the reaction zone.
18 According tc the present process the purified acid 19 product is esterifi~d with ethylene glycol, diethylene glycol, or a ~i~ture of the twa and hydrogenated to Eroduce ethylene glycol r 21 and diéthylene glycol. U.S~ Patent 2~28~44~ granted June 9, 22 1942 describes tbe esterificaticn and hydrogenation of glycolic 23 acid. It has been found that prior to esterification it is 24 deslrable to dehydrat~ the glycolic acid by heating to a teloperature of from about 120C to about 200C, preferable frcm 26 abGut 150~C to abcot 180C under 0.1 to 0. 2 atmospheric pressure.
27 ~ Glycclic acid poss~sses characteristics of bcth a carboxylic acid 28 and an alcohol and is accordingly capable of formi~g linear 29 esters by reactioD ~etween an alcohol grcup of one molecule and the carboxyl grouE of another ~ith the simultaneous formation cf 31 water ~hich is re~cved. These esters may tak~ the form of 1 monoglycolide or polyglycolides. Nany of the glycolides of 2 glycolic acid are solids at normal temperatures and pressures.
3 However, they are soluble in hot ethylene glycol. As used 4 herein~fter the term "anhydrous glycolic acid" includes the various dehydrated forms of the acid, and in particular a mixture 6 of glycolic acid and polyglycolides.
7 Following dehydration, the anhydrous glycolic acid is 8 contacted with ethylene glycol or diethylene glycol under 9 conditions effective to produce the glycolate esters. Preferably complete esterification is achieved by adding hot ethylene or 11 diethylene glycol and removing watar formed during esterification 12 until substantially all the car~oxyl groups of the anhydrous acid 13 are esterified. Suitable conditions for esterification include 14 at temperature of from about 150C to about 250C, preferably from about 170C to about 220C, and a pressure of from about 0 16 psig to about 100 psig, preferably from about 0 psig to about 50 17 psig.
18 The glycol employed during esterification ~s preferably 19 obtained as a recycled portion of the crude glycol product. The~ -following reaction sequence illustrates that in theory 1 mol of 21 ethylene glycol will combine with 1 mol of anhydro~s glycolic 22 acid to produce 2 mols of ethylene glycol, a fraction of which .
23 may be recycled to the es~erification step and the remainder 24 recovsred as product. In practice, it is desirable to recycle sufficient ethylene glycol to insure a molar excess of alcohol 26 during esterification. Suitable mol ratios of glycol to acid 27 during esterification vary from about 1.5:1 to about 10:1, 28 pFc~erably from about 2:1 to about 6~
. . ' .
7~3 o 2 COO~L + HOC~I2CII2O~I IIOCII2-C-O-CII2-C~I2O~I + l52 2 2 ) ¦ 2 110C~2CI~ o~l ) 1 Having prepared the ester, the next step in the 2 process, which is alsc illustrated by the reaction sequence 3 depicted above, com~rises hydrogenating the ester to produce 4 glycol. The liquid phase hydrogenation can ke conducted at S temp~ratures from about 150~C to about 300~C, preferably from 6 about 200C to a~cut 250C and ~ressures from about 500 psig to~
7 about 5000 psig, pleferably from about 1000 psig to about 2000 8 psig. Considerable latitude in the temperature of hydrogenation ; ~ 9 lS possible depending upo~ the use and chcice of hydrogenation ~
~10 catalyst. Metals and metal oxid~s are tbe pre~erable catalysts~ -.
11~ Typical metal oxide catalysts include, for example, copper 02ide-~
~12 ~chromlum ox1de, OI copper o~ide i~ combination with the o~ide of ~13 ~ ~ maqnesium, barium, scdium, nlcke1, sllver, 1lthlum, potass1um, 14~ cesium, zinc, cobalt and the like or mixtures tbereof~ A
preferred catalyst comprises cobalt~metal~in combinatio~ vith l6~ zlnc and copper o~xld~s.
17 ~ As previous~ly~noted, the carbon monoxide-depleted ~;18~ hydrcgen-rich streaw from the~ first~ reaction~ 20~ne provides a l9~ ready~source of~hydroge~for the~ester hydrogenation reaction.
20~ However,~ carbon moDoxide~ lS a polson in ester hydrogenation 21 reactions. Carbo~ mono~ide can ~e removed by any of the ~nown , ~
~ 2Z~ me~hods. A common method is to react carbon monoxide with some - : :, : . .
23 of t~e hydrogen~ to fcIm~ methane over kno~n commercial catalysts,-2 4 ~ usually nickel on an ine~r~t oxide or kieselguhr support. The , 9 _ , ::
.
6~3 hydrogen may also be purified by adsorption of the impurities in cyclic adsorption processes, or by cryogenic separation. Accord-ingly, the carbon monoxide-depleted stream is preferably passed to a hydrogenation vessel in order to convert remaining carbon monoxide to methane. ~ny of the conventional hydrogenation catalysts can be employed for this purpose. United States Patent 3,930,812 granted January 6, 1976, describes a typical hydrogen-ation of carbon oxides to methane.
The carbon monoxide depleted stream from the first reaction zone also contains some hydrogen fluoride catalyst. The catalyst may be removed by known methods. For example, catalyst may be removed by adsorption on NaF pellets to give a complex, from which the catalyst may be recovered for reuse.
Following hydrogenation, the ethylene glycol product is purified, for example by distillation to produce a refined com-mercial grade ethylene glycol.
The following Example is intended to further illustrate practice of the present invention. The example is not intended to limit the scope of the inventlon, inasmuch as various modifi-catlons and alternative embodiments of the principals of the invention will be readily apparent to those of ordinary skill in the art.
EXAMPLE
This Example illustrates a material balance for pro-ducing 200,000,000 lb/yr of~ethylene glycol according to a preferred embodiment of the present cyclic process. Referring to Figure 1, carbonylation reactor 1 is charged through line 2 with 12,960 lb/hr formaIdehyde, 3884 lb/hr water and 570 lb/hr hydrogen fluoride; and through line 3 with synthesis gas com-30 prising 14,056 lb/hr carbon monoxide and 3092 lb/hr hydrogen.
-10-'~3 1 Reactor 1 is operat~d at a temperature of from about 40C to 70C
2 and a pressure of abo~t 1500 psig. Crude glycolic acid and 3 hydrcgen fluoride catalyst are passed from reactor 1 through line 4 4 to hydrogen flu~ride strip2er 5. SimilarLy carbon monoxide-depleted synthesic gas comprising 570 lbs/hr HF, 3092 lb/hr H2 6 and 1960 lb/hr CC is passed from reactor 1 through line 6,to 7 scrubber 24 where any r~sidual HF is removed~ The purified gas 8 is passed to methanat~r 7. 28,940 lb/hr of purified glycolic 9 acid and polyglycolide are passed from stripper 5 to dehydrator 10 through line 9 ~herein 1940 lb/hr water is removed through
2 and a pressure of abo~t 1500 psig. Crude glycolic acid and 3 hydrcgen fluoride catalyst are passed from reactor 1 through line 4 4 to hydrogen flu~ride strip2er 5. SimilarLy carbon monoxide-depleted synthesic gas comprising 570 lbs/hr HF, 3092 lb/hr H2 6 and 1960 lb/hr CC is passed from reactor 1 through line 6,to 7 scrubber 24 where any r~sidual HF is removed~ The purified gas 8 is passed to methanat~r 7. 28,940 lb/hr of purified glycolic 9 acid and polyglycolide are passed from stripper 5 to dehydrator 10 through line 9 ~herein 1940 lb/hr water is removed through
11 line 11. 27,000 lk~hr glycolic acid polymers are passed through
12 line 12 to esterification vessel 13 which is cimultaneously charged
13 with 53,570 lb/hr recycled crude ethylene glycol through line l4.
14 Esterification is con~ucted at a temperature of about 225C and a pressure of about 50 psig. 1890 lb/hr water i9 distilled out 16 through line ~3. lhe ethylene glycol ester is passed through 17 line 15 to an est~r hydrogenation vessel 16. The hydrogenation 18 vessel ~16 is charg~d ky 2,672 lb/hr Hz and 1180 lb/hr methane 19 from vessel 7 thrcugh line 17. Hydrogenation is conducted ~t a temperature of a~cut 225C and a pressure of aboat 1500 psig.
21 Unused, excess bydrcgen along with methane is pa~sed ~ut of the 22 hydrogenator as a bleed gas stream via line 25. Crude ethylene 23 glycol is passed frcm hydrogenator 16 through line 18 to 24~ distillatlon colum~ 19. A portion of the product from line 18 is returnéd to the esterification vessel 13 by line 14 (dotted line 26 in Figure 1) and the remaining fraction is re~ined to give the 27 ethylene glycol product~ 776 lb/hr water, methanol, and ethanol 28 and 690 lb/hr bcttoms are removed from column 19 via lines 20 and 29 21 r~spectively. 25,345 lb/hr ethylene glycol product is .
reGovered at li~e 22. I~
~ ' , ~. ~
~7~i~3 1 Fi~ure 2 illustrates a preferred modification of the 2 process described in the Example. The modification provides 3 alternative products for recycle to the esterification vessel.
4 Referrinq to FIG. 2, crude glycol product from the hydrogenator is passed through line 18 to dehydration still 26. ~ater and 6 ethanol are removed and pass out of the still 26 through llne 27.
7 Dehydr~ted crude product is recovered from the still at line 28.
a At this point, various products can be selected for recycle.
9 Three cases best illustrate typical situations.
In the first case, if the hydrogenation is carried out 11 under conditions ~here the conversion of glycolate in the 12 hydroqenator is relatively high, the crude product in line 18 13 will comprise wet ethylene glycol and a minor amount of 14 unconverted glycolate. A fraction of the dehydrated product in line 28 can be recycled to the esterifier via line 29 and the 16 remainder refined to remove whatever unconverted glycolate is 17 present; or, the dehydrated product in line 28 can be passed via 18 line 30 to the glycol still 31. Still 31 separates the 19 dehydrated glycol into an ethylene glycol overhead product passing through line 32 and a bottoms product passlng through 21 line 33. A fraction of the refined ethylene glycol in line 32 22 can be recycled via line 34 to the esterifler and the remainder 23 recovered vla line 35 as refined ethylene glycol product. Of 24 course, a compromise of recycled Eractions using lines ?9 and 32 is also acceptable in this case.
26 In the second case, if the hydrogenation is carried out 27 under conditions ~here the conversion of glycolate in the 28 hydrogenator is relatively low, the crude product in line 18 ~ill 29 comprise wet ethylene glycol and unconverted glycolate. A
fraction of the dehydrated product recovered through line 28 can 31 ~e recycled to the esterifier, and the remaining fraction passed - 12 - ~
~a37~
1 to the glycol still 31 via line 30. This latter fraction is ? separated in still 31 to produce a refined ethylene glycol 3 recovered through line 32 and a bottoms camprising unconverted 4 glycolate and hea~ies recovered through line 33. Tbe bottoms can.
then be separated iDtC a small bleed stream 37, and a large 6 fraction which is recycled to the esterifier via line 36.~ Of 7 course, if desired, additional ethylene glycol can be recycled 8 via line 34 to supplement that of line 29.
9 In the third case, if diethylen~ glycol is the desired product for recycle, nane of the dehydrated product in line 28 is 11 recycled, as ethylene glyc~l would build up in the esterifier.
12 ~he dehydrated prcduct is passed through line 30 to still 31 13 where diethylene glyccl is separated as a bottcms product and.
14 recycled via line 36.
Further ~cdifications of the exemplified process can be 16 made consistent with this inven~ion as defined by the following 17 clai~s.
, ~ - 13 - ~
21 Unused, excess bydrcgen along with methane is pa~sed ~ut of the 22 hydrogenator as a bleed gas stream via line 25. Crude ethylene 23 glycol is passed frcm hydrogenator 16 through line 18 to 24~ distillatlon colum~ 19. A portion of the product from line 18 is returnéd to the esterification vessel 13 by line 14 (dotted line 26 in Figure 1) and the remaining fraction is re~ined to give the 27 ethylene glycol product~ 776 lb/hr water, methanol, and ethanol 28 and 690 lb/hr bcttoms are removed from column 19 via lines 20 and 29 21 r~spectively. 25,345 lb/hr ethylene glycol product is .
reGovered at li~e 22. I~
~ ' , ~. ~
~7~i~3 1 Fi~ure 2 illustrates a preferred modification of the 2 process described in the Example. The modification provides 3 alternative products for recycle to the esterification vessel.
4 Referrinq to FIG. 2, crude glycol product from the hydrogenator is passed through line 18 to dehydration still 26. ~ater and 6 ethanol are removed and pass out of the still 26 through llne 27.
7 Dehydr~ted crude product is recovered from the still at line 28.
a At this point, various products can be selected for recycle.
9 Three cases best illustrate typical situations.
In the first case, if the hydrogenation is carried out 11 under conditions ~here the conversion of glycolate in the 12 hydroqenator is relatively high, the crude product in line 18 13 will comprise wet ethylene glycol and a minor amount of 14 unconverted glycolate. A fraction of the dehydrated product in line 28 can be recycled to the esterifier via line 29 and the 16 remainder refined to remove whatever unconverted glycolate is 17 present; or, the dehydrated product in line 28 can be passed via 18 line 30 to the glycol still 31. Still 31 separates the 19 dehydrated glycol into an ethylene glycol overhead product passing through line 32 and a bottoms product passlng through 21 line 33. A fraction of the refined ethylene glycol in line 32 22 can be recycled via line 34 to the esterifler and the remainder 23 recovered vla line 35 as refined ethylene glycol product. Of 24 course, a compromise of recycled Eractions using lines ?9 and 32 is also acceptable in this case.
26 In the second case, if the hydrogenation is carried out 27 under conditions ~here the conversion of glycolate in the 28 hydrogenator is relatively low, the crude product in line 18 ~ill 29 comprise wet ethylene glycol and unconverted glycolate. A
fraction of the dehydrated product recovered through line 28 can 31 ~e recycled to the esterifier, and the remaining fraction passed - 12 - ~
~a37~
1 to the glycol still 31 via line 30. This latter fraction is ? separated in still 31 to produce a refined ethylene glycol 3 recovered through line 32 and a bottoms camprising unconverted 4 glycolate and hea~ies recovered through line 33. Tbe bottoms can.
then be separated iDtC a small bleed stream 37, and a large 6 fraction which is recycled to the esterifier via line 36.~ Of 7 course, if desired, additional ethylene glycol can be recycled 8 via line 34 to supplement that of line 29.
9 In the third case, if diethylen~ glycol is the desired product for recycle, nane of the dehydrated product in line 28 is 11 recycled, as ethylene glyc~l would build up in the esterifier.
12 ~he dehydrated prcduct is passed through line 30 to still 31 13 where diethylene glyccl is separated as a bottcms product and.
14 recycled via line 36.
Further ~cdifications of the exemplified process can be 16 made consistent with this inven~ion as defined by the following 17 clai~s.
, ~ - 13 - ~
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for producing ethylene glycol which comprises the steps of: (1) contacting formaldehyde with a synthesis gas com-prising carbon monoxide and hydrogen in the presence of hydrogen fluoride under conditions effective to deplete carbon monoxide from the synthesis gas and produce glycolic acid and diglycolic acid;
(2) contacting the acid product of step (1) with ethylene glycol, diethylene glycol or mixtures thereof under conditions effective to produce ethylene glycol glycolates, diethylene glycol glycolates or mixtures thereof; (3) removing residual carbon monoxide and hydro-gen fluoride from the carbon monoxide depleted synthesis gas of step (1) to produce a hydrogen-rich gas stream; (4) contacting the glycolate product of step (2) with the hydrogen-rich gas stream of step (3) under conditions effective to produce ethylene glycol or diethylene glycol; and (5) recycling sufficient glycol product from the product of step (4) to the esterification zone of step (2) so as to maintain a molar excess of glycol during esterification.
(2) contacting the acid product of step (1) with ethylene glycol, diethylene glycol or mixtures thereof under conditions effective to produce ethylene glycol glycolates, diethylene glycol glycolates or mixtures thereof; (3) removing residual carbon monoxide and hydro-gen fluoride from the carbon monoxide depleted synthesis gas of step (1) to produce a hydrogen-rich gas stream; (4) contacting the glycolate product of step (2) with the hydrogen-rich gas stream of step (3) under conditions effective to produce ethylene glycol or diethylene glycol; and (5) recycling sufficient glycol product from the product of step (4) to the esterification zone of step (2) so as to maintain a molar excess of glycol during esterification.
2. A process according to Claim 1 wherein the source of hydrogen in hydrogenation step (4) is the carbon monoxide depleted hydrogen stream of step (1) which has been hydrogenated to form a hydrogen and methane mixture.
3. A process according to Claim 1 wherein the formaldehyde and synthesis gas are contacted at a temperature between 0°C and about 100°C and a carbon monoxide partial pressure between 10 psig and 400 psig.
4. A process according to Claim 1 wherein the formaldehyde and synthesis gas are contacted at a temperature between 20°C and about 60°C and a carbon monoxide partial pressure between 10 psig and 3000 psig.
5. A process according to Claim 1 wherein step (1) is carried out in the presence of water.
6. A process according to Claim 1 wherein the acid product formed in step (1) is dehydrated prior to step (2) to form various anhydrous forms of glycolic acid.
7. A process according to Claim 1 wherein the glycolic acid is contacted with ethylene glycol or diethylene glycol at a temperature of from about 150°C to about 250°C and a pressure of from about 0 psig to about 100 psig.
8. A process according to Claim 1 wherein the glycolate product is contacted with hydrogen at a temperature of from about 150°C to about 300°C and a pressure of from about 500 psig to about 5000 psig, in the presence of a hydrogenation catalyst.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,049A CA1097693A (en) | 1978-02-02 | 1978-02-02 | Process for the production of ethylene glycol |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,049A CA1097693A (en) | 1978-02-02 | 1978-02-02 | Process for the production of ethylene glycol |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097693A true CA1097693A (en) | 1981-03-17 |
Family
ID=4110668
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,049A Expired CA1097693A (en) | 1978-02-02 | 1978-02-02 | Process for the production of ethylene glycol |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1097693A (en) |
-
1978
- 1978-02-02 CA CA296,049A patent/CA1097693A/en not_active Expired
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