CA1168262A - Treatment of dibasic esters with alkali metal borohydrides, permanganates or methylates - Google Patents
Treatment of dibasic esters with alkali metal borohydrides, permanganates or methylatesInfo
- Publication number
- CA1168262A CA1168262A CA000381884A CA381884A CA1168262A CA 1168262 A CA1168262 A CA 1168262A CA 000381884 A CA000381884 A CA 000381884A CA 381884 A CA381884 A CA 381884A CA 1168262 A CA1168262 A CA 1168262A
- Authority
- CA
- Canada
- Prior art keywords
- esters
- borohydride
- alkali metal
- color
- permanganate
- 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
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/60—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification
Abstract
TITLE
Treatment Of Dibasic Esters With Alkali Metal Borohydrides, Permanganates Or Methylates ABSTRACT OF THE DISCLOSURE
Process for reducing the color forming tendency of alkanedioic acid esters by contact with an alkali metal borohydride or permanganate in the presence of water or an alkali metal methylate.
Treatment Of Dibasic Esters With Alkali Metal Borohydrides, Permanganates Or Methylates ABSTRACT OF THE DISCLOSURE
Process for reducing the color forming tendency of alkanedioic acid esters by contact with an alkali metal borohydride or permanganate in the presence of water or an alkali metal methylate.
Description
TITLE
Treatment Of Dibasic Esters With Alkali Metal Borohydrides, Permanganates Or Methylates BACKGROUND OF THE INVENTION
-Field of the Invention The present invention relates to reducing the color forming tendencies of c~rtain esters and, more particularly, to the treatment of esters with an alkali metal borohydride in the presence of water, an alkali metal permanganate in the presence of water and/or an alkali metal methylate.
Description of the Prior Art Borohydrides are recognized as compounds for the selective reduction of a wide range of functional groups, e.g., aldehydes, ketones, imines, esters and amides, etc. The use of borohydrides is compiled in the publication entitled Process Stream Purification, Bulletin No. BA-8UG, Ventron Corp., September, 1978. This publication lists 6 patents relating to the purification of esters, but it does not include any relating to the remo~al of color formers from aliphatic dibasic esters.
U.S. Patent 2,957,023 issued on October 18, 1960 discloses a method for the stabilization of alcohols contaminated with carbonyl and/or unsaturated compounds such as olefins by adding a borohydride to the alcohol during or before the esterification. The patentees disclose that a solvent is preferred because of the relative insolubility of the borohydride but indicate that the choice of solvent is not critical to their invention. Solvents which are disclosed include water, isopropanol ether, low molecular weight amines and the like.
The production of color free polyvinyl PI-0280 35 alcohol is obtained according to the teachings of ~b q~
~168262 U.S. Patent 3,679,646 issued on July 25, 1972 by pre-treating an alcohol solution of a polyvinyl ester with from about 0.03 to about 3~ by weight based upon the weight of the polyvinyl ester of an alkali metal borohydride followed by alkaline hydrolysis. The patentees prefer to use the borohydride in a finely divided, e.g., powder form.
U.S. Patent 3,681,482 issued on August 1, 1972 discloses a process for improving the color of phosphate esters by contacting the esters with 0.002 to 0.05 percent by weight of sodium or lithium borohydride. The patentees disclose that the borohydride is preferably in solid form but can be in aqueous solution.
German Patent 2,556,258 issued on May 26, 1977 teaches the stabilization of polyhydroxy carboxylate polymers by the addition of sodium borohydride.
U.S. Patent 3,991,100 issued on November 9, 1976 discloses a process for the production of esters of dibasic acids which exhibit a reduced color-forming tendency under alkaline or transesterification conditions. The process involves heating the esters to remove water, oxides of nitrogen and nitric acid, esterifying the thus heated product and finally distilling off volatile materials in the presence of a dry base such as sodium carbonate and calcium hydroxide. It should be noted, however, that this method does not completely eliminate the color-forming tendencies of the esters during trans-esterification.
The art discloses that under ordinary conditions aliphatic nitro compounds are not reactive with sodium borohydride and that for such a reaction to occur to any significant extent transition metals, their salts and complexes of ~ewis acids are required (Sodium Borohydride, Ventron Corporation, December, 1979, pages 35-36).
U.S. Patent 2,831,883 issued on April 22, 1958 discloses the reduction of nitro impurities in alpha, omega-alkanedioic acid esters prepared from diacids via the nitric acid oxidation of organic compounds. The patentees disclose several methods for reduction of the nitro compounds including reduction with a metal and an acid, e.g., zinc dust and an alcoholic solution of a mineral acid; catalytic reduction with Raney nickel or with reduced precipitated nickel and chemical reduction, e.g., by catalytic reduction with palladium or platinum.
U.S. Patent 3,991,100 issued on November 9, 1976 discloses a process for the production of esters of dibasic acids which exhibit a reduced color forming tendency under alkaline or transesterification conditions. The process involves heating the esters to remove water, oxides of nitrogen and nitric acid, esterifying the thus heated product and finally distilling off volatile materials in the presence of a dry base such as sodium carbonate or calcium hydroxide. The disclosed method does not completely eliminate the color forming tendencies of the esters during transesterification.
Belgium Patent 828,5Q8 issued on April 29, 1974 discloses a process for the removal of organic nitrogen containing compounds from dodecanedioic acid by treating the acid with potassium permanganate in an alkali medium. There is no disclosure of treating acids other than dodecandioic acids nor to the treatment of esters of any acids.
A general method for oxidizing the salts of mononitro compounds with neutral potassium permanganate is disclosed in the article appearing in J. Organic Chem. 27, page 3699 (1962). The process disclosed involves converting the nitro compounds to their potassium salts in an aqueous solution which is then added to an aqueous solution of potassium permanganate. The aldehyde and/or ketones that are produced are steamed distilled out of the aqueous reaction mixture.
U.S. Patent 3,642,871 issued on February 15, 1972 discloses the use of an alkali metal alkoxide, e.g., sodium methylate necessarily combined with phosphorus atoms, e.g., phosphoric acid to improve the color stability of a wide variety of organic esters including diesters of aliphatic carboxylic acids, e.g., dimethyl adipate, dibutyl sebacate and diisopropyl succinate.
SUMMARY OF THE INVENTION
A process for reducing the color forming tendency of alkanedioic acid esters, e.g., those esters derived from dicarboxylic acids having 4-12 carbon atoms which comprises contacting the esters with alkali metal borohydride in the presence of water, an alkali metal permanganate in the presence of water and/or an alkali metal ~ethylate. It is preferred to dissolve the borohydride and permanganate in water before contact with the esters.
DETAILED DESCRIPTION OF THE INVENTION
The esters to which the present invention is particularly applicable are those prepared from the acids isolated as co-products from the air oxidation of cyclic hydrocarbons to cyclic ketones and alcohol followed by the oxidation of the ketones and alcohols with nitric acid. The oxidation of cyclohexane to cyclohexanol and cyclohexanone can 1 16826~
be conducted according to the teachings, for example, of U.S. Patent 3,530,185 issued on September 22, 1970.
Cyclohexanol and cyclohexanone produced according to the aforementioned patent are then oxidized with nitric acid according to the teachings of U.S.
Patents 3,359,308 issued on December 19, 1967 and 3,365,490 issued on January 23, 1968. Illustrative of the co-product acids that are produced along with adipic acid in the aforementioned processes are succinic acid and glutaric acid.
The preparation of alkane dicarboxylic acids having from 8 to 12 carbon atoms by the nitric acid oxidation of the corresponding alcohols and ketones is disclosed in U.S. Patent 3,758,564 issued on September 11, 1973. Illustrative of the co-product acids produced in this process are pimelic acid, suberic acid, azelaic acid, sebacic acid and undecanedioic acid.
The principal acids produced in the above described processes, i.e., adipic acid and dodecane-dioic acid are commonly separated from the co-product acids by crystallization and the co-product acids then recovered from the mother liquor by known methods. These co-product acids can be converted to esters by known esterification processes. Even after rigorous distillation, these esters still exhibit a marked tendency to turn yellow when subjected to alkaline conditions or when heated to temperatures for which the esters are eventually 3Q employed, e.g., for the preparation of other esters and polyesters by transesterification.
The color-forming tendency of esters which are treated according to the process of the present invention is believed due to the presence of small amounts of aliphatic nitro compounds which form during the nitric acid oxidation of the ketones or alcohols andtor during acid catalyzed esterification in the presence of residual nitrate ion. These impurities co-distill with the esters; are not adsorbed to any significant extent on activated carbon and are not amenable to bleaching, e.g., with peroxides or aqueous hypochlorites.
The borohydrides which are operable in the present invention include sodium, potassium and lithium borohydride and mixtures of the foregoing.
Sodium borohydride is the preferred borohydride.
The methylates which are operable in the present invention include sodium, potassium and lithium methylate and mixtures of the foregoing.
Sodium methylate is preferred.
The permanganates which are operable in the present invention include sodium, potassium and lithium permanganate and mixtures of the foregoing.
Potassium permanganate is preferred.
The method for contacting the above described additives with the esters is not critical to the present invention provided water is present during contact in the case of the permanganate and borohydride. Low shear stirring at ambient temperature has been found completely satisfactory for mixing, but as one skilled in the art can appreciate, higher shear mixing and/or elevated temperatures will accelerate the reaction. The contacting may be conducted at temperatures in the range of 0-100C and preferably 20-75C for times varying from about 0.5-2 hours. Time can be decreased as the agitat~on and/or temperature is increased. The borohydride and/or permanganate and water may be introduced separately into the esters but preferably, they are dissolved in water before ~168262 introduction. In the case of the borohydride the minimum amount of water required for formation of the solution depends on the solubility of the borohydride at the temperature of the water, but the amount of water can be up to twice the weight of the borohydride or more~ In any event, it is desirable to ir,troduce only the minimum amount of water necessary and thereby minimize the drying required after reaction. The presence of water markedly reduces the effectiveness of the methylate and it is preferred to maintain water at the lowest practical level, e.g., less than 0.1% by weight based upon the weight of the esters.
Since the borohydrides decompose rapidly in the presence of acid, the esters should be neutral or slightly basic for optimum utili~ation of the hydride and for color reduction. This also applies to treatment with the methylate. Usually a precipitate is formed during the contact of the ester and the methylate which can if desired be removed by known methods, e.g., filtration before further processing of the treated esters.
The amount of additive required will, of course, depend upon the amount of color-formers present which is dictated by the conditions used in preparing the acids and/or the esters. It has been determined that two parts by weight of borohydride per 1000 parts by weight of ester is usually sufficient for complete reduction in color. However, in many instances less than one part of borohydride per 1000 parts of ester can accomplish complete color reduction. Generally, 0.05-5% and prefera~ly about 0.1-0.3% by weight of borohydride based upon the weight of the ester is employed. It has been determined that 2-25 and usually about 5 parts by 1 16~26.~ , weight of methylate per 1000 parts by weight of ester is usually sufficient for complete reduction in color.
In many instances less than one part of methylate per 1000 parts of ester can accomplish complete color reduction. It has been determined that 6.6 parts by weight of permanganate per 1000 parts by weight of ester is usually sufficient for complete reduction in color. However, in many instances less than 6.6 parts of permanganate per 1000 parts of ester can accomplish complete color reduction.
Generally, 0.1-2% and preferably about 0.4-0.8~
by weight of permanganate based upon the weight of the ester is employed. In any event, the amount of additive required is readily determined by increasing or decreasing the amount until the desired le~el of color is obtained. Excess additive can be employed to assure an essentially complete reduction in color forming tendency.
The following eY~amples are presented to illustrate but not to restrict the present invention.
Parts and percentages are by weight unless otherwise specified. The color forming tendencies of the esters treated according to the process of the present invention were determined by adding two drops of a 40% by weight solution of benzyltrimethyl ammonium-hydroxide in methanol to 5 ml of esters, followed by shaking the solution. All esters reported in the Examples were treated in this manner before determining the color. The polyesters were not treated before determining the color. Color was judged usin~ a Hellige* Color Comparator equipped with a Gardner color disc ~color system of the Institute of Paint and Varnish Research). This technique measures the yellowness of samples on a * denotes trade mark ..... .. ................. .... ... . ........ .... .. . .
g scale from 1 (very light yellow~ to 10 (dark yellow).
A colorless sample exhibits a Gardner color of less than 1.
EXAMPLE I
S To a 12 liter flask fitted with a simple distillation head and suitable heating equipment was added 10 kilograms of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I and a Gardner color of 6.
TABLE I
Dimethyl succinate 2%
Dimethyl glutarate 71~
Dimethyl adipate 27%
This ester mixture was prepared as described hereinabove by esterification of the acids obtained by the nitric acid oxidation of a mixture of cyclo-hexanol and cyclohexanone followed by removal of the majority of adipic acid by crystallization.
Approximately 10 grams of sodium borohydride was dissolved in 20 grams of water and the resultant solution introduced into the fla~k. After standing overnight at room temperature (about 16 hours at 20C), the ester had a Gardner number less than 1. This ester was then distilled under 25 mm Hg vacuum. A
small foreshot was removed and 9.5 kilograms of distillate at a boiling point in the range of 110-118C was collected, The distillate also exhibited a Gardner color of less than 1 and when a polyester was made from this material by trans-esterification with ethylene glycol in the presence of n-butyl stannoic acid, a polyester having a Gardner color of less than 1 was obtained.
-Comparative A
Example I was repeated except that 10 grams 116~262 of powdered sodium borohydride (no water) were thoroughly mixed with the esters. The Gardner color of the distillate was 4 indicating that only a small amount of color-formers were removed in the absence of water.
Comparative B
Example I was repeated except that 40 grams of sodium borohydride (no water) were employed. A
polyester prepared from this ester had a Gardner color of 6.
The foregoing illustrates that even a substantial excess of sodium borohydride does not provide satisfactory color reduction in the absence of water.
EXA~LE II
To a 12 liter flask fitted with a simple distillation head and suitable heating equipment was added 8153 grams of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I of Example I and a Gardner color of 6.
This ester mixture was prepared as described in Example I.
Approximately 57 grams of potassium permanganate was dissolved in 323 grams of water at 85C and the resultant solution introduced into the flask and the mixture was maintained at 77-93C for 65 minutes. The mixture was then distilled under 25 mm Hg vacuum. A small foreshot containing water was removed and 7264 grams of distillate at a boiling point in the range of 110-115C was collected.
The distillate exhibited a Gardner color of less than 1 and when a polyester was made from this material by transesterification with ethylene glycol in the presence of n-butyl stannoic acid, a polyester lQ
having a Gardner color of less than 1 was obtained.
A similar polyester made from the untreated esters was dark orange.
EXA~lPLE III
To a 500 ml flask fitted with a simple distillation head and suitable heating equipment was added 227 grams of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I of Example I and a Gardner color of 4.
This ester mixture was prepared as described in Example I.
Approximately 3.5 grams of sodium methylate was introduced into the flask. The resultant slurry was heated with stirring at 75C for one hour whereupon the contents of the flas~ turned yellow.
This ester was then distilled with essentially no fractionation under 25 mm Hg vacuum. Approximately 215 grams of distillate having a ~ardner color of ~1 was collected.
EXAMPLE IV
.
A mixture of C7_12 straight chain dibasic acids recovered from the nitric acid oxidation of cyclododecanone and cyclododecanol as described hereinabove were esterified with methanol using a dodecylbenzene sulfonic acid catalyst. The resultant esters were then distilled under 1 mm Hg pressure and a distillate boiling in the range of 99-150C
and having a Gardner color of 7 was recovered. This ester distillate had the composition given in Table II.
TABLE II
Dimethyl pimelate 0.5% Dimethyl sebacate 7.0%
Dimethyl suberate 2.4% Dimethyl undecandioate 47.6%
Dimethyl azelate 3.3% Dimethyl dodecandioate 39.2%
To 150 parts of this ester distillate was ll~8262 added 6 parts of a 25% by weight aqueous solution of sodium borohydride. The mixture was then stirred at room temperature for 1 hour and then re-distilled under the above described conditions. A small foreshot boiling below 99C was taken and discarded.
A product was collected at a boiling range of 99-155C which had a Gardner color of less than 1.
EXAMPLE V
To 124 parts of the ester distillate as described in Example IV and having a Gardner color of 9 was added 1.6 parts of potassium permanganate dissolved in 4.8 parts of hot water (85C) with mild agitation at room temperature.
The mixture was then distilled at Cl mm Hg pressure.
After a small foreshot containing water was discarded, 87 parts of treated esters were collected which had a Gardner color of less than 1.
EXAMPLE VI
To 124 parts of the ester distillate of Example V was added 2 parts of sodium methylate with mild agitation at room temperature. The mixture was then distilled at ~1 mm Hg pressure. After a small foreshot which was discarded, 104 parts of treated esters were collected which had a Gardner color of less than 1.
Treatment Of Dibasic Esters With Alkali Metal Borohydrides, Permanganates Or Methylates BACKGROUND OF THE INVENTION
-Field of the Invention The present invention relates to reducing the color forming tendencies of c~rtain esters and, more particularly, to the treatment of esters with an alkali metal borohydride in the presence of water, an alkali metal permanganate in the presence of water and/or an alkali metal methylate.
Description of the Prior Art Borohydrides are recognized as compounds for the selective reduction of a wide range of functional groups, e.g., aldehydes, ketones, imines, esters and amides, etc. The use of borohydrides is compiled in the publication entitled Process Stream Purification, Bulletin No. BA-8UG, Ventron Corp., September, 1978. This publication lists 6 patents relating to the purification of esters, but it does not include any relating to the remo~al of color formers from aliphatic dibasic esters.
U.S. Patent 2,957,023 issued on October 18, 1960 discloses a method for the stabilization of alcohols contaminated with carbonyl and/or unsaturated compounds such as olefins by adding a borohydride to the alcohol during or before the esterification. The patentees disclose that a solvent is preferred because of the relative insolubility of the borohydride but indicate that the choice of solvent is not critical to their invention. Solvents which are disclosed include water, isopropanol ether, low molecular weight amines and the like.
The production of color free polyvinyl PI-0280 35 alcohol is obtained according to the teachings of ~b q~
~168262 U.S. Patent 3,679,646 issued on July 25, 1972 by pre-treating an alcohol solution of a polyvinyl ester with from about 0.03 to about 3~ by weight based upon the weight of the polyvinyl ester of an alkali metal borohydride followed by alkaline hydrolysis. The patentees prefer to use the borohydride in a finely divided, e.g., powder form.
U.S. Patent 3,681,482 issued on August 1, 1972 discloses a process for improving the color of phosphate esters by contacting the esters with 0.002 to 0.05 percent by weight of sodium or lithium borohydride. The patentees disclose that the borohydride is preferably in solid form but can be in aqueous solution.
German Patent 2,556,258 issued on May 26, 1977 teaches the stabilization of polyhydroxy carboxylate polymers by the addition of sodium borohydride.
U.S. Patent 3,991,100 issued on November 9, 1976 discloses a process for the production of esters of dibasic acids which exhibit a reduced color-forming tendency under alkaline or transesterification conditions. The process involves heating the esters to remove water, oxides of nitrogen and nitric acid, esterifying the thus heated product and finally distilling off volatile materials in the presence of a dry base such as sodium carbonate and calcium hydroxide. It should be noted, however, that this method does not completely eliminate the color-forming tendencies of the esters during trans-esterification.
The art discloses that under ordinary conditions aliphatic nitro compounds are not reactive with sodium borohydride and that for such a reaction to occur to any significant extent transition metals, their salts and complexes of ~ewis acids are required (Sodium Borohydride, Ventron Corporation, December, 1979, pages 35-36).
U.S. Patent 2,831,883 issued on April 22, 1958 discloses the reduction of nitro impurities in alpha, omega-alkanedioic acid esters prepared from diacids via the nitric acid oxidation of organic compounds. The patentees disclose several methods for reduction of the nitro compounds including reduction with a metal and an acid, e.g., zinc dust and an alcoholic solution of a mineral acid; catalytic reduction with Raney nickel or with reduced precipitated nickel and chemical reduction, e.g., by catalytic reduction with palladium or platinum.
U.S. Patent 3,991,100 issued on November 9, 1976 discloses a process for the production of esters of dibasic acids which exhibit a reduced color forming tendency under alkaline or transesterification conditions. The process involves heating the esters to remove water, oxides of nitrogen and nitric acid, esterifying the thus heated product and finally distilling off volatile materials in the presence of a dry base such as sodium carbonate or calcium hydroxide. The disclosed method does not completely eliminate the color forming tendencies of the esters during transesterification.
Belgium Patent 828,5Q8 issued on April 29, 1974 discloses a process for the removal of organic nitrogen containing compounds from dodecanedioic acid by treating the acid with potassium permanganate in an alkali medium. There is no disclosure of treating acids other than dodecandioic acids nor to the treatment of esters of any acids.
A general method for oxidizing the salts of mononitro compounds with neutral potassium permanganate is disclosed in the article appearing in J. Organic Chem. 27, page 3699 (1962). The process disclosed involves converting the nitro compounds to their potassium salts in an aqueous solution which is then added to an aqueous solution of potassium permanganate. The aldehyde and/or ketones that are produced are steamed distilled out of the aqueous reaction mixture.
U.S. Patent 3,642,871 issued on February 15, 1972 discloses the use of an alkali metal alkoxide, e.g., sodium methylate necessarily combined with phosphorus atoms, e.g., phosphoric acid to improve the color stability of a wide variety of organic esters including diesters of aliphatic carboxylic acids, e.g., dimethyl adipate, dibutyl sebacate and diisopropyl succinate.
SUMMARY OF THE INVENTION
A process for reducing the color forming tendency of alkanedioic acid esters, e.g., those esters derived from dicarboxylic acids having 4-12 carbon atoms which comprises contacting the esters with alkali metal borohydride in the presence of water, an alkali metal permanganate in the presence of water and/or an alkali metal ~ethylate. It is preferred to dissolve the borohydride and permanganate in water before contact with the esters.
DETAILED DESCRIPTION OF THE INVENTION
The esters to which the present invention is particularly applicable are those prepared from the acids isolated as co-products from the air oxidation of cyclic hydrocarbons to cyclic ketones and alcohol followed by the oxidation of the ketones and alcohols with nitric acid. The oxidation of cyclohexane to cyclohexanol and cyclohexanone can 1 16826~
be conducted according to the teachings, for example, of U.S. Patent 3,530,185 issued on September 22, 1970.
Cyclohexanol and cyclohexanone produced according to the aforementioned patent are then oxidized with nitric acid according to the teachings of U.S.
Patents 3,359,308 issued on December 19, 1967 and 3,365,490 issued on January 23, 1968. Illustrative of the co-product acids that are produced along with adipic acid in the aforementioned processes are succinic acid and glutaric acid.
The preparation of alkane dicarboxylic acids having from 8 to 12 carbon atoms by the nitric acid oxidation of the corresponding alcohols and ketones is disclosed in U.S. Patent 3,758,564 issued on September 11, 1973. Illustrative of the co-product acids produced in this process are pimelic acid, suberic acid, azelaic acid, sebacic acid and undecanedioic acid.
The principal acids produced in the above described processes, i.e., adipic acid and dodecane-dioic acid are commonly separated from the co-product acids by crystallization and the co-product acids then recovered from the mother liquor by known methods. These co-product acids can be converted to esters by known esterification processes. Even after rigorous distillation, these esters still exhibit a marked tendency to turn yellow when subjected to alkaline conditions or when heated to temperatures for which the esters are eventually 3Q employed, e.g., for the preparation of other esters and polyesters by transesterification.
The color-forming tendency of esters which are treated according to the process of the present invention is believed due to the presence of small amounts of aliphatic nitro compounds which form during the nitric acid oxidation of the ketones or alcohols andtor during acid catalyzed esterification in the presence of residual nitrate ion. These impurities co-distill with the esters; are not adsorbed to any significant extent on activated carbon and are not amenable to bleaching, e.g., with peroxides or aqueous hypochlorites.
The borohydrides which are operable in the present invention include sodium, potassium and lithium borohydride and mixtures of the foregoing.
Sodium borohydride is the preferred borohydride.
The methylates which are operable in the present invention include sodium, potassium and lithium methylate and mixtures of the foregoing.
Sodium methylate is preferred.
The permanganates which are operable in the present invention include sodium, potassium and lithium permanganate and mixtures of the foregoing.
Potassium permanganate is preferred.
The method for contacting the above described additives with the esters is not critical to the present invention provided water is present during contact in the case of the permanganate and borohydride. Low shear stirring at ambient temperature has been found completely satisfactory for mixing, but as one skilled in the art can appreciate, higher shear mixing and/or elevated temperatures will accelerate the reaction. The contacting may be conducted at temperatures in the range of 0-100C and preferably 20-75C for times varying from about 0.5-2 hours. Time can be decreased as the agitat~on and/or temperature is increased. The borohydride and/or permanganate and water may be introduced separately into the esters but preferably, they are dissolved in water before ~168262 introduction. In the case of the borohydride the minimum amount of water required for formation of the solution depends on the solubility of the borohydride at the temperature of the water, but the amount of water can be up to twice the weight of the borohydride or more~ In any event, it is desirable to ir,troduce only the minimum amount of water necessary and thereby minimize the drying required after reaction. The presence of water markedly reduces the effectiveness of the methylate and it is preferred to maintain water at the lowest practical level, e.g., less than 0.1% by weight based upon the weight of the esters.
Since the borohydrides decompose rapidly in the presence of acid, the esters should be neutral or slightly basic for optimum utili~ation of the hydride and for color reduction. This also applies to treatment with the methylate. Usually a precipitate is formed during the contact of the ester and the methylate which can if desired be removed by known methods, e.g., filtration before further processing of the treated esters.
The amount of additive required will, of course, depend upon the amount of color-formers present which is dictated by the conditions used in preparing the acids and/or the esters. It has been determined that two parts by weight of borohydride per 1000 parts by weight of ester is usually sufficient for complete reduction in color. However, in many instances less than one part of borohydride per 1000 parts of ester can accomplish complete color reduction. Generally, 0.05-5% and prefera~ly about 0.1-0.3% by weight of borohydride based upon the weight of the ester is employed. It has been determined that 2-25 and usually about 5 parts by 1 16~26.~ , weight of methylate per 1000 parts by weight of ester is usually sufficient for complete reduction in color.
In many instances less than one part of methylate per 1000 parts of ester can accomplish complete color reduction. It has been determined that 6.6 parts by weight of permanganate per 1000 parts by weight of ester is usually sufficient for complete reduction in color. However, in many instances less than 6.6 parts of permanganate per 1000 parts of ester can accomplish complete color reduction.
Generally, 0.1-2% and preferably about 0.4-0.8~
by weight of permanganate based upon the weight of the ester is employed. In any event, the amount of additive required is readily determined by increasing or decreasing the amount until the desired le~el of color is obtained. Excess additive can be employed to assure an essentially complete reduction in color forming tendency.
The following eY~amples are presented to illustrate but not to restrict the present invention.
Parts and percentages are by weight unless otherwise specified. The color forming tendencies of the esters treated according to the process of the present invention were determined by adding two drops of a 40% by weight solution of benzyltrimethyl ammonium-hydroxide in methanol to 5 ml of esters, followed by shaking the solution. All esters reported in the Examples were treated in this manner before determining the color. The polyesters were not treated before determining the color. Color was judged usin~ a Hellige* Color Comparator equipped with a Gardner color disc ~color system of the Institute of Paint and Varnish Research). This technique measures the yellowness of samples on a * denotes trade mark ..... .. ................. .... ... . ........ .... .. . .
g scale from 1 (very light yellow~ to 10 (dark yellow).
A colorless sample exhibits a Gardner color of less than 1.
EXAMPLE I
S To a 12 liter flask fitted with a simple distillation head and suitable heating equipment was added 10 kilograms of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I and a Gardner color of 6.
TABLE I
Dimethyl succinate 2%
Dimethyl glutarate 71~
Dimethyl adipate 27%
This ester mixture was prepared as described hereinabove by esterification of the acids obtained by the nitric acid oxidation of a mixture of cyclo-hexanol and cyclohexanone followed by removal of the majority of adipic acid by crystallization.
Approximately 10 grams of sodium borohydride was dissolved in 20 grams of water and the resultant solution introduced into the fla~k. After standing overnight at room temperature (about 16 hours at 20C), the ester had a Gardner number less than 1. This ester was then distilled under 25 mm Hg vacuum. A
small foreshot was removed and 9.5 kilograms of distillate at a boiling point in the range of 110-118C was collected, The distillate also exhibited a Gardner color of less than 1 and when a polyester was made from this material by trans-esterification with ethylene glycol in the presence of n-butyl stannoic acid, a polyester having a Gardner color of less than 1 was obtained.
-Comparative A
Example I was repeated except that 10 grams 116~262 of powdered sodium borohydride (no water) were thoroughly mixed with the esters. The Gardner color of the distillate was 4 indicating that only a small amount of color-formers were removed in the absence of water.
Comparative B
Example I was repeated except that 40 grams of sodium borohydride (no water) were employed. A
polyester prepared from this ester had a Gardner color of 6.
The foregoing illustrates that even a substantial excess of sodium borohydride does not provide satisfactory color reduction in the absence of water.
EXA~LE II
To a 12 liter flask fitted with a simple distillation head and suitable heating equipment was added 8153 grams of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I of Example I and a Gardner color of 6.
This ester mixture was prepared as described in Example I.
Approximately 57 grams of potassium permanganate was dissolved in 323 grams of water at 85C and the resultant solution introduced into the flask and the mixture was maintained at 77-93C for 65 minutes. The mixture was then distilled under 25 mm Hg vacuum. A small foreshot containing water was removed and 7264 grams of distillate at a boiling point in the range of 110-115C was collected.
The distillate exhibited a Gardner color of less than 1 and when a polyester was made from this material by transesterification with ethylene glycol in the presence of n-butyl stannoic acid, a polyester lQ
having a Gardner color of less than 1 was obtained.
A similar polyester made from the untreated esters was dark orange.
EXA~lPLE III
To a 500 ml flask fitted with a simple distillation head and suitable heating equipment was added 227 grams of the mixed methyl esters of succinic, glutaric and adipic acid, having the analysis set forth in Table I of Example I and a Gardner color of 4.
This ester mixture was prepared as described in Example I.
Approximately 3.5 grams of sodium methylate was introduced into the flask. The resultant slurry was heated with stirring at 75C for one hour whereupon the contents of the flas~ turned yellow.
This ester was then distilled with essentially no fractionation under 25 mm Hg vacuum. Approximately 215 grams of distillate having a ~ardner color of ~1 was collected.
EXAMPLE IV
.
A mixture of C7_12 straight chain dibasic acids recovered from the nitric acid oxidation of cyclododecanone and cyclododecanol as described hereinabove were esterified with methanol using a dodecylbenzene sulfonic acid catalyst. The resultant esters were then distilled under 1 mm Hg pressure and a distillate boiling in the range of 99-150C
and having a Gardner color of 7 was recovered. This ester distillate had the composition given in Table II.
TABLE II
Dimethyl pimelate 0.5% Dimethyl sebacate 7.0%
Dimethyl suberate 2.4% Dimethyl undecandioate 47.6%
Dimethyl azelate 3.3% Dimethyl dodecandioate 39.2%
To 150 parts of this ester distillate was ll~8262 added 6 parts of a 25% by weight aqueous solution of sodium borohydride. The mixture was then stirred at room temperature for 1 hour and then re-distilled under the above described conditions. A small foreshot boiling below 99C was taken and discarded.
A product was collected at a boiling range of 99-155C which had a Gardner color of less than 1.
EXAMPLE V
To 124 parts of the ester distillate as described in Example IV and having a Gardner color of 9 was added 1.6 parts of potassium permanganate dissolved in 4.8 parts of hot water (85C) with mild agitation at room temperature.
The mixture was then distilled at Cl mm Hg pressure.
After a small foreshot containing water was discarded, 87 parts of treated esters were collected which had a Gardner color of less than 1.
EXAMPLE VI
To 124 parts of the ester distillate of Example V was added 2 parts of sodium methylate with mild agitation at room temperature. The mixture was then distilled at ~1 mm Hg pressure. After a small foreshot which was discarded, 104 parts of treated esters were collected which had a Gardner color of less than 1.
Claims (4)
1. A method of reducing the color-forming tendency of esters obtained from alkanedioic acids having 4-12 carbon atoms produced by the nitric acid oxidation of cycloaliphatic hydrocarbons selected from the class consisting of ketones, alcohols and mixtures of the foregoing which method comprises contacting said esters with a compound selected from the class consisting of an alkali metal borohydride in the presence of water, an alkali metal permanganate in the presence of water and/or an alkali metal methylate and thereafter recovering the thus treated esters.
2. The process of claim 1 wherein the borohydride is sodium borohydride, the permanganate is potassium permanganate and the methylate is sodium methylate.
3. The process of claim 1 wherein the borohydride and/or permanganate is dissolved in the water before contact with the ester.
4. The process of claim 3 wherein the borohydride is sodium borohydride and the permanganate is potassium permanganate.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US169,734 | 1980-07-17 | ||
| US06/169,734 US4321407A (en) | 1980-07-17 | 1980-07-17 | Treatment of dibasic esters with alkali metal borohydrides |
| US20225180A | 1980-10-30 | 1980-10-30 | |
| US06/202,250 US4331812A (en) | 1980-10-30 | 1980-10-30 | Treatment of dibasic esters with alkali metal methylates |
| US202,251 | 1980-10-30 | ||
| US202,250 | 1980-10-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1168262A true CA1168262A (en) | 1984-05-29 |
Family
ID=27389703
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000381884A Expired CA1168262A (en) | 1980-07-17 | 1981-07-16 | Treatment of dibasic esters with alkali metal borohydrides, permanganates or methylates |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1168262A (en) |
| DE (1) | DE3128204A1 (en) |
| FR (1) | FR2486935A1 (en) |
| GB (1) | GB2079752B (en) |
| IT (1) | IT1138090B (en) |
| NL (1) | NL8103401A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4766236A (en) * | 1987-06-30 | 1988-08-23 | Hoechst Celanese Corporation | Purification of diphenyl phthalates |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2831883A (en) * | 1954-08-18 | 1958-04-22 | Cp Hall Co | Chemical reduction of nitro compounds to purify alpha, omage alkanedioic acid esters |
| US2957023A (en) * | 1957-03-11 | 1960-10-18 | Exxon Research Engineering Co | Treatment of plasticizer esters with alkali metal borohydrides |
| US3642781A (en) * | 1968-10-15 | 1972-02-15 | Warner Lambert Co | Substituted acrylic acids and process for their production |
| US3991100A (en) * | 1974-01-02 | 1976-11-09 | E. I. Du Pont De Nemours And Company | Process for making esters of dibasic acids from acid by-products |
| DE2420765C3 (en) * | 1974-04-29 | 1981-02-12 | Chemische Werke Huels Ag, 4370 Marl | Process for cleaning decanedicarboxylic acid (l, lo) |
-
1981
- 1981-07-16 CA CA000381884A patent/CA1168262A/en not_active Expired
- 1981-07-16 DE DE19813128204 patent/DE3128204A1/en not_active Ceased
- 1981-07-16 GB GB8122032A patent/GB2079752B/en not_active Expired
- 1981-07-16 FR FR8113850A patent/FR2486935A1/en active Granted
- 1981-07-16 IT IT22978/81A patent/IT1138090B/en active
- 1981-07-17 NL NL8103401A patent/NL8103401A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| GB2079752B (en) | 1984-07-25 |
| NL8103401A (en) | 1982-02-16 |
| GB2079752A (en) | 1982-01-27 |
| IT1138090B (en) | 1986-09-10 |
| FR2486935A1 (en) | 1982-01-22 |
| IT8122978A0 (en) | 1981-07-16 |
| DE3128204A1 (en) | 1982-04-22 |
| FR2486935B1 (en) | 1983-12-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6310235B1 (en) | Method for producing ester plasticizers | |
| US3268588A (en) | Process for producing hexamethylenediamine from 1-6-hexanediol | |
| EP1991519B1 (en) | Branched carboxylic acid diesters | |
| US20080245995A1 (en) | Improved Process for the Production of Derivatives of Saturated Carboxylic Acids | |
| MXPA99010734A (en) | Method for producing ester plasticizers | |
| EP0488467B1 (en) | Preparation of alkoxyalkanoic acids | |
| DE69830437T2 (en) | Preparation of tertiary amine oxides | |
| JPH07502035A (en) | Method for producing carboxylic acid or its ester by oxidative decomposition of unsaturated fatty acid or its ester | |
| DE3210617A1 (en) | METHOD FOR PRODUCING METHYL LACTATE | |
| JPS5944341A (en) | Purification of carboxilic acid ester containing aldehyde, acetal and/or unsaturated compound | |
| CA1168262A (en) | Treatment of dibasic esters with alkali metal borohydrides, permanganates or methylates | |
| JP2530864B2 (en) | Process for producing cyclohexanone and cyclohexanol | |
| US4321407A (en) | Treatment of dibasic esters with alkali metal borohydrides | |
| US3441604A (en) | Process for producing dicarboxylic acids | |
| RU2186054C2 (en) | Method of obtaining aliphatic diacids, in particular adipic acid | |
| US20030050499A1 (en) | Process for production of high-purity bis-beta-hydroxyethyl terephthalate | |
| US3399035A (en) | Process for the recovery of boric acid from the oxidation mixtures of liquidphase oxidation of hydrocarbons | |
| JP2500977B2 (en) | Method for producing cyclohexanone | |
| JP2004528393A (en) | Method for removing formic acid from aqueous solution | |
| US4331812A (en) | Treatment of dibasic esters with alkali metal methylates | |
| DE2714564A1 (en) | PROCESS FOR PREPARING CYCLIC ESTERS OF THE UNDECANDISAEUR | |
| US2587904A (en) | Esterification of monohydric ether alcohols | |
| US4803295A (en) | Purification of diphenyl phthalates | |
| CN1162391C (en) | Process to separate linear alkyl 5-formylvalerate | |
| 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 |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |