CA1332424C - Spent acid recycle in methacrylic acid or ester manufacture - Google Patents
Spent acid recycle in methacrylic acid or ester manufactureInfo
- Publication number
- CA1332424C CA1332424C CA 575132 CA575132A CA1332424C CA 1332424 C CA1332424 C CA 1332424C CA 575132 CA575132 CA 575132 CA 575132 A CA575132 A CA 575132A CA 1332424 C CA1332424 C CA 1332424C
- Authority
- CA
- Canada
- Prior art keywords
- acid
- spent
- spent acid
- feed
- water
- 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 - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/06—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid amides
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/06—Preparation of carboxylic acid amides from nitriles by transformation of cyano groups into carboxamide groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/18—Preparation of carboxylic acid esters by conversion of a group containing nitrogen into an ester group
- C07C67/20—Preparation of carboxylic acid esters by conversion of a group containing nitrogen into an ester group from amides or lactams
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
TITLE
SPENT ACID RECYCLE IN
METHACRYLIC ACID OR ESTER MANUFACTURE
ABSTRACT OF THE DISCLOSURE
Improvement of yield and reduction in virgin sulfuric acid needs is methacrylamide formation during the two-stage preparation of methacrylic acid or its alkyl esters by recycling spent acid either as produced or after its water content has been reduced.
SPENT ACID RECYCLE IN
METHACRYLIC ACID OR ESTER MANUFACTURE
ABSTRACT OF THE DISCLOSURE
Improvement of yield and reduction in virgin sulfuric acid needs is methacrylamide formation during the two-stage preparation of methacrylic acid or its alkyl esters by recycling spent acid either as produced or after its water content has been reduced.
Description
~1332~24 ~
SPENT ACID RECYCLE IN
METHACRYLIC ACID OR ESTER MANUFACTURE
.~ .
BACKGROUND OF THE INVENTION
Methacrylic acid and its esters have previously been prepared by (1) reacting acetone cyanohydrin with ;
sulfuric acid to obtain methacrylamide, and (2) ~`
reacting methacrylamide with water or with an alkyl alcohol to obtain the methacrylic acid or alkyl methacrylate, respectively. Once methacrylamide is obtained by this two-stage process, hydrolysis with water will produce a mixture containing methacrylic ~-~
acid, while reaction with water and an alkyl alcohol such as methanol will produce methacrylic ester, e.g.
methyl methacrylate. Such preparations are described in U.S. Patents 2,042,458 and 2,416,756. Improvement in the yield of either stage would improve the economics of the process.
It is also known that increasing the ratio of sulfuric acid to acetone cyanohydrin in the first stage improves the yield of acetone cyanohydrin to methacrylamide. Yield improvement from an increase in ratio is limited by the expense of producing or providing sufficient virgin sulfuric acid The expense of the extra acid is often greater than the value of the extra methacrylamide recovered. Therefore, the usual practice is to limit the ratio to that which gives a reasonable commercial yield, but not the ; 3b maximum yield. ~`
The process described above results in the production of spent acid. By the term nspent acid~ is ~`
meant the solution left after the final product, i.e., ~
either methacrylic acid or methacrylate ester, is ; `
removed from the reaction mixture. The solution contains primarily sulfuric acid, along with ammonium I
~ 3 3 ~
bisulfate produced during the reaction, plus minor amounts ~f unreacted organic compsunds and organic by-products. The spent acid is normally considered a waste by-product, and considerable costs are encountered in disposal or isolation of ammonium bisulfate for other uses, or in conversion of the bisulfate to sulfate for other uses, or in conversion of the spent acid back to virgin acid by means of high temperature catalytic combustion.
SUMMARY OF THE INVENTION
In the present invention, the yield of the methacrylamide stage is increased by recycling the spent acid remaining after the final product is obtained. The present invention is based on the discovery that the spent acid, including the bisulfate present in the spent acid, can be directly substituted for virgin sulfuric acid on a substantially 1:1 molar basis. High value virgin sulfuric acid can accordingly be replaced with low value spent acid in the methacrylamide stage, providing improved yield at minimal cost. In addition, the disposal problems associated with the spent acid are obviated.
Specifically, the present invention provides an improvement in the process for producing methacrylic acid or its alkyl esters by contacting a sulfuric acid or oleum feed which has an acid strength of about from 96%
to 101% with acetone cyanohydrin, thereby forming a solution containing methacrylamide, and then contacting ' 30 the methacrylamide mixture with at least about one mole of water per mole of methacrylamide to obtain a mixture containing methacrylic acid, or with water and an alkyl alcohol to obtain a mixture containing an alkyl methacrylate, the improvement which comprises:
(a) separating the methacrylic acid or alkyl methacrylate, as the case may be, from the mixture to obtain spent acid, (b) adding the spent acid to the sulfuric acid or oleum feed to comprise about from 6 to 90% of the feed and to provide an acid strength of the feed of about from 96% to 101%.
DETAILED DESCRIPTION OF THE INVENTION
The production of methacrylic acid or alkyl -methacrylates from sulfuric acid and acetone cyanohydrin is carried out by a two stage process. In the first stage, acetone cyanohydrin is treated with sulfuric acid which contains sufficient sulfur trioxide ;~
to provide an acid strength of at least about 96% in the reaction mixture after all sulfuric acid and acetone cyanohydrin have been added. This produces a mixture containing methacrylamide. Preferably the , sulfuric acid used is in the form of fuming sulfuric acid, or oleum. The amount of such sulfuric acid used is preferably an amount which provides a weight ratio to the acetone cyanohydrin of about from 1.3 to 1.8 and especially about from 1.5 to 1.8. The two ingredients are advantageously mixed at a temperature below about llO-C and then subjected to a temperature in the range of 130-150C for a time sufficient to obtain optimum ~;
yield. The optimum yield can be determined by withdrawal of samples at regular intervals and analysis ;
of the samples.
A polymerization inhibitor, such as phenothiazine, is ordinarily employed. If desired, the acetone - ;
cyanohydrin can be added in two or more portions. In -this embodiment the first portion (50-75% of the total cyanohydrin) is added below 110C and held at that temperature for about 10 minutes, when the remainder of ~33242~
the cyanohydrin is added, preferably below 110C. The well mixed sample is then treated at a temperature of 130-150C for a time sufficient to obtain optimum yield.
In the second stage, the mixture obtained from the first stage is treated with at least about 1 mole of water per mole of methacrylamide at about from 100 to 150~C to obtain methacrylic acid, or is treated with an excess of water and an alkyl alcohol (preferably of 1-8 carbon atoms) at about from 100 to 140C to obtain an alkyl ester of methacrylic acid.
After the methacrylic acid or alkyl ester thereof has been removed by the usual means such as decantation, distillation or extraction, a ~spent acid~
solution remains, which is aqueous sulfuric acid containing by-products, primarily ammonium bisulfate.
In the process of the present invention, the spent acid can either be used directly or concentrated.
Concentration is generally carried out to reduce the water content to less than about 12%, and prefereably about from 8 to 10% by weight. If concentration is carried out, water contents greater than about 12%
provide minimal benefit relative to the cost of the concentration. Water contents of less than about 8%
are insufficient to maintain the ammonium bisulfate in solution, increasing the difficulty of transporting the spent acid.
The ammonium bisulfate content in the spent acid can vary widely, and is a direct function of the ratio ! !' 30 of acid to acetone cyanohydrin in the amidation step of the present process, as well as the amount of water added during the hydrolysis or esterifcation step. For example, with an acid to acetone cyanohydrin ratio of 1.4 to 1.8 in the methacrylamide step, and usual 35 operation of the esterification step, the spent acid ':
~332~2~
from production of methyl methacrylate will normally contain about from 25 to 75% by weight of ammonium bisulfate.
Contrary to the prior understanding in the art, the presence of ammonium bisulfate is of benefit to the overall process, and the purification procedures previously used to eliminate this byproduct have been found unnecessary. For example, in Borrel et al., U.S.
Patent 2,890,101, ammonium bisulfate is treated as a waste product, and sulfuric acid is recycled only after removal of the major part of the ammonium bisulfate.
The spent acid or a portion thereof is returned, or recycled, to the acid feed used in the first stage.
This recycled spent acid may substitute for virgin sulfuric acid to maintain or achieve the preferably high 1.5-1.8 ratio. The bisulfate ion (present as -;
ammonium bisulfate) and sulfuric acid in the spent acid can be substituted on an approximate 1 to 1 molar basis .. . .
for virgin sulfuric acid. This use of spent acid instead of virgin sulfuric acid makes high acid ratio operation for high yield economically viable.
The amount of spent acid which is added to the initial acid feed, in general, can be about from 6 to 90% of the feed. The maximum amount of unconcentrated ~-~ 25 spent acid which can be added to the first stage is I generally limited to about from 6 to 25% of the total acid, in order to maintain the required acid strength at 96% or greater after all of the acetone cyanohydrin -has been added.
Preferably, the spent acid is concentrated~by evaporation of water until the water content is below about 12%, and especially about from-8 to 10%. The amount of spent acid concentrate that is added is generally between 10 and 90% of the total sulfuric acid weight, and usually between 25-40S. The mixture of ~ ' "
f - 6 - ~ 3 3 2~2 4 spent acid plus virgin acid, or spent acid concentrate plus virgin acid is then fed to the first stage of the process.
The recycle of spent acid provides great flexibility in the makeup of the initial acid feed.
For example, the amount of virgin acid used to make up the feed can be reduced, being partly replaced by the the spent acid. If the amount of virgin acid is either maintained at the same level or increased, then the spent acid can be used to increase the ratio of acid to acetone cyanohydrin and thus increase yield of methacrylamide.
Recycle of spent acid has the additional benefits of reducing the cost of disposal of the spent acid, eliminating the need and cost of removing ammonium bisulfate or converting it to ammonium sulfate, eliminating the need to purify the remaining sulfuric acid before recycle of the sulfuric acid alone, and reducing or eliminating the cost of burning the spent acid to regenerate virgin sulfuric acid.
Another benefit of unconcentrated spent acid recycle is that organic residues in the spent acid are transferred back to the reactor scheme and partially recovered as useful methacrylic acid or alkyl ester of methacrylic acid. In concentrated spent acid recycle, the distillate can be further rectified by standard methods to recover useful organic compounds.
The invention is further illustrated by the following Examples and Comparative Examples, in which parts and percentages are by weight unless otherwise noted.
~ 7 ~ ~332424 ~
Comparative Exam~le A
~ethacrylamide was prepared as follows:
445 parts sulfuric acid of 100.1% strength was prepared from 437 parts of 101.88% sulfuric acid plus 8 parts of water. To 150 parts of the resulting 100.1%
acid was slowly added 100 parts of acetone cyanohydrin (98.7% pure) with good agitation, plus 0~1% -~
phenothiazine to give a final sulfuric,acid to acetone cyanohydrin ratio of 1.50. The temperature was maintained below 80C during the first 2/3 of the acetone cyanohydrin addition, and below 110C for the remainder of the addition. Samples of approximately ;~
1.5 grams each were withdrawn and heated to 140C for various times to determine the optimum yield, which was after approximate~y 25 minutes. The optimum yield was -91.3% based on acetone cyanohydrin originally present. ;
Yields were determined by dilution of the sample 400:1 by weight with water buffered to pH 3.5, followed by analysis by HPLC (Hewlett-Packard Model 1085-B).
The column used was Du Pont Instruments Zorbax ODS ~ ;
4.6mm x 15cm, at 40C. Percentages of methacrylamide were determined by comparision to an external standard of known percentage methacrylamide. Detection was by - 25 ultraviolet at 240 nm.
Comparative Exam~le B
The procedure of Comparative Example A was~
repeated, except 170 parts of the 100.1% sulfuric acid was used, to give a final acid to acetone cyanohydrin ratio of 1.70. The optimum yield was 92.9~.
.
Spent acid was obtained from a commercial unit producing methyl methacrylate. The spent acid * denotes trade mark t~ . .
- 8 - ~3 contained approximately 16% water, 68% ammonium bisulfate, 13% sulfuric acid, and 3% organic and sulfonated organic compounds. The spent acid was heated under vacuum of 50mm Hg absolute until the pot temperature reached 110 degrees C. The overhead composition contained mostly water, with traces of organic compounds which were not identified. The pot contents contained all the sulfuric acid and ammonium bisulfate and any high boiling impurities. Water conten~ was 10.2%. These pot contents are designated ~concentrated spent acid.~
65 parts of concentrated spend acid and 380 parts of virgin sulfuric acid (strength 101.88%) were mixed to give 445 parts of mixed acid of 100.1% strength.
150 parts of the 100.1% sulfuric acid were then used to duplicate the reaction of Comparative Example A.
Optimum yield was 91.6% compared to 91.3% in Comparative Example A. The difference in yield is within experimental error, and confirms that substantially the same yield can be obtained from the same ratio of acid to acetone cyanohydrin, but with the `
substitution of concentrated spent acid for a substantial portion of the virgin acid.
The procedure of Example 1 was repeated, except that 170 parts of the concentrated spent acid plus virgin acid mixture was used. Optimum yield was ~3.2%, I compared to 92.9% in Comparative Example ~. The difference in yield is within experimental error.
Spent acid was obtained from a commercial unit producing methyl methacrylate. The spent acid contained approximately 16% water, 13% sulfuric acid, -:
'~
9 1332~2~
68% ammonium bisulfate, and 3% organic and sulfonated ~-organic compounds. This spent acid is designated ~unconcentrated spent acid.
45 parts of unconcentrated spent acid and 400 parts of virgin sulfuric acid (strength 101.88%) were mixed to give acid of 100.1% strength. 150 parts of -the sulfuric acid mixture were then used in the ~ -~
reaction procedure of Comparative Example A. Optimum yield was 91.7%, compared to 91.3% in Comparative Example A. The difference in yield is within experimental error, and illustrates that substantially the same yield can be obtained from the same ratio of acid to acetone cyanohydrin, but with the substitution of unconcentrated spent acid for a portion of the virgin acid. It also illustrates that less recycle can be used when unconcentrated spent acid is used rather than concentrated spent acid.
The lower amount of recycle permitted is related to the extra water in the unconcentrated case, and the need to maintain acid strength of the spent acid plus virgin acid mixture.
The procedure of Example 3 was repeated, except that 170 parts of the unconcentrated spent acid plus ;
virgin acid mixture was used. Optimum yield was 93.2%, compared to 92.9%. in Comparative Example B. The difference in yield is within experimental error.
;30l EXAMPLE 5 In Example 5, the procedure of Example 3 was repeated, except that 97 parts of unconcentrated spent acid was mixed with 348 parts of 104.5% strength acid (20% oleum), to give 445 parts of 100.1% acid. 150 parts of this sulfuric acid mixture were then used in _ g _ ~332~24 "
the procedure of Comparative Example A. Optimum yield was 91.3~, compared to 91.3% in Comparative Example A.
This illustrates that more unconcentrated spent acid may be recycled if virgin acid strength is higher.
;,, ~ 25 :~
.`: , . ,:,'' " 30~
'', .~,''~:
: ~ 35 ;~:~
~ - 10 - ,,, ;, ~. ,,
SPENT ACID RECYCLE IN
METHACRYLIC ACID OR ESTER MANUFACTURE
.~ .
BACKGROUND OF THE INVENTION
Methacrylic acid and its esters have previously been prepared by (1) reacting acetone cyanohydrin with ;
sulfuric acid to obtain methacrylamide, and (2) ~`
reacting methacrylamide with water or with an alkyl alcohol to obtain the methacrylic acid or alkyl methacrylate, respectively. Once methacrylamide is obtained by this two-stage process, hydrolysis with water will produce a mixture containing methacrylic ~-~
acid, while reaction with water and an alkyl alcohol such as methanol will produce methacrylic ester, e.g.
methyl methacrylate. Such preparations are described in U.S. Patents 2,042,458 and 2,416,756. Improvement in the yield of either stage would improve the economics of the process.
It is also known that increasing the ratio of sulfuric acid to acetone cyanohydrin in the first stage improves the yield of acetone cyanohydrin to methacrylamide. Yield improvement from an increase in ratio is limited by the expense of producing or providing sufficient virgin sulfuric acid The expense of the extra acid is often greater than the value of the extra methacrylamide recovered. Therefore, the usual practice is to limit the ratio to that which gives a reasonable commercial yield, but not the ; 3b maximum yield. ~`
The process described above results in the production of spent acid. By the term nspent acid~ is ~`
meant the solution left after the final product, i.e., ~
either methacrylic acid or methacrylate ester, is ; `
removed from the reaction mixture. The solution contains primarily sulfuric acid, along with ammonium I
~ 3 3 ~
bisulfate produced during the reaction, plus minor amounts ~f unreacted organic compsunds and organic by-products. The spent acid is normally considered a waste by-product, and considerable costs are encountered in disposal or isolation of ammonium bisulfate for other uses, or in conversion of the bisulfate to sulfate for other uses, or in conversion of the spent acid back to virgin acid by means of high temperature catalytic combustion.
SUMMARY OF THE INVENTION
In the present invention, the yield of the methacrylamide stage is increased by recycling the spent acid remaining after the final product is obtained. The present invention is based on the discovery that the spent acid, including the bisulfate present in the spent acid, can be directly substituted for virgin sulfuric acid on a substantially 1:1 molar basis. High value virgin sulfuric acid can accordingly be replaced with low value spent acid in the methacrylamide stage, providing improved yield at minimal cost. In addition, the disposal problems associated with the spent acid are obviated.
Specifically, the present invention provides an improvement in the process for producing methacrylic acid or its alkyl esters by contacting a sulfuric acid or oleum feed which has an acid strength of about from 96%
to 101% with acetone cyanohydrin, thereby forming a solution containing methacrylamide, and then contacting ' 30 the methacrylamide mixture with at least about one mole of water per mole of methacrylamide to obtain a mixture containing methacrylic acid, or with water and an alkyl alcohol to obtain a mixture containing an alkyl methacrylate, the improvement which comprises:
(a) separating the methacrylic acid or alkyl methacrylate, as the case may be, from the mixture to obtain spent acid, (b) adding the spent acid to the sulfuric acid or oleum feed to comprise about from 6 to 90% of the feed and to provide an acid strength of the feed of about from 96% to 101%.
DETAILED DESCRIPTION OF THE INVENTION
The production of methacrylic acid or alkyl -methacrylates from sulfuric acid and acetone cyanohydrin is carried out by a two stage process. In the first stage, acetone cyanohydrin is treated with sulfuric acid which contains sufficient sulfur trioxide ;~
to provide an acid strength of at least about 96% in the reaction mixture after all sulfuric acid and acetone cyanohydrin have been added. This produces a mixture containing methacrylamide. Preferably the , sulfuric acid used is in the form of fuming sulfuric acid, or oleum. The amount of such sulfuric acid used is preferably an amount which provides a weight ratio to the acetone cyanohydrin of about from 1.3 to 1.8 and especially about from 1.5 to 1.8. The two ingredients are advantageously mixed at a temperature below about llO-C and then subjected to a temperature in the range of 130-150C for a time sufficient to obtain optimum ~;
yield. The optimum yield can be determined by withdrawal of samples at regular intervals and analysis ;
of the samples.
A polymerization inhibitor, such as phenothiazine, is ordinarily employed. If desired, the acetone - ;
cyanohydrin can be added in two or more portions. In -this embodiment the first portion (50-75% of the total cyanohydrin) is added below 110C and held at that temperature for about 10 minutes, when the remainder of ~33242~
the cyanohydrin is added, preferably below 110C. The well mixed sample is then treated at a temperature of 130-150C for a time sufficient to obtain optimum yield.
In the second stage, the mixture obtained from the first stage is treated with at least about 1 mole of water per mole of methacrylamide at about from 100 to 150~C to obtain methacrylic acid, or is treated with an excess of water and an alkyl alcohol (preferably of 1-8 carbon atoms) at about from 100 to 140C to obtain an alkyl ester of methacrylic acid.
After the methacrylic acid or alkyl ester thereof has been removed by the usual means such as decantation, distillation or extraction, a ~spent acid~
solution remains, which is aqueous sulfuric acid containing by-products, primarily ammonium bisulfate.
In the process of the present invention, the spent acid can either be used directly or concentrated.
Concentration is generally carried out to reduce the water content to less than about 12%, and prefereably about from 8 to 10% by weight. If concentration is carried out, water contents greater than about 12%
provide minimal benefit relative to the cost of the concentration. Water contents of less than about 8%
are insufficient to maintain the ammonium bisulfate in solution, increasing the difficulty of transporting the spent acid.
The ammonium bisulfate content in the spent acid can vary widely, and is a direct function of the ratio ! !' 30 of acid to acetone cyanohydrin in the amidation step of the present process, as well as the amount of water added during the hydrolysis or esterifcation step. For example, with an acid to acetone cyanohydrin ratio of 1.4 to 1.8 in the methacrylamide step, and usual 35 operation of the esterification step, the spent acid ':
~332~2~
from production of methyl methacrylate will normally contain about from 25 to 75% by weight of ammonium bisulfate.
Contrary to the prior understanding in the art, the presence of ammonium bisulfate is of benefit to the overall process, and the purification procedures previously used to eliminate this byproduct have been found unnecessary. For example, in Borrel et al., U.S.
Patent 2,890,101, ammonium bisulfate is treated as a waste product, and sulfuric acid is recycled only after removal of the major part of the ammonium bisulfate.
The spent acid or a portion thereof is returned, or recycled, to the acid feed used in the first stage.
This recycled spent acid may substitute for virgin sulfuric acid to maintain or achieve the preferably high 1.5-1.8 ratio. The bisulfate ion (present as -;
ammonium bisulfate) and sulfuric acid in the spent acid can be substituted on an approximate 1 to 1 molar basis .. . .
for virgin sulfuric acid. This use of spent acid instead of virgin sulfuric acid makes high acid ratio operation for high yield economically viable.
The amount of spent acid which is added to the initial acid feed, in general, can be about from 6 to 90% of the feed. The maximum amount of unconcentrated ~-~ 25 spent acid which can be added to the first stage is I generally limited to about from 6 to 25% of the total acid, in order to maintain the required acid strength at 96% or greater after all of the acetone cyanohydrin -has been added.
Preferably, the spent acid is concentrated~by evaporation of water until the water content is below about 12%, and especially about from-8 to 10%. The amount of spent acid concentrate that is added is generally between 10 and 90% of the total sulfuric acid weight, and usually between 25-40S. The mixture of ~ ' "
f - 6 - ~ 3 3 2~2 4 spent acid plus virgin acid, or spent acid concentrate plus virgin acid is then fed to the first stage of the process.
The recycle of spent acid provides great flexibility in the makeup of the initial acid feed.
For example, the amount of virgin acid used to make up the feed can be reduced, being partly replaced by the the spent acid. If the amount of virgin acid is either maintained at the same level or increased, then the spent acid can be used to increase the ratio of acid to acetone cyanohydrin and thus increase yield of methacrylamide.
Recycle of spent acid has the additional benefits of reducing the cost of disposal of the spent acid, eliminating the need and cost of removing ammonium bisulfate or converting it to ammonium sulfate, eliminating the need to purify the remaining sulfuric acid before recycle of the sulfuric acid alone, and reducing or eliminating the cost of burning the spent acid to regenerate virgin sulfuric acid.
Another benefit of unconcentrated spent acid recycle is that organic residues in the spent acid are transferred back to the reactor scheme and partially recovered as useful methacrylic acid or alkyl ester of methacrylic acid. In concentrated spent acid recycle, the distillate can be further rectified by standard methods to recover useful organic compounds.
The invention is further illustrated by the following Examples and Comparative Examples, in which parts and percentages are by weight unless otherwise noted.
~ 7 ~ ~332424 ~
Comparative Exam~le A
~ethacrylamide was prepared as follows:
445 parts sulfuric acid of 100.1% strength was prepared from 437 parts of 101.88% sulfuric acid plus 8 parts of water. To 150 parts of the resulting 100.1%
acid was slowly added 100 parts of acetone cyanohydrin (98.7% pure) with good agitation, plus 0~1% -~
phenothiazine to give a final sulfuric,acid to acetone cyanohydrin ratio of 1.50. The temperature was maintained below 80C during the first 2/3 of the acetone cyanohydrin addition, and below 110C for the remainder of the addition. Samples of approximately ;~
1.5 grams each were withdrawn and heated to 140C for various times to determine the optimum yield, which was after approximate~y 25 minutes. The optimum yield was -91.3% based on acetone cyanohydrin originally present. ;
Yields were determined by dilution of the sample 400:1 by weight with water buffered to pH 3.5, followed by analysis by HPLC (Hewlett-Packard Model 1085-B).
The column used was Du Pont Instruments Zorbax ODS ~ ;
4.6mm x 15cm, at 40C. Percentages of methacrylamide were determined by comparision to an external standard of known percentage methacrylamide. Detection was by - 25 ultraviolet at 240 nm.
Comparative Exam~le B
The procedure of Comparative Example A was~
repeated, except 170 parts of the 100.1% sulfuric acid was used, to give a final acid to acetone cyanohydrin ratio of 1.70. The optimum yield was 92.9~.
.
Spent acid was obtained from a commercial unit producing methyl methacrylate. The spent acid * denotes trade mark t~ . .
- 8 - ~3 contained approximately 16% water, 68% ammonium bisulfate, 13% sulfuric acid, and 3% organic and sulfonated organic compounds. The spent acid was heated under vacuum of 50mm Hg absolute until the pot temperature reached 110 degrees C. The overhead composition contained mostly water, with traces of organic compounds which were not identified. The pot contents contained all the sulfuric acid and ammonium bisulfate and any high boiling impurities. Water conten~ was 10.2%. These pot contents are designated ~concentrated spent acid.~
65 parts of concentrated spend acid and 380 parts of virgin sulfuric acid (strength 101.88%) were mixed to give 445 parts of mixed acid of 100.1% strength.
150 parts of the 100.1% sulfuric acid were then used to duplicate the reaction of Comparative Example A.
Optimum yield was 91.6% compared to 91.3% in Comparative Example A. The difference in yield is within experimental error, and confirms that substantially the same yield can be obtained from the same ratio of acid to acetone cyanohydrin, but with the `
substitution of concentrated spent acid for a substantial portion of the virgin acid.
The procedure of Example 1 was repeated, except that 170 parts of the concentrated spent acid plus virgin acid mixture was used. Optimum yield was ~3.2%, I compared to 92.9% in Comparative Example ~. The difference in yield is within experimental error.
Spent acid was obtained from a commercial unit producing methyl methacrylate. The spent acid contained approximately 16% water, 13% sulfuric acid, -:
'~
9 1332~2~
68% ammonium bisulfate, and 3% organic and sulfonated ~-organic compounds. This spent acid is designated ~unconcentrated spent acid.
45 parts of unconcentrated spent acid and 400 parts of virgin sulfuric acid (strength 101.88%) were mixed to give acid of 100.1% strength. 150 parts of -the sulfuric acid mixture were then used in the ~ -~
reaction procedure of Comparative Example A. Optimum yield was 91.7%, compared to 91.3% in Comparative Example A. The difference in yield is within experimental error, and illustrates that substantially the same yield can be obtained from the same ratio of acid to acetone cyanohydrin, but with the substitution of unconcentrated spent acid for a portion of the virgin acid. It also illustrates that less recycle can be used when unconcentrated spent acid is used rather than concentrated spent acid.
The lower amount of recycle permitted is related to the extra water in the unconcentrated case, and the need to maintain acid strength of the spent acid plus virgin acid mixture.
The procedure of Example 3 was repeated, except that 170 parts of the unconcentrated spent acid plus ;
virgin acid mixture was used. Optimum yield was 93.2%, compared to 92.9%. in Comparative Example B. The difference in yield is within experimental error.
;30l EXAMPLE 5 In Example 5, the procedure of Example 3 was repeated, except that 97 parts of unconcentrated spent acid was mixed with 348 parts of 104.5% strength acid (20% oleum), to give 445 parts of 100.1% acid. 150 parts of this sulfuric acid mixture were then used in _ g _ ~332~24 "
the procedure of Comparative Example A. Optimum yield was 91.3~, compared to 91.3% in Comparative Example A.
This illustrates that more unconcentrated spent acid may be recycled if virgin acid strength is higher.
;,, ~ 25 :~
.`: , . ,:,'' " 30~
'', .~,''~:
: ~ 35 ;~:~
~ - 10 - ,,, ;, ~. ,,
Claims (5)
1. In the process for producing methacrylic acid or its alkyl esters by contacting a sulfuric acid or oleum feed which has an acid strength of about from 96% to 10%
with acetone cyanohydrin, thereby forming a solution containing methacrylamide, and then contacting the methacrylamide mixture with at least about one mole of water per mole of methacrylamide to obtain a mixture containing methacrylic acid, or with water and an alkyl alcohol to obtain a mixture containing an alkyl methacrylate, the improvement which comprises:
(a) separating the methacrylic acid or alkyl methacrylate, as the case may be, from the mixture to obtain spent acid, (b) adding the spent acid to the sulfuric acid or oleum feed to comprise about from 6 to 90% by weight of the feed and to provide an acid strength of the feed of about from 96% to 101%.
with acetone cyanohydrin, thereby forming a solution containing methacrylamide, and then contacting the methacrylamide mixture with at least about one mole of water per mole of methacrylamide to obtain a mixture containing methacrylic acid, or with water and an alkyl alcohol to obtain a mixture containing an alkyl methacrylate, the improvement which comprises:
(a) separating the methacrylic acid or alkyl methacrylate, as the case may be, from the mixture to obtain spent acid, (b) adding the spent acid to the sulfuric acid or oleum feed to comprise about from 6 to 90% by weight of the feed and to provide an acid strength of the feed of about from 96% to 101%.
2. A process of Claim 1 in which the amount of unconcentrated spent acid added to the feed is such as to provide an acid strength of at least about 99.5%.
3. A process of Claim 1 in which the spent acid of step (a) is concentrated to remove water to give concentrated spent acid of less than about 12% water by weight.
4. A process of Claim 3 in which the spent acid in step (a) is concentrated to about from 8 to 10% water by weight.
5. A process of Claim 1 wherein the spent acid added to the sulfuric acid or oleum feed is unconcentrated and comprises from about 6 to 25% by weight of the feed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US8751487A | 1987-08-20 | 1987-08-20 | |
| US087,514 | 1987-08-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1332424C true CA1332424C (en) | 1994-10-11 |
Family
ID=22205641
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 575132 Expired - Fee Related CA1332424C (en) | 1987-08-20 | 1988-08-18 | Spent acid recycle in methacrylic acid or ester manufacture |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JP2679819B2 (en) |
| CA (1) | CA1332424C (en) |
| DE (1) | DE3828253C2 (en) |
| ES (1) | ES2012539A6 (en) |
| FR (1) | FR2619563B1 (en) |
| GB (1) | GB2208864B (en) |
| NL (1) | NL8802064A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5393918A (en) * | 1993-12-02 | 1995-02-28 | Rohm And Haas Company | High yield process for the production of methacrylic acid esters |
| ZA200303241B (en) * | 2002-05-01 | 2003-11-04 | Rohm & Haas | Improved process for methacrylic acid and methcrylic acid ester production. |
| DE102006058250A1 (en) * | 2006-12-08 | 2008-06-12 | Evonik Röhm Gmbh | Integrated process and apparatus for producing methacrylic acid esters from acetone and hydrocyanic acid |
| DE102006060161A1 (en) * | 2006-12-18 | 2008-06-26 | Evonik Röhm Gmbh | Process for the adsorptive purification of alkyl methacrylates |
| CN103130671B (en) * | 2013-03-28 | 2015-06-17 | 重庆紫光化工股份有限公司 | Preparation and purification method of clean methacrylamide |
| JP2023547392A (en) | 2020-10-23 | 2023-11-10 | レーム・ゲーエムベーハー | Optimized production method for methacrylic acid (MAS) and/or alkyl methacrylates with reduction of unnecessary by-products |
| JP2023547391A (en) | 2020-10-23 | 2023-11-10 | レーム・ゲーエムベーハー | Optimized production method for alkyl methacrylates by reducing unnecessary by-products |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2042458A (en) * | 1933-10-31 | 1936-06-02 | Ici Ltd | Production of esters of methacrylic acid |
| US2416756A (en) * | 1941-10-23 | 1947-03-04 | Du Pont | Continuous production of esters of methacrylic acid |
| GB815163A (en) * | 1955-07-22 | 1959-06-17 | Electro Chimie Metal | Improvements relating to the manufacture of acrylic acids or esters |
| US2890101A (en) * | 1955-07-22 | 1959-06-09 | Electro Chimie Metal | Recovery of ammonium bisulphate from the distillation residues from the manufacture of acrylic acids and their esters |
| DE1468419A1 (en) * | 1964-09-23 | 1969-05-29 | Nitrokemia Ipartelepek | Process for the production of methyl methacrylate |
| FR2406623A1 (en) * | 1977-10-24 | 1979-05-18 | Chemie Linz Ag | PROCESS FOR THE PREPARATION OF MONO- OR DICARBOXYLIC ACID ESTERS BY REACTION OF CARBOXYLIC ACID AMIDS WITH ALCOHOLS, SULFURIC ACID OR AMMONIUM BISULPHATE |
-
1988
- 1988-08-18 CA CA 575132 patent/CA1332424C/en not_active Expired - Fee Related
- 1988-08-18 ES ES8802573A patent/ES2012539A6/en not_active Expired - Lifetime
- 1988-08-19 GB GB8819764A patent/GB2208864B/en not_active Expired - Lifetime
- 1988-08-19 JP JP63204894A patent/JP2679819B2/en not_active Expired - Lifetime
- 1988-08-19 FR FR8811028A patent/FR2619563B1/en not_active Expired - Fee Related
- 1988-08-19 NL NL8802064A patent/NL8802064A/en not_active Application Discontinuation
- 1988-08-19 DE DE19883828253 patent/DE3828253C2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB2208864A (en) | 1989-04-19 |
| JPS6470433A (en) | 1989-03-15 |
| NL8802064A (en) | 1989-03-16 |
| DE3828253C2 (en) | 1999-10-28 |
| FR2619563B1 (en) | 1994-04-01 |
| DE3828253A1 (en) | 1989-03-02 |
| GB2208864B (en) | 1991-07-10 |
| FR2619563A1 (en) | 1989-02-24 |
| ES2012539A6 (en) | 1990-04-01 |
| JP2679819B2 (en) | 1997-11-19 |
| GB8819764D0 (en) | 1988-09-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3841834B2 (en) | Malonic acid and its esters | |
| JP3934163B2 (en) | Purification method of butyl acrylate | |
| KR100278059B1 (en) | Process for producing acrylic ester or methacrylic ester | |
| EP0379691B1 (en) | Process for preparing unsaturated carboxylic acid or ester thereof | |
| TW364900B (en) | Process for producing highly pure terephthalic acid | |
| CA1332424C (en) | Spent acid recycle in methacrylic acid or ester manufacture | |
| EP0487285A2 (en) | Purification process for methyl acetate | |
| US6281374B1 (en) | Fluorinated alkanoic acid purification process | |
| KR101269493B1 (en) | Process for recovering valued compounds from a stream derived from purification of methyl methacrylate | |
| US4775447A (en) | Process for the production of 2,2-dimethoxypropane | |
| US5393888A (en) | Non-catalytic liquid phase conversion of butyrolactone and ammonia to 2-pyrrolidone product in high yield and selectivity | |
| JP3782032B2 (en) | Improved process for the preparation of 2-ethylhexyl acrylate | |
| JP3597551B2 (en) | Continuous process for industrial production of dimethoxyethanal | |
| US4087623A (en) | Catalyst recovery process | |
| EP0225738B1 (en) | Method of recovering useful components at least containing dimethyl terephthalate from high-boiling byproducts occurring in the production of dimethyl terephthalate | |
| JPS60149558A (en) | Purification of tertiary butylhydro peroxide containing primary and secondary alkylhydro peroxide polutants | |
| JPH05271143A (en) | Production of cyclohexanone | |
| US6494996B2 (en) | Process for removing water from aqueous methanol | |
| JPH05186391A (en) | Method for purifying ethyl acetate | |
| GB1596651A (en) | Process for the recovery of laevulinic acid in the form of its internal ester alphaangelica lactone from mixtures of compounds of similar boiling-point | |
| US3247246A (en) | Cyclic process for production of terephthalic acid | |
| KR960006664B1 (en) | Process for the extractive separation of a carboxylic acid from an aqueous solution of the said acid | |
| JP2533980B2 (en) | Method for producing perpropionic acid | |
| DE1917034A1 (en) | Process for the preparation of epoxy compounds | |
| US3445506A (en) | Method for preparing ethyl acrylate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |