CA1193282A - Method for esterifying methacrylic acid - Google Patents
Method for esterifying methacrylic acidInfo
- Publication number
- CA1193282A CA1193282A CA000415870A CA415870A CA1193282A CA 1193282 A CA1193282 A CA 1193282A CA 000415870 A CA000415870 A CA 000415870A CA 415870 A CA415870 A CA 415870A CA 1193282 A CA1193282 A CA 1193282A
- Authority
- CA
- Canada
- Prior art keywords
- methacrylic acid
- water
- acid
- esterification
- ester
- 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
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
- C07C69/52—Esters of acyclic unsaturated carboxylic acids having the esterified carboxyl group bound to an acyclic carbon atom
- C07C69/533—Monocarboxylic acid esters having only one carbon-to-carbon double bond
- C07C69/54—Acrylic acid esters; Methacrylic acid esters
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
Abstract
ABSTRACT
What is disclosed is a method for the continuous esterification of aqueous methacrylic acid containing 5 to 60 weight percent water with an alkanol to form the corresponding alkyl methacrylate, with complete conversion of the methacrylic acid used, by feeding the aqueous methacrylic acid into a boiling esterification mixture containing sulfuric acid or an organic sulfonic acid in an amount corresponding to 50 to 500 grams SO3/liter, continuously distilling off the ester formed together with water and a portion of the alkanol, and, after layer separation of the distillate, returning a portion of the ester layer to the distillation unit.
What is disclosed is a method for the continuous esterification of aqueous methacrylic acid containing 5 to 60 weight percent water with an alkanol to form the corresponding alkyl methacrylate, with complete conversion of the methacrylic acid used, by feeding the aqueous methacrylic acid into a boiling esterification mixture containing sulfuric acid or an organic sulfonic acid in an amount corresponding to 50 to 500 grams SO3/liter, continuously distilling off the ester formed together with water and a portion of the alkanol, and, after layer separation of the distillate, returning a portion of the ester layer to the distillation unit.
Description
~3~
M HOD FO~ ESTERIFYING MET~C~YLIC ACID
The presenk invention relates to the production of lower alkyl esters of methacrylic acid, and in particular methyl methacrylate (MMA), from an aqueous solution of methacrylic acid which may contain further constituents such as acetone and acetic acid.
More in particular, the invention relates to part of a manufacturing process for lower esters of methacrylic acid wherein an aqueous solution of methacrylic acid, obtained by the oxidation or dehydrogenation of isobutylene, methacrolein or, preferably, isobutyric acid, is then esterified.
There are many descriptions of such esterification processes which, however, so far have found little practical use. As a rule, they involve the initial extraction of methacrylic acid from an aqueous solution by means of an organic solvent such as benzene or hexane.
After fractional distillation of the extract, the suhstantially anhydrous methacrylic acid is esterified in the usual way.
For example, German paten-t application DE-AS 29 07 602 proposes a mixture of xylene and MMA as an extractant. The methacrylic acid may also be esterified in the extract with an alkanol, the ester then being obtained by ~ractionation of the reacted extract. The use of an organic solven-t as extractant gives rise to further separation problems and requires a number of separation steps, which add to the cost of the process.
32~3~
From U.S. Patent 3,663,375 it is known to mix aqueous methacrylic acid with a sufficient amoun-t of inorganic salts such as sodium sul:Eate that a methacrylic acid layer low in water separates from the salt solution.
However, because of the large amounts of salt which it requires, this process is rather uneconomical.
A similar route is followed i.n the process of .S. Patent 3,821,286, where sulfuric acid is used as an additive to bring about a separation of an aqueous solution 1.0 of methacrylic acid into an organic layer low in water and into aqueous sulfuric acid. The latter is concentrated by heating and the evaporation of water and is then used as an esterification catalyst for the previously separated methacrylic acid layer. The process involves two phase-separation steps which in practice proceed slowly and incompletely.
In the process of German patent application DE-OS
20 35 228, aqueous methacrylic acid is esterified directly by the addition of sulfuric acid and methanol. MMA is recovered from the esterification mixture by extraction with organic solvents. The extract must be fractionally distilled.
In a similar process according to German patent application DE-OS 28 32 202, an esterification mixture of ~A, water, methanol, and methacrylic acid, free of mineral acid, is separated by fractional di.stillation into a distillate of ~, methanol and water from which the major portion of the wa~er and methanol is separa~ed by layer separation, and into a bottom product formed predominantly 3~:82 of methacrylic acid, The bottom product is recycled to the esterification unit.
From German patent applicati.on DE-~S 25 09 729, it is known to esterify aqueous methacrylic acid in the vapor phase over a tungsten oxide catalyst. However, esterification is incomplete so that methacrylic acid has to be recovered from the esterification mixture.
German patent application DE-OS 16 93 174 describes the continuous esterification of anhydrous methacrylic acid with lower alcohols in the still of a distillation uni~ in the presence of ~rom 8 to 30% (calculated as S03 as a percentage o~ the methacrylic acid) of sulfuric acid or o~
an organic sulfonic acid. In this process, the ester formed is continuously distilled off along with the water formed in the reaction so that an esterification mixture whose composition remains constant is~present in the still.
The distillate is separated into layers and a portion of the ester layer is refluxed to the distillation unit. There is nothing to indicate that this process can be carried out with aqueous methacrylic acid.
The object of the invention is continuously to conv,ert aqueous methacrylic acid containlng from 5 to 60 weight percent wa-ter into a lower alkyl ester without the use of separate, auxiliary organic li.~uids in just a ~ew reaction and processing vessels and in high yield. This object is accomplished by the method in accordance with the claims.
28~
STATEMENT OF INVENTION
This invention is a method for the continuous esterification of methacrylic acid con-taining from 5 to 60 weight percent water with a lower alkarlol such as methanol.
This process comprises feeding the methacrylic acid and at least an equivalent amount of the alkanol into a boiling esterification mixture having a temperature between 70 and 170C and containing sulfuric acid or an organic sulfonic acid in an amount corresponding to 50 to 500 grams SO3/liter. The methacrylic ester/water azeotrope containing water introduced with the methacrylic acid as well as water formed by esterification is continuously distilled off. The condensed distillate is separated into an upper ester layer and a lower alkanol/water layer, and a portion of the ester layer is returned as reflux to the still for distillation of the azeotrope.
- 3a -8~
The method of the in-vention is suited to ~he processing of aqueous solutions of methacrylic acid having a water content between 5 and 60 weight percent. With water contents above 40 weight percent, and particularly above 60 weight percent, the separation of distillation of the water from the esterification mixture as an MMA/H20 aæeotrope becomes so onerous that the prior art extraction processes are more economical. With water contents under 5%, the process of the invention offers no advantages over other, known processes. The methacrylic acid used preferably contains from 10 to 40 weight percent of water.
The method of the invention is suitable also for the processing of aqueous solutions of methacrylic acid which contain further constituents that are volatile under the conditions of esterification, such as acetic acid or acetone. The methacrylic acid content should no-t be under 35% Surprisingly, acetone, which under the influence of acids tends to gum, does not result in residues in the esterification mixture.
The content of less ~olatile constituents, for example, polymerization inhibitors, in the aqueous methacrylic acid used should be as low as possible, generally not over 1 weight percent. The less volatile constituents collect in the esterification mixture and can be removed by the con-tinuous withdrawal of a portion of the liquid phase in the still.
_~ _ ~ 3 ~ ~ ~
The process of the invention lends itsel:E
especially to the processing of aqueous solutions of methacrylic acid resulting from the vxidation or dehydrogenation of isobutylene, isobutanol, methacrolein, and particularly isobutyric acid. If the products of dehydrogenation are absorbed in water, the upper limit of 60V/o water is frequently exceeded. It is more advantageous ~o condense the gaseous oxidation or dehydrogenation products by cooling, because a methacrylic acid solutlon containing less than 60U/o water can -then be obtained. The processing of dehydrogenation mixtures produced without the addition of steam is particularly advantageous. The water content of such mixtures may range from 10 to 40 weight percent.
Since extractants are dispensed with according to the present invention, there is no need for any of the separation operations which usually are necessary from the viewpoint of end-product purity or of residues in off gases or of waste waters.
Although it seemed likely that the introduction of substantial amounts of water into a process tha~ is usually carried out with anhydrous methacrylic acid would shift the esterification e~uilibrium far to the side of the acid and prevent complete esterification of the methacrylic acid feed, it has been found that, surprisingly, es~erification can be carried out at a high rate with complete conversion of the methacrylic acid feed.
Since the methacrylic acid used i.s completely converted to the ester, there is no methacrylic acid to be recovered. Only vaporous constituents escape from the esterification mixture and these can readily be separated ~y distillation. The process thus requires only a minimum of separating and processing vessels and entails no waste water or off gas problems.
The esterification mixture used according to the present invention is mainly a mixture of methacrylic acid and the sulfuric or sulfonic acid used as catalyst.
S~lfuric acid is pre-ferred. Suitable sulfonic acids are benzene sulfonic acid, toluene sulfonic acid and methane sulf~nic acid, for example. Any sulfonic acid that is liquid, nonvolatile, and stable under the reaction condi-tions can be used. The proportion of this catalyst in the esterification mixture should ba such that the S03 componer-t of the sulfuric or sulfonic acid is present in a concentration of from 50 to 500 gramslliker. In continuous operation, a portion of the sulfuric acid used may convert to monoalkyl sulfuri.c acid.
The amount of esterification mixture present under steady state conditions may range from 5 to 200 weight percent, based on the aclueous methacrylic acid feed per hour.
A lower alkanol is added to the mixture continuously, along with the aqueous methacrylic acid, in an at least equivalent amount, and optionally in a stoichiometric ex-cess of up to double the methacrylic acid feed. The -6~
preferred molar ratlo oE methacryl.ic acid to alkanol ranges from 1:1.2 to 1:1.6. Lower alkanols having not more than 4 carbon atoms are suitable ~or use ~ethanol is preEerred Further appropriate alkanols are ethanol, isopropanol, n-propanol, isobutanol, and n-butanol. The alkanol used may contain a small amount of water. However, the combined water contents of the alkanol and the aqueous methacrylic acid should not be more than 60 weight percent, based on the total weight of the water and the methacrylic acid.
The esterification mixture is preferably ~.aintained at ebullition at reduced pressure and temperatures between 70 and 170 C. This requires pressures ranging from 60 to 1000 millibars. The esterification mixture forms the bottom product (sump) o~ a distillation unit.
If nonvolatile residues should collect in the esterification mixture, a portion of the mixture may be withdrawn, either continuously or at intervals, and discarded or purified in an appropriate manner. Any solid undissolved residues may be removed by filtration and the filtrate may then be returned to the still.
The bottom product or sump is heated by means of a heating jacket or heating coil and maintained at ebulli~ion in such a way that t~e amount of the migture is held cons-tant.
The still is ad~antageously constructed as a forced circulation reboiler in order to obtain good mi.xing of the esterification mixture wi~hout mechanical agitation.
~3~
The distillate which escapes from the still is preferably taken off through a distillation column. As a rule, the distillate consists of a mixture of an ester/
water azeotrope and the alkanol. ~t normal pressure, an ~A/water azeotrope is composed of 86% MMA and 14% water.
After condensation, the distillate separates into an upper ester layer and a lower water layer, which are separated from each other in a settling tanlc. A portion, usually the major portion, of the ester layer is returned to the column as reflux, a portion of it advantageously to the middle or lower part of the column to improve the separation action.
The reflux ratio depends on the amount of the water in the feed and on the amount of water being formed during esterification. As a rule of thumb, for every part of water it will be necessary to distill off from six to seven parts of the ester.
In addition to the main product, the ester layer may con~ain high- and low-boiling products, which may be separated from one another conventionally through several stagQs of distillation. The aqueous methacrylic acid used frequently contains a small amount of isobutyric acid. The latter is esterified simultaneously with the methacrylic acid and can be separated from the resulting ester mixture by distillation. This requires that the distillation column have a large number of plates. Nevertheless, the distillation will not require much effort since the isobutyric ester is generally present in a small aMount and is taken off as ~313;~:~32 overhead product. Thus only a small amount of distillate is formed which, in addition, need not be completely freed of the methacrylic ester.
The aqueous phase of the condensate contains, in addition to water, the major portion of the unused alkanol, for example, methanol, and, according to their solubility, accessory components such as acetone. The alkanol can be removed by fractional distillation and recycled to the esterification mi~ture.
T~ prevent undesired polymerization, a polymerization inhibitor may be added, preferably at the top of the distillation column. Less volatile inhibitors such as hydroquinone or hydroquinone monomethyl ether are preferred.
They will eventually get into the bottom product and will be removed as the latter is worked up. Small amounts of oxygen may also be conducted through the ~mit.
ples 1.-9 (A) Description of laboratory apparatus ~0 The still is constructed as a forced circulation reboiler (reaction volume, 130 ml) and is equipped with inlets for aqueous crude methacrylic acid, alkanol, and a small amount of air. Heating is effected through oil circulating in a heating jacket. Superimposed on the still is a dis-tillation column (length, 90 cm; inside diameter,
M HOD FO~ ESTERIFYING MET~C~YLIC ACID
The presenk invention relates to the production of lower alkyl esters of methacrylic acid, and in particular methyl methacrylate (MMA), from an aqueous solution of methacrylic acid which may contain further constituents such as acetone and acetic acid.
More in particular, the invention relates to part of a manufacturing process for lower esters of methacrylic acid wherein an aqueous solution of methacrylic acid, obtained by the oxidation or dehydrogenation of isobutylene, methacrolein or, preferably, isobutyric acid, is then esterified.
There are many descriptions of such esterification processes which, however, so far have found little practical use. As a rule, they involve the initial extraction of methacrylic acid from an aqueous solution by means of an organic solvent such as benzene or hexane.
After fractional distillation of the extract, the suhstantially anhydrous methacrylic acid is esterified in the usual way.
For example, German paten-t application DE-AS 29 07 602 proposes a mixture of xylene and MMA as an extractant. The methacrylic acid may also be esterified in the extract with an alkanol, the ester then being obtained by ~ractionation of the reacted extract. The use of an organic solven-t as extractant gives rise to further separation problems and requires a number of separation steps, which add to the cost of the process.
32~3~
From U.S. Patent 3,663,375 it is known to mix aqueous methacrylic acid with a sufficient amoun-t of inorganic salts such as sodium sul:Eate that a methacrylic acid layer low in water separates from the salt solution.
However, because of the large amounts of salt which it requires, this process is rather uneconomical.
A similar route is followed i.n the process of .S. Patent 3,821,286, where sulfuric acid is used as an additive to bring about a separation of an aqueous solution 1.0 of methacrylic acid into an organic layer low in water and into aqueous sulfuric acid. The latter is concentrated by heating and the evaporation of water and is then used as an esterification catalyst for the previously separated methacrylic acid layer. The process involves two phase-separation steps which in practice proceed slowly and incompletely.
In the process of German patent application DE-OS
20 35 228, aqueous methacrylic acid is esterified directly by the addition of sulfuric acid and methanol. MMA is recovered from the esterification mixture by extraction with organic solvents. The extract must be fractionally distilled.
In a similar process according to German patent application DE-OS 28 32 202, an esterification mixture of ~A, water, methanol, and methacrylic acid, free of mineral acid, is separated by fractional di.stillation into a distillate of ~, methanol and water from which the major portion of the wa~er and methanol is separa~ed by layer separation, and into a bottom product formed predominantly 3~:82 of methacrylic acid, The bottom product is recycled to the esterification unit.
From German patent applicati.on DE-~S 25 09 729, it is known to esterify aqueous methacrylic acid in the vapor phase over a tungsten oxide catalyst. However, esterification is incomplete so that methacrylic acid has to be recovered from the esterification mixture.
German patent application DE-OS 16 93 174 describes the continuous esterification of anhydrous methacrylic acid with lower alcohols in the still of a distillation uni~ in the presence of ~rom 8 to 30% (calculated as S03 as a percentage o~ the methacrylic acid) of sulfuric acid or o~
an organic sulfonic acid. In this process, the ester formed is continuously distilled off along with the water formed in the reaction so that an esterification mixture whose composition remains constant is~present in the still.
The distillate is separated into layers and a portion of the ester layer is refluxed to the distillation unit. There is nothing to indicate that this process can be carried out with aqueous methacrylic acid.
The object of the invention is continuously to conv,ert aqueous methacrylic acid containlng from 5 to 60 weight percent wa-ter into a lower alkyl ester without the use of separate, auxiliary organic li.~uids in just a ~ew reaction and processing vessels and in high yield. This object is accomplished by the method in accordance with the claims.
28~
STATEMENT OF INVENTION
This invention is a method for the continuous esterification of methacrylic acid con-taining from 5 to 60 weight percent water with a lower alkarlol such as methanol.
This process comprises feeding the methacrylic acid and at least an equivalent amount of the alkanol into a boiling esterification mixture having a temperature between 70 and 170C and containing sulfuric acid or an organic sulfonic acid in an amount corresponding to 50 to 500 grams SO3/liter. The methacrylic ester/water azeotrope containing water introduced with the methacrylic acid as well as water formed by esterification is continuously distilled off. The condensed distillate is separated into an upper ester layer and a lower alkanol/water layer, and a portion of the ester layer is returned as reflux to the still for distillation of the azeotrope.
- 3a -8~
The method of the in-vention is suited to ~he processing of aqueous solutions of methacrylic acid having a water content between 5 and 60 weight percent. With water contents above 40 weight percent, and particularly above 60 weight percent, the separation of distillation of the water from the esterification mixture as an MMA/H20 aæeotrope becomes so onerous that the prior art extraction processes are more economical. With water contents under 5%, the process of the invention offers no advantages over other, known processes. The methacrylic acid used preferably contains from 10 to 40 weight percent of water.
The method of the invention is suitable also for the processing of aqueous solutions of methacrylic acid which contain further constituents that are volatile under the conditions of esterification, such as acetic acid or acetone. The methacrylic acid content should no-t be under 35% Surprisingly, acetone, which under the influence of acids tends to gum, does not result in residues in the esterification mixture.
The content of less ~olatile constituents, for example, polymerization inhibitors, in the aqueous methacrylic acid used should be as low as possible, generally not over 1 weight percent. The less volatile constituents collect in the esterification mixture and can be removed by the con-tinuous withdrawal of a portion of the liquid phase in the still.
_~ _ ~ 3 ~ ~ ~
The process of the invention lends itsel:E
especially to the processing of aqueous solutions of methacrylic acid resulting from the vxidation or dehydrogenation of isobutylene, isobutanol, methacrolein, and particularly isobutyric acid. If the products of dehydrogenation are absorbed in water, the upper limit of 60V/o water is frequently exceeded. It is more advantageous ~o condense the gaseous oxidation or dehydrogenation products by cooling, because a methacrylic acid solutlon containing less than 60U/o water can -then be obtained. The processing of dehydrogenation mixtures produced without the addition of steam is particularly advantageous. The water content of such mixtures may range from 10 to 40 weight percent.
Since extractants are dispensed with according to the present invention, there is no need for any of the separation operations which usually are necessary from the viewpoint of end-product purity or of residues in off gases or of waste waters.
Although it seemed likely that the introduction of substantial amounts of water into a process tha~ is usually carried out with anhydrous methacrylic acid would shift the esterification e~uilibrium far to the side of the acid and prevent complete esterification of the methacrylic acid feed, it has been found that, surprisingly, es~erification can be carried out at a high rate with complete conversion of the methacrylic acid feed.
Since the methacrylic acid used i.s completely converted to the ester, there is no methacrylic acid to be recovered. Only vaporous constituents escape from the esterification mixture and these can readily be separated ~y distillation. The process thus requires only a minimum of separating and processing vessels and entails no waste water or off gas problems.
The esterification mixture used according to the present invention is mainly a mixture of methacrylic acid and the sulfuric or sulfonic acid used as catalyst.
S~lfuric acid is pre-ferred. Suitable sulfonic acids are benzene sulfonic acid, toluene sulfonic acid and methane sulf~nic acid, for example. Any sulfonic acid that is liquid, nonvolatile, and stable under the reaction condi-tions can be used. The proportion of this catalyst in the esterification mixture should ba such that the S03 componer-t of the sulfuric or sulfonic acid is present in a concentration of from 50 to 500 gramslliker. In continuous operation, a portion of the sulfuric acid used may convert to monoalkyl sulfuri.c acid.
The amount of esterification mixture present under steady state conditions may range from 5 to 200 weight percent, based on the aclueous methacrylic acid feed per hour.
A lower alkanol is added to the mixture continuously, along with the aqueous methacrylic acid, in an at least equivalent amount, and optionally in a stoichiometric ex-cess of up to double the methacrylic acid feed. The -6~
preferred molar ratlo oE methacryl.ic acid to alkanol ranges from 1:1.2 to 1:1.6. Lower alkanols having not more than 4 carbon atoms are suitable ~or use ~ethanol is preEerred Further appropriate alkanols are ethanol, isopropanol, n-propanol, isobutanol, and n-butanol. The alkanol used may contain a small amount of water. However, the combined water contents of the alkanol and the aqueous methacrylic acid should not be more than 60 weight percent, based on the total weight of the water and the methacrylic acid.
The esterification mixture is preferably ~.aintained at ebullition at reduced pressure and temperatures between 70 and 170 C. This requires pressures ranging from 60 to 1000 millibars. The esterification mixture forms the bottom product (sump) o~ a distillation unit.
If nonvolatile residues should collect in the esterification mixture, a portion of the mixture may be withdrawn, either continuously or at intervals, and discarded or purified in an appropriate manner. Any solid undissolved residues may be removed by filtration and the filtrate may then be returned to the still.
The bottom product or sump is heated by means of a heating jacket or heating coil and maintained at ebulli~ion in such a way that t~e amount of the migture is held cons-tant.
The still is ad~antageously constructed as a forced circulation reboiler in order to obtain good mi.xing of the esterification mixture wi~hout mechanical agitation.
~3~
The distillate which escapes from the still is preferably taken off through a distillation column. As a rule, the distillate consists of a mixture of an ester/
water azeotrope and the alkanol. ~t normal pressure, an ~A/water azeotrope is composed of 86% MMA and 14% water.
After condensation, the distillate separates into an upper ester layer and a lower water layer, which are separated from each other in a settling tanlc. A portion, usually the major portion, of the ester layer is returned to the column as reflux, a portion of it advantageously to the middle or lower part of the column to improve the separation action.
The reflux ratio depends on the amount of the water in the feed and on the amount of water being formed during esterification. As a rule of thumb, for every part of water it will be necessary to distill off from six to seven parts of the ester.
In addition to the main product, the ester layer may con~ain high- and low-boiling products, which may be separated from one another conventionally through several stagQs of distillation. The aqueous methacrylic acid used frequently contains a small amount of isobutyric acid. The latter is esterified simultaneously with the methacrylic acid and can be separated from the resulting ester mixture by distillation. This requires that the distillation column have a large number of plates. Nevertheless, the distillation will not require much effort since the isobutyric ester is generally present in a small aMount and is taken off as ~313;~:~32 overhead product. Thus only a small amount of distillate is formed which, in addition, need not be completely freed of the methacrylic ester.
The aqueous phase of the condensate contains, in addition to water, the major portion of the unused alkanol, for example, methanol, and, according to their solubility, accessory components such as acetone. The alkanol can be removed by fractional distillation and recycled to the esterification mi~ture.
T~ prevent undesired polymerization, a polymerization inhibitor may be added, preferably at the top of the distillation column. Less volatile inhibitors such as hydroquinone or hydroquinone monomethyl ether are preferred.
They will eventually get into the bottom product and will be removed as the latter is worked up. Small amounts of oxygen may also be conducted through the ~mit.
ples 1.-9 (A) Description of laboratory apparatus ~0 The still is constructed as a forced circulation reboiler (reaction volume, 130 ml) and is equipped with inlets for aqueous crude methacrylic acid, alkanol, and a small amount of air. Heating is effected through oil circulating in a heating jacket. Superimposed on the still is a dis-tillation column (length, 90 cm; inside diameter,
2.5 cm) which is filled with packing. In the lower third there is an inlet for preheated or vaporized recycle ester which is branched off the ester phase of the distillate Or %~
the pure distillate of the ester phase. The top of the column is equipped with a reEl-ux controller to assure direct reflux to the column.
The entire vapor phase leaving the column is condensed in a total condenser. All components separate into two phases on the basis of their solubili-ty and distribution coefficients. The upper organic phase primarily containing the ester is separated from the lower a~ueous phase which mainly contains the eliminated water.
The apparatus can be operated at reduced pressure or at normal pressure.
(B) Concentrated sulfuric acid is used as the initial catalyst. The particular amount used is given in the Table which -Eollows. A catalyst charge exhibited no appreciable loss of activity after 175 hours of operation.
(C) Procedure The ini~ial catalyst (e.g., concentrated sulfuric acid), the mixture of crude methacrylic and alcohol to be esterified, and an inhibitor are charged to the s-till of the esterification apparatus. The latter is then brought to operating pressure and temperature.
2S Crude methacryli.c acid and alcohol are then metered in in the desired mixing ratio at such a rate that the still volume remains constant.
the pure distillate of the ester phase. The top of the column is equipped with a reEl-ux controller to assure direct reflux to the column.
The entire vapor phase leaving the column is condensed in a total condenser. All components separate into two phases on the basis of their solubili-ty and distribution coefficients. The upper organic phase primarily containing the ester is separated from the lower a~ueous phase which mainly contains the eliminated water.
The apparatus can be operated at reduced pressure or at normal pressure.
(B) Concentrated sulfuric acid is used as the initial catalyst. The particular amount used is given in the Table which -Eollows. A catalyst charge exhibited no appreciable loss of activity after 175 hours of operation.
(C) Procedure The ini~ial catalyst (e.g., concentrated sulfuric acid), the mixture of crude methacrylic and alcohol to be esterified, and an inhibitor are charged to the s-till of the esterification apparatus. The latter is then brought to operating pressure and temperature.
2S Crude methacryli.c acid and alcohol are then metered in in the desired mixing ratio at such a rate that the still volume remains constant.
3~
At the same time, methacrylic ester or crude ester, which after the phase separation has been withdrawn from the organic distillate phase, is fed as vapor or preheated liquid into the lower part of the distillation column. The flow rate must be such that no carboxylic acid can be detected in the distillate.
In steady-state operation, a portion of the crude ester obtained as organic phase is recycled to the distilla-tion column.
In following Examples 1 to 4, the crude methacrylic acid used was composed of 30 weight percent of water and 70 weight percent of methacrylic acid. In following Examples 5 to 9, a miY~ture of 74. l~/o of methacrylic acid, 1.0% of isobutyric acid, 21.7% of water, 2.1% of acetic acid, and 1.1% of acetone was used.
The Table which follows gives the data for different steady-state operation conditions.
--' 1--Unable to recognize this page.
At the same time, methacrylic ester or crude ester, which after the phase separation has been withdrawn from the organic distillate phase, is fed as vapor or preheated liquid into the lower part of the distillation column. The flow rate must be such that no carboxylic acid can be detected in the distillate.
In steady-state operation, a portion of the crude ester obtained as organic phase is recycled to the distilla-tion column.
In following Examples 1 to 4, the crude methacrylic acid used was composed of 30 weight percent of water and 70 weight percent of methacrylic acid. In following Examples 5 to 9, a miY~ture of 74. l~/o of methacrylic acid, 1.0% of isobutyric acid, 21.7% of water, 2.1% of acetic acid, and 1.1% of acetone was used.
The Table which follows gives the data for different steady-state operation conditions.
--' 1--Unable to recognize this page.
Claims (2)
1. A method for the continuous esterification of methacrylic acid containing from 5 to 60 weight percent water with a lower alkanol which comprises feeding the methacrylic acid and at least an equivalent amount of the alkanol into a boiling esterification mixture having a temperature between 70° and 170°C and containing sulfuric acid or an organic sulfonic acid in an amount corresponding to 50 to 500 grams SO3/liter, continuously distilling off a methacrylic ester/water azeotrope containing water introduced with the methacrylic acid as well as water formed by esterification, separating the condensed distillate into an upper ester layer and a lower alkanol/water layer, and returning a portion of the ester layer as reflux to the still for distillation of the azeotrope.
2. A method as in Claim 1 wherein said lower alkanol is methanol.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19813146191 DE3146191A1 (en) | 1981-11-21 | 1981-11-21 | METHOD FOR CONTINUOUSLY ESTABLISHING METHACRYLIC ACID |
| DEP3146191 | 1981-11-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1193282A true CA1193282A (en) | 1985-09-10 |
Family
ID=6146896
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000415870A Expired CA1193282A (en) | 1981-11-21 | 1982-11-18 | Method for esterifying methacrylic acid |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0080023B1 (en) |
| JP (1) | JPS5892638A (en) |
| CA (1) | CA1193282A (en) |
| DE (2) | DE3146191A1 (en) |
| ES (1) | ES8402254A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4999452A (en) * | 1989-05-15 | 1991-03-12 | Union Carbide Chemicals And Plastics Company Inc. | Process for producing acrylic ester |
| US5231222A (en) * | 1991-07-02 | 1993-07-27 | Union Carbide Chemicals & Plastics Technology Corporation | Esterification process |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6081149A (en) * | 1983-09-14 | 1985-05-09 | イー・アイ・デユポン・デ・ニモアス・アンド・カンパニー | Manufacture of n-butylmethacrylate |
| DE19536178A1 (en) * | 1995-09-28 | 1997-04-03 | Basf Ag | Process and device for the continuous production of alkyl esters of (meth) acrylic acid |
| DE19727234C1 (en) * | 1997-06-26 | 1999-07-15 | Basf Ag | Process for the preparation of an alkyl (meth) acrylate |
| CA2252748A1 (en) * | 1997-11-17 | 1999-05-17 | Rohm And Haas Company | Process for preparing alkyl (meth) acrylates |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1211946A (en) * | 1957-12-31 | 1960-03-18 | Standard Oil Co | Process for the production of alkyl esters of unsaturated aliphatic acids |
| DE1288596B (en) * | 1962-01-30 | 1969-02-06 | Knapsack Ag | Process for the production of acrylic acid n-butyl ester from aqueous acrylic acid and n-butanol |
| DE2913218A1 (en) * | 1979-04-03 | 1980-10-23 | Bayer Ag | Prepn. of (meth)acrylic acid ester(s) - by esterification of (meth)acrylic acid with poly:hydric alcohol(s) in presence of phosphite ester and a phenol |
-
1981
- 1981-11-21 DE DE19813146191 patent/DE3146191A1/en not_active Withdrawn
-
1982
- 1982-08-05 EP EP82107078A patent/EP0080023B1/en not_active Expired
- 1982-08-05 DE DE8282107078T patent/DE3261766D1/en not_active Expired
- 1982-11-18 CA CA000415870A patent/CA1193282A/en not_active Expired
- 1982-11-18 JP JP57201229A patent/JPS5892638A/en active Pending
- 1982-11-19 ES ES517511A patent/ES8402254A1/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4999452A (en) * | 1989-05-15 | 1991-03-12 | Union Carbide Chemicals And Plastics Company Inc. | Process for producing acrylic ester |
| US5231222A (en) * | 1991-07-02 | 1993-07-27 | Union Carbide Chemicals & Plastics Technology Corporation | Esterification process |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0080023B1 (en) | 1985-01-02 |
| JPS5892638A (en) | 1983-06-02 |
| EP0080023A1 (en) | 1983-06-01 |
| ES517511A0 (en) | 1984-01-16 |
| DE3261766D1 (en) | 1985-02-14 |
| ES8402254A1 (en) | 1984-01-16 |
| DE3146191A1 (en) | 1983-05-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |